Fracture Effect Limitation on Residual Oil Saturation: Aperture Shrinkage

摘要

Oil production in the fractured reservoirs shows, varying saturation values through the reservoir. This is due to the microscopic fissures and heterogeneity of the fractured environment that could not have been well swept. Higher, production/injection rates also empower the fingering effect by passing the unswept oil in the reservoir. In order to get rid of/minimize this effect, a polymer gel application is applied to fractured cores to decrease the residual oil saturation and increase the oil production. In this study, naturally and artificially fractured cores were used. Analytical calculations were done in different environments, for the experimental flow rates using cubic law under laminar flow for equivalent fracture aperture calculations for all experiments. Cubic law is verified with the fractured cores flow definition whereas not for homogeneous cores. There is a direct relation between fracture permeability with equivalent fracture aperture. The compared experiments with different environments (initially oil saturated and water saturated) in the cores, with calculations of equivalent fracture aperture and fracture permeability, showed similar results (minor deviation due to rate and saturation environment). The effect of polymer gel conformance to increase recovery by decreasing/plugging equivalent fracture aperture was proven. The calculated fracture permeability decrease was observed with decreasing equivalent fracture aperture in the core#3, #5 and #7 respectively. A case study was prepared for Polymer Gel Injection operations in R#17 and R#18 wells. Equivalent fracture apertures were calculated analytically for the field application of polymer gel injection, verified in laboratory study. It was obviously seen that before and after the polymer gel treatments in both wells, analytical calculations for the equivalent fracture aperture, were represented with the cubic law.