Abstract
Abstract
This study investigated the effect of dimethyl ether (DME) that was mixed with CO2 to improve of oil recovery in the heterogeneous reservoir. Dykstra-Parsons’ coefficient (VDP) was used to quantitatively represent the heterogeneity of reservoir. Changes in vertical sweep efficiency and displacement efficiency were observed through oil viscosity, swept area, and oil saturation. When the same volume of solvent injected, the slope of the front of the swept area increased by about 1.6 times when the DME content is 20% compared to only CO2 is used for the homogeneous reservoir and increased by about 1.4 times for the most heterogeneous reservoir, VDP=0.79. At breakthrough, the swept area increased by up to 17% for the homogeneous reservoir and up to 7% for the most heterogeneous reservoir, confirming that the more heterogeneous the reservoir, the lower the sweep efficiency increase effect of DME. At the end of the WAG process, the area in which the remaining oil saturation was 0.6 or more increased significantly in the heterogeneous reservoir. Oil recovery improved by about 21% from 58.4% when only CO2 was injected, to 70.5% when the DME content was 20% for the homogeneous reservoir and improved by about 11% from 40.5% when only CO2 was injected to 45.1% when the DME content was 20% for the most heterogeneous reservoir. Since DME is an expensive solvent, the NPV maximization scenario was calculated in consideration of different oil prices and solvent reuse. Without considering solvent reuse, if the oil price is $30/bbl, NPV is negative due to the high DME price even though the oil recovery is high if only DME is used. When the oil price is 90$, NPV has a maximum value of $571,071 when the DME content is 1%, and when the DME content is 20%, it has a maximum value of $852,054 when the DME content is 20%. Considering solvent reuse, NPV is maximum at $884,751 when DME is 38% in homogeneous reservoirs for oil price $90/bbl and maximum at $581,986 when DME is 16% in most heterogeneous reservoir.