Model for predicting optimum time for gas injection in WAG enhanced oil recovery process.

Water alternating gas (WAG) processes are usually applied in gas floods to improve oil recovery. However, the best time to inject gas during WAG enhanced oil recovery process is a major challenge in the petroleum industry. Some of the factors that affect WAG performance were investigated using Schlumberger ECLIPSE 100 dynamic simulator. Simulation of several WAG scenarios before incorporation of optimum time yielded total oil recovery efficiencies between the ranges of 53.6% to 64.7%. The simulation results and regression analysis were used to generate a model for optimum time for gas injection (Topt). The model’s ability to predict Topt was tested using one month and three months WAG cycle. The Topt obtained for one month WAG cycle was 22 days while that of three months WAG cycle was 68 days. The incorporation of optimum time for gas injection improved oil recovery efficiency to 75% and 71% for one month and three months cycles respectively. It could be adduced that the optimum time for gas injection enabled complete mass transfer between the injected gas and the oil including gas trapping such that microscopic displacement efficiency and volumetric sweep efficiency are maximized to achieve maximum oil recovery.