Study on Remaining Oil Distribution Characteristics and Water Flooding Efficiency Improvement Technology after Polymer Flooding

Abstract It has become a focus of concern for polymer flooded oilfields to further produce remaining oil after polymer flooding at the subsequent water flooding stage. Based on the basic theory of hydrodynamic flow field distribution, a method to produce remaining oil at the diversion lines was proposed in this paper, which controls the increase rate of water cut by developing rational fluid control and water flooding efficiency improvement measures according to remaining oil saturation and the polymer injection rate at the diversion lines. A pilot test block has been selected and it has entered into the subsequent water flooding stage after polymer flooding. The distribution of remaining oil in the pilot test block is more complicated than that before polymer flooding, and the water cut is as high as 97.9%. Both the fluid production rate and injection rate are high among similar blocks. Low efficiency or invalid circulation is very serious, and development problems are becoming worse. This paper systematically analyzed the distribution characteristics of remaining oil. At the subsequent water flooding stage, the distribution of remaining oil is more scattered, most of it distributes near the faults and at the fringes of blocks, and remaining oil at the top of thick layers is produced by shutting in some water injectors and executing fracturing. By identifying preferential flow pathways, stopping water injection, increasing or decreasing the injection rate, water injection is rationalized. After one year of application in the pilot test block, the fluid production has been reduced by 146,000t, and 722,900t of water has been conserved due to properly controlled water injection.