Sweep-Improvement Options for the Daqing Oil Field

Abstract

Summary This paper investigates the potential of various approaches for improving sweep in parts of the Daqing oil field that have been enhanced-oil-recovery (EOR) targets. Our studies indicated that the polymer flood should have provided excellent sweep throughout the vast majority of the patterns under consideration. However, because alkaline/surfactant/polymer (ASP) flooding is being considered to increase recovery efficiency from the Daqing oil field, mobility control and sweep improvement will be especially important and challenging during implementation of any future ASP process. Fractures were present in a number of Daqing wells (both injectors and producers). Because the fractures were narrow and far from the wellbore, severe channeling did not occur. On the contrary, fractures near the wellbore aided reservoir sweep. Nearwellbore fractures increased the injectivity index substantially during the injection of polymer solutions and increased oil-productivity index in the production wells. These observations may be valuable during implementation of future floods where very-low-mobility chemical (i.e., ASP) banks must be injected to maintain mobility control. Several modes of polymer degradation were considered, with mechanical (shear) degradation being of greatest concern. Appropriate use of near-wellbore fractures may mitigate mechanical degradation effectively, as well as improving injectivity. Several new polymers show potential for cost-effective improvements at Daqing. Increased polymer concentration was also considered. A number of other approaches are (or have been) under investigation, including colloidal dispersion gels, foams, ASP foams, steam, microbes, and polymer solutions prepared with reduced salinity.