Experimental study on combining heterogeneous phase composite flooding and streamline adjustment to improve oil recovery in heterogeneous reservoirs

Abstract

The heterogeneity of reservoirs is the key factor restricting the development performance of oilfields. Heterogeneous phase composite flooding (HPCF) and streamline adjustment (SA) are both viable strategies for improving oil recovery of heterogeneous reservoirs. However, both strategies have their own deficiencies, which limits further development. In recent years, a hybrid strategy combining HPCF and SA has attracted considerable interest from oil industry. In this paper, two-dimensional (2D) large-scale physical model experiments were performed to verify whether the hybrid strategy could offer better development performance than the single strategy, and the mechanism of hybrid strategy for improving oil recovery was elucidated. On this basis, the influence of SA angle on improved development performance was investigated. Finally, the affected regions of remaining oil in different strategies were proposed. The experimental results indicate that HPCF can effectively improve sweep efficiency and oil displacement efficiency in the main streamline regions; furthermore, it prolongs the time of incremental oil production. Streamline adjustment can forcibly utilize the remaining oil in the low-permeability regions at non-main streamline where water flooding and HPCF are poorly affected. The hybrid strategy can give full play to the respective strengths of each single strategy. Meanwhile, SA provides a good induction effect on HPCF, which creates an excellent opportunity for the latter to effectively displace the remaining oil in the low-permeability regions at non-main streamline over extended periods. When the SA angle is 90°, the best development performance can be achieved. The affected regions of remaining oil in different strategies were proposed in this paper, which affords significant guidance for effective development of heterogeneous reservoirs.