Carbon Dioxide—Challenges and Opportunities/media/Files/resources/oilfield_review/ors15/sept15/... · September 2015 37 Carbon, one of the two constituents of carbon dioxide [CO

36 Oilfield Review

Carbon Dioxide—Challenges and Opportunities

In the early days of the oil and gas industry, companies noted that carbon dioxide had

corrosive effects on well internals; operators later found opportunities to use the

compound to their advantage. Projects now underway in the oil field reflect several

priorities—managing carbon dioxide’s corrosive effects, using it to recover more oil

after waterflood and storing it in underground formations. Because of its role in

climate change, carbon dioxide has emerged as a topic of significant public interest

and scientific investigation as well as the focus of hydrocarbon producers.

Mehdi AnsarizadehCalgary, Alberta, Canada

Kevin DoddsAustralian National Low Emissions Coal Research and DevelopmentCanberra, Australian Capital Territory, Australia

Omer GurpinarLawrence J. PekotDenver, Colorado, USA

Ülker KalfaSecaeddin S‚ahinSerkan UysalTurkish Petroleum CorporationAnkara, Turkey

T.S. RamakrishnanCambridge, Massachusetts, USA

Norm SacutaPetroleum Technical Research CentreRegina, Saskatchewan, Canada

Steve WhittakerCommonwealth Scientific and Industrial Research OrganisationPerth, Western Australia, Australia

Oilfield Review 27, no. 2 (September 2015).Copyright © 2015 Schlumberger.

Carbon dioxide is in the news. Whether because of the link to climate change and its consequences or for the concept of long-term storage, carbon diox-ide has captured the interest of the public and the global scientific community.1 The oil and gas indus-try has a long history of addressing the effects of

this compound, ranging from studies of carbon dioxide–methane hydrates in the 1940s to current studies on corrosion.2 Although anthropogenic—human-generated—carbon dioxide plays a nega-tive role in climate change, its role is positive in enhanced oil recovery (EOR).

Figure 1. Carbon dioxide phases. Phase boundary lines (blue) define the areas in which each CO2 phase exists. At the triple point, all three phases—solid, liquid and gaseous CO2—coexist in thermodynamic equilibrium. Along the solid-gas line below the triple point, CO2 sublimes—converts directly—from a solid to a gas without going through a liquid phase. The marked sublimation point corresponds to 0.101 MPa [14.7 psi] of CO2 vapor. Along the solid-liquid line above the triple point, solid CO2 melts to a liquid. Along the liquid-gas line above the triple point, liquid CO2 evaporates to a gas. At the critical point, the liquid and gaseous states of CO2 are indistinguishable, and phase boundaries no longer exist. These attributes at the critical point and at higher temperature and pressure characterize the area in which CO2 is a supercritical fluid (green). (Adapted with permission from Bassam Z. Shakhashiri, University of Wisconsin–Madison, USA.)

CO2 solid CO2 liquid

CO2 gas

Pres

sure

, MPa

Temperature, °C

Sublimationpoint

Triple point,–56.6°C, 0.519 MPa

Critical point,31.1°C, 7.37 MPa

CO2 supercriticalfluid

0.0001

0.001

0.01

0.1

1.0

10

–120–140 –100 –80 –60 –40 –20 0 20 40 60 80 100

100

Liquid and gas

Solid

and g

as

Solid

and

liquid

Oilfield Review SPRING 15CO2 Fig 1ORSPRNG 15 CO2 1

1. Zimmer C: “Ocean Life Faces Mass Extinction, Broad Study Says,” The New York Times (January 15, 2015), http://www.nytimes.com/2015/01/16/science/earth/study-raises-alarm-for-health-of-ocean-life.html (accessed January 15, 2015).

Fountain H: “Turning Carbon Dioxide Into Rock, and Burying It,” The New York Times (February 9, 2015), http://www.nytimes.com/2015/02/10/science/burying-a-mountain-of-co2.html (accessed June 1, 2015).

Cannell M, Filas J, Harries J, Jenkins G, Parry M, Rutter P, Sonneland L and Walker J: “Global Warming and the E&P Industry,” Oilfield Review 13, no. 3 (Autumn 2001): 44–59.

2. Unruh CH and Katz DL: “Gas Hydrates of Carbon Dioxide–Methane Mixtures,” Journal of Petroleum Technology 1, no. 4 (April 1949): 83–86.

Choi Y-S, Young D, Nešic S and Gray LGS: “Wellbore Integrity and Corrosion of Carbon Steel in CO2 Geologic Storage Environments: A Literature Review,” International Journal of Greenhouse Gas Control, 16S (January 2013): S70–S77.

3. “Global Ecology—Understanding the Global Carbon Cycle,” Woods Hole Research Center, http://whrc.org/global/carbon/ (accessed January 15, 2015).

Falkowski P, Scholes RJ, Boyle E, Canadell J, Canfield D, Elser J, Gruber N, Hibbard K, Högberg P, Linder S, Mackenzie FT, Moore B III, Pedersen T, Rosenthal Y, Seitzinger S, Smetacek V and Steffen W: “The Global Carbon Cycle: A Test of Our Knowledge of Earth as a System,” Science 290, no. 5490 (October 13, 2000): 291–296.

4. Riebeck H: “The Carbon Cycle,” NASA Earth Observatory, http://earthobservatory.nasa.gov/Features/CarbonCycle/ (accessed January 15, 2015).

5. Riebeck, reference 4.

September 2015 3737

Carbon, one of the two constituents of carbon dioxide [CO2], is an essential element on Earth. The mass of carbon on Earth is 5.37 × 1016 kg [11.83 × 1016 lbm], which is distributed among several reservoirs: the Earth’s atmosphere; plants; animals; soil; minerals; the shallow and deep ocean; and coal, oil and gas.3 The movement of carbon between these reservoirs—the carbon cycle—maintains a balance between carbon in the atmosphere and in the ocean and rocks.4 This cycle has two components: a slow cycle that takes 100 to 200 million years to move carbon between the oceans, soil, rock and the atmosphere and a fast cycle that takes 50 to 100 years to move car-bon through the biosphere.

Historically, the carbon cycles have resulted in a nearly constant level of carbon in the atmo-sphere, but that is changing. Current data point to deforestation and combustion of fossil fuels as

prime causes for changes in the fast carbon cycle.5 Plants, trees and microscopic marine plants are important components of the fast car-bon cycle. During decay, burning and consump-tion of these life forms, carbon, present as CO2, is released and accrues in the atmosphere. Similarly, much of the CO2 from anthropogenic activities also accumulates in the atmosphere. Plants and the oceans absorb about 55% of this anthropogenic CO2, but the rest stays airborne. Scientists attribute persistent changes in the composition of the atmosphere, such as the increasing CO2 content, to be an important driver of climate change.

The role of CO2 in climate change is signifi-cant, but the compound has a different function in the oil and gas industry. Carbon dioxide can be captured and stored in depleted reservoirs,

which helps arrest atmospheric accumulation. For EOR, CO2 enables increased yield from oil fields after primary recovery and waterflood. This article discusses and illustrates these aspects of CO2, its effect on climate change and its role in the oil and gas industry. Examples from oil and gas fields in Canada, Algeria and Turkey demon-strate the use and storage of carbon dioxide.

Carbon Dioxide CharacteristicsCarbon dioxide, a molecule that consists of two oxygen atoms covalently bonded to a single carbon atom, has a molecular weight of about 44 g/mol. Depending on temperature and pressure, CO2 can exist as a solid, liquid or gas (Figure 1). At tem-peratures and pressures at or above the critical point, CO2 is a supercritical fluid, which has some properties of a gas and some of a liquid. As a super-critical fluid, CO2 develops miscibility—the ability

Oilfield Review SPRING 15CO2 Fig OpenerORSPRNG 15 CO2 Opener

PhotosynthesisPhotosynthesis

Plantrespiration

Plantrespiration

Anthropogeniccarbon

Anthropogeniccarbon

Soil carbonSoil carbon

Ocean sediment carbonOcean sediment carbon

DecompositionDecomposition DecompositionDecompositionPhotosynthesisPhotosynthesis

CO2CO2

CO2CO2

CO2CO2

CO2CO2 CO2CO2O2COCCOCOCO2OO22

Year

Tem

pera

ture

cha

nge,

°F

1890

0

1

2

1920 1950 1980 2010

38 Oilfield Review

to mix homogeneously—with crude oil and improves oil recovery.

