COMPARATIVE PRODUCTION PERFORMANCE BETWEEN CONVENTIONAL WATER ALTERNATING GAS FLOODING AND WATER DUMPFLOOD ALTERNATING GAS INJECTION

Water dumpflood alternating gas injection (WDAG) to improve oil recovery is proposed in this thesis. Eliminating water flooding system at surface, water flows freely through a dumping well from an aquifer to the oil reservoir alternating gas injection from surface. The water dumping well is perforated in both the aquifer and oil zones to allow cross flow of water. A reservoir simulation model was built to investigate conventional water alternating gas injection (WAG) and water dumpflood alternating gas injection from underlying and overlying aquifer. Several scenarios of aquifer depths, target gas injection rates and water-gas injection cycles were investigated. It has been found that conventional WAG and WDAG yield the highest recovery factor at water-gas injection cycles of 1: 1 month and at high target gas injection. Target gas injection rate and water-gas injection cycle slightly affect the performance of conventional WAG but significantly impact WDAG. The sensitivity study indicates that an increase in volumetric ratio of aquifer to oil reservoir slightly increases the recovery factor in WDAG. The depth of underlying aquifer shows minor effect the performance of WDAG while a shallower overlying aquifer yields slightly better oil recovery factor than those for a deeper overlying aquifer. At the highest target gas injection rate of 16 MMSCF / D, WDAG recovery factor is about 2% lower than conventional WAG. However, WDAG does not require any water injection from surface.