Book of Abstracts

CONFERENCE COMMITTEEHjalti Páll Ingólfsson (chair)

Amel BarichTomasz Urban

Alicja Wiktoria StokłosaCarine Chatenay

Sigurður Tómas BjörgvinssonRúnar Unnþórsson

SCIENCE COMMITTEESigurður Magnús Garðarsson (chair)

Brynhildur DavíðsdóttirDavid Bruhn

Guðni AxelssonMagnús Þór JónssonMariane Peter-Borie

Ragnheiður Inga ÞórarinsdóttirKristín Vala MatthíasdóttirIngólfur Örn Þorbjörnsson

Sveinbjörn BjörnssonSunna Ólafsdóttir Wallevik

Sæunn Halldórsdóttir

PUBLISHING INFOEditors:

Amel BarichHjalti Páll Ingólfsson

Sigurður Magnús Garðarssonand Tomasz Urban

Design, layout and photos:Tomasz Urban - GEORG

November 2018

ContentConference Committee . . . . . . . . . . . . . . . . . . . . . . . 4Science Committee . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Invited Speakers Opening session . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Plenary session . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Panelists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Closing session . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Sponsors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Gallery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

Program 14 . November 2018 . . . . . . . . . . . . . . . . . . . . . . . . . 12 15 . November 2018 . . . . . . . . . . . . . . . . . . . . . . . . . 13

Abstracts Session A1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Session A2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Session A3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26 Session A4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Session A5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 Session B1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Session B2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49 Session B4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .54 Session B5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .59 Posters Session . . . . . . . . . . . . . . . . . . . . . . . . . . . .65

List of Attendees . . . . . . . . . . . . . . . . . . . . . . . . . . . . .78

Best Poster Award . . . . . . . . . . . . . . . . . . . . . . . . . . . 81Volunteers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .82

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Conference Committee

Hjalti Páll IngólfssonChair

Amel Barich

Tomasz Urban

Carine Chatenay

Sigurður Tómas Björgvinsson

Rúnar Unnþórsson

Alicja Wiktoria Stokłosa

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Science Committee

Sigurður Magnús GarðarssonChair

Brynhildur Davíðsdóttir

David Bruhn Guðni Axelsson

Magnús Þór Jónsson Mariane Peter-Borie

Ragnheiður Inga Þórarinsdóttir Kristín Vala Matthíasdóttir

Ingólfur Örn Þorbjörnsson Sveinbjörn Björnsson

Sunna Ólafsdóttir Wallevik Sæunn Halldórsdóttir

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Invited Speakers

Opening session

LILJA DÖGG ALFREÐSDÓTTIRMinister of Education Science and Cultureof Iceland

JOHN LUDDENExecutive Director– British Geological Survey

INGÓLFUR ÖRN ÞORBJÖRNSSONHead of Geothermal Engineering– Iceland Geosurvey

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Invited Speakers

Plenary session

SIGURÐUR H. MARKÚSSONProject ManagerGeothermal Power ProjectLandsvirkjun

SIGURÐUR BOGASONProject ManagerGEORG Geothermal Research Cluster

LILJA KJALARSDÓTTIRCOOSaga Natura- Key Natura

RAGNAR ATLI TOMASSONCo-FounderJurt Hydroponics- Nordic Wasabi

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Invited Speakers

Panelists

RAGNHEIÐUR I. THORARINSDÓTTIRManaging DirectorSvinna - Engineering Ltd.

SIGURÐUR BOGASONProject ManagerGEORG Geothermal Research Cluster

LILJA KJALARSDÓTTIRCOOSaga Natura

JOHAN SINDRI HANSENCo-FounderJurt Hydroponics

KRISTIN VALA MATTHÍASDÓTTIRVP Resource ParkHS Orka

SIGURÐUR H. MARKÚSSONProject ManagerGeothermal Power ProjectLandsvirkjun

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Invited Speakers

Closing session

SUNNA GUÐMUNDSDÓTTIRSpecialistEIMUR

SIGURÐUR MAGNÚS GARÐARSSONDean of Engineering and Natural SciencesUniversity of Iceland / Board of Directors Chair – GEORG

MARIT BROMMERExecutive DirectorInternational Geothermal Association

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Sponsors

Platinum

Gold

Gold

Silver

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Program 14. November 2018

08:30-09:00 Registration and morning coffee

09:00-10:00Opening session

Session Chair: Prof . Sigurður Magnus Garðarsson

10:00-10:30 Coffee break

10:30-11:45Session A1: Upstream -

DEEPEGS Chair: Ólafur Pétur Pálsson

Session B1: Upstream - Modelling

Chair: Steinunn Hauksdóttir

11:45-13:00 Lunch

13:00-14:00

Session A2: Upstream - Super-Hot Geothermal -

DEEPEGS - KMT Chair: Bjarni Pálsson

Session B2: Upstream Chair: Halldór Geirsson

14:00-14:45 Poster Session - with geothermal refreshments

14:45-16:00Session A3: Midstream - Super-Hot Geothermal

- DEEPEGS - KMT Chair: Einar Jón Ásbjörnsson

16 .00-18 .00

MINI FIELDTRIP - swim in the Laugardalslaug (ticket included in Workshop Admission Fee)

and a guided walk through Laugardalur, to VOX Club (if wheather allows)

18:00-20:00 VOX Club - Social event

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Program15. November 2018

08:30-09:00 Registration and morning coffee

09:00-10:00Session A4: Upstream

Chair: Prof . Sigurður Magnus Garðarsson

Session B4 Upstream - Geology & Exploration

Chair: Amel Barich

10:00-10:30 Coffee break

10:30-12:15Plenary Session: NEW GEOTHERMAL GENERATION

- Sustainable Food Chair: Carine Chatenay

12:15-13:15 Lunch

13:15-14:00Session A5: Midstream

/ Downstream Chair: Auður Andresdóttir

Session B5: Downstream / Cross-cutting

Chair: Carine Chatenay

14:15-14:45 Coffee break

14:45-16:00Closing session

Session Chair: Óli Grétar Blöndal Sveinsson

Light Refreshments

Session A1Upstream – DEEPEGS

Chair: Ólafur Pétur Pálsson

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Book of Abstracts

FLUID INCLUSION STUDY FROM THE IDDP2 BOREHOLE

Bali, E.,1 Aradi L.E.2, Szabó, Á.2, Berkesi., M.2, Szabó, Cs.2, Friðleifsson, G.Ó.3

1. Institute of Earth Sciences, University of Iceland 2. Lithosphere Fluid Research Lab, Eötvös University, Budapest 3. HS Orka

Fluid inclusions were studied in felsic veins from drill core 11 (4634.20 to 4638.00 m depth) of the IDDP2 borehole, Reykjanees peninsula. The major aim of this study was to characterise the physical state, temperature and the chemical composition of the geothermal fluid. We combined petrographic and microthermometric observations, Raman microspectroscopy and Focused Ion Beam-Scanning Electron Microscopy slice & view (FIB-SEM) techniques to answer these questions.

Based on petrographic observations, we distinguished primary and secondary fluid inclusions. Our work focused on the secondary inclusions as those are more representative of the current geothermal fluid than the primary ones.

In general, three types of inclusions were observed, commonly coexisting in the same secondary inclusion plane. These are vapour-rich inclusions, brines and silicate melt inclusions. The bubble to brine ratio is very variable in the fluid inclusions, which indicates boiling during inclusion entrapment. Therefore, the fluid is not a single supercritical fluid, but separated into two phases.

Vapour-rich inclusions are composed of a large dark vapour bubble and a thin liquid film at the edges. Additionally, a small opaque phase can also be observed in some vapour-rich inclusions. Based on Raman microspectroscopic measurements, these inclusions are dominated by CO2 and H2O (in the liquid film), and contain additional H2S, N2 and H2 in minor amounts. Brine inclusions are composed of four different solid phases, a vapour bubble, ± a minor liquid phase. Solid1 is a green to yellow mineral with one polarizer and is strongly anisotropic with crossed polarizers. It has characteristic Raman bands at 3451, 1626 and 200 cm-1 and it disappears from the fluid inclusions at ~175-180°C during heating experiments. FIB-SEM analyses revealed that this phase is a Fe-K-chloride with significant OH- component. Solid2 is also green with one polarizer but isotropic with crossed polarizers. It is not Raman active and it disappears between 220 and 240 °C upon heating. Based on FIB-SEM analyses, this mineral is another Fe-K-chloride with a different stoichiometry compared to solid1. Solid3 is an isotropic and transparent mineral, commonly showing cubic crystal habit. It is not Raman active, it disappears at 380-390 °C in all brine inclusions upon heating. FIB-SEM analyses suggest that this mineral is a sylvite-halite solid solution. Solid4 is an opaque mineral, a Fe-Cu sulphide, which disappears at ~600°C upon heating.

When heating experiments are combined with Raman microspectroscopy it is evident that neither the brine nor the vapour-rich inclusions are homogenized below 590 °C. The disappearance of the sulphide phase in the brine inclusions and the disappearance of the liquid film in the vapour-rich inclusions however happens at 600 ±10 °C, which should be representative of the real fluid temperature.

Silicate melt inclusions are composed of a colourless silicate glass and a vapour bubble. The vapour bubble contains CO2 and H2S. As melt inclusions are commonly found in the secondary inclusion assemblage, it is clear that melt was percolating in the system after the formation of the felsic veins.

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Book of Abstracts

COMPOSITION OF RESERVOIR FLUIDS IN WELL IDDP-2

Finnbogi Óskarsson

ÍSOR (Iceland GeoSurvey)

Well IDDP-2 was drilled into the Reykjanes geothermal field to a depth of about 4.5 km by deepening the 3 km deep vertical well RN-15. The well has three feed zones, at approximate depths of 2.3 km, 3.4 km and 4.5 m. The temperature and pressure logs collected during drilling and partial thermal recovery of the well after drilling suggest that during discharge, only the lower two feed zones will contribute to the flow, with an estimated 90–95% coming from the 3.4 km feed zone and the rest from the feed zone at 4.5 km.

The purpose of this contribution is to estimate the chemical composition of the fluid produced during a planned discharge test of the well in 2019. As no well fluids have been sampled and information on the temperature and pressure at the feed zones are not well constrained, this work is highly hypothetical, but an effort is made to constrain the chemistry of the fluids. Temperature and pressure logs suggest that the fluid produced from the 3.4 km feed zone will be vapour-saturated liquid at approximately 350°C and 1600 kJ/kg whereas the fluid from the 4.5 km feed zone will have a temperature of about 530°C and pressure 280–310 bar. Comparison with the fluid scenarios proposed before drilling suggests that the deeper fluid will either be a superheated vapour-phase in equilibrium with solid sodium chloride or a two-liquid-phase super-critical fluid. Hypersaline fluid inclusions in cores collected near the bottom of the well suggest the latter scenario – which will be considered here.

The approach to this task was as follows: (1) Estimation of the well fluids at 3.4 km, by reconstructing and heating the conventional Reykjanes reservoir fluid, while dissolving basalt and sulphide minerals as needed to maintain fluid-rock equilibrium. (2) Estimation of the well fluids at 4.5 km, by using reported chemical compositions of fluids from hydrothermal vents on the ocean floor. (3) Mixing of the two fluids in the relevant proportions. (4) Simulation of fluid composition and mineral deposition during depressurisation boiling of the hypothetical deep fluid to an estimated well-head pressure of 70 bar. This was carried out using the SOLVEQ-XPT and CHIM-XPT geochemical codes.

The reconstructed Reykjanes reservoir fluid at 350°C has seawater salinity and a pH of about 5.5. The sulphide concentration is somewhat higher and copper, iron, zinc and lead concentrations substantially higher, compared to the conventional Reykjanes fluid at 295°C. Mixing of this heated conventional fluid with dilute and concentrated supercritical seawater yields fluids with slightly lower pH, higher silica and substantially higher sulphide concentrations. During boiling to 70 bar-a, the fluid mixtures precipitate 10–20 mg per kg produced, mainly anhydrite, haematite, bornite and phyllosilicates. The boiled fluid has pH ranging from 3.8 to 4.5, and high sulphide concentrations. It is somewhat undersaturated with respect to amorphous silica. Upon further boiling of the fluid, it is likely to precipitate metal sulphides and amorphous silica.

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Book of Abstracts

THE IDDP-2 DEEPEGS DEMONSTRATOR AT REYKJANES

Friðleifsson, G.Ó.1, Albertsson, A.1, Þórólfsson, G.1, Sigurðsson, Ó.1, Robert Zierenberg2, Wilfred A. Elders3, Þorleikur Jóhannesson4, Finnbogi Óskarsson5

1. HS Orka, Svartsengi, 240 Grindavik, Iceland. 2. University of California, Davis, USA. 3. University of California, Riverside, USA. 4. Verkís, Reykjavik, Iceland. 5. ÍSOR, Reykjavik, Iceland

IDDP-2 well was drilled to a slant depth of 4,659 m, below rig floor, in the Reykjanes high-temperature geothermal field in SW Iceland (Friðleifsson et al., 2017, 2018). An existing 2.5 km deep well, RN-15, was taken over and deepened as the IDDP-2 well, and directionally drilled towards the main up flow zone of the system. January 3d 2017 during drilling, after only six days of heating, a temperature of 426°C at 34.0 MPa pressure was logged, confirming that supercritical conditions exist at ~4,550 m measured depth. Inflection points in the temperature log occurred at ~3,400 m due to cooling at a major loss of circulation zone, while smaller loss zones showed at ~4,375 m and ~4,500 m. The well was subsequently deepened to 4,626 m, and a perforated 7” hanging liner inserted to 4,582 m. A 6” pilot hole was then drilled with a tricone bit below and through the liner to 4,634 m depth, followed by three successive 6” spot core drilling, retrieving three magnificent cores to the very bottom of the well with close to 100% recovery. This was very rewarding for IDDP as most of the drilling itself had been with a total circulation loss and hardly any cutting recovery except intermittently at 3.0-3.2 km depth. Core recovery below that depth in 10 coring attempts with 8 ½” core bit had also been very poor.

Additional information on the downhole conditions of the IDDP-2 comes from the drill cores obtained. These sampled a series of dolerites with chilled margins that are interpreted as a sheeted dike complex (Zierenberg et al., 2017; Friðleifsson et al., 2017). Alteration mineral assemblages indicate a complex history of response to dike emplacement and variable hydrothermal conditions. The shallowest IDDP-2 rocks are extensively altered to greenschist facies mineral assemblages that include epidote, actinolite, plagioclase, quartz, and chlorite. Deeper than 3,825 m, igneous clinopyroxene is pervasively altered to hornblende, and amphibolite facies mineralogy prevails that includes, in addition to hornblende, calcic plagioclase, hydrothermal olivine, orthopyroxene, clinopyroxene and biotite. Such assemblages require a minimum of 400°C to form. The closest estimate on present day temperature at the bottom is about 570°C +/-30°C, just recently supported by fluid inclusion study (E. Bali et al., 2018 – at this GGW 2018).

Injection was stopped 23d September 2018, almost 2 weeks after the well had been P-T logged to 2.3 km and tested for injectivity10 September (Tulinius, 2018). The injectivity proved to be around 3.0 kg/s per bar, similar to the earlier estimate of 3.1 kg/s per bar. This is not surprising as there should still be some AltaVert blocking material in the 3.4 km feed zone, which should disappear once the well heats above 200°C. Permeability however seemed to have increased but the skin increased as well, which may relate to the AltaVert blocker? Two days before the hot water injection was stopped GFZ and TNO experts connected to the fiber optic cable in IDDP-2. Three of the 9 Petrospec thermocouples, cemented in outside the production casing, are still working and showed a good correlation to the fiberoptic data. The three thermocoulples still working are at 330 m, 630 m and 1228 m depths, and showed 116°C, 133°C and 151°C respectively the 18.10.2018.

Regular geochemical monitoring of a nearby well, RN-12, carried out twice a year since 2006, shows a clear influence from the IDDP-2 drilling and injection activity during 2016-2017 (Óskarsson and Gałeczka, 2018). About 2 million tons of cold fresh water was injected in 2016 and 2017, part of it before a production casing to 2,941 m was cemented in and accordingly open to the utilized geothermal reservoir, and the rest below 3 km depth, partly connected to the utilized reservoir. Total circulation loss of the drilling fluid was experienced after cementing of the casing and the main feed zone, masking out those above, is located at about 3.4 km. The implication of the chemical changes is discussed, but temporal decrease in salinity (Cl, SO4 Na, Ca, B), increases in the concentrations of N2 and Ar and changes in stable isotopes (δD and δ18O), show clear affinity of the freshwater dilution. The latest sample (from June 2018) shows that the dilution effect is already diminishing. The link(s) between the upper and lower reservoirs at Reykjanes is of importance to the DEEPEGS demonstration effort, which both involved deep injection through a 3 ½” drill string almost to the bottom as well as tracer injections, both of which will be reviewed briefly.

Preparation for a flow test is about to be completed and purchasing the flow testing surface equipment has begun. The design of the equipment needed to meet a worst-case scenario of very high pressure, up to 500°C hot steam, and corrosive or agitating fluid. The first flow test is expected to take place March/April 2019.