Carbon dioxide is stable in the atmosphere. Its concentration in the atmosphere depends on competing processes within the carbon cycles that consume or release CO2. Photosynthesis is one chemical reaction that involves CO2. During photosynthesis, plants, algae, ocean plankton and certain types of bacteria use light energy to convert CO2 and water to oxygen, carbohydrates and water.6 Each year, more than 10% of the atmo-spheric CO2 is reduced to carbohydrates by pho-tosynthesis. Plants, algae and plankton use carbohydrates for growth whereas animals, including humans, use it as an energy source.

Carbon dioxide may be produced in several ways. Natural sources of CO2 production include plant and animal respiration and decay, fires and volcanic release. Anthropogenic sources include fossil fuel combustion and certain manufacturing activities, including cement and ammonia produc-tion, natural gas processing and petrochemical manufacturing. Humans release CO2 indirectly through deforestation.7

Carbon dioxide may undergo several reac-tions of interest in the oil field. For example, dis-solved in water, CO2 forms carbonic acid [H2CO3] and other H2CO3 analogs.8 The CO2 may also react with the minerals of the reservoir; in carbonate reservoirs, the reaction can be relatively rapid

while in silicate reservoirs, the reactions are gen-erally much slower. These reactions may result in some of the CO2 being mineralized and perma-nently trapped.9

Another important set of reactions involving CO2 is associated with corrosion. Carbon dioxide may be corrosive or noncorrosive depending on the materials employed, temperature at the con-tact surface, water vapor concentration and CO2 partial pressure. The most likely metal to corrode is carbon steel in storage environments and cas-ing and tubular steel in wells. At a moderate pres-sure of 1.0 MPa [145 psi], the corrosion rate of X65 pipeline steel is independent of temperature from 50°C to 130°C [120°F to 270°F].10 Increasing water concentration, on the other hand, causes a significant increase in corrosion for steel. For example, at a pressure of 8 MPa [1,160 psi] and a temperature of 40°C [104°F], increasing the water concentration in supercritical CO2 from 1,000 to 10,000 parts per million (ppm) causes the corrosion rate of steel to increase by 87%.11 Similarly, for carbon steel in aqueous CO2 solu-tions at 25°C [77°F], increasing the CO2 partial pressure from 0.1 MPa [14.5 psi] to 1 MPa pro-duces a corrosion rate increase of about 450%.12

Another potential area of concern for oilfield operators is the effect of CO2 on cement in wells.13 Carbon dioxide saturated with water deteriorates the cement used in wells. This dete-rioration can occur in cement that is adjacent to the well casing either in the annulus between the casing and rock or at the interface between the casing and a cement well plug (Figure 2).14 Therefore, the cement used in CO2 injection wells must be able to resist the damaging effects of CO2 because operational periods can last from 25 to 100 years and mandated safety periods that last much longer. For wells to reach these time objectives intact, using additives that make the cement more resistant to harm from CO2 may be advantageous. Reaction of CO2 with wellbore cement is slow in a well in which good construc-tion practices and appropriate materials were used; in these cases, CO2 should not pose a prob-lem. Many old, abandoned wells—completed and shut in using practices and cement accept-able at the time—are not suitable to use in long-term CO2 storage systems. Leakage from abandoned wells has been identified as a signifi-cant risk in geologic storage of CO2.

Greenhouse Gas Effect and Climate ChangeThe greenhouse gas (GHG) effect is the process by which atmospheric insulation, imparted by certain gases, keeps the Earth warmer than it

Figure 2. CO2 migration. Wells offer several potential pathways for gas migration. The pathways consist of the following: between the casing and the annular cement (A), between the cement plug and casing (B), through the cement plug and annular cement pore space as a result of deterioration (C), through the casing as a result of corrosion (D), through fractures in the annular cement (E) and between the annular cement and rock (F). (Adapted with permission from Michael Celia, Princeton University, New Jersey, USA.)


Rock formationAnnular cementWell casing

Cement well plug

A

B

C

D

E

F

September 2015 39

would be without them (Figure 3).15 Although the concept of climate change associated with green-house gases may seem recent, the idea of the GHG effect dates back to the 19th century.16 Scientists then were intrigued by the possibility that lower levels of CO2 might explain the ice ages. In 1896, Swedish scientist Svante Arrhenius calculated that industrial emissions from coal combustion might someday cause an increase in the Earth’s surface temperature.17 More recently, in the 1960s and 1970s, Russia considered ways to warm its large areas of icy tundra and convert them to fertile farmland through human-engi-neered climate change. These and subsequent attempts to alter the climate are encapsulated by the term climate engineering, also known as geo-engineering.18 Geoengineering is the intentional manipulation of planetary-scale processes to affect Earth’s climate system—for example, to cool down the Earth’s atmosphere or remove CO2 from the Earth’s atmosphere.

The GHG effect comprises a natural and an enhanced component. Warming of the Earth’s sur-face associated with indigenous gases is the natu-ral GHG effect. The main GHGs are, in order of abundance, water vapor [H2O], CO2, methane [CH4], nitrous oxide [N2O], ozone [O3] and other minor components. These gases in the atmosphere heat the Earth’s surface by absorbing and reradiat-ing some of the infrared radiation coming from the surface. In addition to the natural GHG effect, an enhanced effect occurs when human activities increase the level of greenhouse gases—primarily CO2 but also CH4, N2O, sulfur hexafluoride [SF6]

and other fluorinated hydrocarbons.19 Increased concentrations of these gases add to the atmo-sphere’s insulating qualities, thereby increasing Earth’s surface temperatures.

In 2012, CO2 accounted for 82% of all GHG emissions in the US.20 Electrical power genera-tion was responsible for 32% of the CO2 emitted,

and transportation contributed 28%. Industry accounted for 20% and the remaining 20% was attributable to emissions from residences, com-mercial buildings and agricultural activity. The end result of the enhanced GHG effect and increased concentrations of CO2 is that the Earth’s surface is getting warmer.

6. Whitmarsh J and Govindjee: “The Photosynthetic Process,” in Singhal GS, Renger G, Sopory SK, Irrgang K-D and Govindjee (eds): Concepts in Photobiology: Photosynthesis and Photomorphogenesis. Dordrecht, The Netherlands: Springer Science+Business (1999): 11–51.

7. “Overview of Greenhouse Gases: Carbon Dioxide Emissions,” US Environmental Protection Agency, http://www.epa.gov/climatechange/ghgemissions/gases/co2.html (accessed January 10, 2015).

8. When CO2 dissolves in water, it forms H2CO3* and H2CO3°. The former is the concentration of H2CO3 present and is typically about 0.3% of the CO2. The latter is another state entirely and could be called liquid CO2. For more on H2CO3 states: Langmuir D: Aqueous Environmental Geochemistry. Upper Saddle River, New Jersey, USA: Prentice Hall, 1997.

9. Cardoso SSS and Andres JTH: “Geochemistry of Silicate-Rich Rocks Can Curtail Spreading of Carbon Dioxide in Subsurface Aquifers,” Nature Communications 5, article 5743 (December 11, 2014).

10. Sim S, Cole IS, Choi Y-S and Birbilis N: “A Review of the Protection Strategies Against Internal Corrosion for the Safe Transport of Supercritical CO2 via Steel Pipelines for CCS Purposes,” International Journal of Greenhouse Gas Control 29 (October 2014): 185–199.

11. Sim S, Bocher F, Cole IS, Chen X-B and Birbilis N: “Investigating the Effect of Water Content in Supercritical CO2 as Relevant to the Corrosion of Carbon Capture and Storage Pipelines,” Corrosion 70, no. 2 (February 2014): 185–195.

Figure 3. Greenhouse gas effect. Most solar radiation (left ) is absorbed by and warms the Earth’s surface while some radiation is reflected by the Earth and the atmosphere back into space. Some solar radiation that reaches Earth’s surface is emitted as infrared radiation (right ), some of which passes directly back through the Earth’s atmosphere into space. Greenhouse gas molecules absorb and reemit infrared radiation in all directions, including back toward the Earth’s surface. The net effect is a warming of the Earth’s surface and lower atmosphere. (Adapted from the US EPA, reference 15.)


Solarradiation

Earth’s surface

Atmosphere Infraredradiation

12. DeBerry DW and Clark WS: “Corrosion Due to Use of CO2 for Enhanced Oil Recovery,” US Department of Energy, Report DOE/MC/08442-1, September 1979.

13. Rutqvist J: “The Geomechanics of CO2 Storage in Deep Sedimentary Formations,” Geotechnical and Geological Engineering 30, no. 3 (June 2012): 525–551.

14. Ramakrishnan TS: “Climate Initiative and CO2 Sequestration,” presented at the Fourth Annual Conference on Carbon Capture and Sequestration, Alexandria, Virginia, USA, May 2–5, 2005.

