Modeling DME-Water Flooding and Feasibility Study of Using this Method for Enhanced Oil Recovery in the Condition of a Heavy Oil Reservoir

DME-enhanced water flooding is considered as a novel enhanced oil recovery method. In this method, DME-rich water is injected into an oil reservoir. In addition, upon the contact of DME-rich water with trapped oil in the reservoir, DME partitions between the oleic and the aqueous phase. Due to the partitioning process DME transfers from the aqueous phase into the oleic phase until reaching a thermodynamic equilibrium. Consequently, two zones are generated in the oleic phase: 1- an interface region, which is DME-rich, and 2- the DME-free zone, which is far from the interface. The variation of DME concentration in the oleic phase causes a DME transfer from the DME-rich zone into the DME-free zone due to the molecular diffusion. The DME dissolution in the oleic phase causes an oil swelling process and thus an increase in the saturation of the oleic phase along with oil viscosity reduction. Moreover, both effects improve the oleic phase mobility leading to a more favorable oil displacement efficiency in porous media. The present work demonstrates the feasibility of application of DME-enhanced water flooding in recovery of heavy oils via a 1D modelling study. Therefore, several pieces of work were performed to achieve proper results. First, mass conservation of components was combined with the Darcy equation while using a constant partition coefficient (linear PVT model) to obtain governing fluid flow equations. Then, the system of equations was completed using auxiliary equations and equations were combined to reduce the number of independent variables. Afterwards, equations were numerically solved using a finite difference scheme to find the independent variables, i.e. pressure and saturation of the aqueous phase, and also concentration of DME in the aqueous phase. Numerical modeling results showed that the use of DME-enhanced water flooding improves oil recovery in heavy oil reservoirs. For instance, the DME-enhanced water flooding led to an additional oil recovery of 17 percent of the OIIP on top of water flooding oil recovery. Moreover, results showed the injection of DME-water into the porous media causes the formation of an oil bank and also a reduction in the water cut. Furthermore, it was shown that a part of DME can be recovered at the injection well, and this can affect the project economy positively. Finally, the results showed the potential application of DME in the recovery of heavy oil.