THE PERFORMANCE OF POLYMER FLOODS IN PARTIALLY FRACTURED RESERVOIRS

With the growing demand for oil and the prospect of higher prices, the application of enhanced oil recovery (EOR) processes is becoming an important strategy for many oil-producing companies around the world, including in the Middle East region. In this region, there are a large number of oil and gas reservoirs that are naturally fractured. In fact, most hydrocarbon reservoirs are fractured to some degree. Among EOR processes, polymer flooding represents an attractive option that could be applied in many of these reservoirs. Therefore understanding what parameters affect polymer flooding in naturally fractured reservoirs and their impact on performance prediction is critical in the decision on the applicability of this recovery technique. Using fine-mesh numerical reservoir simulations, this study investigated the performance of polymer floods in fully to slightly fractured reservoirs. A random distribution of fractures was assumed to simulate the irregularity of typical fracture networks. A dual-porosity, dual-permeability model was used to simulate the displacement phenomena. Extensive simulation runs were performed to determine the functional relationship between recovery performance and various design parameters during polymer flooding. These parameters included (1) fracture intensity; (2) well configurations; (3) polymer slug size; and (4) polymer concentration. Results show that these parameters have significant effects on the efficiency of a polymer flood. A critical value of fracture intensity appears to delineate favorable from unfavorable performance in polymer floods. The ranges for the values of parameters under which polymer floods may yield better performance are presented.