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Book of Abstracts

REFERENCES

Bali, E., Aradi L.E., Szabó, Á., Berkesi., M., Szabó, Cs., Friðleifsson, G.Ó., 2018. Fluid inclusion study from the IDDP-2 borehole. GGW-2018 abstract volume.

Friðleifsson, G.Ó., Elders, W.A., Zierenberg, R.A., Stefánsson, A., Fowler, A.P.G., Weisenberger, T.B., Harðarson, B.S., Mesfin, K.G., 2017. The Iceland Deep Drilling Project 4.5 km deep well, IDDP-2, in the sea-water recharged Reykjanes geothermal field in SW Iceland has successful reached its supercritical target. Sci. Drill. 23, 1–12.

Friðleifsson, G.Ó., W. A. Elders , R. A. Zierenberg , A. P.G. Fowler , T.B.Weisenberger, K.G. Mesfin , Ó. Sigurðsson , S. Níelsson , G. Einarsson , F. Óskarsson , E.Á. Guðnason , H. Tulinius , K. Hokstad, G. Benoit , F. Nono, D. Loggia, F. Parat , S.B. Cichy , D. Escobedo, D. Mainprice. The Iceland Deep Drilling Project at Reykjanes: Drilling into the root zone of a black smoker analog, J. Volcanol. Geotherm. Res. (2018), https://doi.org/10.1016/j.jvolgeores.2018.08.013.

Óskarsson, F., Gałeczka, I.M., 2018. Reykjanes production field: Geochemical monitoring in 2017. Iceland GeoSurvey report, ÍSOR-2018/017.

Tulinius, H., 2018. Injection test in well RN-15/IDDP-2 on 10th September 2018. DEEPEGS Working Document, 14 p.

Zierenberg, R.A., Fowler, A.P.G., Friðleifsson, G.Ó., Elders, W.A., Weisenberger, T.B., 2017. Preliminary description of rocks and alteration in IDDP-2 drill core samples recovered from the Reykjanes Geothermal System, Iceland. GRC Transaction 41, 1599–1615.

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Book of Abstracts

DRILLING THE LIMIT: INCREASING EFFICIENCY IN GEOTHERMAL DRILLING

Young Katherine R.1, Carsten Sørlie2

1. National Renewable Energy Laboratory, United States. 2. Equinor, Norway.

The cost of drilling new geothermal wells can be a significant barrier to geothermal development. Drilling costs can amount to 50% or more of the capital costs of developing a utility-scale geothermal power plant and can be a prohibitive barrier to geothermal exploration. The recent trend in dropping solar and wind prices has led to a challenge for developers —drilling costs must be lowered in order for many geothermal projects to be competitive. Drilling the average petroleum well is often significantly more efficient than its geothermal counterpart – and not just due to geological differences. Recent trends in petroleum drilling focused solely on increasing efficiency have shown significant decrease in drilling costs – sometimes greater than 50%. The “technical limit” is a term that describes a theoretical maximum in safety, efficiency and production during drilling operations.  “Drilling the limit” (DTL) describes the drive to reach this limit - minimizing waste and inefficiency – without sacrificing safety or well integrity. This improved well delivery performance requires integrated strategy and decision making, followed by detailed preparation and execution through an integrated team of staff from all disciplines - subsurface, drilling, completion, production - and all partners, including clients, contractors, and vendors. A key success factor is buy-in and full support from the client’s senior management team in trying out new concepts and methodologies. Drilling the limit could have similarly significant impacts on the geothermal industry. This talk will introduce the main concepts behind drilling the limit, highlight case studies in implementing this strategy, provide estimates on the potential impact DTL can have on geothermal deployment, and discuss a path forward for implementing DTL in geothermal projects.

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Book of Abstracts

LOCAL INJECTIVITY INDEXES OF THE IDDP-2 WELL

Sturla Sæther

Equinor, Norway

In geothermal wells there are always very interesting to know the prognosis for production potential and the energy content of hot producing wells. Estimation of the production potential is often done by performing injectivity tests on a cold well before start-up. This injectivity index gives an overall number for the total well and will normally not say anything of production from different parts of the well. This is especially interesting in very deep wells as in the Iceland Deep Drilling Project (IDDP). This work establishes a method to point out local injectivity indexes and point at the potential for production at different production zones of a well.

This work uses the overall injectivity index number together with temperature and pressure measurements inside the well and reservoir pressure calculations. By using this information, it is possibly to estimate injectivity indexes at different potential production zones.

There are 4 injectivity indexes tests performed in the IDDP-2 well. These injectivity test results are used in this work to predict the best possible local injectivity indexes and to point out the result of the stimulation at the different locations of the well.

This work uses the temperature measurements inside the well to point out potential production zone localization. The different injection rates during the injectivity test is used to estimate the local injectivity index for the main potential production zones. The fact that the pressure inside the well is different during the different injection rates are used in the prediction.

The result of these estimates can tell from which depths the production of the hot well in IDDP2 will produce from.

Session A2Upstream – Super-Hot Geothermal

DEEPEGS KMT

Chair: Bjarni Pálsson

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Book of Abstracts

FLUID CHEMISTRY OF HIGH-ENTHALPY GEOTHERMAL SYSTEMS

Andri Stefansson

University of Iceland

Active volcanoes are commonly associated with high-enthalpy geothermal system and a magmatic heat source. The fluid temperatures range from <200 to >450°C with reservoir fluids being liquid only, two phase liquid and vapor. Here, a new combined hydrological and chemical model for such high-enthalpy geothermal systems across temperature and pressure conditions is demonstrated and compare fluid composition and alteration mineralogy observations for natural systems in Iceland. The model is based on combining heat and fluid mass transfer modelling with fluid-fluid and fluid-rock interactions as a function of temperature, pressure, enthalpy and composition (T-P-h-X). Within the reservoir at temperatures of 250-350°C liquid water predominates. Under these conditions, the concentrations of most major elements are controlled by equilibrium with secondary minerals formed at low pressure and <350°C. Around the magma intrusions, supercritical fluid is formed with temperatures of ~400-500°C. According to the model, such fluid is produced upon heat addition by the intrusion to the surrounding geothermal fluid resulting in boiling to dryness, precipitation of non-volatiles (Si, Fe, Mg, Al, SO4, Na, K, Ca) where volatiles (CO2, H2S, Cl, F, B) are unaffected. By mass, quartz is observed to be the predominant secondary mineral around the intrusions. Upon ascent and depressurization of the subcritical and supercritical fluid, various processes may occur, including supercritical fluid condensation, mixing and depressurization boiling. This leads to formation of two-phase liquid and vapor fluids, dilute acid fluids produced upon supercritical fluid condensation and mixtures thereof. Such fluids are indeed observed within active high-enthalpy geothermal systems in Iceland.

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Book of Abstracts

GEOWELL – INNOVATIVE MATERIALS AND DESIGNS FOR LONG-LIFE WELLS

Árni Ragnarsson

ÍSOR – Iceland GeoSurvey

The GeoWell research project is funded through the European Union’s Horizon 2020 research and innovation programme under grant agreement No 654497. It is a three-year project that started in February 2016 with a total budget of 4.7 million €. Participants are the research institutions ÍSOR in Iceland (project coordinator), IRIS in Norway, GFZ in Germany, TNO in the Netherlands and BRGM in France, and the industrial companies Equinor in Norway, HS Orka in Iceland and Akiet in the Netherlands.

The GeoWell project addresses important bottlenecks in geothermal development like high investment and maintenance costs by developing innovative materials and designs that are superior to the state of the art concepts. The aim is to develop reliable, economical and environmentally friendly technologies for the design, completion and monitoring of high-temperature geothermal wells with the intent to expedite the development of geothermal exploitation globally. GeoWell will addresses relevant steps in the geothermal well construction process to enhance the lifetime of high-temperature geothermal wells. These include novel cement properties and new cementing technologies, novel casing materials and material combination (e.g. internal cladding) and flexible coupling of casings to minimize thermo-mechanical loadings. Fibre optic cable technology and applications are being developed to measure at real time downhole temperature and strain to monitor well integrity along with methods for risk assessment regarding the well planning phase and operation of high-temperature geothermal wells. These highlights of the Geowell Project will enhance the well construction process and operations of geothermal wells, especially targeting well integrity improvement.

To assure the quality of the approach and the final results of the project, the research is focused on both conventional production wells and deeper wells where the pressure is as high as 150 bar and temperatures exceed 400°C. The developed technologies and material candidates are tested under simulated conditions in laboratories and partly in-situ in existing geothermal environment.

The work within the GeoWell project has shown interesting results. Several reports have been prepared and those that are public are available on the project website, together with general information about the project (http://geowell-h2020.eu). The work has resulted in tangible products, indicating that implementing the GeoWell project will have a positive impact on the targeted geothermal technologies related to construction and operation of geothermal wells.

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Book of Abstracts

IMPORTANCE OF MAGMA FOR A SUSTAINABLE HIGH-ENTHALPY FLUID GEOTHERMAL SYSTEM

John C Eichelberger1, Yan Lavallee2, Jefferson William Tester3

1. International Arctic Research Center, University of Alaska Fairbanks, 2. Department of Volcanology and Magmatic Processes, University of Liverpool, 3. Smith School of Chemical and Biomolecular Engineering, Cornell University

Super-heated steam or super-critical fluid is an order of magnitude more effective in transporting energy to the surface and generating electricity than the lower temperature steam used in conventional geothermal systems. Super-heated steam or super-critical fluid is an order of magnitude more effective in transporting energy to the surface and generating electricity than the lower temperature steam used in conventional geothermal systems. However, a robust energy source is required. The volume of hot rock in Earth’s crust that can be accessed by drilling is immense, but rock is a poor energy source because of its low heat capacity (and hence low energy density) and low thermal conductivity. This means that to be productive the working fluid must contact a large rock surface area either through natural or enhanced permeability so that the volume of rock accessed is large and the path length for heat conduction from rock to fluid is short. In contrast, magma has a high effective heat capacity (and hence high energy density) because of latent heat of crystallization and can rapidly transport heat by convection. Moreover, permeability from thermal fracturing by contraction of cooling rock adjacent to magma is much less likely than injecting fluid at high pressure, hydraulic fracturing, to induce seismicity and may be self-sustaining. Thermal fracturing of magma chamber wall rock or crystallized magma also maintains a short distance between magma and the hydrothermal system as heat is withdrawn. We suggest that the best target for sustainable, high-enthalpy fluid energy extraction is adjacent to active magma bodies, as exemplified by Krafla Caldera, Iceland. The proposed Krafla Magma Testbed aims to test this hypothesis and develop the engineering and technological innovations necessary to put magma-sourced geothermal energy into practice.

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Book of Abstracts

PUSHING SENSORS CLOSE TO PROCESS

Randy A Normann

On Measurement (Perma Works)

A brief look at high-temperature electronics (as HT SOI, SiC and others) along with fibre optic sensor options are covered. Some economic reasoning supporting the development of magma sensors is provided along with basic sensor construction requirements/techniques.

Actual sensor deployment concepts for monitoring the magma recovery process are considered. These include: using thermocouples for a temperature gradient measurement, using acoustic pulses in the pipe to monitor the changing acoustic response of the bottom-hole formation, monitoring changing the acoustic timing to estimate bottom-hole temperatures and potentially using displacement to indicate magma pressure.

Session A3Midstream – Super-Hot Geothermal

DEEPEGS KMT

Chair: Einar Jón Ásbjörnsson

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CORROSION TESTING IN SIMULATED SUPERHEATED GEOTHERMAL ENVIRONMENT

Andri Isak Thorhallsson

University of Iceland

Corrosion behavior of materials (i.e. metal alloys) in superheated geothermal environment is not yet fully understood. During discharge of IDDP-1 well, corrosion testing of metal alloys, was conducted in superheated conditions at 350°C and 12-13 barg at wellhead. The results of the corrosion testing in IDDP-1 were extremely low corrosion rates but all the alloys were though prone to localized corrosion in form of pitting or cracking. The corrosive species in the IDDP-1 fluid were H2S,CO2, HCl, H2, HF and questions arose in the testing wether SiO2 had some corrosion contribution. To enhance the understanding in the corrosion behavior of the alloys in the superheated geothermal environment, it was decided to set up laboratory flow through system to do corrosion testing in simulated, controlled geothermal environment at 350°C and 10 barg. In the first simulated testing trials, only H2S, CO2 and HCl were applied as the corrosive species in the simulated geothermal fluid. Extremely low corrosion rates were measured in the corrosion testing but not as much localized damage was observed as experienced in IDDP-1. Other corrosive components such as HF, H2 and SiO2 were excluded in the simulated testing. Future work aims to add more corrosive species in the simulated geothermal fluid. The research will be contribution in the selection and material design in casing and equipment for superheated geothermal systems in future.

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ENGINEERING CHALLENGES IN UTILIZING FLUIDS EXTRACTED FROM DEEP ROOTS OF GEOTHERMAL SYSTEMS

Kristinn Ingason, Sturla Sæther

Mannvit

The Iceland Deep Drilling Project (IDDP) has been ongoing since 2000. The drilling of IDDP-1 was completed in 2009 and drilling of IDDP-2, reaching 4,5 km depth, was completed in beginning of 2017. Preparations for drilling IDDP-3 have started. Knowledge that has been gained from the drilling of these wells and from the discharge of IDDP-1 gives indications on challenges and gains which may be expected when drilling for and utilizing the high-temperature and high-pressure fluids which may be extracted from the deep roots of geothermal systems. The engineering challenges and opportunities associated with this kind of utilization is discussed in the presentation.

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MATERIAL ANALYSIS OF STEEL AND WELL CEMENT CASING MATERIALS OF THE IDDP-1 WELL

Sigrún N. Karlsdóttir, Sunna Ó. Wallevik, Kolbrún R. Ragnarsdóttir, Kristján Alexandersson, Helen Ó. Haraldsdóttir

Gerosion/University of Iceland

The IDDP-1 well was the hottest flowing geothermal well in the world producing 450°C and 140 bar superheated steam. The steam contained dissolved gases such as CO2, H2S, H2, HCl and HF, causing the steam upon condensation to become highly corrosive. After several months of discharging, the well was shut-down (pumped with cold water) to due to failure of the master valves. During inspection of the well with down-hole camera several failures were revealed; the production casing had ruptured at approximate depths of 300 m, 356 m and 505 m and collapsed at around 620 m depth, causing it to fall inward and partially block the well. After the extent of damage of the well was realized the well was plugged by cementing. It was decided to retrieve the top part of the well, around 10 m, for inspection of the well casing materials. In this study microstructural characterization was performed on steel and well cement casing samples from the top 10 m of the IDDP-1 well to investigate the effect of exposure to the IDDP-1 geothermal well environment on the material. Mechanical testing was also performed on the well cement casing samples to measure the compressive strength. The microstructural and chemical composition analyses were performed with SEM equipped with EDS analyser. The result showed that the samples from the production casing have extensive corrosion damages in the form of internal micro-cracks and fissures. These are filled with corrosion products and are parallel to the surface. The corrosion damages were present deep into the material. The samples were etched for metallurgical analysis which revealed disappearance of pearlite close to the micro-cracks and fissure. High Temperature Hydrogen Attack (HTHA) is believed to be the cause of decarburization of the steel and the corrosion damages of the samples. Samples from the well cement casing between the production casing and the anchor casing at the top part showed decrease in compressive strength, by up to around 50%, compared to samples from outer cement casing layers and reference sample. Also there were indications of phase transformation of samples from all the cement casing layers due to thermal effects (superheat).

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MULTIFUNCTIONAL CEMENTITIOUS BLENDS FOR ULTRA-HIGH TEMPERATURE GEOTHERMAL WELLS

T. Pyatina and T. Sugama

Brookhaven National Laboratory

This work presents multifunctional high-temperature geothermal well cement composites applicable in both the conventional hydrothermal reservoirs at temperature of 300°C and the Enhanced Geothermal System (EGS) environments at heating temperatures up to 600°C. The developed multifunctional cements possess the following five advanced properties, 1) thermal shock (TS) resistance in 5 cycle heat-cool water quenching testing (one cycle: 500°- or 600°C-24 hrs heating, and then immersion in 25°C water), 2) improved compressive toughness, 3) enhanced protection of carbon steel (CS) against brine-caused corrosion, 4) superior bond durability to CS surfaces, and 5) good resistance to pH 0.5 H2SO4 solution at 90°C, compared with those of two conventional geothermal well cements, the Class G modified with SiO2 and calcium aluminum phosphate (CaP). The latter cement was originally formulated and developed at BNL as CO2-resistante cement under the previous geothermal technology office project.

Additionally, the multifunctional thermal-shock resistant cement (TSRC) possesses self-healing properties, where it recovers more than 80% or more than 100% of its original compressive strength (when modified with healing aid) after multiple damage events, re-adheres to the carbon steel casing after the debonding and seals the cracks and fractures in a short period of several days under high-temperature (300oC) hydrothermal conditions.

Elemental, crystalline, and microstructural analyses identified phases responsible for the composite resistivity to aggressive environments, self-healing properties, mechanical stability and durability of the bond between the cement composite and carbon steel.

The placement technology of TSRC was tested in thickening time tests of American Petroleum Institute (API) at 85 and 100oC.

