(685b) Understanding the Factors That Affect CO2 Transport, Storage, and Enhanced Oil Recovery Potential in Unconventional Reservoirs

Investigations on the use of subsurface geologic formations for carbon dioxide (CO₂) storage have been ongoing for many years and have traditionally focused on saline aquifers, depleted oil and gas formations, and unminable coal seams (Goodman and others, 2014; U.S. Department of Energy National Energy Technology Laboratory, 2012). In the last decade, improvements in directional drilling technology (Watney, 2016) and hydraulic fracturing (King, 2010) of organic-rich shale and other tight rock formations have opened new opportunities for CO₂ storage, with the potential cobenefit of enhancing gas and oil recovery in reservoirs that typically have less than 10% primary recovery.

Past and ongoing work at the Energy & Environmental Research Center (EERC), funded by the U.S. Department of Energy National Energy Technology Laboratory in conjunction with partners from the oil and gas industry, has been focused on better understanding the factors that affect CO₂ transport as it relates to both enhanced oil recovery (EOR) and CO₂ storage in unconventional oil reservoirs and organic-rich shales. Much of this work has been performed in several of the EERCâ??s laboratories using rock samples from the Bakken petroleum system, the results of which can be applied to unconventional formations across the United States. The analytical work conducted to date has focused on supercritical CO₂ extraction experiments, CO₂ sorption experiments, and extensive physical and geochemical characterization using rock samples from several Bakken wells to better understand the factors that can affect CO₂ migration, oil extraction, sorption, and storage. Sample characterization has been accomplished using a variety of analytical techniques including whole-core and microcomputerized tomography imaging, conventional scanning electron microscopy (SEM) coupled with energy-dispersive x-ray spectroscopy, field emission SEM, focused ion beam SEM, x-ray fluorescence, x-ray diffraction, optical microscopy, Rock-Eval pyrolysis, vitrinite reflectance, mercury injection capillary pressure testing, and geomechanical testing. Initial characterization work focused on better understanding the occurrence and characteristics of fracture and pore networks and has expanded to the use of advanced analytical and image analysis techniques to quantify fracture and pore occurrence and mineralogical content at various resolutions. Work is ongoing to better understand and quantify the occurrence and accessibility of pores, fractures, clay minerals, and kerogen and the potential implications that those features have on CO₂ transport for EOR and on CO₂ sorption for storage. The sample characterization efforts are being used to better understand the results of supercritical CO₂ extraction experiments and ongoing CO₂ sorption experiments using Bakken samples that have undergone extensive characterization. These results are being integrated into modeling research activities to determine the fundamental mechanisms controlling fluid transport and CO₂ storage in the Bakken, resulting in the development of improved model simulations. The results of the EERCâ??s laboratory-based work and its implications for CO₂ EOR and storage, as well as future research needs, will be discussed.

REFERENCES

Goodman, A., Fukai, I., Dilmore, R., Frailey, S., Bromhal, G., Soeder, D., Gorecki, C., Peck, W., Rodosta, T., and Guthrie, G., 2014, Methodology for assessing CO₂ storage potential of organic-rich shale formations: Energy Procedia, v. 63, p. 5178â??5184.

King, G.E., 2010, Thirty years of gas shale fracturing: what have we learned? Society of Petroleum Engineers: Annual Technical Conference and Exhibition, September 19â??22, Florence, Italy, SPE 133456.

U.S. Department of Energy National Energy Technology Laboratory, 2012, The United States 2012 Carbon Utilization and Storage Atlas, Fourth Edition: www.netl.doe.gov/File%20Library/Research/Coal/carbon-storage/atlasiv/Atl... (accessed January 2016).

Watney, W.L., 2016, Horizontal drilling â?? technology review, current applications, and its future in developing Kansasâ?? petroleum resources: Kansas Geological Survey, Lawrence, Kansas, www.kgs.ku.edu/PRS/Unger/Watney-KBA-KIOGA--Horizontal_Drilling.pdf (accessed January 2016).