Study On Post-fracturing Performance Of Shale Gas Reservoir

The post-fracturing productivity prediction of shale gas plays as the critical basis of program formulation as well as implementation.But the current investigation of domestic researchers upon the multi-scale transport mechanism,performance evaluation theory and fracturing plan designing of the shale gas is still far behind the development of practice.Therefore,this paper aimed at the complex micro flow characteristics of shale gas reservoir,based on the seepage theory of fracturing well in the dual medium gas reservoir,adopting the method of well test analysis as well as mathematical physics to investigate a novel productivity calculation model considering the multi-scale migration mechanism and the complicated morphology of hydraulic fractures.The main work completed are as follows:(1)The fracturing technology and calculation method of shale gas wells were investigated sufficiently,especially the solution and research status of analytical models;the distinct storage pattern,multi-scale migration mechanism,complex shape of fracture network and different flow stages in the production process of shale gas reservoir were also systematically analyzed.(2)Based on a modified Warren&Root’s model,considering the micro flow characteristics including adsorption and desorption,Knudsen diffusion and slip flow,stress sensitivity of micro fractures,and high-velocity non-Darcy flow within the main hydraulic fractures,and other factors,a novel productivity calculation model of multi-fractured horizontal well with closed boundary and finite conductivity fractures in shale gas reservoir has been established;then using the well test analysis method and the mathematical physics method respectively to solve the shale gas production model of early/late transient flow and pseudo-steady flow period.(3)A production calculation programming of the whole seepage process has been completed.Then the adaptability and accuracy of the model was verified by the actual production data in gas field pratice.(4)The influence of adsorption and desorption of shale gas,the Knudsen diffusion and slip flow,the stress sensitivity effect and the non-Darcy effect upon post-fracturing productivity have been analyzed respectivily.Then the model was compared with the calculation result of simplified general model of tight gas reservoir.And a sensitivity analysis of reservoir parameters and fracture parameters was carried out,then the influence degree of hydraulic fracture parameters were obtained through an orthogonal experiment.The optimal fracture mode has also been investigated.This paper established a comprehensive model considers the adsorption and desorption of shale gas,the Knudsen diffusion and slip flow,the stress sensitivity effect and the complicated fracture morphology,which can provide a valid guidance for the evaluation of fracturing effect and the designing of fracturing construction.