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SILICA SCRUBBING FROM SUPERHEATED STEAM USING AQUEOUS POTASSIUM CARBONATE

Vijay Chauhan, Maria Gudjonsdottir, Gudrun Saevarsdottir

Reykjavik University

High temperature geothermal systems have potential to deliver superheated steam. The superheated steam offers potential to extract more power with higher thermodynamic efficiency. However, among the main challanges with extraction of such fluid, are related to high chloride and silica content. Presence of these impurities makes the fluid challenging for utilization due to increased risk of corrosion and scaling. It is, therefore, necessary to apply mitigation techniques to high enthalpy steam with such characteristics before utilizing it for power generation.

The traditional way of cleaning geothermal steam is wet scrubbing. The technique include injecting water or brine into the steam flow and creating a two phase mixture where the impurities are removed with the liquid phase. The method however causes loss in power output if applied to superheated steam due to quenching of superheat. This study proposes an alternative way of scrubbing superheated steam using aqueous potassium carbonate solution as a scrubbing medium. The boiling point elevation property of aqueous potassium carbonate solution helps the droplets to stay in the liquid phase in the superheated steam without salt precipitation due to its high dielectric constant. The steam thus retains its superheat which is consumed by liquid droplets for evaporation during normal wet scrubbing.

A detailed study using computational modeling and experimental methods were carried out for understanding the behaviour of aqueous potassium carbonate droplets in superheated steam. Experiments are carried out to understand the effect of salt solution concentration on scrubbing efficiency and the degree of superheat retained. Finally, to show the scope of improving thermodynamic performance utilizing aqueous potassium carbonate solution for scrubbing, comparative study in terms of the thermodynamic performance was done and compared to cycle utilizing wet scrubbing. The comparison study was performed for the case of well IDDP-1 thermodynamic state conditions.

Results from the simulation and experimental measurements shows increased degree of superheat with increase in injection solution concentration. Experimental measurements show increase in scrubbing efficiency with increase in injected salt solution concentration. Results from the thermodynamic simulation for the IDDP-1 case study shows 7% point increase in utilization efficiency obtained using the proposed technique. This corresponds to nearly 12% increase in work output. The percentage increase is significant in terms of revenue for a geothermal power plant considering a number of wells with similar flow characteristics. Application of the proposed technique for superheated geothermal steam scrubbing can help in improving the output of the power plant. However, economic feasibility of the proposed technique is needed.

Session A4 Upstream

Chair: Sigurður Magnús Garðarsson

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POTENTIAL FIELD METHODS IN GEOTHERMALEXPLORATION

Gaud Pouliquen; Birgit Woods

Geosoft Europe ltd.

We present three recent case studies where potential field methods were the primary methods used to image and characterise geothermal systems. These passive geophysical methods were supplemented by seismic, paleomagnetic, borehole and core measurements. Despite three different geological scenarios, these studies shared a similar goal: to better understand the subsurface and mitigate risk by using low cost exploration techniques.

In the Warner Valley, Southwest Oregon, 20 hot springs and the Crump Geyser characterize this area. The geology is dominated by Neogene volcanics forming a half graben bounded by both NW and NNE trending faults. The geothermal system is assumed to be sustained by deep meteoric water circulation controlled by normal faults. A combination of 2D/3D magnetic and gravity modelling, constrained by seismic, borehole, paleomagnetic and core samples played an important role in understanding the geothermal system since the intra-basin structures are concealed by Quaternary alluvium. The 3D models reveal basin structures that indicate intra-basin fluid flow and provide a structural basis for assessing the potential for future commercial power generation (Glen et al., 2015).

In the Roer Valley Graben, Netherlands, the aim was to characterize an ultra-deep (>4 km) geothermal reservoir by leveraging existing subsurface data before funding new exploration (Van Heiningen et al., 2018). Initial targets were the Carboniferous and Permian formations, which were out-of-reach of the existing 2D seismic and well data. 2D gravity and magnetics determined the top and base of the Carboniferous limestone while the models were further constrained by seismic interpretation, velocity and density well log data (Van Hoegaerden et al., 2018).

In the Umatilla Indian Reservation, Northeast Oregon, the geology is dominated by basaltic lava flows and fluids are controlled by faults and folds (Grober and Palmer, 2018). Multiple geophysical methods were used to collect data including gravity, aeromagnetics, magnetotellurics, LiDAR, and paleomagnetics. Hand samples were collected to provide constraints. 2-D models were then created over two profiles across major faults in the region. These models relied on potential field only and provided accurate depictions of geologic units and structures in the subsurface.

These examples show how potential field supplemented by seismic, wells, paleomagnetic, hand and core samples play a key role in delineating and characterising geothermal reservoirs where complex geology makes seismic imaging challenging. Integrated interpretation creates a low cost, new or improved geological model of the subsurface and hence contributes to minimized exploration costs and inherent financial risk.

REFERENCES

Glen, Jonathan MG, et al. “Assessing structural controls on geothermal fluids from a three-dimensional geophysical model of Warner Valley, Oregon, USA.” Proceedings World Geothermal Congress. Melbourne, Australia. 2015.

Grober, Benjamin L., and Zachary A. Palmer. “2-D potential field modeling across the Hawtmi and Wiahatya faults in search of geothermal resources within the Umatilla Indian Reservation.” Geosoft Earth Explorer, https://www.geosoft.com/news/, 2018.

Van Heiningen, P., et al. “Identification of Dinantian as Potential Geothermal Reservoir in the Roer Valley Graben by Gravity and Magnetic Modeling.” 80th EAGE Conference and Exhibition 2018. 2018

Van Hoegaerden, V., et al. “Novel Log Upgrading Method to Improve Seismic-to-Well Matches with Application on Hydrocarbon and Geothermal Exploration.” 80th EAGE Conference and Exhibition 2018. 2018.

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GROUND DEFORMATION DUE TO STEAM CAP PROCESSES AT REYKJANES, SW-ICELAND: EFFECTS OF GEOTHERMAL

EXPLOITATION INFERRED FROM INTERFEROMETRIC ANALYSIS OF SENTINEL-1 IMAGES 2015-2017

Mylène Receveur1, Freysteinn Sigmundsson1, Vincent Drouin1, Michelle Parks2

1. Institute of Earth Sciences, University of Iceland 2. Nordic Volcanological Center

The Reykjanes geothermal system is a high-temperature seawater system situated in SW-Iceland. Interferometric analysis of the Sentinel-1 satellite synthetic aperture radar (InSAR) data has been used to determine a time series of ground deformation induced by geothermal utilization between April 2015 and October 2017.

Surface displacements have been estimated at coherent pixels, indicating a steady and linear subsidence within a sub-circular bowl centered on the well field at a maximum near-vertical rate of about 25 mm/yr, together with horizontal contraction. The average line-of-sight (LOS) displacement from ascending and descending tracks are inverted to determine the characteristics of the deformation source at depth, modeling the geothermal reservoir as a body of simple geometry within an elastic half space.

The results indicate a deformation source at about 1 km depth contracting at a rate of about 0.09 million cubic meters per year in the 2015-2017 period. Using pressure and temperature monitoring data at 900 m depth as well as an analysis of the reservoir structure and rock properties, we find that the recent estimated volume change can be attributed to a combination of compaction under pressure decrease and/or thermal contraction due to cooling of the rocks within or near a steam cap situated in the topmost part of the geothermal reservoir, in the 800–1200 m depth range. This steam cap was formed in response to a sudden pressure drop resulting from the increase in extraction of geothermal fluids for a new power plant in 2006.

The quality of the results obtained with high resolution Sentinel-1 time series of deformation at Reykanes for a period of only two years gives promising opportunities to efficiently monitor “real-time” effects of geothermal production at a low cost. Together with regular in-situ measurements of pressure and temperature, this technique is able to contribute to a better understanding of long term behavior of geothermal systems, their response to utilization, thereby supporting the management of the resources.

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WATER-ROCK INTERACTION AT A GABBRO BOUNDARY

Hjalti Franzson, Moneer Althenary, James Brett and Guðmundur Heiðar Guðfinnsson

Iceland GeoSurvey - ÍSOR

One or more deep-seated intrusions are most often assumed to be the ultimate heat source of high-temperature geothermal systems. These are, however, rarely intersected in a molten state in drilled geothermal systems nor observed in a direct relationship with the geothermal system in question, which partly is due to the difficulty in attaining reliable data from deep drillholes. This study uses an alternative method which involves a study of relatively deeply eroded strata of the Tertiary Hafnarfjall-Skarðsheiði central volcano in West Iceland, where a clear relationship can be found between a cooling gabbro intrusion and the surrounding rock hosting a geothermal system. The main research question of this study is to evaluate water-rock interaction occurring during the cooling of this gabbro intrusion, and eventually compare these data with studied active geothermal systems.

The methods used to reach this goal were a combination of field mapping, rock sampling, rock geochemistry, fluid inclusions, petrography, SEM and mineral microprobe analyses.

The field mapping shows that the gabbro magma intruded at the boundary between a lava series and a highly permeable hyaloclastite caldera filling, as shown in the accompanying figure.

The former shows high-temperature alteration assemblage, while the latter has low-temperature mineralogy, even adjacent to the

gabbro. The hornfels at the gabbro boundary is relatively thick on the south side, while nearly absent on the northern side where it abuts the hyaloclastite. This has been interpreted as showing contrasting permeability; copious on the northern side, where the influx of groundwater mined heat from the magma and limited alteration, whereas low permeability

predominates in the south where the gabbro supplied heat by conduction. The original depth of the intrusion was 700-1200 m, as assessed from fluid inclusion studies and based on the assumption that the geothermal system reached boiling condition.

The mineralogy of the hornfels shows predominance of clinopyroxene, calcium-rich plagioclase and magnetite, and less abundant orthopyroxene, actinolite and pyrope-almandine garnets. Whole-rock chemical analyses of the hornfels show only minor chemical change, though there may be minor increase in Ni, Cu and Zn contents.

The volatile content of the hornfels indicates pronounced dehydration nearest to the gabbro, decreasing away from the boundary, strongly implying that heat conduction drove water away from the gabbro intrusion.

Around intrusions intersected by drillholes within high-temperature areas in Iceland, there are clear indications for contact metamorphism reaching the hornfels facies. This clearly indicates thermal charging of the surrounding rocks through conduction, perhaps mined at a later stage by renewed permeability.

Figure. Geological map of the field area showing the basalt succession (blue), the gabbro (dotted) and the hyaloclastite caldera filling (brown). The red boundary indicates the hornfels. zone.

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UNKNOWN GEOTHERMAL RESOURCES IN THE AXIALRIFT ZONE

Ólafur G. Flóvenz

Iceland GeoSurvey - ÍSOR

The axial volcanic rift-zone (AVR) in Iceland covers area of 32,000 km2. It contains all the known high-temperature fields in Iceland but they only account for less than 2% of its total area. The AVR consist of en-echelon arranged volcanic centres associated fissure swarms and frequently with a caldera formation in the centre. The Reykjanes peninsula is an exception where clear volcanic centres are missing. The known conventional high temperature fields where hydrothermal activity rises to the surface are mostly located within the volcanic centres but to less extent in their fissure swarms.

The temperature condition within the AVR is poorly explored outside the known fields. The uppermost 1 km of the bedrock is highly porous and fractured that result in high permeability. This causes high flow of cold groundwater along the rift-zone that wash out all heat transfer from below. No wells have been drilled considerably deeper than 1km in the AVR and they show almost zero temperature gradient in the permeable part. However, reliable measurements of temperature gradient outside the AVR show systematic increase in the gradient towards the AVR with a value of 80-100°C/km at its boarder. Therefore, it can be concluded that temperature gradient of at least 100°C/km is to be expected at 1 km depth within the AVR.

Geophysical methods, mainly resistivity and passive seismics, are necessary to put constraint on the temperature with depth in the AVR. Two pronounced conductive layers are found in the AVR. The bottom of the upper one corresponds to change in alteration mineralogy that occurs at ~230°C. The lower layer is considerable deeper and its nature is still disputed. A recent profile in AVR in NE-Iceland however indicates that the top of it might coincide with the brittle-ductile transition within the crust as mapped by maximum depth of earthquakes. The temperature of the brittle ductile boundary has been estimated to be close to 600°C +/- 100°C. The temperature of the crust within the AVR can therefore be estimated fairly well by using TEM/MT measurements to determine the depth to the bottom of the upper conductive layer and passive seismics to find the depth to the brittle-ductile boundary. This methodology has been demonstrated in a small part of the AVR í NE-Iceland indicating the brittle ductile boundary at 5-6km depth. Experience with the IDDP-2 well shows that drilling to 4-5 km depth is possible in Iceland.

Environmental concerns in Iceland and the increased value of tourism to the economy are leading to protection of most of the non-exploited known high temperature fields. By systematic geophysical mapping of the volcanic rift-zone it should be possible to identify areas outside the known and protected high temperature fields where it is feasible to harness geothermal energy for power production without considerable environmental impact.

Session A5 Midstream/Downstream

Chair: Auður Andresdóttir

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UTILIZATION OF LOW-TEMPERATURE GEOTHERMAL WATER FOR ELECTRICITY GENERATION AT KÓPSVATN

Egill Maron Þorbergsson

EFLA Consulting Engineers

Low and medium temperature geothermal water has been utilized for a long time in Iceland. This utilization has been nearly all direct use, such as space heating, industrial processing or swimming pools.

Utilization of low temperature geothermal water for electricity production has not been a commercial success in Iceland. Sveinbjörnsson (2016) did a detailed research and mapped out the feasibility of producing electricity with medium enthalpy areas in Iceland. The largest obstacles in utilizing the low temperature geothermal water is the low price of electricity, and the high capital cost.

At Kópsvatn near Flúðir is a geothermal well that has a temperature of 115°C. There are plans to connect the well to the district heating system in Flúðir, in the near future. The temperature is too high for the district heating system. Therefore, there is a possibility to harness the heat of the fluid from 115°C to e.g. 80°C before the fluid is used in the district heating system.

In the spring of 2018, Flúðaorka started construction of a power plant that will utilize the low temperature geothermal water. The power plant will lower the temperature of the geothermal water from 115°C to 75°C to produce 600 kW electricity, in the first phase of the project. The power plant is based on four units developed and produced by the Swedish company Climeon. The Climeon technology is an innovative ORC technology, and is a modular and vacuum based ORC, for low temperature resource. This is promising technology, that can possible lower cost of harnessing low temperature geothermal water.

The first phase of the project uses four Climeon units that are connected in serial to the geothermal hot water, and each unit will lower the temperature of the geothermal water of approximately around 10°C. There will be three cooling towers that will produce the cooling water for the power plant. The energy cost associated with the cooling towers fans is relatively high and decreases the net output of the power plant. Another cooling technology will be implemented in the next phase. This cooling method uses a mist cooling, which is developed and produced in India. This method has the potential to lower the energy cost for the cooling, and increase the net output of the power plant.

The power plant that is under construction at Kópsvatn is the first step to start to utilize low and medium enthalpy geothermal resource in Iceland.

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RADIAL JET DRILLING STIMULATION IN WELL HN-13IN BOTN, ICELAND

Gunnar Skúlason Kaldal1, Ingólfur Thorbjornsson1, Bjarni Gautason1, Þorsteinn Egilson1, Sigurveig Árnadóttir1, Gunnlaugur M. Einarsson1, Thomas Reinsch2

1. Íslenskar orkurannsóknir/ Iceland GeoSurvey (ÍSOR), 2. Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum

One of the main goals within the EU Horizon 2020 supported project SURE (No 654662) is to investigate and test Radial Jet Drilling (RJD) technology for increasing performance of geothermal wells with low productivity/injectivity. Viability of using RJD as a potential technology to stimulate low performing geothermal wells is tested. The aim is to connect permeable structures to the main wellbore with multiple jetted laterals and subsequently test the effect and sustainability of such stimulation treatment. Two RJD operations were planned in the project, one in continental Europe and one in Iceland. The operation in Iceland, e.g. site selection, geological characteristics, targeting and the RJD field test, is described. Well HN-13, located in Botn N-Iceland and operated by power company Norðurorka, was selected for the RJD operation that was conducted in October 2018.

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COMBINED HEAT, POWER AND METAL EXTRACTION

Vigdís Harðardóttir and Árni Ragnarsson

Iceland GeoSurvey - ÍSOR

The strategic objective of the CHPM2030 project (Combined Heat, Power and Metal extraction from ultra-deep ore bodies), is to develop a novel technological solution which will help reducing Europe’s dependency on the import of metals and fossil fuels, and at the same time, lower the environmental impact of the energy supply. In the envisioned technology, an Enhanced Geothermal System (EGS) is established on a metal-bearing geological formation, which will be manipulated in a way that the co-production of energy and metals will be possible. The project, at a laboratory scale, intends to prove the concept that the composition and structure of ore bodies have certain characteristics that could be used as an advantage when developing an EGS.

The work plan has been set up in a way to provide proof-of-concept for the following hypotheses: 1. The composition and structure of orebodies have certain advantage that could be sued to our advantage when developing an EGS; 2. Metals can be leached form the orebodies in high concentrations over a prolonged period of time and many substantially influence the economics of EGS; 3. The continuous leaching of metals will increase system’s performance over time in a controlled way and without having to use high-pressure reservoir stimulation, minimizing potential detrimental impacts of both heat and metal extraction. As a final outcome the project will deliver blueprints and detailed specifications of a new type of future facility that is designed and operated from the very beginning as a combined heat, power and metal extraction system. According to our expectations, this will provide new impetus to geothermal development in Europe. In the frame of the project, a Roadmap will also be developed to support the pilot implementation of CHPM systems before 2025, and full-scale commercial implementation before 2030.

