A Semi-Analytical Solution of Dimethyl Ether Enhanced Water Flooding

Summary Dimethyl Ether Enhanced Water Flooding (DEW) is a promising water-soluble solvent-based EOR method. In this paper, we developed a semi-analytical solution to describe a one-dimensional (1D) DEW process that considers the effect of Dimethyl Ether (DME) partition coefficient. The 1D flow equations of DEW process were presented by Buckley-Leveret methodology in a linearized form to generate a series of fractional flow curves during oil displacement by DEW. The premise of the study was that once the DME-water solution is injected into the reservoir and comes in contact with oil, DME molecules partition into the oleic phase, which mobilizes waterflood residual oil as a consequence of oil swelling and oil viscosity reduction effects. The dependence of these effects on the DME partition coefficient significantly affects the oil- water fractional flow curve. Accordingly, results showed that there are two shock fronts during DEW process which are related to water and DME advancement. We also obtained the velocity of DME shock front as a function of DME partition coefficient that enables us to describe the fractional flow solution of the DEW process. As to the results, when the DME partition coefficient increases, the distance between water and DME fractional flow curves increases mainly due to the mobility enhancement of the oleic phase as a result of higher partitioning of DME into the oil. In addition, model results showed that increase of the DME partition coefficient up to 10 improved the ultimate oil recovery to as much as 15% of the OIIP on top of water flooding for the case of a heavy crude oil with a viscosity of 20 cp. As to the results, increase of the DME partition coefficient accelerates the oil recovery rate as well. At the end, this paper provided a semi-analytical solution based on the fractional flow theory to describe DEW process with the emphasis on the partitioning effect..