Mobility and Conformance Control for CO2 EOR via Thickeners, Foams, and Gels - A Literature Review of 40 Years of Research and Pilot Tests

Abstract

Abstract Carbon dioxide (CO2) has been used commercially to recover oil from geologic formations by enhanced oil recovery (EOR) technologies for over 40 years. The U.S. Department of Energy Office of Fossil Energy and its predecessor organizations have supported a large number of laboratory and field projects over the past decades in an effort to improve the oil recovery process including investments to advanced reservoir characterization, mobility control, and conformance of CO2 flooding. Currently, CO2 EOR provides about 280,000 barrels of oil per day, just over 5 percent of the total U.S. crude oil production. Recently CO2 flooding has become so technically and economically attractive that CO2 supply, rather than CO2 price, has been the constraining developmental factor. Carbon dioxide EOR is likely to expand in the United States in upcoming years due to "high" crude oil prices, natural CO2 source availability, and possible large anthropogenic CO2 sources through carbon capture and storage (CCS) technology advances. Despite its well-established ability to recover oil, the CO2 EOR process could be improved if the high mobility of CO2 relative to reservoir oil and water can be effectively and affordably reduced. The CO2 EOR industry continues to use water-alternating-with-gas (WAG) as the technology of choice to control CO2 mobility and/or mechanical techniques (e.g., cement, packers, well control, infield drilling, and horizontal wells) to help control the CO2 flood conformance. If the "next generation" CO2 EOR target of 67 billion barrels is to be realized, new solutions are needed that can recover significantly more oil than the 10–20% of the original oil in place associated with current flooding practices. A recent literature review [Enick and Olsen, 2011] concentrates on the history and development of CO2 mobility control and profile modification technologies in the hope that stimulating renewed interest in these chemical techniques will help to catalyze new efforts to overcome the geologic and process limitations such as poor sweep efficiency, unfavorable injectivity profiles, gravity override, high ratios of CO2 to oil produced, early breakthrough, and viscous fingering. This paper is a concise overview of the recent, comprehensive literature review available on the NETL website entitled "Mobility and Conformance Control for Carbon Dioxide Enhanced Oil Recovery (CO2-EOR) via Thickeners, Foams, and Gels – A Detailed Literature Review of 40 Years of Research" [Enick and Olsen, 2011] that focuses on attempts to enhance carbon dioxide mobility control (in-depth, long-term processes that cause CO2 to exhibit mobility comparable to oil) and profile modification/conformance control (near-wellbore, short-term process primarily intended to greatly reduce the permeability of a thief zone) using CO2 thickeners and CO2 foams. In particular, this paper focuses on the history of CO2 thickeners.