Investigating the Impact of Water and Polymer Flooding Techniques on Reservoir Performance in Heterogeneous Unconsolidated Formations

The global oil and gas industry increasingly leverages advanced enhanced oil recovery (EOR) methods to optimize hydrocarbon extraction from mature reservoirs. Among these, water flooding remains a widely adopted technique, typically achieving recovery rates ranging from 10% to 40% of the original oil in place (OOIP). Polymer flooding, a prominent EOR strategy, enhances recovery by introducing water-soluble polymers to increase the viscosity of the injected water, thereby improving the mobility ratio and vertical sweep efficiency compared to conventional waterflooding. This study evaluates the comparative performance of water flooding and polymer flooding with respect to oil production rates, cumulative production, recovery factors, and the timing of water breakthrough. A three-dimensional, two-phase (oil and water) reservoir model was developed using a black-oil simulator. The investigation incorporated the injection of a flexible biopolymer, such as xanthan gum, into a heterogeneous and unconsolidated reservoir using a direct-line drive method. The study further conducted a sensitivity analysis of polymer flooding, focusing on various injection well configurations, with an emphasis on the five-spot pattern, to identify the optimal injection strategy. The results demonstrate that polymer flooding using a direct-line drive achieves a recovery factor of approximately 44%. In contrast, employing a five-spot injection pattern significantly enhances recovery efficiency to 52% while substantially delaying water breakthrough. These findings underscore the effectiveness of integrating polymer flooding with a five-spot injection pattern to maximize oil recovery from heterogeneous reservoirs.