Grant agreement No. 640979

ShaleXenvironmenT

Maximizing the EU shale gas potential by minimizing its environmental footprint

H2020-LCE-2014-1

Competitive low-carbon energy

D2.2 Reservoir conditions for rock library samples

WP 2 – Shale Core Acquisition and HTHP Handling Capabilities

Due date of deliverable Month 12 – September 2016 Actual submission date 31 / 08 / 2016 Start date of project September 1st 2015 Duration 36 months Lead beneficiary Halliburton Last editor Nils Backeberg (UCL) Contributors UCL, Halliburton, UoM, ARMINES Dissemination level Public (PU)

This Project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement no. 640979.

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History of the changes

Version Date Released by Comments

1.0 16-08-16 Nils Backeberg First draft circulated internally to WP2 members

1.1 22-08-16 Nils Backeberg Proposed final version circulated to the consortium

1.2 31-08-16 Nils Backeberg, Pauline Chetail

Final version compiling comments from the consortium

Table of contents Key word list ...................................................................................................................... 3

Definitions and acronyms ................................................................................................. 3

1. Introduction .......................................................................................................... 4

1.1 General context .......................................................................................... 4

1.2 Deliverable objectives ................................................................................ 4

2. Methodological approach ..................................................................................... 5

3. Summary of activities and research findings ........................................................ 6

4. Conclusions and future steps ................................................................................ 9

5. Publications resulting from the work described ................................................... 9

6. Bibliographical references................................................................................... 10

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Key word list Shale rock library

European shale gas basins

Pressure – Temperature conditions

Total organic carbon range

Maturity range

Exploration target areas

Definitions and acronyms

SXT ShaleXenvironmenT European Consortium

UCL University College London

HB Halliburton

PTx Pressure – temperature – composition

TOC Total organic carbon, measured in volume percent (%)

Ro Vitrinite reflectance (%); measure of thermal maturity

Tcf Trillion cubic feet (for gas reservoir estimates)

MPa Mega pascal (pressure)

EIA U.S. Energy Information Administration

BGS British Geological Survey

USGS United States Geological Survey

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1. Introduction

WP2 has the main task of providing shale core samples for experimental characterization. The specific objectives as part of WP2 include:

1. Provide shale rock samples (some at reservoir pressure) for scientific research;

2. Develop capability for laboratory exchange and analysis of pressurised samples recovered from depth;

3. Provide pressure temperature composition (PTx) properties of shale rocks under reservoir conditions to be used in physical, chemical, thermodynamic models, and mechanical experiments.

1.1 General context

Deliverable D2.2 reports the reservoir conditions for rock library samples, which will be expanded to cover all European basins with shale gas potential (deliverable D2.3 – month 36). We report pressure and temperature data for prospective shale gas areas in Europe, based on promising thermal maturity (Ro) and total organic carbon (TOC) ranges. The data is reported from publically available reports and publications (see list of references), world shale resource assessment by the U.S. Energy Information Administration (EIA) and United States Geological Survey (USGS), and down-hole measurements and in-house research by Halliburton (HB).

1.2 Deliverable objectives

The report provides PTx conditions of the shale rock library under evaluation by SXT. The current rock library of European shale rocks held by the SXT consortium, covers the Bowland Shale in the UK, one of the primary shale gas exploration targets in Europe. PTx data is documented for the Bowland Shale in this report. We include PTx data for other European shale rock basins, which forms part of the final D2.3 PTx report on all European shale rocks.

The PTx conditions form the basis parameters input into experiments, technical analyses and models, covered by the SXT research consortium.

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2. Methodological approach

Various shale gas basins are located across Europe. In contrast to the North American shale gas plays, European sedimentary basins have experienced more tectonically active basins throughout their geological history. This imposes a more complex structural environment of overprinting geological events that have affected the shale rocks under exploration.