Gasda SE, Bachu S and Celia MA: “Spatial Characterization of the Location of Potentially Leaky Wells Penetrating a Deep Saline Aquifer in a Mature Sedimentary Basin,” Environmental Geology 46, no. 6–7 (October 2004): 707–720.

Celia MA, Bachu S, Nordbotten J, Gasda S and Kavetski D: “Implications of Abandoned Wells for Site Selection,” presented at the International Symposium on Site Characterization for CO2 Geological Storage, Berkeley, California, USA, March 20–22, 2006.

Ide ST, Friedmann SJ and Herzog HJ: “CO2 Leakage Through Existing Wells: Current Technology and Regulations,” in Proceedings of the 8th International Conference on Greenhouse Gas Technologies. Kidlington, Oxford, England: Elsevier Ltd. (2006): 2531–2536.

15. Cannell et al, reference 1. US Environmental Protection Agency (US EPA): “Climate

Change Indicators in the United States, 2nd ed.,” Washington, DC: US EPA, Report 430-R-12-004, December 2012.

16. Weart SR: The Discovery of Global Warming. Cambridge, Massachusetts, USA: Harvard University Press, 2008.

17. Svante Arrhenius was a recipient of the 1903 Nobel Prize in chemistry for his electrolytic theory of dissociation. He also proposed what came to be known as the Arrhenius equation, which shows the temperature dependence of reaction rate constants.

18. Keith DW: “Geoengineering the Climate: History and Prospect,” Annual Review of Energy and the Environment 25 (November 2000): 245–284.

Caldeira K, Bala G and Cao L: “The Science of Geoengineering,” Annual Review of Earth and Planetary Sciences 41 (May 2013): 231–256.

19. Sulfur hexafluoride [SF6] is used for high-density plasma etching and as a dielectric. According to the Intergovernmental Panel on Climate Change, SF6 is the most potent greenhouse gas and has a global warming potential of 23,900 times that of CO2 based on a 100-year timeframe. For more on the warming potential of SF6 in relation to the other greenhouse gases: “Direct Global Warming Potentials,” Intergovernmental Panel on Climate Change, http://www.ipcc.ch/publications_ and_data/ar4/wg1/en/ch2s2-10-2.html (accessed May 10, 2015).

20. “Overview of Greenhouse Gases: Carbon Dioxide Emissions,” reference 7.

40 Oilfield Review

Global surface temperatures measured since 1900 have risen 0.79°C [1.4°F].21 During the same period, the CO2 level in the atmosphere rose from 296 ppm in 1900 to 392 ppm in 2010.22

The CO2 level in 1900 was typical of levels for the 400,000 years before 1950, in which the CO2 level was never above 300 ppm (Figure 4).23 The effect of rising CO2 on the Earth’s surface tem-

21. Five independent government agencies or their predecessors have measured surface temperatures annually since 1900. These agencies are the US National Aeronautics and Space Administration Goddard Institute for Space Studies, the US National Oceanic and Atmospheric Administration National Centers for Environmental Information, the Met Office Hadley Centre and the University of East Anglia Climatic Research Unit in England and the Japan Meteorological Agency in Japan. Data from all these agencies show nearly identical long-term trends and variations. “Despite Subtle Differences, Global Temperature Records in Close Agreement,” NASA Goddard Institute for Space Studies (January 13, 2011), http://www.giss.nasa.gov/research/news/20110113/ (accessed May 17, 2015).

22. US EPA Office of Air and Radiation: “Climate Change Science Facts,” Washington, DC: US EPA, Report 430-F-10-002, April 2010.

23. “Global Temperature,” NASA Global Climate Change: Vital Signs of the Planet, http://climate.nasa.gov/vital-signs/global-temperature/ (accessed May 29, 2015).

“Trends in Atmospheric Carbon Dioxide: Recent Monthly Average Mauna Loa CO2,” NOAA Earth System Research Laboratory Global Monitoring Division, http://www.esrl.noaa.gov/gmd/ccgg/trends/ (accessed May 17, 2015).

24. Although surface temperatures appear to be directly correlated with CO2 levels, this has not been proven from first principles. This correlation is based on evidence-based fact.

25. Archer D, Eby M, Brovkin V, Ridgwell A, Cao L, Mikolajewicz U, Caldeira K, Matsumoto K, Munhoven G, Montenegro A and Tokos K: “Atmospheric Lifetime of Fossil Fuel Carbon Dioxide,” Annual Review of Earth and Planetary Sciences 37 (2009): 117–134.

Doney SC, Fabry VJ, Feely RA and Kleypas JA:

Figure 4. Increase in CO2 in the atmosphere. The levels of atmospheric CO2 can be measured from the distant past by analyzing ancient air bubbles trapped in polar ice. Data from 400,000 years before 1950 and to the present show a cyclic pattern dipping lower than 200 ppm during cold cycles and rising to nearly 300 ppm during warmer periods. Starting in the mid-1950s (inset ), atmospheric CO2 level rose above 300 ppm and continues to rise to the current level—slightly more than 400 ppm. (Adapted from “Global Temperature” and “Trends in Atmospheric Carbon Dioxide: Recent Monthly Average Mauna Loa CO2,” reference 23.)


–50,000–100,000–200,000–250,000–300,000–350,000

Years before 1950–400,000

200

250

350

450

300

400

CO2, p

pm

–150,000 0

400

1960 1970Year

CO2, p

pm

1980 1990 2000 2010 2015

320

340

360

380

peratures is well documented.24 Less well docu-mented is the effect of increased atmospheric CO2 on global oceans.

Researchers believe that the effects of increased CO2 can be observed in global oceans.25 Oceans absorb about one-third of the CO2 added to the atmosphere. Ocean absorption of CO2 is not benign—CO2 has caused a significant increase in ocean acidification. The weather sta-tion at Mauna Loa, Hawaii, USA, measured atmo-spheric CO2 and ocean pH from 1990 to 2010. During that 20-year period, atmospheric CO2 rose from 352 ppm in 1990 to 387 ppm in 2010. Concomitant with this rise in CO2, the ocean pH decreased from 8.12 to 8.08, indicating an increase in ocean acidification.26

Acidification of oceans and the warming effects from climate change are leading to the extinction of some types of ocean animal life.27 Coral reefs are sensitive to both acidification and warming. The net effect of acidification is an increase in the hydronium ion [H3O+] concentra-tion and a corresponding decrease in the carbon-ate ion [CO3

–2], which results in less coral being formed than in healthy ocean waters.28 Coral reefs are also sensitive to increases in temperature as small as 1°C to 2°C [1.8°F to 3.6°F] over times that are too short for the corals to adapt. These changes in temperature affect many of the microscopic and higher marine life forms that live in a symbiotic relationship with coral.

“Ocean Acidification: The Other CO2 Problem,” Annual Review of Marine Science 1 (January 2009): 169–192.

26. Since pH is on a logarithmic scale, this 0.5% decrease in pH represents a 9.6% increase in the acidity as measured by the hydronium [H3O+] ion concentration.

27. Zimmer, reference 1. McCauley DJ, Pinsky ML, Palumbi SR, Estes JA,

Joyce FH and Warner RR: “Marine Defaunation: Animal Loss in the Global Ocean,” Science 347, no. 6219 (January 16, 2015): 1255641-1–1255641-7.

Urban MC: “Accelerating Extinction Risk from Climate Change,” Science 348, no. 6234 (May 1, 2015): 571–573.

28. Coral reefs are composed of calcium carbonate [CaCO3] and small amounts of other minerals. Coral formation is dependent on the concentrations of the calcium ion and the carbonate ion—a decrease in the carbonate ion means less coral is formed.

29. Lake LW, Schmidt RL and Venuto PB: “A Niche for Enhanced Oil Recovery in the 1990s,” Oilfield Review 4, no. 1 (January 1992): 55–61.

Al-Mjeni R, Arora S, Cherukupalli P, van Wunnik J, Edwards J, Felber BJ, Gurpinar O, Hirasaki G, Miller CA, Jackson C, Kristensen MR, Lim F and Ramamoorthy R: “Has the Time Come for EOR?,” Oilfield Review 22, no. 4 (Winter 2010/2011): 16–35.

30. International Energy Agency Greenhouse Gas R&D Programme (IEA GHG): “CO2 Storage in Depleted Oilfields: Global Application Criteria for Carbon Dioxide Enhanced Oil Recovery,” Stoke Orchard, Cheltenham, England: IEA GHG, Technical Report 2009-12, December 2009.

31. The 10 basins in the world that have oil recoverable using CO2 are the following: In the Middle East, the Mesopotamian Foredeep, Greater Ghawar Uplift, Zagros Fold Belt and the Rub Al Khali basins; in Russia, the

West Siberian and Volga Ural basins; in South America and Mexico, the Maracaibo and Villahermosa Uplift basins; in the US, the Permian basin; and in Europe, the North Sea Graben basin.

