Modeling of Dimethyl Ether Enhanced Water Flooding in a Heavy Oil Sandstone Reservoir

Abstract

Summary After natural recovery period and water flooding period from heavy oil reservoirs, due to an unfavorable mobility ratio, oil recovery is not complete, therefore, substantial amounts of oil remains in the reservoir. In this paper, we investigated the improvement of water flooding performance in a heavy oil reservoir by the addition of Dimethyl Ether (DME) to brine, i.e. DME Enhanced Water flooding (DEW) technique. DME showed a promising potential for enhanced oil recovery purposes. In this method, an aqueous phase containing dissolved DME is injected into an oil reservoir to improve the recovery efficiency. DME is transferred from the aqueous phase into the oleic phase due to partitioning, which leads to an extra oil recovery on top of water flooding recovery. We developed a workflow to model DEW in a heavy oil sandstone reservoir. The numerical model comprises a simplified PVT model and Darcy's law. The results of our study shows that as the injected aqueous phase advances, more DME partitions into oil and leading to oil swelling and a large oil viscosity reduction. Due to these mechanisms, an oil bank forms and leads to an extra and faster oil recovery. For instance, an incremental oil recovery of 17% of the OIIP was achieved by DME on top of conventional water flooding. In the case of double DME partition coefficient, an incremental oil of 24% of the OIIP was obtained. Moreover, DME concentration increased from 0.05 to 0.15 and 0.35 volume/volume, oil recovery enhanced from 10% to 15% and 23% of the OIIP. Results show that the impact of oil viscosity reduction mechanism is more important than the impact of oil swelling in recovery of heavy oil. Overall, DME showed a good potential for EOR application in the heavy oil sandstone reservoir.