STUDY ON WATER INJECTION DEVELOPMENT OF UNCONSOLIDATED SANDSTONE RESERVOIRS IN SHENGLI OILFIELD, CHINA

It is well known that the unconsolidated sand reservoirs (USR) has high permeability and high oil-water viscosity ratio. Continuous water injection development process will form high permeability and large pore channels in the reservoirs. At the same time, high displacement phase fluidity can easily causes oil-water interface moves fast to the bottom of production wells and reduces final recovery efficiency. In order to solve this problem, a reservoir geological model of A area has been established by analyzing the existing static and dynamic production data. Based on this, the seepage mechanism of USR has been comprehensively analyzed, and evaluates the influence of water-flooding mode (WFM) difference of depth displacement between injector producer pair effect by means of numerical analogue. And then, a new evaluation standard called sum of field oil recovery (SFOE) is introduced, which is defined as the sum of the values of anhydrous field oil recovery (AFOK) and Held oil recovery (l;OF). The results revealed that, the optimum injection/production ratio based on this evaluation criterion is 1.1, the optimum WFM is low injection and high production. In addition, the result of economic evaluation shows that a higher economic return gets by using this development factor in A area. The evaluation system studied in this paper can effectively increase the sweep area among USR during waterflooding development, and provide a reliable reference for the development of similar reservoirs.