Research on the Adaptability of SP Flooding in Sand-Gravel Mixture Reservoir Based on the Inverted Seven-Spot Well Pattern

As one of the leading technologies for chemical enhanced oil recovery (cEOR), surfactant-polymer (SP) flooding technology has drawn the attention of petroleum scientists and engineers for many years. However, most of its application scenarios are based on the five-spot well pattern. Rarely reported is its EOR potential in an inverted seven-spot well pattern. Based on the physical properties of Karamay Oilfield in China, this paper studied the adaptability of the SP system in the inverted seven-spot well pattern. Firstly, the numerical simulation method and the single-core flooding experiment were used to compare the seepage intensities of the two well patterns and the EOR ability of the SP system under different seepage intensities. Then, the migration law and the oil displacement effect of the SP system under the conditions of sand-gravel mixture were evaluated. Finally, the EOR ability under different injection strategies in the well patterns was evaluated. The results show that the inverted seven-spot well pattern shows a weak swept state, accounting for 61% of the whole region. Appropriately increasing the viscosity and slug size of the SP system improves the oil production of the low-permeability conglomerate layer. Step-down viscosity injection can further enlarge the sweep range of injection fluid and enhance oil recovery compared to constant viscosity injection. Compared with the five-spot well pattern, the swept area of the SP system in the inverted seven-spot well pattern is larger while the strength is weaker. The injection and production wells should be reasonably arranged when the well pattern is converted to efficiently recover the remaining oil and residual oil that are not recovered in the five-spot well pattern by utilizing the inverted seven-spot well pattern characteristics.