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TOO HOT GEOTHERMAL

Heimir Hjartarson

EFLA

The district heating system in Öxafjörður in north east of Iceland, is serving the small municipality of Kópasker and the surrounding area. The district heating system has been operated since 1994 and utilizes geothermal water from well ÆR-3. The well is located in the Skógarlón geothermal field that is classified as boiling low-temperature geothermal field. The well is drilled close to the ocean shore and in a river mouth. During the winter, the well is only accessible by boat because the area is flooded. The district heating equipment is therefore located 450m from the well on higher ground. The geothermal water is saline and gas concentration is low. About 2-6% of the volume of the geothermal gas is of organic origin due to thick sedimentary strata in the reservoir rocks. In geothermal water, that has such high salinity, oxygen uptake is a concern, as it causes corrosion problems and enhance possible scaling.

At the start of operation, the wellhead temperature was just below boiling or 96°C and the district heating system was designed accordingly. But the well head temperature has been steadily increasing and is now at 116°C causing problems for the operation of the district heating system. The geothermal water is at equilibrium with calcite and therefore boiling or deaeration will cause supersaturation and scaling. To mitigate this problem the geothermal fluid must be cooled down under pressure to avoid supersaturation. As a temporary solution to keep the district heating system operating an air cooler was installed in 2009 and has been operating since.

It’s expensive to run air cooled heat exchanger and therefore the operator has been looking for more feasible alternative for cooling the geothermal water. A preliminary study was done on number of alternatives to cool the geothermal fluid.

The first alternative that was studied was to send the geothermal water uncooled, with a temperature of 116°C, into the district heating system and then use the return water to cool down the temperature of the geothermal water. The second alternative was to overhaul the current equipment and inspect if it is possible to increase the efficiency. The third alternative was to examine if it is possible to generate electricity and to cool down geothermal fluid. The fourth alternative was to cool down the geothermal water before it enters the pumping station by dissipating the heat into the environment. The fifth, was to fully open the well, and increasing the output, and see if the well cools down. The main conclusion from the study is that it is most favorable to choose an alternative that utilizes the heat, first and third alternative. There are obstacles though with both solutions as regards the rural location and sparse population as well as the current electricity net. mThe alternative has also to be economical for the operator and are second fourth and fifth alternative less capital intensive but not as energy conservative.

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PERMANENT AND EFFICIENT CARBON CAPTURE AND MINERAL STORAGE IN BASALTS – THE CARBFIX STORY

AND OUTLOOK

Edda S.P. Aradottir, Bergur Sigfusson, Sandra Ó. Snæbjörnsdóttir, Deirdre Clark, Martin Voigt, Chiara Marieni, Thomas Ratouis, Vala Hjörleifsdóttir, Gunnar Gunnarsson, Sigurður R. Gíslason and Eric Oelkers

Reykjavik Energy

The recently published IPCC report on global warming of 1,5°C demonstrates the huge benefits of limiting temperature increase to this value. For humankind to reach this challenging but necessary goal, unprecedented changes in society are needed as anthropogenic CO2 emissions need to go down by 45% by 2030 and reach ‘net-zero’ by around 2050. As global emissions continue to rise, nations, cities, municipalities, industries, businesses and individuals must increase their efforts significantly. Only through such joint efforts involving widespread application of the various technical solutions already available in reducing emissions and lowering CO2 levels in the atmosphere can severe consequences of global warming be prevented.

The CarbFix method involves capturing otherwise emitted CO2, dissolving it in water and injecting it into basaltic geological formations. There, the CO2 is turned into rock in less than two years and thereby permanently removed from the atmosphere. The CarbFix team has developed the method from scratch over the past twelve years; moving from laboratory-scale and numerical simulations, through pilot-scale field injections, to stage-wise build-up of industrial-scale capture and injection. Innovative equipment and methods for capturing, injecting, and monitoring have been designed and built. These efforts were partly made possible through funding from the European Union. The annual CO2 emissions of Hellisheidi geothermal power plant, the home of CarbFix, have been reduced by 34% since industrial scale carbon capture and storage (CCS) operations began in 2014 until 2017. Furthermore, collaboration with the Swiss company Climeworks has allowed for a pilot-scale demonstration of a conjugate process of direct capture of CO2 from ambient air at Hellisheidi followed by injection of captured CO2 through the CarbFix method. Plans call for upscaling these activities at Hellisheidi.

The CarbFix method provides a safe and efficient alternative to conventional CCS-methods in which CO2 is stored in less reactive rock formations as a supercritical phase. It only takes two years to petrify the injected CO2 in CarbFix, whereas mineralization happens on the scale of hundreds to thousands of years in conventional CCS. Risks of leaks are also eradicated in CarbFix as the injected phase is denser than the surrounding groundwater and therefore sinks as opposed to rising to the surface through buoyancy forces. Water used for dissolving CO2 can be circulated through the subsurface and re-used after petrification of the CO2. Research related to transforming the method so that seawater can be used for mineral storage in the ocean floor is furthermore underway. Cost of the overall CCS chain at Hellisheidi amounts to less than $25/ton.

The CarbFix team in collaboration with 15 European industrial and academic partners, and through financial support from the European Union, is starting a new chapter in the project’s history involving export of the developed CCS method to four distinct geothermal systems in Iceland, Turkey, Italy and Germany. Research and industrial demonstration of gas capture and purification for reuse is furthermore underway in relation to CarbFix activities at Hellisheidi.

Session B1Upstream –Modelling

Chair: Steinunn Hauksdóttir

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GEOTHERMAL RESERVOIR MANAGEMENT USINGSTATISTICAL METHODS

Halldora Gudmundsdottir, Roland N. Horne

Stanford University

Reservoir characterization and prediction modeling are among the more challenging tasks in geothermal reservoir engineering. A common practice for predicting future performance is to develop a numerical model of the geothermal field and calibrate the model parameters with inverse modeling and observed dynamic data. A full inverse analysis can be very time consuming and computationally expensive because it requires an optimization with multiple iterations over a high dimensional model parameter space. Furthermore, in this approach it is assumed that matching historical values such as past pressure and temperature profiles gives a model that can be used for future predictions. This assumption is flawed because the inverse process is not deterministic, meaning that the input, i.e. observed data, can result in more than one possible outcome, i.e. geological model, which can often be geologically unrealistic with limited forecasting ability. In this work, we investigate the applicability of using statistical methods for reservoir characterization and prediction modeling. First, we use a novel framework called Bayesian Evidential Learning (BEL) to estimate future production temperatures of synthetic fractured geothermal reservoirs. In BEL, the subsurface numerical model is used to generate samples to learn a statistical model that describes the relationship between data and prediction variables, and once this relationship is established it can be used for predictions based on observed data. In our case, data variables are historical temperature and response profiles and the prediction variable a future temperature profile. Second, we explore applying artificial intelligence to estimate the connectivity between injection and production wells using flow rates and tracer response data. Here, a neural network model is developed to define the mapping between producers and their surrounding injectors based on injection and production data. A sensitivity study is then applied on the model parameters to infer about the significance that each injector has on the producers. The ultimate goal of developing a model of a geothermal field is not necessarily to obtain the model parameters themselves but to attain predictions made by the model along with key decision variables, such as where and how much to inject. Statistical methods can be great tools for geothermal management, mitigating the need for full inversion of geological model parameters and thus facilitating informed decision making.

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ITOUGH2-FLOWELL COUPLING OF THE FLOWELLWELLBORE SIMULATOR WITH THE ITOUGH2SIMULATION-OPTIMIZATION FRAMEWORK

Jean-Claude Berthet1, Andri Arnaldsson1, Halldóra Guðmundsdóttir2, Magnús Þór Jónsson3, Stefan Finsterle4

1. Vatnaskil Consulting Engineers, 2. Stanford University 3. University of Iceland, 4. Finsterle GeoConsulting

FloWell is a wellbore simulator that was initially developed as part of a M.Sc. degree project at the University of Iceland in 2012. The original FloWell simulator was implemented in Matlab and coupled with iTOUGH2 through the PEST interface (1). Later developments were introduced in (2). Development of a Fortran version of the simulator began in 2013 and was integrated into the iTOUGH2 framework, operating as an extension module to the reservoir simulator. More recently, new functionalities have been added to the coupled iTOUGH2-FLOWELL simulator (3). The simulator can now model multi-radius, deviated boreholes extracting from multiple feedzones. A new interface was designed to accommodate the definition of more complex well geometries. The parameters calculated by FloWell can be easily extracted as time-series using the OUTPU facility available in iTOUGH2 version 7.1.1. New friction, correction-correlation, and void-fraction models were also added to the coupled iTOUGH2-FLOWELL simulator. Wellfield data were used to determine what combinations of these models were most suitable for geothermal modeling. FloWell supports two modes of production: a user-specified wellhead flow rate and a user-specified well-head pressure mode. A solver was added to FloWell which calculates individual flow rates for each defined feed-zone, corresponding to the user-specified wellhead pressure or wellhead flow rate. Based on pressure and enthalpy changes in the reservoir over time, FloWell automatically switches between the two modes of production. The user specifies a maximum production rate and a minimum well-head pressure. If the pressure remains above the minimum, production occurs at the specified flow rate. If the pressure falls below the minimum, the simulator adjusts the flow rate to maintain a constant pressure at the minimum defined value. This approach to simulating production brings the modeling process closer to the way geothermal wells are operated in the field. The coupled iTOUGH2-FLOWELL simulator can also be used to model injection scenarios. In injection mode, the user-specified wellhead pressure is defined as a maximum value instead of a minimum. When the pressure increases above the specified maximum value, the injection rate is reduced to maintain a constant pressure at the maximum defined value. The coupled iTOUGH2-FLOWELL simulator can also be used to model boreholes themselves without modeling the actual reservoir. The inversion facilities in iTOUGH2 can be used to optimize the wellbore model and determine feedzones within a well. Wellhead data (pressure, flow rate, enthalpy, etc.) can be used to optimize both the wellbore and reservoir models.

REFERENCES

1. Guðmundsdóttir, Halldóra. A Coupled Wellbore-Reservoir Simulator utilizing Measured Wellhead Conditions. Faculty of Industrial Engineering, Mechanical Engineering and Computer Science, University of Iceland. 2012. p. 119, MSc Thesis.

2. Guðmundsdóttir, Halldóra and Jónsson, Magnús Þór. The Wellbore Simulator FloWell – Model Enhancement and Verification. Melbourne, Australia, 19-25 April 2015 : Proceedings World Geothermal Congress 2015, 2015.

3. Berthet, Jean-Claude, et al. iTOUGH2-FLOWELL: Simulating Wellhead Conditions Coupled to Geothermal Reservoir. Energy Geosciences Division, Lawrence Berkeley National Laboratory. Berkeley, CA : Lawrence Berkeley National Laboratory, 2018. p. 57, User’s Guide. LBNL-7017E, FGC-17-08.

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MONITORING KEY INDICATORS OF GEOTHERMAL FIELDS USING AUTOMATIC RESERVOIR SIMULATIONS

Lárus Þorvaldsson, Egill Júlísson, Andri Arnaldsson

Vatnaskil ehf., Landsvirkjun

Managing the utilization of geothermal reservoirs is a challenging task which requires striking a delicate balance between the profitability of the operation and the sustainability of the resource. Three-dimensional reservoir models of multicomponent, multiphase fluid flow in porous and fractured media have been used to aid in decision-making processes in reservoir management for several decades. However, in recent years there has been an increasing demand from geothermal field operators that model results give clear and quantitative answers about the state of the reservoir at increasingly smaller timescales.

To address those concerns, Landsvirkjun and Vatnaskil have taken the first steps towards a new methodology in reservoir modelling, which is summarized as follows. The geothermal operator (Landsvirkjun) collects data regarding the geothermal reservoir and its utilization into a standardized form and makes it available to the modelling contractor (Vatnaskil) on an SQL database. This enables Vatnaskil to retrieve the latest data from Landsvirkjun and conduct automatic reservoir simulations at regular intervals. Using the results from those simulations, several key indicators are then calculated which give a quantitative measure on the state of the reservoir. Those key indicators are then uploaded to Landsvirkjun’s SQL database, giving them an up-to-date estimate of how the reservoir is responding to the current utilization strategy.

This approach has several advantages over the traditional methodology in reservoir modelling. The time-consuming step of gathering data from various sources with varying quality and different formats is avoided for the modeler. In addition, data can be automatically converted into a format that the simulation software can understand.

Having the option of being able to update the model automatically with the latest data means that the model can be run at regular intervals without manual input from the modeler. This greatly increases the utility of the geothermal model. Rather than being static tools where the results are presented in written reports every few years, the client receives up-to-date simulation results on a much more frequent basis. These simulation results are presented in the form of several key indicators, such as inflow of mass and energy into the reservoir, the timing of make-up wells, the estimated limit of sustainable energy production and total primary energy in the reservoir. All of this information is uploaded to an SQL database at regular intervals and is easily accessible to the operator of the geothermal field.

A comprehensive overview of the state of the reservoir is vital for sustainable and responsible utilization of a geothermal resource. The new methodology developed in this project gives geothermal operators access to up-to-date model results condensed in several easily understood key indicators. This methodology therefore has the potential to become standard practice in the industry, allowing for continuous monitoring of the state of the reservoir and thereby fostering sustainable utilization.

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MODIFICATIONS TO THE EOS1SC MODULE IN ITOUGH2

Lilja Magnusdottir, Magnus Thor Jonsson

University of Iceland

Deep geothermal wells have reached supercritical fluid in over 25 cases around the world. The utilization of supercritical fluid is of high interest because of its promising possibilities for improving the economics of geothermal energy production. The enthalpy of water increases significantly at temperatures and pressures above the critical point (374°C and 22.064 MPa) and higher rate of mass transfer through wells is possible due to increased ratios of buoyancy forces to viscous forces. Consequently, a tenfold increase in energy output per well could be expected when utilizing supercritical fluid instead of a conventional well producing subcritical fluid.

In order to optimize production and gain a better understanding of these magmatic geothermal systems, a numerical simulator capable of modeling supercritical conditions is crucial. This study describes modifications and improvements made to the supercritical equation-of-state module EOS1sc for iTOUGH2. The supercritical module was implemented into iTOUGH2 as a part of a project based on the deep roots of geothermal systems funded by GEORG, thereby providing forward and inverse modeling capabilities of high-temperature geothermal reservoirs. Modeling supercritical conditions is a difficult task because of rapid variations in thermal properties close to the critical point and in some cases convergence is not achieved. Hence, the supercritical module is being modified to increase its reliability.

In EOS1sc, the IAPWS-IF97 thermodynamic formulation is used to calculate thermodynamic properties across five regions; liquid, vapor, supercritical, two-phase, and high temperature vapor. Backward equations released for the supercritical region of IAPWS-IF97 were implemented into EOS1sc for calculating specific volume as a function of pressure and temperature. The backward formulation is more reliable than the Newton-Raphson method previously used to iteratively calculate density in the supercritical region and it is approximately eight times faster. In EOS1sc, discrepancies across region boundaries in the IAPWS-IF97 formulation can cause convergence issues. Hence, cubic Bézier curves were implemented to provide a smooth continuous function for thermodynamic properties across the supercritical boundaries. Thereby, poor convergence at intersection points between thermodynamic regions are resolved and the reliability of the supercritical EOS1sc module is increased. Additionally, the weighting procedure for flux terms at grid block interfaces is being studied and its effect on the accuracy and efficiency of the simulation. These modifications to the EOS1sc module in iTOUGH2 provide better reliability and higher computational speed than previous versions of the module for modeling supercritical geothermal reservoirs.

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MODELLING OF CONDITIONS CLOSE TO GEOTHERMALHEAT SOURCES

Sæunn Halldórsdóttir (ÍSOR), Inga Berre (UiB), Eirik Keilegavlen (UiB) and Guðni Axelsson (ÍSOR)

Iceland GeoSurvey - ÍSOR, University of Bergen

As drilling into supercritical conditions has already been realized in the Reykjanes IDDP-2 well, understanding how the heat transport on a field scale is affected by flow and permeability on a local scale near the heat sources, is the next step in developing models for estimating the potential for harnessing superheated resources.

Generally, it is assumed that the main mechanism that transfers heat from heat sources of volcanic geothermal systems is driven by a Convective Downward Migration (CDM) process: a cooling front, driven by convecting water, migrates into hot rock through fractures that open up due to thermo-elastic contraction by cooling of the rock. The heat sources are believed to be cooling magma chambers or intrusions and this process transports thermal energy, derived from the cooling intrusions, by convection upwards to the geothermal systems. The CDM process has been implemented in numerical models by increasing the permeability near the heat sources and the resulting heat transport could explain the existence of geothermal systems above magmatic sources.

The present study gives on overview of the state-of-art modelling approaches for simulating conditions in the hot rock close to the brittle ductile boundary and the magmatic heat sources. Furthermore, explains the necessity to verify the proposed conditions that enhance permeability and favour convection by opening of fractures with thermo-mechanical modelling.

