SANDSTONE RESERVOIRS

This research investigates the feasibility and performance of polymer flooding as an enhanced oil recovery (EOR) method for Nigerian sandstone reservoirs. With the growing need to improve oil recovery from mature fields and reduce dependency on primary and secondary recovery techniques, polymer flooding has emerged as a promising tertiary recovery strategy. The study focuses on evaluating the technical and operational effectiveness of injecting hydrolyzed polyacrylamide (HPAM) polymer solution under representative Nigerian reservoir conditions using the CMG-STARS simulation software. A detailed reservoir model was developed, incorporating a six-layer sandstone formation characterized by an average porosity of 20%, initial pressure of 2299.2 psi, and oil viscosity of 5 cP. Two simulation cases were analyzed: a base case (without EOR) and a polymer flooding case with a 2000 ppm polymer solution injected over a 30-year production period (2025–2055). The performance of both scenarios was evaluated based on field oil production rate, bottom-hole pressure, water cut, and cumulative oil recovery. The results revealed that polymer flooding significantly improved reservoir performance compared to the base case. While the base case exhibited a steady decline in pressure and oil rate leading to early depletion around 2047, the polymer injection maintained an average pressure of about 2100 psi throughout the simulation. The polymer case also achieved a cumulative oil
recovery of 23.6 million stock tank barrels (MMSTB), representing an incremental gain of 5.8 MMSTB (32.6%) over the base case. Furthermore, water cut was reduced from 89% to 68%, indicating better mobility control and sweep efficiency. These findings confirm that polymer flooding is a technically viable and cost-effective EOR method for Nigerian sandstone reservoirs, capable of improving oil displacement efficiency and extending field life. The study recommends that field pilot projects be implemented to validate simulation outcomes and optimize polymer formulation for local reservoir conditions. Overall, this research demonstrates that polymer flooding can play a vital role in maximizing Nigeria’s oil recovery potential, supporting energy sustainability, and promoting efficient reservoir management.