A Prudent Approach to Reduce CO2 Emissions While Enhancing Oil Recovery

Emissions of carbon dioxide (CO2) resulting from steam-driven enhanced oil recovery (EOR) operations present an environmental challenge as well as an opportunity to further enhance oil recovery. Using numerical simulations with realistic input data from field and laboratory measurements, we demonstrate a prudent approach to reduce CO2 emissions by capturing CO2 from steam generators of a steam-driven enhanced oil recovery (EOR) project and injecting it in a nearby oil field to improve oil recovery in this neighboring field. The proposed use of CO2 as a water-alternating-CO2 (WAG-CO2) EOR project in a small, 144-acre, sector of a target limestone reservoir would yield 42% incremental EOR oil while sequestering CO2 with a net utilization ratio (NUR) of 3100 standard cubic feet CO2 per stock tank barrel (SCF/STB) of EOR oil in a single five-spot pattern consisting of a central producer and four surrounding injectors. This EOR application sequesters 135,000, 165,000, and 213,000 metric tons of CO2 in five, ten, and twenty years in the single five spot pattern (i.e., our sector target), respectively. As a related matter, the CO2 emissions from nearby steam oil recovery project consisting of ten 58-ton steam/hr boilers amounts to 119,000 metric tons of CO2 per year with an estimated social cost of USD 440 million over 20 years. Upscaling the results from the single five-spot pattern to a four-pattern field scale increases the sequestered amount of CO2 by a factor of 4 without recycling and to 11 with recycling produced CO2 from the EOR project. Furthermore, the numerical model indicates that initiating CO2 injection earlier at higher residual oil saturations improves EOR efficiency while somewhat decreases sequestration per incremental EOR barrel. The most significant conclusion is that the proposed venture is an economically viable EOR idea in addition to being an effective sequestration project. Other sources of CO2 emissions in oil fields and nearby refineries or power generators may also be considered for similar projects.