32. In miscible conditions, two or more fluids mix in all proportions and form a single homogeneous phase. In immiscible conditions, two fluids are incapable of forming molecularly distributed mixtures or attaining homogeneity.

For more on the evolution of CO2 flooding: Holm LW: “Evolution of the Carbon Dioxide Flooding Processes,” Journal of Petroleum Technology 39, no. 11 (November 1987): 1337–1342.

33. Holm LW and O’Brien LJ: “Carbon Dioxide Test at the Mead-Strawn Field,” Journal of Petroleum Technology 23, no. 4 (April 1971): 431–442.

Hill B, Hovorka S and Melzer S: “Geologic Carbon Storage Through Enhanced Oil Recovery,” Energy Procedia 37 (2013): 6808–6830.

34. Martin FD and Taber JJ: “Carbon Dioxide Flooding,” Journal of Petroleum Technology 44, no. 4 (April 1992): 396–400.

35. Mohan H, Carolus M and Biglarbigi K: “The Potential for Additional Carbon Dioxide Flooding Projects in the United States,” paper SPE 113975, presented at the SPE/DOE Improved Oil Recovery Symposium, Tulsa, April 19–23, 2008.

36. IEA GHG, reference 30.37. Mohan et al, reference 35.38. Benson S: “Status and Opportunities in CO2 Capture,

Storage and Utilization,” presented at the American Physical Society Workshop on Energy Research and Applications for Physics Students and Postdocs, San Antonio, Texas, USA, March 1, 2015.

September 2015 41

Carbon Dioxide FloodingThe oil and gas industry injects CO2 into oil and gas fields for two primary purposes—rejuvenating producing fields and storing in depleted or unused reservoirs; these processes contribute to the global effort to minimize climate change. Carbon dioxide can be used in EOR to recover additional oil following primary production and waterflood.29 In addition, CO2 can be captured from a variety of sources and stored underground.

The amount of technically recoverable oil worldwide has been estimated at 450 billion bbl [72 billion m3].30 Oil that could theoretically be recovered using CO2 is concentrated in ten large basins worldwide—in the Middle East, Russia, South America, Mexico, the US and Europe.31 Oil recovery on this scale using CO2 EOR would require large sources of CO2 close to the reser-voir; proximity to a CO2 source is a challenge for most basins. Because the volume of potential recoverable oil worldwide is large, operators have been able to use a variety of EOR techniques to recover additional oil from reservoirs for decades, despite the difficulty of matching CO2 sources with sinks.

In the 1950s, researchers looking at CO2 flooding found that the compound was miscible in oil at pressures above 700 psi [5 MPa].32 Building on this and subsequent findings about CO2 behavior in oil, operators conducted the early successful field test of miscible CO2 flooding at the Mead-Strawn field near Abilene, Texas, USA, in 1964.33 Test results showed a 35% increase in incremental oil recovery using CO2 over the results of conventional waterflooding. Since that field test, many successful operations using mis-cible CO2 flooding have been conducted.

Carbon dioxide flooding for EOR can be grouped into two broad categories—miscible and immiscible. The process that is ultimately employed by the oilfield operator will depend on reservoir conditions and characteristics of the oil. Miscible CO2 flooding is the most common application although immiscible flooding may be applied in some situations because of oil density or reservoir pressure.34

Several factors make miscible CO2 flooding an effective method for additional oil recovery. Carbon dioxide is soluble in crude oils, swells net oil volume and reduces oil viscosity even before it achieves miscibility. As the point of complete mis-cibility is approached, the CO2 phase and the oil phase start to flow together homogeneously as a result of reduced interfacial tension and the increase in volume of the combined oil-solvent phase relative to the water phase.

At constant temperature, the lowest pressure at which liquids achieve miscibility is defined as the minimum miscibility pressure (MMP). Miscible CO2 flooding is applicable in many reser-voirs and is most effective when the reservoir has a pressure greater than the MMP. Typically this occurs at a depth greater than 760 m [2,500 ft].35 Additionally, the oil should have greater than 22 degree API gravity [less than 0.92 specific gravity] and less than 10 cP [10 mPa.s] viscosity. For best results, the reservoir needs to have oil saturation greater than 20% of the pore volume.

Ideally, a typical miscible flood injects CO2 at one end of the desired zone and recovers oil driven to producer wells (Figure 5).36 Although miscible floods account for the majority of CO2 EOR projects, some systems may benefit from immiscible flooding. Immiscible CO2 EOR proj-ects depend on a reduction in oil viscosity accompanied by oil swelling to achieve addi-tional oil recovery. Projects that would benefit from immiscible CO2 EOR have low-gravity crude oil and reservoir pressures less than the MMP.

A dependable source for CO2 is a prerequisite for both miscible and immiscible CO2 flooding. Natural and industrial sources of CO2 are avail-able.37 In 2008, the US produced about 3 bil-lion ft3/d [80 million m3/d] of CO2, primarily from natural sources in New Mexico, Colorado and Mississippi. Approximately 75% of the naturally produced CO2 in the US is sent by pipeline to the

Permian Basin, Texas, from the McElmo Dome, which is located near the border between Utah and Colorado and has one of the world’s largest accumulations of naturally occurring CO2.

Industrial sources of CO2 within the US include natural gas processing plants in Texas, Oklahoma, Wyoming and Michigan, an ammonia plant in Oklahoma, a coal gasification plant in North Dakota and power plants that have carbon capture capability. In Europe, significant indus-trial CO2 sources are located in the UK, the Netherlands, Belgium, France and Germany. However, none of these sources have yet been used for CO2 EOR operations.

Carbon Dioxide StorageMore than 80% of the world’s energy comes from the combustion of fossil fuels, and a rapid transi-tion to low-carbon energy sources will likely be difficult and expensive.38 One method of mitigat-ing the effects of CO2 on climate change is carbon capture and storage (CCS). Because about 7,400 industrial sources worldwide have CO2 emissions greater than 100 thousand metric tons/yr [110 thousand tonUS/yr], CCS and other strate-gies will be necessary over a 50-year period just to arrest the increase of CO2 in the atmosphere. To actually reduce CO2 will require an even greater effort (See “Taming Carbon Dioxide Emissions,” page 42).

Figure 5. Miscible CO2 flooding. Purchased and recycled CO2 are injected into a formation (top left ); water is also injected and acts as a driver. Some of the CO2 dissolves in the oil and is stored in the formation (bottom left ). The remainder of the CO2 causes vaporization of the lighter oil fractions into the CO2 phase (bottom center ) while the CO2 condenses into the oil phase. Driven by the water flood, the oil, and any residual CO2, reaches the production well (bottom right ) and both are pumped to the surface. At the surface (top right ), the oil and CO2 are separated, and the CO2 is recycled back to the injection point. (Adapted with permission from the IEA GHG, reference 30.)

Drivewater Water Miscible

zone

Immobile oil

Zone of efficient sweepIndustrial plant Producer

well

Immobile oil

Oilbank

OilrecoveryCO2

StoredCO2

DissolvedCO2

CO2


Injected CO2Purchased CO2 Recycled CO2

(continued on page 44)

42 Oilfield Review

Data about the state of the Earth suggest that CO2 must be brought under control to arrest the deleterious effects of climate change. Although not the only culprit, of all potential factors, CO2 carries the most weight in influ-encing undesired changes in the atmosphere, surface temperatures and oceans. A variety of proposals have been suggested to bring CO2 under control. Two such proposals illustrate the magnitude of the CO2 emissions challenge and show workable paths for halting emissions

growth and reducing the absolute level of those emissions over the next 15 to 35 years. Climate change caused by CO2 and other fac-tors can be arrested and reduced, but con-crete action must be taken now to accomplish the task.

Stabilization WedgesThe stabilization wedge concept, introduced in 2004 and refined in 2007, shows how CO2

emissions could be brought under control.1 A

plot of carbon emission rate versus time helps explain the concept and its application to con-trolling CO2 levels in the atmosphere (Figure S1).

To frame CO2 emissions stabilization and how it might be achieved, the stabilization tri-angle is divided into eight wedges. Each wedge represents the amount required from an area of focus, or major effort, to accomplish this objective. Carbon dioxide capture and storage is recognized as one area of focus (Figure S2). The strategies in each area can

Taming Carbon Dioxide Emissions

50 years

Year

Carb

on e

mis

sion

rate

, bill

ion

met

ric to

ns/y

r

19500

8

16

2000 2050 2100

Historicalemissions

Extrapolatedemissions path

Reduced emissions path

Constant emissions path

Eight carbon wedges

Double the fuel efficiency of 2 billion cars from 13 to 25 km/l[30 to 60 mi/galUS].