Session B2Upstream

Chair: Halldór Geirsson

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THE 2017-2018 UPLIFT EPISODE IN THE HENGILL AREA, SW ICELAND, FROM GEODETIC DATA

Cécile Ducrocq1, Halldór Geirsson1, Þóra Árnadóttir1, Vincent Drouin1, 2, Daniel Juncu1, 3, Bjarni Reyr Kristjánsson4, Gunnar Gunnarsson4

1. Institute of Earth Sciences, University of Iceland, Reykjavík, Iceland 2. National Land Survey of Iceland, Iceland 3. University of Leeds, UK 4. Reykjavík Energy, Reykjavík, Iceland

Some high-temperature geothermal systems and volcanoes around the world have been shown to display recurrent temporal episodes of uplift and subsidence (e.g. Etna, Campi Flegrei, and Yellowstone). The link between magmatic and hydrothermal dynamics of those episodes and the observed crustal deformation has been debated. The study area here is the Hengill area, a volcanic system whose last eruption was estimated to be ~2000 years ago in South-west Iceland. The enhanced permeability of the central volcano and young cooling intrusions at depth of the Hengill area is ideal for efficient geothermal production. Currently, two power plants - Nesjavellir and Hellisheiði - located on the North and Western sides of the volcanic system respectively, supply the city Reykjavík in electricity and hot water. The crustal deformation as seen by geodetic data sets (GPS and InSAR) is complex. The extraction of water in the geothermal production areas cause localized subsidence, up to 2.7 cm/yr whose amplitudes evolves temporally and spatially. The Hengill central volcano is also located at a triple junction between the Eurasian, North-American and Hreppar plate, cumulating a total spreading ~1.8 cm/yr. Additionally, a wide spread subsidence taking place since ~2006 in the Eastern part of the complex. However, during 2017-2018 the geodetic data sets show a reversal in trend, with widespread uplift in the same Eastern part of the complex. The location of this recent uplift episode seems to coincide with the source of the subsidence as estimated by Juncu et al., 2017. The source of a longer episode of uplift in the Hengill area, between 1994 and 1999, was estimated 3-4 kilometers SE of the source of our current episode. This source, as well as the later sources, have estimated source depths at approximately 6-7 kilometers depth, which is near the brittle-ductile boundary of this area. Possible sources for the 2017-2018 uplift include magmatic intrusion or hydrothermal fluid displacement. Using a combination of geodetic and geothermal data sets, we focus on defining the 2017-2018 uplift episode in the Hengill area using geodetic data sets and discuss possible sources for the uplift and its relation with the other episodes in this area.

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GEOLOGY AND VOLCANIC EVOLUTION OF PAKA VOLCANO IN THE NORTHERN KENYA RIFT; INSIGHTS FROM A NEW

STRATIGRAPHIC FRAMEWORK

Geoffrey Mibei, Hjalti Franzson, Bjorn Hardarson, Halldor Geirsson and Eniko Bali

United Nations University-Geothermal Training Program

Quaternary volcanoes in the East African Rift System (EARS) have been a subject of attention for a long period due to their association with geothermal resources. However little information on their volcanic and tectonic history is known largely attributed to scarcity in the available radiometric dates. In this paper we present results of a field mapping study on Paka volcano in the northern Kenya rift based on a new stratigraphic framework developed from collation of a substantial number of Ar/Ar dates from two previous studies. Our findings has shown new insights into volcanic and tectonic history. The geology of Paka consist of 7 volcanic units comprising of trachyte and basalt lava flows. It is apparent that eruptive events in Paka was initiated in the middle Pleistocene 582 ka a period much older than the 390 ka proposed before. There was a continued volcanism in the area separated by period of marked hiatuses where intense faulting occurred, climactic phase on volcanism was attained in Holocene (8 ka). Eruptions was largely characterised by effusive and limited explosive eruptive phase’s notable in volcanic units 3, 5 and 7. We proposed that the caldera collapse is older than 35 ka, a much older period than 11 ka suggested previously as the recent trachyte deposited in the caldera floor is dated at 35 ka. The caldera floor lava deposit is such that it is constrained within the caldera walls and only breached northern rim spewing lava periodically notably at 20 ka and 11 ka. This is consistent with the presence of a Lava Lake likened to the modern time Erta ale in Ethiopia’s Danakil depression. The area experienced intense tectonics at 278 ka, a period marked by hiatus in volcanism creating much of the Paka localised faults as seen today, this is constrained by the dates of volcanics deposits on the eastern Paka. In the subsequent volcanic hiatuses of 245 and 126 ka, subdued tectonic events were experienced. The series of events indicate intricate interplay of volcanism and tectonism in addition to geothermal activity in the area. Silica deposits in the northeast of caldera indicate the presence of a hot spring that emerged at 80 ka and disappear after 64 ka possible linked to changes in water table due to volcano-tectonic events preceding caldera formation and possibly climate variation. As part of this project 39 rock samples have been collected to decipher more information on Paka magmatic processes. Understanding the volcanic and tectonic history of Paka is critical as the geothermal development company is plaining to begin geothermal drilling soon.

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ELECTRICAL RESISTANCE STUDY USING GEOTHERMAL STEEL CASINGS AS LONG ELECTRODES

Lilja Magnusdottir, Magnus Thor Jonsson

University of Iceland

Connectivity of fractures in geothermal systems is essential to ensure adequate supply of geothermal fluids and efficient thermal operation of the wells. Resistivity methods are commonly used to estimate the configuration of fractures in geothermal systems to better understand the fluid-flow patterns. However, modelling fractures deep in the ground is a difficult task and none of the geophysical exploration methods currently used to explore geothermal reservoirs is capable of providing an accurate high-resolution model of the reservoirs at the required scale, depth and cost for running the power plants in an optimal way.

This project focuses on investigating the possibility of using geothermal steel casings to transfer electric current deeper into the ground during resistivity surveys. Measurements are performed at Reykjanes geothermal reservoir in Iceland on several wells including the IDDP-2 well that has been deepened down to 4.7 km. A direct current resistivity survey using casings as electrodes is performed and the electric potentials between casing pairs are measured. A 4-wire resistance method is used where three 12 V batteries are connected in series with the positive terminal connected with wires to one casing and the negative terminal connected to another casing in order to inject current from one well to the other. A 10.8 ohm resistor is added to the circuit as well as an ammeter to measure the electric current flowing between the casings. Then, another wire is connected to both casings and a voltmeter added to that circuit to measure the potential difference between the two casings. One of the wells tested is not connected to any surface pipelines, thus ensuring the current only flows between the wells through the ground. The low resistance measured between the casings indicates that the current is flowing through a channel of saline geothermal fluid from one well to another.

Several pairs of casings are tested and the connection between them studied. Wells believed to be producing from the same aquifer have lower electrical resistance between their casings than other well pairs. Hence, the experiment shows the benefits of using the casings as electrodes to get the electric current deeper into the ground and to better understand how the wells are connected. Future work includes measuring the electric resistance between wells as water with higher resistivity than the geothermal fluid flows through the fracture network and using the time-lapse resistance between well pairs to estimate the connectivity in the reservoir. The knowledge of the fracture connectivity is extremely valuable to design the recovery strategy appropriately, optimize the placing of injection or production wells and increase the overall efficiency of the power production.

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INDUCED SEISMICITY DURING REINJECTION OF WASTEWATER IN HELLISHEIDI GEOTHERMAL FIELD,

SW ICELAND

Sigríður Kristjánsdóttir, Ólafur Guðmundsson, Kristján Ágústsson, Þorbjörg Ágústsdóttir, Ari Tryggvason, Michael Fehler

Iceland GeoSurvey - ÍSOR

In 2011 and 2012, a large number of earthquakes were induced during the reinjection of wastewater at the Hellisheidi geothermal power plant near Hengill volcano in SW Iceland. The area is tectonically active, located close to the triple junction of an oblique spreading zone (Reykjanes Peninsula), a rift zone (the Western Volcanic Zone) and a transform zone (the South Iceland Seismic Zone). The injection started in September 2011 and the seismicity increased shortly after, with thousands of events recorded in the following months by the local network of the Icelandic Meteorological Office (IMO). The majority of events were small (Ml < 3.0), but the two largest events reached Ml 3.8 and were widely felt in the area. An increase in seismicity was also observed during the drilling of the injection wells, associated with the loss of drilling fluid.

From 2009 until 2013, Uppsala University, Massachusetts Institute of Technology, Reykjavik University, and Iceland Geosurvey operated a dense temporary network of seismographs in the area. Data from this temporary network and the permanent IMO network was used to make a detailed analysis of the induced seismicity. The events that had been located by the IMO network were grouped into families based on waveform similarity. By using a typical event from each family as a template for cross correlation of the continuous dataset, we were able to quadruple the number of previously located events. Cross correlation differential travel time measurements were then used to relocate the expanded dataset of events with high accuracy. We analyzed the spatial and temporal relationship between earthquakes and injection processes, and calculated focal mechanisms for the master events, giving an insight into the local stress field. The authors would like to acknowledge the IMO for access to waveform data.

Session B4Upstream – Geology & Exploration

Chair: Amel Barich

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CONCEPTUAL MODEL OF KRAFLA

Knutur Árnarson

Iceland GeoSurvey (ÍSOR)

The complexity of the geothermal activity in Krafla has puzzled geoscientist for decades. New and old geoscientific studies are reviewed in order to shed light on this complexity. The geological structure of the volcano seems more complex than hitherto believed. The 110 ka caldera hosts, now buried, 80 ka inner caldera and both calderas are bisected by a WNW-ESE transverse low density structure. Resistivity surveys show that geothermal activity has mainly been within the inner caldera, but is cut through by the WNW-ESE structure. Seismicity indicates lower crustal temperatures in the structure than north of it. A difference in the local crustal spreading directions south and north of the calderas lead to a N-S opening component, favouring ascent of basaltic magma and explaining why most of the volcanic activity is in the eastern part of the calderas.

The present geothermal activity can be understood by considering the tectonic history. 8 to 3 ka ago, the spreading moved from the eastern part of the 110 ka caldera to the western part. Intrusions in the eastern part, formed a two-phase geothermal system and the alteration mapped by resistivity surveys. When the spreading moved back to the presently active fissure swarm, permeability increased drastically causing vigorous convection that quickly exhausts heat sources. This happened west of Hvíthólar as observed in well KV-1. North of the transverse structure, a WNW-ESE intrusion/dike complex formed due to the N-S opening component. Below 1 – 1.5 km depth, intrusions maintain adequate permeability for a two-phase system, but increased permeability above caused, about 200°C, isothermal convection. Increase in permeability did not extend east of Hveragil and a two-phase system persist there. The geothermal systems in Hvíthólar and Sandabotnaskarð are probably due to heat sources at the caldera rims and might be in a fading stage.

Hydrogen isotope ratios in geothermal fluids vary in Krafla. West of Hveragil, δ2H indicates local meteoric water. δ2H is lower east of Hveragil and similar to Hvíthólar, suggesting hydrological connection. Recent studies indicate that low δ2H east of Hveragil is due to phase separation in boiling of local meteoric water. What seemed like different geothermal systems north of the transverse structure, is actually one system with variable permeability. Fluids from KS-1 in Sandabotnaskarð have still lower δ2H, similar to Námafjall, indicating origin at higher elevation further south. It seems like there is little, if any, hydrological connection across the WNW-ESE transverse structure.

The silicic magma encountered in K-39 and IDDP-1 indicates hitherto overlooked heat transport mechanism in evolved volcanos. Basalts that intrude subsided altered rocks re-melt the rock, producing superheated, volatile rich, low viscosity silicic melt which is buoyant and migrates up. As the melt ascents, it cools and de-gases, becoming more viscous and finally trapped as magma pockets, i.e. a heat source for the geothermal system. IDDP-1 entered superheated steam above the magma. Recent tomography studies show low P-wave velocity at about 2 km depth, roughly coinciding with the S-wave shadows which could indicate the extent of rocks with melt pockets. Krafla, like some other evolved volcanos e.g. Askja, shows a bimodal behaviour with occasional silicic, often phreatic, eruptions but purely basaltic in-between. It is suggested that evolved volcanos and their geothermal systems are coupled systems, enhancing heat flow from the mantle and “distilling” out silicic magma/rocks. When substantial amount of silicic intrusions/magma have accumulated, major basalt intrusion(s) may “ignite” them causing silicic eruption and the cycle starts again; distilling silicic heat sources.

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TRACKING HYDROGEN SULPHUR CIRCULATIONS BY MEANS OF COMPLEX ELECTRICAL RESISTIVITY: FIELD AND LABORATORY INVESTIGATIONS AT THE KRAFLA VOLCANO,

ICELAND.

Léa Lévy, Benoit Gibert, Freysteinn Sigmundsson, Svetlana Byrdina, Jean Vandemeulebrouck, Damien Deldicque, Gylfi Páll Hersir, Ólafur G. Flóvenz, Pierre Briole

University of Iceland and Ecole Normale Supérieure (Paris)

Hydrogen Sulphur (H2S), a gas of magmatic origin, flows naturally towards the surface in volcanic areas, but is also a by-product of geothermal energy exploitation, contributing to air pollution. Interaction of H2S and basaltic rocks leads to pyrite mineralization, witnessing active hydrothermal circulation, as well as H2S sequestration upon re-injection. We study the possibility to track these underground processes using geo-electrical methods, in order to provide geothermal industry with constraints for exploration and remediation.

Electrical Resistivity Tomography (ERT) and Induced Polarization (IP) are two complementary geo-electrical methods of subsurface investigation, as they map two electrical properties: the electrical conduction and the electrical charge storage capabilities of rocks (polarization). Electrical conduction and polarization of rocks, combined together into the „complex electrical resistivity“, are particularly sensitive to the presence of three minerals abundant in volcanic environments: smectite, pyrite and iron-oxides.

In the field, we performed ERT and Time-Domain IP soundings along 1.24 km-long profiles, at three different sites around the eastern caldera rim of the Krafla volcano (Iceland). We completed two-dimensional inversions, down to 200 m, of the complex resistivity: the maximum phase angle and relaxation time (polarization) and the resistivity (conduction). We identified layers of high maximum phase angle (MPA) at two sites, which we interpreted as pyrite-rich and iron-oxides-rich, respectively. Indeed, thanks to laboratory frequency-domain complex resistivity measurements (in the range 10 mHz-1MHz) of 88 core samples from four boreholes at the Krafla volcano, we showed that, in natural volcanic environments, pyrite could be discriminated from smectite and iron-oxides by considering together the MPA, resistivity and relaxation time. Since each of the sites are located around a borehole, the relative abundance of smectite, pyrite and iron-oxides could be estimated and confirmed our interpretations. In addition, a comparison of in-situ electrical logs and laboratory electrical measurements on core samples from the boreholes to the field soundings allowed us to evaluate, at the field scale, the effect of temperature on resistivity and MPA.

We also observe in the laboratory that the MPA increases with the volume of pyrite and decreases with increased fluid conductivity or smectite volume. Smectite volume can be estimated based on the resistivity, provided that the fluid conductivity is known. Indeed, we show that smectite is a highly-conductive clay mineral, thanks to a special conduction pathway, which does not allow polarization. However, a current limit for upscaling the laboratory frequency-domain quantifications at great depths is the limited frequency-range investigated by time-domain IP, compared to frequency-domain IP.

Our field time-domain IP measurements illustrate the possibility to detect the presence of pyrite, at shallow depth, in volcanic environments. Furthermore, our frequency-domain laboratory observations on natural volcanic samples, containing a wide range of iron-oxides, pyrite and smectite volumes, are an important step to bridge the gap between field studies and theoretical models. While future technological improvements will improve both the depth- and frequency- ranges resolved by time-domain IP, our results can guide, at this point, interpretations of geophysical soundings towards an estimation of pyrite and smectite volumes in volcanic environments.

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PROBABILISTIC GEOLOGIC MODELS OF KRAFLA CONSTRAINED BY GRAVIMETRIC DATA

Samuel Scott, Cari Covell, Egill Júliusson, Águst Valfells, Juliet Newson, Birgir Hrafnkelsson, Halldor Pálsson, Maria Guðjónsdóttir

Reykjavik University

Geologic models constitute essential tools for decision making in geothermal exploration and development. However, the underlying primary observational data used to construct the models are sparse and uncertain. This uncertainty is not reflected in deterministic geologic models that provide only a single possible realization of subsurface geology. Additionally, while quantitative comparison of a forward-modeled geophysical field with measured data might constrain uncertainty estimates in geologic models, geologic models are usually only qualitatively compared with the geophysical datasets.

To explicitly consider uncertainties and better integrate geophysical data into the model building process, we use gravimetric data to constrain probabilistic geologic models of the Krafla geothermal field. Our approach combines statistical analyses of rock properties obtained from the Iceland Rock Property Database, 3D geologic modeling, and Markov Chain Monte Carlo stochastic simulation methods. Building on a simplified reference geologic model of the Krafla system built by Iceland Geosurvey in 2015, we use the GeoModeller software package (developed by Intrepid Geophysics) to generate multiple realizations of subsurface geology and assess the likelihood of a given geologic model realization through a quantitative comparison of a forward-modeled gravity response with measured data.

