Experimental investigation of oil recovery by different injection scenarios under low oil/gas IFT and mixed-wet condition: water-flood, gas injection, WAG and SWAG injection

Water flooding and gas injection are two widely used improved oil recovery techniques that can be applied individually or combined as water alternating gas (WAG) or simultaneous gas and water (SWAG) injection. To do reservoir development planning, for possible implementation of these oil recovery schemes, reliable reservoir performance prediction is needed. Most of the existing reservoir simulators are unable to adequately account for all the
complex multiphase and multiphysics processes involved in these oil recovery techniques. We present the results of a comprehensive series of well-controlled coreflood experiments carried out under mixed-wet condition using a very low IFT gas-oil system. The experiments include oil recovery by water flood (WF), continues gas injection (CGI), two series of WAG, and two series of SWAG injection tests. The difference between the two WAG experiments is the order in which gas and water injections are carried out. The results show that for mixed-wet rocks, among the studied injection strategies, SWAG is the worst and alternating injection of water and gas (WAG), starting with a water flood period, is the best injection strategy.