Decrease the distance traveled by hydrocarbon-fueled cars by half.

Use best energy efficiency practices in all residential andcommercial buildings.

Produce coal-based electricity that has twice that of today’s efficiency.

Replace 1,400 coal-fired electric plants with naturalgas–fired plants.

Capture and store emissions for 800 coal-based electric plants.

Capture the carbon from 180 coal-to-synfuel plants and store the captured CO2.

Double the current global nuclear capacity to replacecoal-based electricity.

Increase electricity generated by wind by 10 times the currentrate to be achieved by a total of 2 million windmills.

Increase electricity generated from solar radiation to 100 times the present capacity.

Use 40,000 km2 [15,000 mi2] of solar panels to producehydrogen for fuel cell cars.

Increase ethanol production from biomass by a factor of 12using farms that have an area equal to one-sixth of theworld’s croplands.

Eliminate tropical deforestation.

Adopt the practice of conservation tillage in all agriculturalsoils worldwide.

Produce hydrogen from coal at six times that of today’s rate and store captured CO2.

Efficiency

Fuel switching

Carbon captureand storage

Nuclear power

Wind power

Solar power

Biomass

Natural sinks

Carbon Wedge Strategy

Figure S1. Stabilization triangle and wedges. Historical carbon emission rates (red line) are shown up to 2007, at which time the emission rate was about 8 billion metric tons/yr [9 billion tonUS/yr]. If extrapolated along the current path (black dashed line) for 50 years, the emission rate could reach about 16 billion metric tons/yr [18 billion tonUS/yr], and the atmospheric CO2 level could be nearly 850 ppm in 2057. The triangle (green) formed by the constant emissions path (orange line)—defined here as a 50-year span—and the extrapolated emissions is called the stabilization triangle. The area of this triangle quantifies the amount of carbon that must be removed to stabilize atmospheric CO2 at close to current levels. The stabilization triangle can be divided into eight carbon wedges. Within each wedge, the carbon emission rate grows from zero to 1 billion metric tons/yr [1.1 billion tonUS/yr] of carbon after 50 years and, consequently, its area represents 25 billion metric tons [28 billion tonUS] of carbon emissions. Therefore, the area of the stabilization triangle represents 200 billion metric tons [220 billion tonUS] of carbon that will not be released to the atmosphere over the 50-year span. Once emissions have stabilized, industry and the public must begin to employ technologies that reduce emissions (right, blue line). (Adapted with permission from the Carbon Mitigation Initiative, Princeton University, New Jersey.)

Figure S2. Carbon stabilization wedges and strategies for lowering CO2 emissions to Earth’s atmosphere.

September 2015 43

1. Pacala S and Socolow R: “Stabilization Wedges: Solving the Climate Problem for the Next 50 Years with Current Technologies,” Science 305, no. 5686 (August 13, 2004): 968–972.

“Stabilization Wedges Introduction,” Princeton University Carbon Mitigation Initiative, http://cmi.princeton.edu/wedges/intro.php (accessed March 24, 2015).

2. International Energy Agency (IEA): “Energy and Climate Change: World Energy Outlook Special Report,” Paris: IEA, 2015.

3. IEA, reference 2.4. Energy efficiency is using less energy to provide the

same service.5. Renewable energy sources include solar, wind,

hydropower and biomass.

eventually reduce global carbon emissions by 1 billion metric tons/yr [1.1 billion tonUS/yr] by 2057.

Bridge ScenarioA major climate meeting, the 21st Conference of the Parties (COP21) to the United Nations Framework Convention on Climate Change, will take place in Paris in December 2015. In advance of the COP21 conference, countries have pledged to make intended nationally determined contributions (INDCs) for reduc-ing energy-related greenhouse gas (GHG) emissions toward the objective of slowing the pace of climate change.2 Under this INDC sce-nario, if countries adhere to their pledges, the growth of the carbon emission rate is pro-jected to slow down but not stop (Figure S3).

An alternative path to taming and eventu-ally reducing CO2 emissions has been devel-oped by the International Energy Agency (IEA).3 This concept, called the bridge sce-nario, seeks a more aggressive approach to battling carbon emissions than does the INDC scenario. Implicit in the bridge scenario is the recognition that global economic output and energy-related GHG emissions are indepen-dent phenomena. The bridge scenario calls for implementing five policy measures:• Increase energy efficiency.4

• Reduce the use of inefficient coal-fired power plants.

• Increase investment in renewable energy.5

• Phase out subsidies for fossil-fuel consumption.

• Reduce upstream methane emissions.Adoption of these measures is a start

toward achieving a maximum surface temper-ature rise of 2°C [3.6°F] from current levels. However, other measures will be required to achieve the goal.

If these five strategies are fully employed immediately worldwide, under the bridge sce-nario, the carbon emission rate will peak in 2018 followed by a steady reduction. When compared with the INDC scenario, the bridge scenario promotes a reduction of 1.3 billion metric tons/yr [1.4 billion tonUS] from the calculated 2030 carbon emission rate to the 2010 emission rate of 8.9 billion metric tons/yr [9.8 billion tonUS/yr].

Figure S3. Bridge scenario. Two bounding curves define the emissions reduction envelope of the bridge scenario. The upper curve (black) is the trend line for the carbon emission rate if the global community honors its INDC pledges. The bottom curve (red) represents the emission rate reduction possible under the bridge scenario. The largest contributor to reduced carbon emissions in 2030 is energy efficiency (light orange), which contributes a 49% reduction. Increased investments in renewable energy sources (green) provide a 17% reduction. Upstream methane reduction (light blue), fossil fuel subsidy reform (purple) and reducing inefficient coal use (brown) make up the remaining 34% reduction. (Adapted from the IEA, reference 2.)

Carb

on e

mis

sion

rate

, bill

ion

met

ric to

ns/y

r

Year

Energy efficiency increaseSubsidy reformRenewables investment

Inefficient coal use reductionUpstream methane reduction

INDC scenario

Bridge scenario

10.5

10.0

9.5

9.0

2015 2020 2025 2030

44 Oilfield Review

39. The potential for reuse in the oil and gas industry is limited. Most of the CO2 in the reuse category will go to CO2 flooding.

40. Benson SM: “Carbon Capture and Sequestration (CCS) 101,” presented at the Stanford University Global Climate and Energy Project Symposium, Stanford, California, September 28–29, 2010.

Alvi A, Berlin EH, Kirksey J, Black B, Larssen D, Carney M, Chabora E, Finley RJ, Leetaru HE, Marsteller S, McDonald S, Senel O and Smith V: “CO2 Sequestration—One Response to Emissions,” Oilfield Review 24, no. 4 (Winter 2012/2013): 36–48.

41. Benson, reference 38.42. Capillary action, or capillarity, is the phenomenon in

which surface tension draws fluid into the interstices of a material.

43. Zoback MD and Gorelick SM: “Earthquake Triggering and Large-Scale Geologic Storage of Carbon Dioxide,” Proceedings of the National Academy of Sciences 109, no. 26 (June 26, 2012): 10164–10168.

44. Hunter S: “The Tiltmeter: Tilting at Great Depths to Find Oil,” Lawrence Livermore National Laboratory Science and Technology Review (October 1997): 14–15.

Granda J, Arnaud A, Payàs B and Lecampion B: “Case Studies for Monitoring of CO2 Storage Sites, Based on Ground Deformation Monitoring with Radar Satellites,” paper C01, presented at the Third EAGE CO2 Geological Storage Workshop: Understanding the Behaviour of CO2 in Geologic Storage Reservoirs, Edinburgh, Scotland, March 26–27, 2012.

45. Benson, reference 38.46. Wright I, Ringrose P, Mathieson A and Eiken O: “An

Overview of Active Large-Scale CO2 Storage Projects,” paper SPE 127096, presented at the SPE International

Carbon capture and storage technologies can be applied to much of the 60% of the CO2 emis-sions that come from stationary sources such as power plants, cement plants and refineries. The remaining 40% is released to the atmosphere and comes from other stationary sources that emit CO2 such as residences, commercial buildings, small cement kilns, small steel plants and com-bustion of biomass.

Implementing CCS requires four sequential steps: CO2 capture, compression, transport via pipeline or marine transport and storage or reuse.39 For power plants, options for CO2 capture include precombustion, such as coal gasification, postcom-bustion and oxygen combustion. Each option has its advantages and disadvantages, and no single option fits every situation.40 The next step—con-version of CO2 to a liquid state—is a mature tech-nology and requires CO2 compression to 7.6 MPa [1,100 psi] or higher. Pipeline transport is also a mature technology; 3,000 mi [4,800 km] of pipe-lines are in place in the US alone. This pipeline network continues to slowly increase. Storage, the last step in CCS, is more complex.

