Evaluation and optimization of double displacement process

Abstract

Double Displacement Process or DDP is the combination between water injection and gas injection. At the end of water injection, there is still a certain amount of oil remaining in the reservoir. Therefore, we can inject gas on top of the reservoir in order to recover more oil by displacing the oil with gas. In this study, we investigate the effect of dip angles, stopping time for water injection, water injection rate, gas injection rate, and well pattern to determine the best strategy for DDP. Moreover, the sensitivity due to uncertainty in relative permeability, vertical to horizontal permeability ratio, and type of wettability is also included. The more the dip angle, the better the DDP performance. Using the water cut of 60% as the stopping criteria for water injection yields the best production performance. In term of water and gas injection rate, using the rate of 8,000 RB/D yields the best oil recovery factor. For well pattern, using horizontal well as the producer at the bottommost of the reservoir yields the best performance. For sensitivity analysis, the results show that different relative permeability correlations provide insignificant different results. Regarding the effect of vertical to horizontal permeability ratio, it can be concluded that the higher the ratio, the higher the oil recovery due to higher ability to flow in the vertical direction. Type of wettability has a large effect on the performance of DDP. Each type of wettability has a good potential for different periods. Water-wet is better at the early time of DDP while oil-wet shows the better performance at the late time.