Using CO2 Emission from a Steam Injection Project to Improve Oil Recovery in a Light Oil Reservoir

Abstract This study complements a 2024 study by the authors emphasizing the favorable wettability alteration change by CO2 dissolution in brine. However, the paper is a systematic approach to assessing and quantifying the beneficial effects of implementing a water-alternating-CO2 (WAG-CO2) flood in a carbonate reservoir, utilizing CO2 from nearby steam injection boilers. The numerical findings indicate that this initiative represents a viable enhanced oil recovery (EOR) strategy, concurrently sequestering substantial amounts of CO2 emissions from a steam injection process. WAG-CO2 flooding results in a promising 42% EOR while sequestering 3,100 SCF of CO2/ STB of incremental oil. Conversely, continuous CO2 injection produces 34% EOR and sequesters 9,600 SCF of CO2/STB of incremental oil. The key contribution of this study is the experimental and numerical demonstration that altering wettability of carbonate rock toward more water wet is one of the mechanisms by which CO2 injection increases hydrocarbon recovery while sequestering CO2 in carbonate reservoirs. It is shown, experimentally, that carbonated brine significantly reduces oil-wetness of limestone reservoirs, decreasing interfacial tension (IFT) by 2 to 4.1 dynes/cm and contact angle by 16° to 12.1° (compared to a reduction of 1.6° to 6.7° for brine injection only) for both crude oil and synthetic hydrocarbon systems. The integration of experimental findings into the numerical reservoir model through a correlation indicates a decrease in residual oil saturation by 5.2% and an increase in oil recovery by 2%. The results support the residual saturation endpoints used in the numerical model.