Depleted oil and gas reservoirs and deep saline formations either onshore or offshore are options for geologic storage of CO2. To store CO2, the gas is injected into reservoirs that are at depths of 1 km [0.6 mi] or greater to ensure the CO2 remains in a dense liquid or supercritical fluid state. Several mechanisms trap and keep CO2 immobile.41 The primary trapping mecha-nism is usually a seal of low-permeability rock above the storage area, similar to that for natural oil and gas accumulations. Secondary mecha-nisms include solubility trapping, a mechanism by which a portion of the CO2 dissolves in water, and residual gas trapping, a mechanism by which the CO2 is trapped by capillarity.42 In some forma-tions, CO2 can be eventually trapped by its reac-tion with the rock and conversion to solid minerals. These secondary trapping mechanisms tend to become more effective over time, yield-ing, in most cases, a more secure storage site.

An ideal storage site is close to stationary sources of CO2, has the capacity to contain the projected volume of material over a long period of time, is able to sustain a high injection rate and has a low-permeability barrier to act as a caprock or seal. In addition, the storage site must be at an appropriate depth for CO2 to be liquid and have good mechanical strength to withstand injection pressures.

The injection of high volumes of fluid under high pressure into fault zones near a CCS site may create problems; doing so may cause faults to slip and generate microseismic activity.43 Passive seis-

Figure 6. Tiltmeter. A tiltmeter, which measures surface deformation, is similar to a sensitive carpenter’s level. The tiltmeter can measure a tilt of about 1 × 10−9 radians [57 × 10−9 degrees], which is equivalent to lifting one end of a 4,000 km [2,500 mi] long beam just 0.64 cm [0.25 in.] from level. To measure deformation of this size, the tiltmeter uses a sensor that has a glass case that contains a gas bubble, conductive liquid and several electrodes (inset ). When the tiltmeter case tilts to one side, the gas bubble changes position, and the resistance between the electrodes changes. This resistance change is calibrated to give the degree of deformation. (Photograph courtesy of Steven Hunter, Lawrence Livermore National Laboratories, California, USA.)


CaseElectrode

Liquid conductor

Gas bubble

Conference on CO2 Capture, Storage and Utilization, San Diego, California, November 2–4, 2009.

For more on the Sleipner project: Bennaceur K, Gupta N, Monea M, Ramakrishman TS, Randen T, Sakurai S and Whittaker S: “CO2 Capture and Storage—A Solution Within,” Oilfield Review 16, no. 3 (Autumn 2004): 44–61.

47. Fairley P: “A Coal Plant That Buries Its Greenhouse Gases,” MIT Technology Review 118, no. 1 (January/February 2015): 84–87.

48. IEA GHG, reference 30.49. Barnhart WD and Coulthard C: “Weyburn CO2 Miscible

Flood Conceptual Design and Risk Assessment,” paper 95-120, presented at the Sixth Petroleum Conference of the South Saskatchewan Section of the Society of Canadian Institute of Mining, Metallurgy and Petroleum, Regina, Saskatchewan, Canada, October 16–18, 1995.

Brown K, Jazrawi W, Moberg R and Wilson M: “Role of Enhanced Oil Recovery in Carbon Sequestration—The Weyburn Monitoring Project, a Case Study,” presented at the First National Conference on Carbon Sequestration, Washington, DC, May 14–17, 2001.

50. Protti G: “Win-Win: Enhanced Oil Recovery and CO2 Storage at EnCana’s Weyburn Oilfield,” paper WPC-18-0986, presented at the 18th World Petroleum Congress, Johannesburg, South Africa, September 25–29, 2005.

Bennaceur et al, reference 46.51. For more on the Great Plains Synfuels Plant: Dakota

Gasification Company, http://www.dakotagas.com/index.html (accessed May 12, 2015).

52. Fairley, reference 47.

September 2015 45


Project area

Williston basin

S a s k a t c h e w a n

N

Weyburn

Regina

U N I T E D S T A T E S

C A N A D A


N o r t h D a k o t a

M a n i t o b aS a s k a t c h e w a n

Bismarck

Estevan

Weyburn

Beulah

0 km

0 mi 100

100

Oil field

CO2 pipeline tap

CO2 pipeline

mic methods may be used to monitor and record any injection-induced seismicity. Increased forma-tion pressure may cause some degree of uplift, which can be monitored using interferometric syn-thetic aperture radar (InSAR) satellite imagery or tiltmeters (Figure 6).44

The practice of carbon capture and storage continues to expand worldwide. Eight operating industrial-scale projects have come on stream in the past 40 years. These projects represent storage of about 14 million metric tons [15 million tonUS] of CO2 annually.45 Eight additional projects are under construction, representing 13 million metric tons [14 million tonUS] of CO2 annual storage capacity.

At the Sleipner project in the North Sea, CO2 is produced with natural gas, separated offshore and then injected into a disposal interval. About 1 million metric tons [1.1 million tonUS] of the produced CO2 has been injected annually into the Utsira formation over a 15-year period.46 The Boundary Dam Power Plant CCS project is located at Estevan, Saskatchewan, Canada. SaskPower, the owner and operator of the proj-ect, invested more than US$ 1 billion to equip one of its generators for carbon capture. SaskPower sells the captured CO2 to Cenovus Energy Inc. who uses it for EOR to boost output from matur-ing wells nearby.47 SaskPower also operates its own injection well at the power plant site.

Although CCS is a major initiative in several oil fields, CO2 is also being used for EOR in many production environments. A project in Canada is a good example of combined EOR and CCS.

Miscible CO2 Flooding and StorageCenovus Energy Inc. has embraced a long-term commitment to use CO2 for miscible flooding and to store excess amounts underground at the Weyburn-Midale field in Canada. This project is at the forefront of combined CO2-EOR and geo-logic CO2 storage.48

The Weyburn-Midale field, discovered in 1954, is located in southeast Saskatchewan (Figure 7).49 The operation covers 180 km2 [70 mi2] and is one of the largest medium-sour oil reservoirs in Canada. Original oil in place (OOIP) was estimated at 1.4 bil-lion bbl [220 million m3]. Following initial produc-tion over a 9- to 10-year period, the operator started waterflooding in 1964 followed by horizontal drilling in the 1990s. Although these measures helped pro-duction, the operator opted to use CO2 EOR to reverse the long-term production decline and to demonstrate large-scale geologic storage of CO2.50

The Dakota Gasification Company operates a synfuel plant in Beulah, North Dakota, that gener-ates natural gas from coal.51 The byproduct CO2

produced at the Beulah plant is compressed to 2,200 psi [15 MPa] and transported 210 mi [340 km] via pipeline to the Weyburn-Midale field. Deliveries of CO2 from the Beulah plant vary, rang-ing from 6,000 to 8,500 metric tons/d [6,600 to 9,400 tonUS/d]. The nearby Boundary Dam CCS project supplies an additional 2,300 metric tons/d

[2,500 tonUS/d] to the Weyburn-Midale field.52 Storage of CO2 was initiated in September 2000 in a limited area of the field. This early phase of the operation had 16 vertical and 13 horizontal injec-tion wells. A study of this injection area is ongoing and will address all of the technical aspects of long-term geologic storage (Figure 8).

Figure 7. Weyburn-Midale project. Located near Weyburn, Saskatchewan, Canada, this project uses CO2 for enhanced oil recovery and stores it in underground formations. The Weyburn-Midale reservoir is located principally in North Dakota, USA, and Saskatchewan; the fields extend west into Montana, USA, and east into Manitoba, Canada. Most of the CO2 used at the Weyburn-Midale project is piped (red) from a coal gasification plant near Beulah, North Dakota; the remainder comes from the nearby Boundary Dam Project at Estevan, Saskatchewan.

Figure 8. Weyburn-Midale research project. The Petroleum Technology Research Centre (PTRC) conducted research at the Weyburn-Midale project. The project area encompasses a 100,000-km3 [24,000-mi3] volume (dashed lines) and is part of the Williston basin (red line). The oil reservoirs and the levels above and below them in the area earmarked for CO2 storage were characterized before the initial injection. During the injection of CO2, measurements were made in a smaller area (gray rectangle) of the Weyburn-Midale field. In this field, PTRC scientists carried out an array of monitoring and verification research that included soil, gas and water sampling, subsurface monitoring, seismic monitoring, sampling from wells and risk assessment; these studies are ongoing. (Adapted with permission from PTRC.)

