Improve Oil Recovery Mechanism of Multi-Layer Cyclic Alternate Injection and Production for Mature Oilfield at Extra-High Water Cut Stage Using Visual Physical Simulation Experiment

In order to achieve sustainable development of mature oilfield, a series of adjustment measures should be implemented to improve production performance at the extra-high water cut stage. South Kumkol reservoir is a typical multi-layer low viscosity oil reservoir, which has the characteristics of small sandstone body, high shale volume, and strong heterogeneity. At present, the water cut of the South Kumkol reservoir is about 90%, which is on the verge of being abandoned. Multi-layer cyclic alternate injection and production (MCA-IP) is an ideal adjustment measure for multi-layer oil reservoir to improve oil recovery (IOR) at the extra-high water cut stage. In this paper, we designed the double-plate visual physical device and the MCA-IP experimental program and then calculated the sweep coefficient using image recognition method. Furthermore, the sweep coefficient was quantitatively calculated by image recognition method. The results show that the sweep area extends to both sides of the main streamline and the sweep efficiency is gradually improved after the completion of MCA-IP. In addition, the IOR mechanism of MCA-IP mainly includes reperforation, well-pattern encryption, and asynchronous injection-production. The reperforation and well-pattern encryption increased the sweep coefficient by about 19.52%, while asynchronous injection-production increased the sweep coefficient by about 1.2%, and the overall sweep coefficient increased by about 20.7%. According to the experimental data statistics, the MCA-IP method can increase oil recovery by about 11% and reduce water cut by about 6%.