Reservoir Sweep Improvement With Cross-Linked Polymer Treatments

Abstract

ABSTRACT Poor reservoir volumetric sweep efficiency results in bypassing, trapping of such of the in-place hydrocarbons, and in the early production of large volumes of water. This paper discusses technology and field results of treating wells in reservoirs with natural water drive as well as reservoirs under waterfloods with polymer solutions containing delayed cross-linkers to improve reservoir sweep efficiency. The continuais monitoring and analysis technique has been applied successfully to selectively treat water saturated zones and to preserve the integrity of oil production. The uniqueness of the profile control system application is the continuous monitoring during the treatment which allows assessment of formation response and provides a valuable tool for treatment design refinement and optimization of injected slug volume. A large number of wells have been treated utilizing delayed cross-linked polymer systems specially tailored for the specific reservoirs. Continuous reservoir monitoring and analysis of data on-site during the polymer application has resulted in better than an 85 percent success ratio. Wells treated were cased as well as openhole completions, long to very short pay sections, naturally fractured, and hydraulically fractured. The reservoirs treated were bottom water drive and waterfloods, as well as reservoirs under gas injection. The treatments were performed successfully in sandstone and limestone, as well as dolomitic formations. Cross-linked polymer treatments have resulted in a significant reduction in water production, and, as a result, many temporarily abandoned wells have been put back on production due to savings in operating costs and enhancement of oil inflow into the wellbore.