We identified the main shale gas plays and their depth under exploration or with exploration potential (Figure 1) and have researched each basin in publically available reports and publications to identify shale gas potential areas (Table 1). The temperature conditions we report for these areas are estimates for their depth range, using a continental a geothermal gradient of approximately 23°C/km with a surface temperature of 16°C. Similarly, for reservoir pressure we use a hydrostatic gradient of 0.433psi/foot (value taken from EIA), which converts to approximately 9.8 MPa/km. In addition, HB has provided in-house research and down-hole pressure – temperature measurements.

Figure 1: Map of Europe showing shale rock sedimentary basins (yellow) with shale gas potential areas highlighted in colour. Colour represents the age of the shale gas play (blue – Jurassic, red – Carboniferous, green – Cambrian to Silurian).

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3. Summary of activities and research findings

This report is a desktop research study covering European shale gas basins. The findings are meant as a guide to outline potential shale gas regions and provide pressure and temperature estimates and measurements for depths that fall within the range of shale gas plays. The pressure-temperature conditions reflect present day conditions and are not maximum burial and maturity conditions experienced by the shale gas plays.

The prospective areas shown in Figure 1 correlate with the thermal maturity range of the gas window (Ro = 0.9 to 3.0 %) that each basin experienced preserved through its geological history, as well as an economic cut-off of greater than 2% average TOC for shale plays with a thickness greater than 100 feet (approximately > 30 m). The TOC and thermal maturity data from published reports reflect borehole samples analysed within the prospective regions. These are extrapolated together with geophysical studies (where available) to show the extent of potential shale gas plays (coloured areas in Figure 1). Pressure and temperature data in the Halliburton rows (Table 1) are downhole measurements from samples with gas potential and are a reference of comparison to standard condition estimates.

It is important to note that the complete range and heterogeneity of each individual basin is not represented in this report, but we have researched the broad available literature in order to summarise representative values and ranges for each region. We emphasise that the findings of this report are to be used as a starting point and guide for further research of the individual basins of interest.

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Table 1: Summary of European shale gas plays with present day temperature and pressure estimates and measurements for selected depths within play range.

Table 1: continued.

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The results and findings of shale rock basins are summarised in Table 1. The table includes a brief summary of the basin location and prospective region, which are shown on the map in Figure 1. The literature review rows in Table 1 include research articles and survey reports and we present data for the Bowland Shale, Midland Valley Basin and Alum Shale. The other European shale rocks are under review and form part of the final PTx report (D2.3).

The Bowland Shale has a broad range in depth and thickness that differs between research reports. The average depth from the EIA database falls within a range of 5000 – 13000 feet, much deeper than the average depth used in the pressure and temperature calculation in the “estimates” rows (Table 1). This is because the EIA includes the Hodder mudstone formation, a much thicker unit that lies beneath the Bowland Shale Group. The Hodder mudstone is also prospective for shale gas, but due to less drilling penetrating this deep unit, exploration and resource estimations have focussed on the better constrained Bowland Shale, also referred to as the “upper Bowland-Hodder unit” by Andrews (2013). The Midland Valley Basin in Scotland is a time and tectonic equivalent basin to the Bowland Shale, but has experienced longer post burial exhumation, which resulted in the significantly shallower occurrences of shale gas mature plays (see Table 1). The temperature measured for the Paris basin from the Halliburton data is approximately 30°C higher than the estimate based on the geothermal gradient of 23°C/km, due to a geothermal system in the region elevating the gradient to 35°C/km.

Table 1 excludes the compositional variable (x). This is due to the broad heterogeneity of shale rock units and the potential implications to shale gas prospectivity associated with the mineralogy with respect to “brittleness”. Shale rocks are typically characterised by their clay content, contrasted against quartz, feldspar, pyrite and carbonate contents. High clay content shales have a lower brittleness due to the more ductile behaviour of clays compared to the other shale-rock-forming minerals. The published shale gas reviews by EIA characterise the basins by clay contents of “low, medium or high”. As a rule of thumb, ranges of clay volume percentages can be considered as 5 – 10% (low), 10 – 30% (medium) and 30 - 60% (high), however other petro-physical factors will also affect the overall brittleness of shale rocks. For the Bowland Shale, EIA reports a “medium” clay content and reports by the British Geological Survey (BGS) indicate high (50 – 60%) clay contents. Samples collected from the BGS as part of the SXT research program from drill core of the Bowland Shale, have been characterised predominantly by low clay contents of 6 – 8%. These results are still an ongoing study and further classification will help define the compositional variations and characteristics of European shale rocks.

