Reservoir Simulation Study on Improvement of Waterflooding Effect for a Naturally Fractured Low Permeability Field in Daqing, China: A Successful Case

摘要

Xinzhao field, developed in 2000, is one of the major naturally fractured reservoirs of Daqing oilfield, China. Production is obtained from the Putaohua(P) sandstone formation at an average depth of 1,338m. After several years’ waterflood development, the development effect was deteriorating, many wells were becoming to be stripper wells, and watercut increased greatly, even some wells were seriously watered out. In order to improve the development effect of Xinzhao oilfield, a reservoir study was made in sufficient depth to understand past performance and to develop a long-range development plan, and the proposed pattern modification was performed in Xinzhao oilfield. The purpose of the study is to develop an optimization strategy for waterflood performance. The first step in the process is to better understand the reservoir. One of tools used are Sourceless Microseismic Fracture Monitoring Technology. The Sourceless Microseismic Fracture Monitoring tool is used to determine the characteristics of fractures. The results of Sourceless Microseismic Fracture Monitoring Technology show that the orientation of most of fractures is east-west. The second step is to analyze the past waterflood production performance to know the development characteristics of existing pattern(inverted nine-spot well pattern). The production rate decline is analyzed, and the reasons causing the current poor development effect are identified. The third step is to develop optimization and surveillance recovery strategies. Reservoir simulation approaches are utilized to optimize the well pattern. The recommended plan is pattern modification with strategy of implementing conversions step by step. A field test of waterflood pattern realignment was carried out. This paper presents the results of pattern modification, and the following tracking and modifications strategies. This field test in Xinzhao field is successful and also is an excellent opportunity to demonstrate the method to improve the development effect of naturally fractured reservoir.