CO2-EOR Mobility and Conformance Control: 40 Years of Research and Pilot Tests

Abstract

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 154122, ’Mobility and Conformance Control for CO2 EOR - Thickeners, Foams, and Gels: A Literature Review of 40 Years of Research and Pilot Tests,’ by R.M. Enick, SPE, University of Pittsburgh; D. Olsen, SPE, IBM Global Business Services; J. Ammer, US Department of Energy, National Energy Technology Laboratory; and W. Schuller, URS Corporation, prepared for the 2012 SPE Improved Oil Recovery Symposium, Tulsa, 14-18 April. The paper has not been peer reviewed. Carbon dioxide (CO2) has been used commercially for enhanced oil recovery (EOR) for more than 40 years. The CO2-EOR process could be improved if the high mobility of CO2 relative to reservoir oil and water could be reduced effectively and affordably. The water-alternating-with-gas (WAG) technology is the preferred method to control CO2 mobility, along with the use of 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 bbl is to be realized, new solutions are needed that can recover significantly more oil than the 10–20% of the original oil in place (OOIP) associated with current flooding practices. This literature review concentrated on the history and development of CO2-mobility-control and profile-modification technologies. Introduction Every day, more than 110 field projects in the US, 60% of which are in the Permian Basin in west Texas, inject 3.1 Bscf of CO2 into sandstone and carbonate formations to recover more than 280,000 bbl of oil. This corresponds to approximately 5% of the nearly 5 million BOPD of US oil production. The number of CO2-flood projects has increased steadily in recent years, in contrast to other EOR methods. The limiting factor for expanding CO2 flooding is the availability of large volumes of high-pressure CO2 because most CO2 suppliers are operating at full capacity. For example, new projects in the Permian Basin are constrained by the need for an additional 0.3–0.4 Bscf/D of CO2 in the region. Conversely, the rapid growth of CO2 EOR in Mississippi reflects the growth of CO2 supplies in that region. Approximately 74.4% of the CO2 used for EOR comes from gas-treating and -processing facilities associated with the production of CO2-rich natural gas, while 19.4% originates from natural-gas plants, 4.8% from coal-synfuel plants, and the remainder from various chemical and petroleum facilities. The dehydrated, high-pressure CO2 from various sources is transported to oil fields where it is compressed to the desired injection pressure, combined with recycled CO2 and injected into the reservoir.