Oil Recovery Improvement Using CO2-enriched Water Injection (SPE-121170)

摘要

CO2 injection is increasingly considered as having potential applications as a possible enhanced oil recovery (EOR) process for oil reservoirs. However, poor sweep efficiency has been a problem in CO2 floods of many oil reservoirs and hence, injection strategies like WAG (water-alternating-gas) injection have been proposed and applied as a way to mitigate the problem.An alternative injection strategy is CO2- enriched (carbonated) water injection (CWI). This paper presents the results of an integrated experimental and theoretical study on the application of CO2-enriched water flooding for enhanced oil recovery. Direct flow visualization experiments have been carried out using high-pressure transparent porous media. The results of our visualization experiments demonstrate that CWI, compared to unadulterated water injection, improves oil recovery. The main mechanisms of oil recovery by CWI are swelling, viscosity reduction and coalescence of the isolated oil ganglia as a result of CO2 diffusion and also improved sweep efficiency. This injection strategy is particularly attractive in waterflooded oil reservoirs in which high water saturation adversely affects the performance of conventional CO2 injection methods. CWI can be carried out in combination with reservoir pressure draw down carried out subsequent to CWI or in a cyclic manner in which carbonated and plain water cycles are injected in succession. The results of a mathematical model is also presented which honours the experimental observations and simulates the dynamic process of oil swelling and shrinkage due to CO2 dissolution whilst CW and WI.