Synergistic effects of low-salinity water and associated gas injection in a WAG process for enhanced oil recovery

Abstract Conventional waterflooding often results in limited oil recovery, highlighting the need for more effective enhanced oil recovery (EOR) methods. Low-salinity water (LSW) injection improves oil recovery through wettability alteration, while associated gas injection offers operational and economic advantages. However, previous low-salinity water alternating gas (LSWAG) studies have mainly focused on CO 2 , and the application of produced associated gas remains largely unexplored. This study investigates low-salinity water alternating associated gas (LSWAAG) injection as a hybrid EOR technique. Wettability alteration was evaluated using contact angle measurements, and displacement performance was assessed through core flooding experiments under reservoir conditions. Contact angle measurements showed a 41.4% reduction in contact angle using ten-fold diluted seawater (10DSW), indicating a pronounced shift toward more water-wet conditions. Core flooding experiments demonstrated that the LSWAAG process using 10DSW achieved an oil recovery of 82.59%, representing 14.03% points higher recovery than low-salinity water flooding (10DSW) and 7.96% points higher recovery than seawater alternating gas (SWAG) injection. The contact-angle measurements indicate wettability alteration as a potential contributor to the improved recovery observed during LSWAAG injection. Unlike previous LSWAG studies based primarily on CO 2 , this work experimentally demonstrates the feasibility of integrating produced associated gas with low-salinity water, providing a technically effective, operationally attractive, and environmentally beneficial hybrid EOR strategy while promoting the utilization of associated gas that would otherwise be flared.