Investigation of the Flow Intensity in an Inverted Seven-Point Well Pattern and Its Influence on the EOR Efficiency of S/P Flooding

Abstract

Polymer and surfactant (S/P) binary flooding is a widely used chemical flooding technology for enhanced oil recovery (EOR). However, it is mostly used in the five-spot well pattern, and there is little research on the effect of well patterns on its flow law and EOR efficiency in the reservoir. In this paper, the flow intensity of S/P flooding in an inverted seven-spot well unit and its EOR efficiency are investigated. Based on the theoretical derivation and simulation, the flow distribution at different positions in the inverted seven-spot well pattern unit was calculated. The oil displacement efficiency was evaluated by simulating different flow intensities with various flow velocity. The microscopic residual oil of the core at the end of displacement was scanned and recognized. The 2D model was used to simulate the well pattern to clarify the EOR of S/P flooding. The results show that the swept area in the well unit can be divided into the strong swept region (>0.2 MPa); medium swept region (0.1–0.2 MPa); weak swept region (0.03–0.1 MPa); and invalid swept region (<0.03 MPa), according to the pressure gradient distribution. Compared to the five-spot well pattern, the inverted seven-spot well pattern featured a weak swept intensity, but a large swept area and lower water cut rise rate. Increasing the flow intensity can improve oil displacement efficiency, and disperse and displace continuous cluster remaining oil. The 2D model experiments show that the incremental oil recoveries by SP flooding after water flooding in the five-spot well pattern and inverted seven-spot well pattern are 25.73% and 17.05%, respectively. However, the ultimate oil recoveries of two well patterns are similar by considering the previous water flooding.