Study On Residual Oil Distribution And Fracturing Optimization In S Zone

The development of S block enters into high-water-cut period after long-term full water injection beginning from 1964.It is a big problem that most of water flooding circulation is low efficiency,due to the special location of this area locating on the obvious phase transitional zone which caused great differences of crude oil viscosity in different sedimentary facies and low degree of water flooding.The distribution of residual oil is scattered which leads to difficulties to select wells and layers during fracturing program.In order to explore above development problems,firstly studying the distribution law of remaining oil in transition zone by means of numerical simulation and theoretical calculation,combined with the fine geological study of the reservoir.We obtain several types of residual oil based on quantitative results of residual oil between layers and planes in this transition zone.There are mainly four types of residual oil:well pattern failed control,longitudinal heterogeneity,incomplete injection and production,and plane differential oil layers which respectively stands about 176.48×10~4t,231.3×10~4t,56.51×10~4t,and 309.46×10~4t.Through calculation and analysis of the remaining oil reserve abundance in this area,it is determined that the main excavation layer is that reserve abundance is larger than 20×10~4t/km~2,and the thickness of the small layer is between 0.5m and 1m,accounting for 40%of the total geological reserves.Then the high potential areas of the remaining recoverable reserves are SII2a,SII2b,SII2a,SII3,SII4,SII8,and SII12.Secondly,based on the research results of remaining oil,the data mining method and reservoir numerical simulation method is used to verify the fracturing feasibility of wells with low production and efficiency and high remaining oil reserves abundance in the study area.Then,we get the optimized design parameters according to numerical simulation evaluating the sensitivity of fracture length,fracture permeability,fracture height and other parameters during optimized fracturing wells.It is concluded that the fracture half length of optimized fracturing design is 30m,the optimal fracture permeability is1500 m D,the thickness is 0.6-2.5m,and the optimal fracturing reserve abundance is30×10~4t/km~2.Finally,designed the comprehensive fracturing scheme and tracked the fracturing effect,two years'accumulative increase of oil is predicted to achieve26210t after fractured the 12 wells in accordance to designed scheme,which illustrated the fracturing design effect is well,...