The stochastic inversion scheme generates multiple realizations of subsurface lithology and density distribution that closely reproduce the measured gravity field. The summary statistics calculated on the full suite of accepted models indicate that uncertainty is greatest along the interfaces between different lithologic units and in areas of the field with a relatively few drilled wells. The calculated gravity response is most sensitive to the depth to basement intrusions and the density and thickness of hyaloclastites. The WNW-ESE trending gravity low in the center of the caldera, postulated to be associated with a buried graben, corresponds to a zone with thicker and less dense hyaloclastites. The relatively low density of hyaloclastites in this area might indicate a low degree of alteration in this area.

To test whether the gravimetric data might be able to constrain the properties of subsurface magmatic intrusions, we consider a different reference model with a rhyolitic intrusion underneath the area of IDDP-1 and Viti. Based on this different reference model, the inversion scheme is able to produce multiple geologic models that account for measured gravimetric data, suggesting that the gravimetric data is not very informative of deep density variations (<1.5 km depth). The large influence of the reference model on the accepted model realizations suggests a need for better exploration of the plausible model solution space when performing the stochastic inversion.

This study demonstrates how Bayesian inference methods coupled with litho-constrained geophysical inversions allow geologic hypotheses to be tested by quantitative comparison of model results with geologic and geophysical data. A probabalistic assessment of sparsely explored regions of the field may contribute to better decision-making for field development and management. However, statistical approaches to inferring of subsurface properties from field observations don’t circumvent the non-uniqueness problem in geophysical inversion.

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GROUND DEFORMATION AT ÞEISTAREYKIR: INFLUENCE OF GEOTHERMAL UTILISATION AND MAGMA INTRUSIONS.

Vincent Drouin, Freysteinn Sigmundsson, Siqi Li

Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland

Þeistareykir is the northernmost on-land and active volcanic system in Iceland. Eruptive activity of the central volcano is low, the last eruption taking place about 2500 years ago. Other lava flows are older than 10,000 years. Rifting events without eruptions may have occurred in the area in 1618 and 1885 but it is uncertain if these originated from the Þeistareykir central volcano or from a nearby off-shore volcano. However, geodetic measurements since the 1990’s have shown two possible inflation episodes during the past 25 years: in 1995-1996 and in 2006-2008. There is an active geothermal area in one part of the central volcano and a 90 MW powerplant operated by Landsvirkjun entered in production last November.

We use a combination of campaign GPS measurements and Sentinel-1 SAR satellite radar interferometry to have a good understanding of the deformation field in the area prior to the onset of production at the powerplant. We observe that the area is deforming at fairly stable rate since 2009. The main noticeable feature is a slow subsidence in the north-west part of the central volcano in a similar location to where the 2006-2008 inflation episode took place. We then compare this deformation field to the summer 2017 - summer 2018 deformation field to observe any change that could be related to geothermal fluid extraction. Results indicate additional subsidence at the Þeistareykir geothermal area: the subsiding area is elongated north-south along the fissure swarm and the rate is < 5 mm/yr. This deformation rate is small when compared to what is observed at the onset of production at other geothermal powerplants operating in Iceland.

Knowing the deformation induced by geothermal fluid extraction is important to estimate the effect of the current production rate on the geothermal reservoir and assess its sustainability and the potential of increasing the production in the future. Monitoring the activity of the volcano also gives us insight on how much heat is added in the system during intrusive episodes.

Session B5 Downstream / Cross-cutting

Chair: Carine Chatenay

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GEOTHERMAL SOURCE OF LOCAL DEVELOPMENT

Katarzyna Kurek, Wim Heijman, Johan van Ophem

Wageningen University and Research, The Netherlands

Among the renewable energy resources geothermal is specific to a local production and consumption. Geothermal energy based activities accompany human development from ancient times and indicate its role in building a competitive advantage of a location of exploitation. Next to the heat and energy production, geothermal resources reveal wide function in tourism and health sector, agriculture and industry due to the water composition and environmental footprint evidence in the long-term use. However, the subject of geothermal energy resources and potential scale of benefits to the local development is still marginalized in the research. The aim of this research is to fill in that gap and present an angle geothermal resources analysis assuming that geothermal based establishments are considered as an impulse of local development. Moreover, geothermal energy presents with opportunities for rural and suburban areas linking sustainable development goals with expansion of new local economy sectors. Geothermal energy impact on local development is measured in direct, indirect and induced effects. This research attempts to establish a methodology that is able to measure such approach to local development. Notwithstanding the relatively marginal importance national authorities have given geothermal resources to date, Poland was chosen as the main object of the research because of its particularly high geothermal potential and private sector experience in bringing up geothermal enterprises. The theoretical conceptualization underpinning this analysis is provided by endogenous growth theories as well as reflections on approach to local development. The model is to demonstrate the statistical relation between exploited geothermal energy and parameters of local development. Exercised on the Polish municipality cases this model is to be possible to apply to any geothermal municipality in the world and its results to motivate further local authorities into geothermal installations investments.

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SOCIAL IMPACTS OF GEOTHERMAL UTILISATION IN PUGA, LADAKH, INDIA

Kunzes Dolma

United Nations University, Geothermal Training Program, Iceland; Reykjavik University

The scope of this paper is to use the existing flowing geothermal well without further drilling in Puga to generate electricity which will be enough to electrify and run the direct heating system for the Nomadic Residential School, Puga (located at 4550 metres above sea level). At present the boarding school is heated using wood or kerosene. For electricity there is a 10kVA standalone generator which supplies electricity to the boarding school from 6pm to 11pm. There are three villages nearby namely Sumdo TR, Sumdo and Korzok. Sumdo and Sumdo TR have no access to electricity at all. The electricity requirement of Korzok is fulfilled by a diesel generator of 82.5 kVA/66 kW which only operates from 6 to 11 pm (District Statistical and Evaluation Office, 2015). With the coming up of the new administration block in Puga there will be more demand for electricity which can be met up from this plant. This utilisation of this source is important keeping in view the fact that the diesel required to electrify these areas must be transported from other states of India in tankers which adds to the increasing carbon di oxide emission. The exploitation of this field is very important at a stage when the whole world is fighting to combat CO2 emission and to fulfil India’s goal in combating Climate change/ global warming along with achieving Sustainable Development Goal 7 which ensures access to affordable, reliable, sustainable and modern energy for all.

The implementation of this project will bring a change in the lives of the students living here. They will have 24 hour electricity which will be a dream come true. They will not have to bother about wood and kerosene for heating and keeping them warm in the cold winter months. They will be able to enjoy living in a clean environment with this sustainable energy solution. They deserve this much luxury as they prepare for their future living at such high altitude.

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SILICIC MAGMA OF THE KRAFLA VOLCANIC SYSTEM

Olgeir Sigmarsson

Institute of Earth Sciences, University of Iceland, Reykjavik, Iceland Laboratoire Magmas et Volcans, CNRS – Université Clermont Auvergne, France

The discovery of silicic magma at shallow depth during the IDDP drilling revealed the presence of crustal melts in the hydrothermal system of Krafla. Its relationship to other silicic magmas produced by the volcano is largely unknown, as well as its age. We present compositional results of major and trace elements comparing the IDDP obsidian with silicic pumice from the 1724 Víti eruption (1724 CE) and the 53 ka rhyolitic obsidian of Hrafntinnuhryggur (A-THO). Moreover, radioactive disequilibrium in the 238U-decay series has been measured.

The IDDP obsidian (SiO2 = 73.4 wt%) is of significantly different major element composition compared to the Víti rhyolite (SiO2 = 76.6 wt%) but indistinguishable from that of Hrafntinnuhryggur, with the exception of significantly lower volatile element concentrations. The IDDP can indeed be considered as “dead” magma without the capacity to erupt on itself. The Víti pumice may correspond to a similar situation being a volatile poor rhyolite remobilised by basaltic magma at the initial phase of the Mývatn Fires.

Silicic magma formed by anataxis of hydrothermally altered mafic crust in the volcanic rift-zones of Iceland as revealed by lower O- and Th-isotope ratios compared to the contemporaneous basalt from same volcanic systems have surprisingly uniform Th concentrations. The incompatible element consistency is being evaluated to expose possible connection between different silicic magma at depth beneath Krafla. The short lived disequilibria reveal that IDDP rhyodacite is much younger than 8 ka given the significant 226Ra-excess over its parent 230Th. Radioactive equilibria between 210Po, 210Pb and 226Ra will be presented and should give tighter time constraints on the age of the IDDP obsidian.

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GEOFOOD – PROVIDING NEW IDEAS FOR STARTUPS

Thorarinsdottir, R., Turnsek, M. Boedijn, A., Baeza, E., Espinal, C., van den Ven, R., Unnthorsson, R., and Palsson O.

Samraekt ehf

The pioneering use of geothermal energy in Iceland and other parts of the world has received increased interest in recent years. Many countries see new opportunities for sustainable food production with direct use of geothermal energy. At the same time circular food production is paving its way to commercial solutions, for example aquaponics and other integrated multitrophic systems. However, only a relatively small number of European startup companies in the field of circular food production have been successful and there is still need for research and development to optimize the production in such complex production cycles.

The GEOTHERMICA supported project GEOFOOD (2018-2021) joins researchers, innovative startup companies and policy makers in Iceland, Slovenia and The Netherlands. The aim of the project is to provide innovative concepts illustrating how to increase the economic viability of joining geothermal heat infrastructure and circular food production systems. The production systems are based on optimised use of energy, water, nutrients, man power and other resources to support viable agri-businesses which can help to cover the costs of running geothermal heat installations and provide ideas for novel sustainable production methods. The methods used are based on modelling the energy, water and nutrient use in the integrated system and comparing the results with conventional linear systems.

The GEOFOOD project showcases the opportunities of direct use of geothermal energy to increase food production in highly productive circular systems. A research plant in the Netherlands and a demonstration plant in Iceland will be built and run during the project period. These plants will be used to validate the mathematical models which will help dimensioning and predicting the best combinations of steps in a thermal treatment train depending on climatic conditions. The model will also be used to design aquaponic systems using geothermal heat in Slovenia.

In addition and in close collaboration between the multidisciplinary consortium members, emphasis is on knowledge sharing and B2B activities to foster the inclusion of the GEOFOOD technology to existing and upcoming geothermal heat installations. The GEOFOOD consortium puts emphasis on dissemination of the results focusing on geothermal areas in Europe and worldwide. The communication covers all stakeholders in the value chain as well as education and training to the general public and students at all levels. The dissemination and communication will cover technological, economic and social aspects of the sustainable models developed in GEOFOOD.

Geothermal cluster and communities have done a great job by disseminating the potential of geothermal energy. This has been assisted further by FAO and the European Commission supporting several projects in this field. The increased use of geothermal energy for food production is likely to have a noticeable impact in Europe in the near future. The aim of GEOFOOD is to support this development by inspiring entrepreneurs and providing new ideas for startups.

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THE IMPLICATIONS OF THE ICELAND DEEP DRILLINGPROJECT FOR REDUCING GREENHOUSE

GAS EMISSIONS WORLDWIDE

Wilfred Elders, Omar Fridleifsson and Jim Shnell

University of California Riverside, HS Orka, Ocean Geothermal Energy Foundation

The success of the IDDP-2, a 4.5 km deep geothermal well at Reykjanes, that penetrated supercritical conditions, (bottom hole temperature of ~600oC, fluid pressure ~34 MPa) opens up new possibilities for improving geothermal economics. Because of the higher enthalpy and more favorable flow characteristics of supercritical water, a supercritical geothermal well should produce an order of magnitude more power than that from a conventional geothermal well. Producing much higher temperature working fluids creates other possibilities to improve geothermal economics by making downstream processes more efficient. Existing geothermal generation provides reliable baseload electricity, but flexible downstream use of the high-temperature fluids produced would not only make the resource even more valuable, but also play a role in reducing Greenhouse Gas (GHG) emissions. This could be done by selling electricity when demand is high, and at times of lower demand using electricity to produce hydrogen by electrolysis of hot water. Electrolysis is more efficient at high temperatures, but electrolytic cells require clean water, so heat exchangers and/or desalination would be necessary. Similarly, when the chemistry of geothermal brine is suitable, salable products such as lithium, base metals, and other mineral products could be extracted from the brines.

However, existing geothermal steam generating plants are not entirely CHG free, although they emit less than a third of the CO2 emitted by a natural gas turbine, which is the least polluting of all hydrocarbon fueled electrical generating plants. The future development of supercritical and superhot geothermal generation should reduce emission of GHG’s by (1) replacing the use of the hydrocarbons that would be used to produce that electricity, (2) using electrolysis to produce hydrogen, as a transportation fuel or as a form of energy storage, (3) production of methanol using the geothermal CO2 and hydrogen, to use as a gasoline additive, (4) sequestration of CO2 in geothermal reservoirs, (5) producing lithium (reducing the price of batteries used in fuel cells), and (5) extracting metals like zinc, silver, lead, manganese, etc., (without the GHG produced by smelting).

Iceland is leading the way in three ways, 1) by IDDP exploring for and developing supercritical geothermal resources, 2) by Carbon Recycling International using geothermal CO2 to produce methanol for use as an additive to gasoline and biodiesel fuel, and 3) by Reykjavik Energy’s Carbfix and GECO (Geothermal Emission Control) sequestering geothermal CO2 by injecting it into the hot rocks of the geothermal reservoir where it is fixed by forming carbonate minerals. These concepts could be used worldwide where ever suitable high temperature geothermal systems exist, such as USA, Indonesia, Philippines, Mexico, New Zealand, Italy, Japan, Turkey, etc. Successful adoption of these technologies would not only contribute to the growing worldwide demand for energy, but at the same time lead to significant reductions in global greenhouse gases.

Posters Session

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STATISTICAL ASSESSMENT OF ICELANDICROCK PROPERTIES

Cari Covell, Samuel Scott, Egill Júlíusson, Ágúst Valfells, Juliet Newson, Birgir Hrafnkelsson, Halldór Pálsson, María Guðjónsdóttir

Reykjavik University

Rock properties such as density, porosity, and permeability control the mechanical behavior of rock units and the productivity of aquifers. However, rock properties are highly variable on the field and hand-sample scale. For example, porosity can vary from <1-60%, and permeability can fluctuate across several orders of magnitude. The uncertainty in rock properties can be quantified through computing probability density functions (PDFs), but require careful selection of the type of distribution that best represents the data.

Statistical analyses are performed on data extracted from the Icelandic Rock Property Database. The data represent surface observations and well samples of different rock types obtained between the years 1992-2004. The database was treated with the purpose of obtaining grain density and total porosity values for statistical assessment on five major types of rocks (hyaloclastite, lava flow, intrusives, gabbros, and felsics). Kernel density estimation (KDEs) are used to explore the effect of an assumed distribution, based on bin width on the computed histogram and bandwidth (i.e. smoothing parameter) on the computed distribution.

Different approaches are used throughout the process of constructing KDEs in order to provide comparison for best representation of data. Four approaches are used to contruct the histograms, and two approaches are used to find optimal bandwidth. Essentially, constructing histograms differ by varying bin width using cost functions to minimize error. For bandwidth selection, the “rule of thumb” method defines a function using the integrated mean square error (IMSE), but only works for univariate Gaussian (normally) distributed data. Therefore, cross-validation was also considered, where machine learning techniques empirically compute the bandwith. Once the KDEs are constructed, there is more ease in visibility of the distribution of data.

Although the Icelandic Rock Property Database provides data for grain density and total porosity, total bulk density is required when forward-modeling gravity potential fields associated with a given geologic configuration.. Total bulk density is computed via Monte Carlo methods by sampling of grain density and total porosity, with the assumption of constant fluid density. The results from KDEs are used to assign distributions for grain density and total porosity, and new PDFs for bulk density are calculated for the given rock types.

Results from KDEs show that grain density can be represented as normally distributed and total porosity as log-normally distributed. Bulk density computed from Monte Carlo sampling shows mean estimates either slightly higher or slightly lower than originally calculated without Monte Carlo sampling. In addition, bulk density standard deviations computed from Monte Carlo were overall lower for four of the five rock types when compared to orignal calculations. Therefore, results show overall higher probability density centered around the mean.

As shown in companion work (Scott et. al.), PDFs computed for total bulk density play a significant role when constructing geologic models that incorporate geophysical data. Furthermore, the effect of porosity on permeability is important to understand when constructing reservoir models. These methods integrate well into Bayesian inference theory to ultimately explore options for decision making in the field.

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HYDROTHERMAL ALTERATION AND PETROPHYSICAL PROPERTIES OF WELL KH6, KRAFLA GEOTHERMAL FIELD,

NE ICELAND

David Escobedo1, Patricia Patrier4, Benoit Gibert1, Léa Levy2,3, Daniel Beaufort4, Bruno Lanson5, Jacinthe Caillaud6

1. Laboratoire Géosciences Montpellier, Université de Montpellier, France, 2. Ecole Normale Supérieure Paris, France, 3. University of Iceland, 4. University of Poitiers, France, 5. Laboratoire ISTerre Grenoble, France, 6. Université du Littoral Côte d’Opale, France

The present study focuses on analysing hydrothermal alteration throughout the well KH6, an exploratory well drilled in 2007 at Krafla geothermal field, NE Iceland. This well presents in-hole temperatures reaching over 200°C and is located in a non-exploited area.

