Feasibility of Foam-Enhanced Water-Gas Flooding for a Low-Permeability High-Fractured Carbonate Reservoir. Screening of Foaming Agent and Flooding Simulation

Abstract

Abstract The carbonate reservoirs of the Alekseevskoye field (Russia, Republic of Tatarstan) are complicated by high heterogeneity and the presence of fractures, which make development difficult due to early water or gas breakthrough depending on the injected agent, as well as low of the productive horizon. To increase sweep efficiency and introduce fractured reservoirs into development, it is necessary to use gas enhanced oil recovery (EOR) technologies. To find the optimal technology in terms of technological complexity and efficiency, three technologies were compared: Water Injection (WI), Water-Alternating Gas (WAG), and Foam Assisted Water-Alternating Gas (FAWAG). Series of core-flooding tests were implemented under reservoir conditions on carbonate cores, and cores with artificial fractures, saturated with original reservoir fluids. For FAWAG method compatible with high-mineralization water surfactant was chosen. Total recovery factor for each test was calculated. It was equal to 33%, 76% and 53% respectively for WI, WAG and SWAG, on the original core models. Therefore, WAG and SWAG were chosen as most effective techniques to improve oil recovery for in comparison with CWI. In artificially fractured cores, the WAG method recovery rate was 40%; subsequent injection of a foaming active substance mixed with FAWAG formation water proved effective, increasing the oil recovery rate to 47% due to partial blockage of the fracture.