Study On Well Logging Evaluation Method Of Shale Gas Reservoir Fracability In Horizontal Wells

As a kind of sedimentary rock with low porosity and permeability,shale gas reservoir usually needs horizontal well fracturing to improve productivity.Therefore,it is very important to evaluate the fracturing ability of shale gas reservoir in horizontal wells before fracturing.Based on the research results of rock mechanics calculation method and stress analysis method of horizontal well shale gas reservoir an evaluation method of horizontal well shale gas reservoir fracturing is formed.The difficulty of rock mechanics calculation of shale gas reservoir in horizontal wells lies in the obvious bedding characteristics of shale and the complex transformation of dynamic and static mechanical parameters.In this paper,HTI medium model is used to describe the structure characteristics of horizontal well shale reservoir,and then the calculation method of dynamic rock mechanics parameters of horizontal well shale reservoir is obtained;through mechanics experiment,the relevant static rock mechanics parameters are obtained,and the dynamic mechanics parameters are calibrated with static mechanics parameters,which realizes the conversion of dynamic-static.The key of horizontal well shale gas reservoir stress analysis is the transformation of stress system.The paper analyzes the calculation method of overburden formation pressure,pore fluid pressure and horizontal stress suitable for horizontal well shale gas reservoir.Through coordinate transformation,the stress parameters in geocoordinate system are changed into the wellbore coordinate system,then the quantitative calculation of horizontal well fracture pressure is realized,and the actual data are compared and verified.Based on the quantitative calculation results of rock mechanics and in-situ stress parameters of shale gas reservoir in horizontal wells,the brittleness index,horizontal stress difference coefficient,natural fracture development index and fracture toughness are determined,and the fracturing index of shale gas reservoir in horizontal wells is obtained by means of analytic hierarchy process.The application results of practical data show that this method has high accuracy and can effectively predict high-quality fractured intervals.