This study emphasises on the clay distribution at the metric scale through the well and on the lithologic and structural control of this distribution. Additionally, petrophysical measurements on the same samples are correlated to this distribution in order to establish the relationship between hydrothermal alteration and local physical properties into the reservoir. A set of 38 centimetric cylindrical mini-cores extracted from cores drilled at depths from 292m to 727m were studied in order to identify their lithology, alteration mineralogy and related physical properties.

The in-hole lithology is composed of basaltic rocks at the upper part and hyaloclastite rocks at the bottom, both parts being intruded by basaltic and doleritic dykes. X-ray diffraction on bulk rock powders and on clay fraction (<2 microns), optical and SEM observations and petrophysical measurements have been completed on most of the samples. Chlorite and corrensite are always associated and are observed in most samples, even those located in the low-temperature parts (40°C).

Although they are formed in a hydrothermal context, systematic observations of this paragenesis is in agreement with recent studies that point out that chlorite/corrensite minerals are also formed during late-magmatic processes. Tri-octahedral smectite is also present in most of the samples. Hyaloclastite rocks contain more smectite minerals while crystalline rocks (basalts and dolerites) are richer in chlorite and corrensite minerals. Aluminium-rich clays (di-octahedral smectite, kaolinite and Illite-smectite mixed-layers) are found in fractured horizons and are markers of intense leaching zones implying important circulation and low-pH. The samples corresponding with these highly altered horizons and hyaloclastite rocks show low resistivity, high porosity and high permeability patterns, whereas samples from weak altered crystalline rocks present opposite physical properties and can even appear as cap rocks within the geothermal reservoir. The vertical distribution of clay minerals with depth is more complex than the classical pattern of hydrothermal alteration used for prospecting high-temperature reservoirs.

This classical pattern presents the temperature distribution as the main factor controlling clay precipitation, but in well KH6, clay minerals are not constrained by temperature boundaries at least between the range of our interval of study. Instead of temperature control, the presence of fractures and lithology variations appears to be the main factor controlling the clay zonation.

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KRAFLA VOLCANIC SYSTEM: CONSTRAINTS ON TEMPERATURE AND SHALLOW HEAT MINING

INFERRED FROM CRUSTAL DEFORMATION FIELDS MAPPED BY INSAR AND GPS

Freysteinn Sigmundsson, Vincent Drouin and Siqi Li

Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland

The crustal deformation field in the Krafla volcanic system has been mapped by combination of satellite radar interferometry (InSAR) and geodetic measurements utilizing the Global Positioning System (GPS). The measurements show regional deformation related to plate boundary processes as well as local geothermal deformation caused by utilization and natural processes.

The style of extension across a divergent plate boundary during quiet periods depends on its thermal structure, which influences the transition from elastic plate stretching in the uppermost few kilometers, to continuous opening at depth in a viscoelastic lower crust. For the Krafla volcanic system, outside the main geothermal areas, this inferred “locking depth” of the plate boundary is found to be about 4.5-6 km, corresponding to an estimated temperature in the range of 450-750°C.

Bounds on eventual temperature change within the Krafla and Bjarnarflag geothermal reservoirs, related to heat mining, can on the other hand be inferred from inferred local deformation sources, that produce up to 5 mm/yr subsidence over 4-5 km wide areas. If all this deformation would be due to shallow heat mining at the level of boreholes, then the multiply of temperature change and the volume involved can be inferred. Such thermal modelling constrained by mapped deformation at Krafla suggest that the local deformation there may be produced by host rock temperature change averaging to less than 1°C per year over a spherical volume with radius of 1.5 km.

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MAPPING AND DYNAMIC ANALYSIS OF FRACTURESIN HENGILL, SW-ICELAND

Hanna Blanck1, Ph.D. Kristín Vögfjörð2, Ph.D. Halldór Geirsson1

1. University of Iceland, 2. Icelandic Meteorological Office

The Hengill geothermal field has been developed and exploited since 2006. Two geothermal power plants, the Nesjavellir and Hellisheiði power plants, lie about 10 km apart from each other NE and SW of the Hengill mountain and together they produce 420 MW electricity and 430 MW of warm water. The Hellisheiði power plant is the biggest power plant in Iceland and the fifth largest in the world. Hence, the Hengill geothermal area is of great importance for electricity and hot water production in Iceland and understanding the dynamics of the area is of great scientific and economical interest.

The Hengill volcano is located on a triple junction in Southwest Iceland connecting the Reykjanes Volcanic Zone, the Western Volcanic Zone and the South Iceland Seimic Zone. Prior to exploitation, between 1993 and 1999, the area was subjected to a significant volcano-tectonic event which caused 8 cm uplift over a period of 5 years, which can possibly be explained by a small magmatic intrusion. The uplift was centered near the NE corner of the triple junction and induced more than 90 thousand earthquakes in the Hengill region which highlights the intensity of the stresses that must have been present in the crust at the onset of the uplift. With time the seismicity propagated south form the uplift-source region and through the South Iceland Seimic Zone, where two events of M>5 were generated in 1998.

Parts of the earthquake swarms recorded 1997 and later have been used to map faults and to analyze their dynamics. The remaining events, mainly in the uplift-source region will be the focus of a new project within the research project “Interaction of geothermal, tectonic, and magmatic processes in the Hengill area, SW-Iceland”, supported by The Iceland Centre of Research (Rannís).

In this study, we focus on fault activation in the source area of the uplift and analyze which fracture were active, analyze their dynamics and development over time. Therefore, we review the events and use cross-correlation methods to refine the location accuracy through double-difference methods. Then we calculate strike, dip and location of the fault that best fits the event distribution. By extracting the event focal mechanisms that best fit the common fault plane, the average slip direction on the fault can be estimated and from that we learn about the stress field. In a second step I will compare the results with fractures active today with the goal to estimate the time scales that are relevant in this highly active and laterally variable area. The mapping of fractures provides valuable information on permeability at depth which can help to position future well bores.

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IDENTIFICATION OF FAILURE MODES AND THEIR EFFECTSIN GEOTHERMAL POWER PLANTS

Helen Ósk Haraldsdóttir, Sigrún Nanna Karlsdóttir, Kolbrún Ragna Ragnarsdóttir

University of Iceland

Geothermal energy is a renewable thermal energy source that can be utilized to produce electricity and heating. Harnessing this energy can be demanding as the properties of the geothermal fluid can create harsh environments for the power plant components. This includes the turbine, which converts kinetic energy of the geothermal steam to electricity. Examples of damages the turbine components can experience are wear, erosion and corrosion. Damage to the turbines can lead to reduced efficiency of the plant. This leads to downtime, lost revenue and costly repairs. It is therefore important to minimize damage to this component. This can be done through proper designs and adequate material selection. Material selection is based on choosing materials which have appropriate mechanical properties to endure the cyclic thermal and mechanical loads that the steam turbine parts are subject to. Additionally, the materials must have adequate corrosion resistance to prevent damage from exposure to the geothermal fluid. Presently, either corrosion resistant alloys used as bulk material or material added through welding is generally being used to protect sensitive areas in turbines. Welding generally requires the addition of post treatment and the use of corrosion resistant bulk material can increase the cost of the components considerably. Using coatings as a solution to protect the components can therefore reduce the cost and process involved in protecting geothermal components. Special experimental setup at Hellisheiði geothermal field was used to perform corrosion and erosion testing of various coatings for potential use in geothermal turbine environment. Surface profiling and thickness measurements showed that the electric arc sprayed Ti and the plasma sprayed Al2O3 coatings showed the least reduction out of the samples tested, followed by a HVOF Ni based coating with 20% Cr. The results overall were most promising for the Ni-20% Cr coating and showed the potential of the Ti and Al2O3 coatings if a sealer could be incorporated as they were porous. Further development of these coatings and others is being continued in a new 3 year project titled Geo-Coat, which received a Horizon 2020 grant and started in February 2018. Further information on this project can be found at http://www.geo-coat.eu/.

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THE GEOTHERMAL AREA OF GRÁUHNÚKAR/MEITLAR

Helga Margrét Helgadóttir, Sigurður Garðar Kristinsson, Steinþór Níelsson, Ásdís Benediktsdóttir and Auður Agla Óladóttir

Iceland GeoSurvey - ÍSOR

The Hengill high-temperature area in SW-Iceland hosts a reinjection site which at the time of drilling proved to have much higher temperature than anticipated. This area is at Gráuhnúkar, in the southwestern section of the Hengill area. The area has, due to its anomalous tempepratures, since been regarded as a potential production area for Reykjavík Energy despite the reinjection.

The evaluation of the geothermal system at Gráuhnúkar and the nearby Meitlar area was therefore requested in order to minimize the risk of well siting. Available data from the area was gathered and compared. The dominating fractures are the NE-SW striking fractures belonging to the Hengill fissure swarm. Other fractures with different strikes have, however, been noted in the landscape, needing further analyses. Resistivity model of the area has been made using a 3D interpretation of MT measurements. The bottom of the low resistivity layer, where high resistivity is noted below, shows where chlorite starts to form and is believed to show the outlines of the geothermal system in Gráuhnúkar-Meitlar.

The depth to the change of low restivity to high resistivity seems to form two ridges, following the contours of the higher parts of the area. The western and the more prominent one has a similar strike to the Hengill fissure swarm in its northern part but the southern part seems to strike N-S, similar to the fracture trend of the South Iceland Seismic Zone (SISZ). However, it is not possible to say beforehand if the resistivity model shows the current temperature regime or if the temperature of the system has changed. In the northern part of the Gráuhnúkar-Meitlar area six reinjection wells and two exploration wells have been drilled. The formation temperature model of the area is based on those wells leaving large unknown areas temperature wise, in the Meitill area in particular.

Temperature in Gráuhnúkar is 260°C at 1000 m b.s. and at the moment regarded as the hottest area. Analyses of alteration minerals in drill cuttings from the wells, compared to the formation temperature, have revealed that the centre of the reinjection area seems to have experienced recent upheating. The area to the east of Gráuhnúkar has, however, experienced cooling and is not feasible for production drilling. The area to the south of the current reinjection area is therefore regarded as a potential site for drilling. The comparing of the data already mentioned has suggested a few feasible drill sites although further studies are recommended. Drilling will reveal if the resistivity model corresponds with the current temperature of the area, i.e. if the area is in equilibrium or not.

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RADIAL WATER JET DRILLING IN GEOTHERMAL

Lies Peters, Holger Cremer, Bob Paap, Hans Veldkamp

Netherlands Organization for applied scientific research TNO

The radial water jet drilling (RJD) technology is a stimulation technique that connects permeable rock structures to the main wellbore by drilling small-diameter laterals into the target formation. RJD has been used for a long time in the petroleum industry and has recently also been considered a promising method in geothermal to enhance performance in low productivity and injectivity wells. After a number of RJD jobs were carried out in geothermal wells in Europe, the value of this technology for geothermal needs to be re-assessed as RJD operations faced a number of challenges. This paper reviews a number of RJD operations and challenges these operations were facing. Our experiences are based on sites in Lithuania, Germany, the Netherlands and France.

Drilling engineering: a number of jobs have serious problems with penetration of the target formation. An obstacle is the completion of the geothermal wells which generally are completed with slotted liners or pre-perforated casing. The absence of cementation for these completions leaves an open annular space that is supposedly difficult to bridge with the coil tubing. Also, the milling process of these completions and the positioning and control of the deflector shoe, particularly in open-hole wells, cause problems. Furthermore, exact positioning of the nozzle and drill path while drilling is impossible at the moment as there are no low-cost measurement tools available for geothermal jobs.

Reservoir lithology and fracture presence: Many geothermal applications are in formations which have low matrix porostiy and are dominated by fracture flow. The formation itself is generally tight and hard to jet and fractures may hamper progress by stopping the jetting process prematurely. In case few, large fractures provide the main flow to the well resulting in a negative skin, RJD cannot improve production much, because the fracture already has the same impact as the radial would have.

Use of chemicals: the addition of chemicals may help the water jet to penetrate into the formation, like for instance acid in carbonate rock. Some geothermal reservoirs contain significant amounts of hardly or non-dissolvable minerals as for example quartzite. These rocks could possibly be treated by new-generation chemicals, but only little practical experience exists with such chemicals. Chemicals may also mobilize minerals that have adverse effects on the reservoir flow characteristics.

Economic challenges: Because many geothermal operators have fewer wells than petroleum operators, technical risks are considered to be more impactful and also the costs per well tend to be higher in geothermal applications.

Analysis of performed RJD operations suggests that the technology needs further developmental steps to become a valuable stimulation tool in geothermal. A number of hypotheses are formulated why RJD faces that many challenges compared to application in the petroleum industry.

The research that led to this paper received funding from European Union’s Horizon 2020 research and innovation programme under grant agreement no. 654662 (SURE) and RVO‘s ‚Renewable Energy‘ programme under project number TEHE117011 (HIPE).

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USING SLIM-WELLS FOR GEOTHERMAL EXPLORATION AND PRODUCTION FOR MINI-GEOTHERMAL DEVELOPMENT

Bjarni Richter, Sverrir Thorhallsson and Thoroddur Sigurdsson

Íslenskar orkurannsóknir (ÍSOR) and Mannvit

Over the last few decades, geothermal development has repeatedly been hampered due to lack of funding when it comes to drilling exploration wells in green geothermal fields. Financial institutions and banks find the risk, at that stage, too high to provide funding. Therefore, the developers have to finance the exploration stage with own assets or find financiers that are willing to take higher risk. Over the last few years, developing agencies have focused on assisting with financing this part of the geothermal development, offering grants and soft loans to bridge the gap.

Normally, when drilling full size wells during the exploration phase, anywhere from 2-6 exploration wells may be needed to confirm, test and measure the resource. This can be extremely costly since each standard geothermal well drilled costs several million USD, not including high infrastructure cost and environmental footprint of large drill rigs. Therefore, the cost of exploration drilling can add up to tens of millions of USD just for the geothermal field to be considered a measured resource.

Using deep slim-wells for the exploration can lower the cost considerably (25-75%). Here, slim-wells are defined as wells drilled with the final diameter of ~ 6” or smaller. Such wells can be drilled with tri cone bit or cored, or combination of both. In general, the smaller the diameter, a smaller drill rig is required, which translates to lower drilling costs, less infrastructure and smaller environmental footprint.

Such slim-wells can be tested. They can provide similar information as the conventional geothermal wells, such as reservoir temperature, chemical composition, gas content as well as information on the hydrothermal alteration and reservoir permeability. If well temperatures are high enough, self-flowing can be initiated and output curves estimated, which can be used to estimate output of larger wells. They may even sustain production over a longer period of time and be utilised as small producers. Drilling slim-wells may benefit the developers in de-risking their projects so that financing of the next steps of development becomes easier and less expensive.

The slimmest well types can be challenging to drill to depths beyond 1500 m and into high temperatures. If an exploration well does not prove the existence of a resource, the investment lost is less with slim-wells than larger diameter wells. If a resource is identified and measured using slim-wells, the risk of further drilling and development will be reduced significantly, simplifying decision making for developers, banks and investors. The slim-wells may serve as monitoring wells during further development and production.

Using deep slim-wells as producers of low productivity is not unheard of and in the proper situation and properly designed they may be used for power generation on a small scale (~0.5-3 MWe). This may be of great interest when developing high temperature geothermal resources close to populated areas that have small power demand and are isolated. A few MWe of production from such geothermal resources can help in de-carbonizing such small communities which often rely on diesel generated energy.

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Book of Abstracts

HORIZONTAL ALIGNMENT OF MANTLE CONVECTION ROLLS

Steingrímur Þorbjarnarson

Nytjar ehf

The main aim of this study is to provide a mathematical base for the study the alignment of mantle convection rolls. Direct and exact coherence is found between the calculated value of convection rolls alignment and tectonics of the crust. The analysis has both vertical and horizontal aspects, and both have been solved to a high degree of accuracy. Using Earth’s radius as the basic length scale for the horizontal point of view, an equation has been derived which, for instance, shows accurate resemblance with the volcanic zones of Iceland.

For horizontal analysis it is found that since inertial motion is the counterpart of a straight, infinitely long, line on a non-rotating plane, it makes sense that on a sphere this motion will only be limited by the radius of the sphere. With uniform velocity of mantle flow, no oscillation is encountered, and the basic length scale is Earth´s radius.

After the convection rolls model had been fully developed, it has been tested by comparing it with features of the Earth’s surface. Iceland provides a good base for this work, due to explicit dynamics of the tectonic framework initiated by mantle flow acting on the tectonic plates. According to the mathematical model here presented, the pulling effect leads to an exact match between calculated alignment of convection rolls on one hand and the volcanic zones on the other hand.

To introduce the results of this analytic work, an exhibition was held at the information center of Ölfus in Iceland July and August this year. It included a model showing the vertical section of upper mantle convection rolls along 64°N, with Hekla and Öræfajökull found at intersection points between mantle rolls, along with the lower mantle division line leading from Ölfus in SW Iceland over to the bay of Skjálfandi at the NE coast. The aim is to clarify further how the western and eastern parts of Iceland are drifting in different directions. For comparison, a map showing the division line between the two tectonic plates of N-America and Eurasia was exhibited.