46 Oilfield Review

Miscible CO2 EOR and geologic storage have been successful at the Weyburn-Midale field, giv-ing the field new life and potentially extending its operational period by more than 25 years. Currently, the field produces about 26,000 bbl/d [4,100 m3/d] of light crude oil (Figure 9). Carbon dioxide injection has tripled oil production from the estimated lowest production rate for the field, about 8,000 bbl/d [1,200 m3/d] in 1988.

To date, about 24 million metric tons [26 mil-lion tonUS] of CO2 have been stored, and about 55 million metric tons [61 million tonUS] will be stored underground over the life of the project.

Carbon Dioxide Storage at In SalahThe In Salah Gas (ISG) project, a joint venture between Sonatrach, BP and Statoil, is currently executing a phased development of eight gas fields in the Ahnet-Timimoun basin in the Algerian cen-tral Sahara desert (Figure 10). These fields com-prise an area of 25,000 km2 [9,600 mi2] and have estimated recoverable gas reserves of 0.23 trillion m3 [8.1 trillion ft3].53 The gas from these fields contains 1% to 10% CO2, which is removed at the Krechba central processing facility (CPF). Carbon dioxide and any residual hydrogen sulfide [H2S] in the pro-duced gas are removed by monoethanol amine (MEA) absorption. The cleaned up gas from the Krechba CPF contains 0.3% or less CO2 and is trans-ported by pipeline to export terminals. The ISG proj-ect started production in 2004 and is currently producing 9 billion m3/yr [320 billion ft3/yr] of gas for export.

Carbon dioxide recovered from the produced gas was injected about 1,900 m [6,200 ft] into the water-filled downdip flank of the Krechba gas field. The three CO2 injection wells have horizontal sec-tions measuring up to 1.8 km [1.1 mi] in length (Figure 11). The joint venture conducted extensive monitoring of CO2 storage using a variety of tech-niques such as surface and soil gas monitoring, downhole gas measurements and tracer chemical tagging. Geophysical and InSAR satellite monitor-ing were also conducted to check for ground deformation and microseismicity (Figure 12).54

53. “In Salah Southern Fields Development Project, Algeria,” Hydrocarbons Technology, http://www.hydrocarbons-technology.com/projects/in-salah-southern-fields-development-project/ (accessed December 12, 2014).

54. Mathieson A, Midgley J, Dodds K, Wright I, Ringrose P and Saoul N: “CO2 Sequestration Monitoring and Verification Technologies Applied at Krechba, Algeria,” The Leading Edge 29, no. 2 (February 2010): 216–222.

Shi J-Q, Sinayuc C, Durucan S and Korre A: “Assessment of Carbon Dioxide Plume Behaviour Within the Storage Reservoir and the Lower Caprock Around the KB-502 Injection Well at In Salah,” International Journal of Greenhouse Gas Control 7 (March 2012): 115–126.

Stork AL, Verdon JP and Kendall J-M: “The Microseismic Response at the In Salah Carbon Capture and Storage (CCS) Site,” International Journal of Greenhouse Gas Control 32 (January 2015): 159–171.


19550

10,000

20,000

30,000

40,000

50,000

1970

Prod

uctio

n, b

bl/d

1985Year

2000 2015Year

Primary and waterflood Horizontal infill wells

CO2 EORVertical infill wells

Figure 9. Weyburn-Midale production. This facility (inset ) has produced oil since 1955. It and others at the Weyburn-Midale field have been used for production during four distinct phases (bottom). In the first phase, primary production and waterflood produced a total of 3.3 million bbl [0.52 million m3] of oil. The second and third phases, which used vertical and horizontal infill wells, produced a total of 5.9 million bbl [0.94 million m3] of oil. The last phase, CO2 EOR, has produced 9.4 million bbl [1.5 million m3] to date. (Adapted with permission from Cenovus Energy Inc.)

Figure 10. In Salah Gas (ISG) project. The In Salah CO2 storage project in central Algeria consists of several gas fields and a central processing facility (CPF, inset ) at Krechba, where CO2 and other impurities are removed from the produced natural gas. The cleaned up gas is sent by pipeline to a distribution station at Hassi R’Mel, Algeria, for further shipment to export terminals and markets in Europe.


Krechba CPF

300

km0

0

300

mi

S P A I N

PORT

UGAL

T U N I S I A

L I B Y A

A L G E R I A

M A L IMAU

RITA

NIA

Hassi R’Mel

AGas fieldExport terminal

ISG pipelineGas export pipeline

MOROCCO

September 2015 47

Figure 11. Carbon dioxide injection at Krechba. At the In Salah project, the Krechba central processing facility (CPF, inset ) consists of several sections—power generation (right ), CO2 removal and dehydration (center ) and CO2 injection. Recovery and injection of the CO2 removed from the natural gas are straightforward. The producing gas reservoir is about 20 m [66 ft] thick and lies about 1,900 m [6,200 ft] deep below a 950 m [3,100 ft] thick caprock formation of Carboniferous mudstones. A 900 m [3,000 ft] thick layer of Cretaceous sandstone and mudstone lies above the mudstone section. Produced gas from the reservoir is treated at the CPF to remove CO2, H2S and other impurities. The treated CO2 is then reinjected into water-saturated rock of the same reservoir from which the gas is produced.

Water

Gas

CO2 injection

Gasproduction


Gasd i

Cretaceous sandstonesand mudstonesCarboniferous mudstones

Gas

Water

Pipeline

Well casing

C

Figure 12. Monitoring ground deformation. Ground deformation is monitored at the In Salah project using interferometric synthetic aperture radar (InSAR). This technique uses a dedicated satellite (left ) to collect infrared radar images of the ground elevation using side-beam radar. Measurement of the vertical and horizontal displacements requires two passes of the satellite. Displacements are determined by comparing the wave phase changes of the radar signal between the two passes. The deformation and CO2 plume spreads at each well (marked by a cross) were estimated from the InSAR data for 2005, 2007 and 2009 (right ). The color intensity indicates the degree of vertical deformation (scale, far right ) while the size of the colored area around each well infers the horizontal spread of the CO2 plume.


KB-503

0

5

10

15

20

0

5

10

15

20

0

5

10

15

20

KB-502

2005

2007

2009

KB-14

KB-11

KB-12

KB-501

+ +

+

++

+

KB-503KB-502

KB-14

KB-11

KB-12

KB-501

+ +

+

++

+

KB-503KB-502

KB-14

KB-11

KB-12

KB-501

+ +

+

++

+

Nor

th, k

mN

orth

, km

Nor

th, k

m

0 5 10 15 20

East, km

20

15

10

5

–5

–10

–15

–20

0

Verti

cal d

efor

mat

ion,

mm

20

15

10

5

–5

–10

–15

–20

0

Verti

cal d

efor

mat

ion,

mm

20

15

10

5

–5

–10

–15

–20

0Ve

rtica

l def

orm

atio

n, m

m

Flight path

Displacement toward satellite

02.83 cm

Second passFirst pass

Flight path

Displacement toward satellite

02.83 cm

Second passFirst pass

48 Oilfield Review

Figure 13. Bati Raman project. The Bati Raman field and associated CO2 EOR project in Turkey are located about 720 km [450 mi] southeast of Ankara. The Bati Raman project has two CO2 injection stations—AP2 (inset ) and 3TP2 (not shown). (Photograph used with permission from the Turkish Petroleum Corporation.)


Ankara

Istanbul

Bati Raman

CYPRUS

BULGARIAR U S S I A

G E O R G I A

LEBANON

S Y R I A I R A Q

T U R K E Y

M e d i t e r r a n e a n S e a

B l a c kS e a

ARMENIA

IRAN

55. Ringrose PS, Mathieson AS, Wright IW, Selama F, Hansen O, Bissell R, Saoula N and Midgley J: “The In Salah CO2 Storage Project: Lessons Learned and Knowledge Transfer,” Energy Procedia 37 (2013): 6226–6236.

56. Sahin S, Kalfa U and Celebioglu D: “Bati Raman Field Immiscible CO2 Application—Status Quo and Future Plans,” SPE Reservoir Evaluation & Engineering 11, no. 4 (August 2008): 778–791.

Since 2004, approximately 3.5 million metric tons [3.9 million tonUS] of CO2 have been separated from the produced gas and reinjected into the Krechba reservoir.

Important lessons were learned about CO2 storage during the design, startup and operation of the ISG project, including the need for detailed geologic and geomechanical character-ization of the reservoir and the overburden.55 These data helped the operator develop the injection strategy and ensured the long-term integrity of the storage facility. The operator also realized the importance of flexibility in the design and control of the capture, compression and injection well systems.