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4. Conclusions and future steps

European shale gas plays cover a broad range in geological environments from Carboniferous continental shelf, to intracontinental Carboniferous basins during the super continental Pangaea, and to Jurassic continental rift basins associated with the break-up of Pangaea. All of these basins are then further affected by Alpine tectonics, complicating the structural history. Within this geological setting, Europe has preserved potentially large recoverable shale gas plays with a varied geological history leading to a broad range in pressure, temperature and compositional characteristics, which are simplified and summarised in Table 1.

The data for the Bowland Shale of the United Kingdom will be incorporated into the experiments and computational models by the SXT European consortium. Characterisation of SXT shale rock samples will contribute to this database for better constraints on compositional ranges. The data table will be expanded throughout the course of the SXT project to incorporate and fully represent all European shale rock basins, to be delivered in the following report (D2.3).

5. Publications resulting from the work described

This data compilation will feed into all sample and basin specific publications.

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6. Bibliographical references

1 Andrews, I.J. 2013. The Carboniferous Bowland Shale gas study: geology and resource estimation. British Geological Survey for Department of Energy and Climate Change, London, UK.

2 Andrews, I.J. 2014. The Jurassic shales of the Weald Basin: geology and shale oil and shale gas resource estimation. British Geological Survey for Department of Energy and Climate Change, London, UK.

3 Bharati et al. 1995. Elucidation of the Alum Shale kerogen structure using a multi-disciplinary approach. Organic Geochemistry, 23 (11/12), 1043 – 1058.

4 Department of Energy and Climate Change, 2012. The unconventional hydrocarbon sources of Britain’s onshore basins – shale gas.

5 Ghanizadeh, A. et al., 2014. Experimental study of fluid transport processes in the matrix system of the European organic-rich shales: I. Scandinavian Alum Shale. Marine and Petroleum Geology, 51, 79 – 99.

6 Nielson, A. T., et al., 2011. The Lower Cambrian of Scandinavia: Depositional environment, sequence stratigraphy and palaeogeography. Earth-Science Reviews, 107, 207 – 310.

7 Monaghan, A.A. 2014. The Carboniferous shales of the Midland Valley of Scotland: geology and resource estimation. British Geological Survey for Department of Energy and Climate Change, London, UK.

8 Pawlewicz, M.J. et al., 2000. Map showing geology, oil and gas fields, and geologic provinces of Europe including Turkey. U. S. Geological Survey, open file report 97-470I

9 Stampfli, G. M., et al. 2013. The formation of Pangea. Tectonophysics, 593, 1 – 19.

10 Thickpenny, A. 1984. The sedimentology of the Swedish Alum Shales. Geological Society, London, Special Publications, 15, 511– 525.

11 Thickpenny, A. 1987. Palaeo-oceanography and depositional environment of the Scandinavian Alum Shale: Sedimentological and geochemical evidence. Chapter 8 in: Marine Clastic Sedimentology (Eds. Legget J. K. and Zuffa G. G.), 156 – 171.

12 Underhill, J.R. et al., 2008. Controls on Structural Styles, Basin Development and Petroleum Prospectivity in the Midland Valley of Scotland. Marine and Petroleum Geology, 25, 1000-1022.

13 U.S. Energy Information Administration (EIA), September 2015. Technically recoverable shale oil and shale gas resources: United Kingdom. www.eia.gov

14 Waters, C.N. et al., 2007. Lithostratigraphical framework for Carboniferous successions of Great Britain (Onshore). British Geological Survey Research Report, RR/07/01/ 60pp.