At the same time, a new website has been launched with the purpose of showing the coherence between convection rolls of the mantle and topography. Some examples were chosen for the exhibition, especially a few Icelandic waterfalls aligned in the same way as the convection rolls. Tourists can therefore have an additional opportunity to enjoy nature, and geologists can compare measured outcomes with calculated values.

A mathematical foundation of geology is a step forward, whereas previously it had to be based primarily on field observation. It takes time to study and evaluate the possibilities it will open for us. Accumulated knowledge can be arranged more systematically, and undiscovered features can be anticipated with the relevant mathematical tools. The possible existence of convection rolls has here been explored in detail, and comparison with geological features in general shows exact match all over the world.

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Book of Abstracts

THE CHEMICAL AND ISOTOPE CHARACTERISTICS OF GEOTHERMAL FLUIDS IN SHANDONG PENINSULA, CHINA

Tingting Zheng123, Andri Stefánsson1, Fengxin Kang3, Haiyang Jiang3, Meng Shi3, Haibo Sui3

1 University of Iceland 2 United Nations University Geothermal Training Programme 3 Shandong Provincial Bureau of Geology and Mineral Resources, China

Utilization of low and medium temperature geothermal fluids is an alternative energy source to fossil fuels and play an increasingly important role in space heating in Northern China. The distribution of the geothermal activity, the fluid chemistry and origin and reservoir temperatures are, however, still largely unexplored.

In order to trace the processes controlling the fluid composition, fluid mixing, fluid origin and reservoir temperatures, major, trace and water isotope analysis were performed for groundwaters (boreholes and springs) in the Shandong area, China.

Based on geochemical relations and modelling, the water composition is controlled mainly by two processes: (1) water-rocks interaction and formation of secondary minerals; (2) variable source waters and mixing between them. Geothermal waters are mainly recharged by modern atmospheric precipitation mixed with seawater with the hydrology controlled by deep faults with NNE strike.

Carbon dating is used to find out the age of geothermal water, which is an important parameter for further hydrogeological studies. F&G model are used with 14C and δ13C data to assess the geothermal water age. The minimum age is around 300 years, while the maximum is around 9000 years. However, this model hasn’t considered seawater mixing in the system. So the next work is taking seawater effect into account and find out more accurate water ages.

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Book of Abstracts

STATISTICAL VALIDATION METHOD OF THERMAL RESPONSE TESTS - HORIZONTAL SERPENTINE, SAN LUIS, ARGENTINA

Eng. STEFANINI Valentín Antonio

Universidad Nacional de San Luis - Argentina

This work was carried out in order to apply a statistical comparison between calibrated lines corresponding to two Thermal Response Tests in situ (TRT), substantially different in design, place and time. Also, a statistical method for comparing straight slopes was used, based on the analysis of variance homogeneity.

That is, for the validation of the results obtained from a TRT of a particular horizontal exchanger, with respect to a conventional vertical exchanger, a mathematical model especially designed was applied to the latter.

In San Luis, Argentina, a horizontal particular exchanger was developed and tested by applying the Kelvin infinite line source model (ILS). From this model, the coefficient of effective subsurface conductivity λeff and thermal resistance of soil Rb were determined by the graphical method of the slope.

This raised a discussion about the reliability of the results obtained from the test mentioned previously. Due to this, in this work a statistical comparison method of slope of calibration lines is applied to the slopes obtained in the TRT tests; this method was conceived by the author.

The reference straight line corresponds to a TRT, made at the National University of the Northeast (UNNe) Argentina, which is a standard vertical exchanger, and is compared with a straight line obtained from a particular horizontal exchanger, made at the National University of San Luis (UNSL) Argentina. The latter was embedded in the middle of a cement block of 15 cm of thickness of an existing excavation. The lower part of the block is in the subsoil and the upper part contains water from a pool; these characteristics make the exchanger different.

First an “F” test is carried out to determine if the variances are homogeneous or not, and then a “t” test determines the similarity of the slopes.

The “F” test establishes that the variances of the slopes are not homogeneous.

The “t” test for inhomogeneous variances, and with probabilities of 95%, 97.5%, and 99%, determines that the slopes of both straight lines are different.

The same “t” test for 99.5% defines similar slopes.

These results establish that the method used in the particular horizontal exchanger to obtain the effective coefficient of heat transfer of soil is valid.

The particular horizontal exchanger was considered as a black box, where the faithful reflection of its behavior is given by the temperatures of entry and exit, that is to say that all the factors that can influence it are given by these temperatures. The method used here for the evaluation of non-conventional exchangers yields acceptable results for the design of a commercial venture. In other words, and in this sense, it is not the same to start from laboratory parameters than from parameters obtained from a TRT in situ.

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Book of Abstracts

TEST OF THERMAL RESPONSE “IN SITE” OF A HORIZONTAL SERPENTÍN SAN LUIS – ARGENTINA

Eng. STEFANINI Valentín Antonio

Universidad Nacional de San Luis - Argentina

The objective is to describe a Thermal Response Test (TRT) “in situ”, obtaining values of the effective thermal conductivity of the subsoil λeff, and the thermal resistance of the borehole of Rb, corresponding to a horizontal system of particular heat exchanger, made in San Luis Argentina.

This “in situ” test was based on the model of the infinite line source (ILS), and the solution to it was made by the graphical method of the slope, which uses the expression of the evolution of the average temperature of the working fluid, as a function of the time (t) and the borehole radius (r), around a linear heat source of constant power (Q) that can be assumed equal to the power of the BHE. Therefore, the thermal conductivity (λeff) is determined based on the slope (k) depending linearly on the medium temperature of the fluid as a function of the natural logarithm of time. (Kun Sang Lee, 2013).

The investigation determined the subsoil characteristics, not registered in the region, of the asymmetric horizontal coil, from the model for symmetric vertical exchangers (Eklöf C, Gehlin S., 1996).

TEST

An excavation for swimming pool (4.5 x 2.3 x 1.5) meters was used. On the 7.5 cm concrete floor, an effective 23.36 m long serpentine was placed PEAD φ ¾¨ K6 pipe suitable for water, holding it to a metal mesh and filling it with a 7.5 cm layer of concrete without additives.

An insulated expansion tank is placed with a solution of 100 litters of water with two litters of glycol, electrical resistance, circulation pump and measuring instruments.

The test begins on 04/19/2013 “without thermal disturbance”, determining the undisturbed subsoil temperature, Tsur = 21.65 ºC.

On 04/20/2013, the (TRT) began with disturbance. With a duration of 73 hours, culminating on 04/23/2013. The data collection was done manually every 10 minutes, with 818.9 watts of average power, 0.00042 (m3 / sec) of circulating flow. The data is loaded into a spreadsheet and processed.

Time criterion, 9 hours, starting point for evaluating the average temperature of the fluid according to the natural logarithm of time.

Obtained the value of λefec, we calculate the thermal resistance of the borehole Rb (ºK / (W / m)).

RESULTS TRT SAN LUIS ARGENTINA

α: Thermal diffu-sivity concrete

(m2/seg)Criterion time Slope

kλeff

(W/m*ºK)Rb

(K / (W/m))

0,91x10-6 Total 1,97 1,42 0,1170,91x10-6 9 hs 2,28 1,23 0,087

CONCLUSION

The λeff, obtained is the reflection of the proposed asymmetric system.

How correct is it? Then it was compared visually with respect to TRT worldwide, observing very similar results.

Applying a fast and economical method for the evaluation of unconventional exchangers, we obtain acceptable results for a commercial enterprise. That is to say, it is not the same to start from laboratory parameters, then those obtained from a TRT “in situ”.

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Book of Abstracts

Name Affiliation Country

Aðalsteinn Möller Veitur IcelandAlbert Albertsson HSOrka IcelandAmanda Kolker AK Geothermal FranceAndri Arnaldsson Vatnaskil IcelandAndri Isak Thorhallsson University of Iceland IcelandAnette Kærgaard Mortensen Landsvirkjun IcelandAngel Monroy Iceland School of Energy IcelandAri Ingimundarson Mannvit IcelandÁrni Ragnarsson ISOR IcelandÁsgerður K. Sigurðardóttir Landsvirkjun IcelandÁsgrímur Guðmundsson. Landsvirkjun IcelandAuður Andrésdóttir Mannvit IcelandBaldur Pétursson Orkustofnun IcelandBergur Sigfússon Reykjavik Energy IcelandBeth House Natural Environment Research Council United KingdomBirgit Woods Geosoft United KingdomBjarni Gautason ISOR IcelandBjarni Pálsson Landsvirkjun IcelandBjarni Reyr Kristjánsson Reykjavik Energy IcelandBjarni Richter ISOR IcelandCari Covell Reykjavik University IcelandCarsten Sørlie Equinor ASA NorwayCécile Ducrocq Universtiy of Iceland IcelandChagaka Kalimbia Iceland School of Energy IcelandCyril Lemaire University of Iceland IcelandDaði Sveinbjörnsson Landsvirkjun IcelandDagný Hauksdóttir ON Power IcelandDario Ingo Di Rienzo University of Iceland IcelandDarri Eyþórsson University of Iceland IcelandDawnika Blatter U.S. Geological Survey USADiego Badilla University of Iceland IcelandDieu Linh Pham UNU GTP IcelandDominic Scott University of Iceland IcelandDost Alper Tunga SUEZ WTS TurkeyDr. Juliet Ann Newson Iceland School of Energy IcelandEdda Sif Aradóttir Reykjavik Energy IcelandEgill Júlíusson Landsvirkjun IcelandEgill Maron Thorbergsson EFLA Consulting Engineers IcelandElif Kaymakci EnBW GermanyElvar Bjarkason University of Auckland New ZealandEmmanuelle Piron POLE AVENIA / GEO-ENERGY EUROPE FranceEnikö Bali University of Iceland IcelandErlingur Geirsson Landsvirkjun IcelandEsteban Gomez Iceland School of Energy IcelandFinnbogi Óskarsson ISOR IcelandFreysteinn Sigmundsson University of Iceland IcelandGabriella Skog Climeon SwedenGaud Pouliquen Geosoft United KingdomGeir Þórólfsson HSOrka IcelandGeoffrey Mibei University of Iceland IcelandGetenesh Hailegiovgis University of Iceland Iceland

List of Attendees

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Book of Abstracts

Gifty Oppong University of Iceland IcelandGreg Thompson Tuaropaki Trust New ZealandGrimur Bjornsson Warm Arctic IcelandGuðjón Helgi Eggertsson HSOrka IcelandGuðmundur Kjartansson ON Power IcelandGuðmundur Ómar Friðleifsson HSOrka IcelandGuðni A. Jóhannesson Orkustofnun IcelandGuðný Inga Ófeigsdóttir University of Iceland IcelandGunnar Gunnarson Reykjavik Energy IcelandGunnar S. Kaldal ISOR IcelandGunnar Þorsteinsson HSOrka IcelandGunnlaugur Brjánn Haraldsson ON Power IcelandHalldór Geirsson University of Iceland IcelandHalldóra Guðmundsdóttir Stanford University USAHanna Blanck University of Iceland IcelandHans Benjamínsson Pirate Party Iceland IcelandHarpa Þ Pétursdóttir Orkustofnun IcelandHeimir Hjartarson EFLA Consulting Engineers IcelandHelga Margrét Helgadóttir ISOR IcelandHjalti Franzson ISOR IcelandHjalti Páll Ingólfsson GEORG IcelandHolger Cremer TNO NetherlandsIngólfur Þorbjörnsson ISOR IcelandIngvi Gunnarsson Reykjavik Energy IcelandIrene Ronoh Iceland School of Energy IcelandIsabella Nardini GZB-International Geothermal Centre GermanyJan Prikryl University of Iceland IcelandJean-Claude Berthet Vatnaskil IcelandJenny Russe University of Bristol United KingdomJohan Sindri Hansen Jurt Hydroponics IcelandJóhann Mar Ólafsson Iceland School of Energy IcelandJohn Eichelberger University of Alaska Fairbanks USAJohn Ludden British Geological Survey United KingdomJónas Ketilsson Orkustofnun IcelandKatarzyna Kurek Wageningen University of Research BelgiumKatherine Young NREL - National Renewable Energy Lab. USAKeith O’Nion British Geological Survey United KingdomKiflom Gebrehiwot Mesfin HSOrka IcelandKnútur Árnason ISOR IcelandKristín Vala Matthíasdóttir HSOrka IcelandKristinn Ingason Mannvit IcelandKristján Einarsson Landsvirkjun IcelandKunzes Dolma Iceland School of Energy IcelandLárus Þorvaldsson Vatnaskil IcelandLéa Lévy ISOR IcelandLilja Dögg Alfreðsdótir Minister of Education, Science and Culture IcelandLilja Kjalarsdóttir SAGA NATURA IcelandLilja Magnúsdóttir University of Iceland IcelandLilja Tryggvadóttir Mannvit IcelandLuis Fourzan Iceland School of Energy IcelandMagnús Þór Jónsson University of Iceland IcelandMaría Guðjónsdóttir Reykjavik University IcelandMaría Guðmundsdóttir Orkustofnun IcelandMariane Peter-Borie BRGM FranceMarit Brommer International Geothermal Association NetherlandsMehmet Pekyavas University of Iceland IcelandNataly Castillo Iceland School of Energy Iceland

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Ólafur Dan Snorrason Orkustofnun IcelandÓlafur G Flóvenz ISOR IcelandÓlafur Pétur Pálsson University of Iceland IcelandÓlafur Sverrisson Landsvirkjun IcelandÓli Grétar Blöndal Sveinsson Landsvirkjun IcelandOlivera Ilic Landsvirkjun IcelandPálmar Sigurðsson Reykjavik Energy IcelandPhilippe Pézard CNRS FranceR. Morgan Greene Iceland School of Energy IcelandRagnar Atli Tómasson Jurt Hydroponics IcelandRagnheidur Thorarinsdottir Samrækt ehf IcelandRandy Normann On Measurement 4U USARebecca Anne Jones University of Iceland IcelandRossano Capocecera CHIMEC ItalyRune Godøy Equinor ASA NorwaySæmundur Guðlaugsson ON Power IcelandSæunn Halldórsdóttir ISOR IcelandSam Barton University of Reykjavik IcelandSamuel Scott Reykjavik University IcelandSandra Ósk Snæbjörnsdóttir Reykjavik Energy IcelandShahin Partovi SUEZ WTS United KingdomSigríður Kristjánsdóttir ISOR IcelandSigrún Karlsdóttir University of Iceland IcelandSigrún Tómasdóttir Reykjavik Energy IcelandSigurður Björnsson Rannis IcelandSigurður Brynjólfsson University of Iceland IcelandSigurður G. Bogason GEORG IcelandSigurður H. Markússon Landsvirkjun IcelandSigurður Magnús Garðarsson Universtiy of Iceland /GEORG IcelandSigurður Tómas Björgvinsson GEORG IcelandSimon Klüpfel Reykjavik Energy IcelandSnæbjörn Sigurðarson EIMUR IcelandSteinar Örn Jónsson Landsvirkjun IcelandSteingrímur Þorbjarnarson Nytjar ehf IcelandSteinþór Níelsson ISOR IcelandSteinunn Hauksdóttir ISOR IcelandStuart Daniel James University of Iceland IcelandSturla Sæther Equinor ASA NorwaySunna Guðmundsdóttir EIMUR IcelandSunna Ólafsdóttir Wallevik Gerosion IcelandSveinborg H Gunnarsdóttir ISOR IcelandTatiana Pyatina Brookhaven National Laboratory USAThomas Ratouis Reykjavik Energy IcelandTomasz Urban GEORG IcelandÞorbjörg Ágústsdóttir ISOR IcelandTingting Zheng University of Iceland IcelandVala Hjörleifsdóttir Reykjavik Energy IcelandValentín Stefanini Universidad Nacional de San Luis ArgentinaVantar nafna lista…. Reykjavik Energy IcelandVedran Zikovic Iceland School of Energy IcelandVictoria Nyaga Iceland School of Energy IcelandVigdís Harðar ISOR IcelandVijay Chauhan Reykjavik University IcelandVincent Drouin University of Iceland IcelandWilfred Elders University of California USAWinnie Apiyo Iceland School of Energy IcelandYixi Su University of Iceland IcelandZhiqian Yi University of Iceland Iceland

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Best Poster Award

Hanna BlanckPhD Student at University of Iceland

winner of the GGW2018 Best Poster Award (Geothermal Rockstar!)

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We thank our team of volunteers who made sure to guide you throughout the workshop whether at the registration desk, or making sure your presentations are uptodate or accompagnying you during our social activities. All of them are aspiring geothermal experts and we wish them all the best!

Registration Desk Team

Technical Team

Social Activities Team

Volunteers

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We sincerely thank you all for your participation in this 2nd edition of the GEORG Geothermal Workshop. Not only have you contributed valuably in bringing forward the geothermal research and innovation, but also made a positive impact to the environment by helping us go paper-free (using the app) and waste-free (returning your badges)! GEORG is committed to environmentally-friendly ethics, and thanks to your collaboration, all returned material will be dutifully recycled.

Thank you!

www.wgc2020.com

Book of Abstracts