Immiscible CO2 FloodingThe Bati Raman field, in southeast Turkey, is one of the largest oil fields in that country (Figure 13). Owned and operated by the Turkish Petroleum Company (TP), the field was discovered in 1961

and produces from a Garzan limestone—a het-erogeneous carbonate from the Cretaceous period.56 The heavy crude produced at the Bati Raman field has 11 degree API gravity [0.99 spe-cific gravity], high viscosity and low solution–gas content. The OOIP was estimated to be 1.85 bil-lion bbl [300 million m3]. From 1965 to 1970, the number of producing wells increased from almost 20 to more than 130.

During the primary production period from 1961 to 1986, reservoir pressure decreased from about 1,800 psi [12 MPa] to as low as 400 psi [2.8 MPa] in some parts of the field. Similarly, crude production declined from a peak rate of 9,000 bbl/d [1,400 m3/d] in 1969 to 1,600 bbl/d [250 m3/d] in 1986. During the primary produc-tion period, recovery was estimated to be less than 2% of OOIP.

Following the primary recovery period, the operator studied several processes for EOR and chose immiscible CO2 flooding primarily because of the proximity of the Dodan gas field.

The Dodan field is 55 mi [89 km] from the Bati Raman field and produces gas that is mostly CO2 and has 3,000 to 4,000 ppm H2S. The wellhead pressure at the Dodan field is about 1,050 psi [7.2 MPa]. After it is cleaned up, the CO2 from the Dodan field is sent to the Bati Raman field via pipeline (Figure 14).

Before implementing full-scale CO2 flooding at the Bati Raman field, TP performed a pilot test using 17 CO2 injection wells in the western part of the field. The original plan was cyclic injection of CO2 followed by water. After studying the pilot test results, TP engineers converted the initial

September 2015 49

injection plan to CO2 flooding. The operator made several observations based on the pilot test: CO2 injection helped produce a considerable amount of oil, and diffusion of CO2 into the oil was effec-tive for displacing oil in the fractured carbonate reservoir. After evaluating the results from the pilot test, TP engineers gradually extended the CO2 flooding to the rest of the field. Currently, 95% of the production wells in the Bati Raman field are influenced by CO2 flooding.

In 2012, the CO2 injection project was 25 years old, far beyond what was envisioned during the initial field design. More than 6% of the OOIP has now been recovered, a significant increase over the less than 2% recovered during primary field production. Primary recovery was 32 million bbl [5.1 million m3] while total field production, including that from primary, secondary and EOR recovery, was 114 million bbl [18 million m3] as of the end of 2014 (Figure 15).

Figure 14. Dodan and Bati Raman process flow. At the Dodan gas plant (left ), produced gas is stripped of H2S and water, compressed and sent by pipeline to the Bati Raman process facility, where it is injected (right ). At the Bati Raman facility, oil and CO2 in the produced stream are separated—the oil

goes to refining and the gas to cleanup. The cleaned up CO2 is compressed and sent to the injection wells. (Adapted with permission from the Turkish Petroleum Corporation.)


Pipeline

Production well

Flash tank

Compressor

Recycle compressors

Flar

e

Rege

nera

tion

Reboiler

Reboiler

Reboiler Tank

Vent

Flash tank

Separator

Separator

To refinery

H 2S a

bsor

ber

H 2O a

bsor

ber

Oil and CO2 production

H2O

H 2O a

bsor

ber

CO2

CO2

CO2

Injection wells

Dodan Gas Plant Bati Raman Recycle Station

Tank

Figure 15. Bati Raman production history. The Bati Raman field started producing in 1961, and as additional wells were brought on stream, production ramped up and peaked in 1970 at almost 10,000 bbl/d [1,600 m3/d]. Following this peak, production declined because of decreasing reservoir pressure. Water flooding started in 1975 and slowed the rate of production decline but did not reverse it. In 1986, primary production reached a low of about 2,000 bbl/d [300 m3/d], and CO2 injection for EOR was initiated. After CO2 EOR was introduced, production peaked around 1992 at about 15,000 bbl/d [2,400 m3/d]. Production decreased until 2004 when the practice of integrated reservoir management was implemented and arrested the decline. Production has held steady at about 7,500 bbl/d [1,200 m3/d] since that time. (Adapted with permission from the Turkish Petroleum Corporation.)


0

15,000

2,500

5,000

7,500

10,000

12,500

Prod

uctio

n, b

bl/d

1965 1970

Year

Primary Production Immiscible CO2 Injection

1975 1980 1985 1990 1995 2000 2005 2010 20141961

50 Oilfield Review

Carbon Dioxide and the FutureScientists have had an interest in CO2 for more than a century. The business sector, government regulators and the public have joined scientists in the quest to slow the atmospheric accumula-tion of CO2. The oil industry is tackling this chal-lenge in part by injecting CO2 underground, both for EOR and for long-term storage purposes.

In addition to EOR and storage, the industry can also take advantage of new, less-expensive sorbents for CO2 capture, which will also help reduce CO2 emissions into the atmosphere. Current technology depends on absorbents, including aqueous MEA, to remove CO2 from streams such as power plant flue gas.57 The MEA solution is corrosive, degrades into toxic byprod-ucts and requires a large amount of energy to clean it up for reuse.

The unfavorable characteristics of current sorbents such as MEA have led researchers to develop new ones—both solid and liquid. One of these new sorbents is solid, microporous carbon that is synthesized from asphalt (Figure 16).58 This sorbent is inexpensive, has high surface area CO2 uptake and excellent properties for revers-ibly capturing CO2. Another new sorbent is a liq-uid carbonate enclosed within polymer microcapsules with shells of highly permeable silicone.59 These microcapsules are reported to have rapid CO2 uptake and release.

Although new sorbent technology can help, it is only part of the solution for emissions. The reduction and mitigation of GHG emissions will require simultaneous implementation of several technologies and significant governmental action on a worldwide basis. These technologies range from efficiency improvements to alternate energy sources to conservation soil tillage. Likewise, gov-ernments can help, for example, by reducing sub-sidies for inefficient hydrocarbon use and intelligent mandates on fuel efficiency.

One area in which the oil and gas industry can play an important role is geologic storage in CCS.60 A technical challenge related to geologic storage is risk associated with faulty CO2 confinement. The oil and gas industry has the technical tools to assess the potential and risk for CO2 migration

away from storage sites. Although extra costs associated with large-scale geologic storage of CO2 will be incurred, these costs are fundamen-tally no different than additional costs already borne by the public for cleaner water and air.

The consequences of climate change are potentially enormous. In the last decade, as evi-dence for the effects of climate change mounts, moving beyond maintaining the status quo and doing business as usual has become important. Although it can help to reduce the problem, the oil and gas industry can offer only some solutions. Worldwide, industries, governments and the pub-lic must be educated and ready to support a vigor-ous effort to arrest climate change. —DA

Figure 16. Carbon dioxide capture. Asphalt (left ) is carbonized by treating it with potassium hydroxide [KOH] at 700°C [1,300°F]. This process yields treated asphalt (center ) that has a surface area of nearly 2,800 m2/g. At a pressure of 30 bar [440 psi] and at room temperature, the treated asphalt (right ) can absorb 93% of its weight in CO2. The CO2 can be desorbed using a simple pressure swing absorption process. (Adapted with permission from Jalilov et al, reference 58.)


50 nm

KOH

700°C

CO2

Treatedasphalt

Asphalt

57. Vericella JJ, Baker SE, Stolaroff JK, Duoss EB, Hardin JO IV, Lewicki J, Glogowski E, Floyd WC, Valdez CA, Smith WL, Satcher JH Jr, Bourcier WL, Spadaccini CM, Lewis JA and Aines RD: “Encapsulated Liquid Sorbents for Carbon Dioxide Capture,” Nature Communications 6, article 6124 (February 5, 2015).

58. Jalilov AS, Ruan G, Hwang C-C, Schipper DE, Tour JJ, Li Y, Fei H, Samuel ELG and Tour JM: “Asphalt-Derived High Surface Area Activated Porous Carbons for Carbon Dioxide Capture,” ACS Applied Materials and Interfaces 7, no. 2 (January 21, 2015): 1376–1382.

59. Vericella et al, reference 57.60. Bryant S: “Geologic CO2 Storage—Can the Oil and Gas

Industry Help Save the Planet?,” Journal of Petroleum Technology 59, no. 9 (September 2007): 98–105.

Documents

Carbon Dioxide—Challenges and Opportunities/media/Files/resources/oilfield_review/ors15/sept15/... · September 2015 37 Carbon, one of the two constituents of carbon dioxide [CO