Effect of High-Multiple Water Flooding and Layered Allocation on Oil Displacement Efficiency in Unconsolidated Sandstone Reservoirs

The main oil layer of Oilfield A is characterized by shallow braided river delta deposits with weak vertical and horizontal continuity of sand bodies and strong heterogeneity. After over 20 years of water flooding development, the oilfield has entered a high water-cut stage, with a recovery factor of less than 25%. It is urgently required to take measures to enhance the oil recovery. To address this, experiments on high-multiple water flooding and interlayer parallel water flooding were conducted using the latest core samples from the oilfield to clarify the improvement of oil displacement efficiency by these two measures. The results show that when the water injection multiple is increased from 30 to 2000 PV, oil displacement efficiency increases by 3.77% (from 58.43% to 62.20%). Compared with commingled injection-production, two groups of experiments show that the oil displacement efficiency of layered allocation increases by 2.88% and 9.61%, respectively, indicating a significant improvement. The study provides a basis for the subsequent optimization development plan of the oilfield by increasing the water injection multiple and implementing fine layered injection and production, and can also provide a reference for similar oilfields.