The CO2 supply-and-demand trends for enhanced-oil-recovery (EOR) projects are diverging, and many EOR projects, especially in the US, are hindered by lack of sufficient economic CO2 volume and infrastructure. The CO2-supply deficiency—and because a portion of the estimated 30+ Gt/year of anthropogenic CO2 worldwide could supply future EOR projects sufficiently—is driving the EOR industry to be an enabler for early carbon-capture-and-storage (CCS)/sequestration technology and infrastructure development. As EOR/CCS develops, the potentially huge, yet unproven, storage capacity of deep saline formations may become more realistic. The methodology of how to quantify and use saline aquifers is in the developing stages with technical debates.
Geotechnical and transportation issues for CCS are similar to those for EOR processes, but there are differences because of their different purposes. EOR projects have fairly short-term time scales, of several 10s of years after initiation of EOR processes. CCS projects have similar 10s of years of injection time, but indefinite time scales (1,000s of years) for the mineralization processes to be effective. Geological and mineralogical models; coupled geochemistry, geomechanical, and transport models; seal-integrity issues typical of hydrocarbon-phase-behavior physics; large time-scale differences; subsurface uncertainties; and limited or no performance data complicate optimization of CO2-capacity determination and efforts to model the CCS process(es) and sites compared with modeling typical or even atypical EOR projects.
Except for natural-gas plants, business models of large stationary facilities generally view CO2 as a waste. To an operator, CO2 is an expensive but useful fluid to enhance hydrocarbon recovery. In May 2010, the US Environmental Protection Agency issued its final rule addressing greenhouse-gas emissions from large stationary sources and defined CO2 as a pollutant at certain high concentrations, not as a waste. Future business venues for EOR/CCS most likely will include partnerships and alliances with power plants and other large stationary generators to provide and economically capture, use, and store CO2, thus creating a limited CCS industry enabled by the EOR industry.
CO2 Applications additional reading available at OnePetro: www.onepetro.org
SPE 139588 • “The Significance of Caprock-Sealing Integrity for CO2 Storage” by A. Busch, Shell, et al.
SPE 134028 • “Drainage and Imbibition CO2/Brine Relative Permeability Curves at Reservoir Conditions for Carbonate Formations” by D. Brant Bennion, SPE, Weatherford, et al.
SPE 131609 • “Static and Dynamic Estimates of CO2-Storage Capacity in Two Saline Formations in the UK” by Min Jin, SPE, Heriot-Watt University, et al.
SPE 139716 • “Perspectives on CCS Cost and Economics” by H.S. Kheshgi, SPE, ExxonMobil, et al.