Simulation Study of Gel Conformance Treatments
Poor vertical and areal sweep because of channeling of injected water to high-permeability zones leads to significant amounts of bypassed oil in many waterfloods. Chemical treatments involving injection of a gel formed in-situ are used to reduce the preferential channeling through high-permeability zones to improve the vertical sweep efficiency. The objective of this study was to optimize the design of gel treatments through more realistic simulations using UTCHEM (a chemical flooding simulator) with various parameters such as reservoir description, types of gel, the amount of gelant, well control, and gel treatment strategies. In this work, the simulations of gel treatments of producers or injectors involving the injection of various gels were performed in the model reservoirs with layered or stochastically generated permeabilities. The effectiveness of gel treatments was investigated by varying the strategies of gel treatments such as zonal isolation, wells operating under a constant bottomhole pressure versus a constant rate, the confinement of the reservoir, and near-wellbore treatment versus in-depth gel treatment. In-depth gel treatments were simulated using environmentally safe gels such as polymer/chromium malonate gel, silicate gel, and polymer/Cr(III) gel with temperature-dependent gelation. Simulations of gel treatments in reservoirs with multiple unconfined wells and horizontal wells were performed. The UTCHEM simulator was modified to simulate several gel reactions with various kinetics and components. Using geochemical reaction equilibria, dynamic effects of pH change on gelation and the retention of crosslinker (precipitation of chromium hydroxide) were modeled.