Improving Oil Recovery Using Miscible Selective Simultaneous Water Alternating Gas (MSSWAG) Injection in One of the Iranian Reservoirs

Abstract

In the current investigation, feasibility study has been done for miscible selective simultaneous water alternating gas (MSSWAG) injection compared with immiscible and miscible water alternating gas (IWAG and MWAG) injection in one of the Iranian reservoirs which has been subject to water flooding for several years and the recovery factor (RF) for water flooding is about 23% of the original oil in place. Through IWAG injection, the effect of gas types comprising lean and rich has been investigated which led to increase the recovery factor to 29% for rich and 28% for lean gas. Moreover, miscible injection results show that the recovery factor for rich MWAG with optimized injection pore volume led to 41.74% which shows 12% greater values than the value for immiscible one. Also, sensitivity analysis represents that under rich MWAG injection with 1:2 WAG ratio and 100-day injection period, recovery factor has improved by 7% and reached 48.55%. In continuation to the study with emphasis on the advantages of miscibility, rich MSSWAG with RF: 54.73% has led to increase the recovery factor by 6% compared to rich MWAG with RF: 48.55% (being the best scenario in this study based on simulation results). Finally, considering the economic aspects, the net present value for rich MWAG and rich MSSWAG is significantly increased by approximately average 31% relative to water flooding.