Geological Characteristics And Fracturing Parameter Optimization Of Chang 7 Reservoir In Xunyi Area

The chang 7 formation in Xunyi area is an extreme low-porosity and low-permeability reservoir with no natural production capacity.It needs to obtain industrial production through fracturing,but it has a high water content after fracturing,even no oil.Against the main problems in the research area,this paper studies the basic geological characteristics of chang7 formation by studying the structural features,sedimentary characteristics,reservoir characteristics,etc.Combined with laboratory tests and logging data,reservoir rock mechanics parameters and distribution characteristics of crustal stress were obtained.Through comprehensive analysis,the poor fracturing results is mainly due to the widespread distribution of the water layer in the reservoir and the unreasonable design of fracturing parameters.The fracturing parameters of the Chang 7 reservoir in the reserch area were optimized by the three-dimensional fracturing software FracproPT10.4,then the suitable fracturing parameters for the chang 7 reservoir in reserch area were obtained.The main results and conclusions obtained in this paper are as follows:(1)The Chang 7 reservoir in Xunyi area is extra low porosity and low permeability reservoir.The complex structure,wide distribution of water layer and small thickness of interlayer are one of the reasons for the poor fracturing result.(2)Through the study of rock mechanics parameters and crustal stress field,it is concluded that the maximum principal stress in the reserch area is vertical stress,the minimum principal stress is in the horizontal direction,and the azimuth is from northeast to southwest,and vertical cracks are easily generated.(3)The main reason for the poor fracturing result of the Chang 7 reservoir is that the fracturing parameters are unreasonable,and the displacement volume,the sand-carrying agent volume,the pad fluid volume,and the replacement fluid volume are excessive.(4)The thickness and permeability of Chang 7 reservoir are divided into four grades respectively,and the fracturing parameters are optimized according to different reservoir thickness and permeability.The optimized fracture length is between 85 and 125meters;the optimized dimensionless diversion capacity is between 2.5 and 7.5;the optimal perforation density is 20 holes/m,the aperture is 1 centimeters,and the opening degree is 20%~30%;The optimized displacement volume is between 0.9~1.4 m3/min,the sand amount is between28.1~45.7m~3,the sand-carrying agent volume is between 139.7~224.3m~3,the sand ratio is about 20%,and the optimized pad fluid volume ranged from 23.7%to 25.6%.The displacement volume was related to the depth of the reservoir.