Stochastic Inversion And Productivity Simulation Of Shale Gas Stimulated Reservoir Volume Based On Embedded Discrete Fracture Model

Fracturing technology is an indispensable method in the development of shale gas reservoir.However,accurate description of fracture morphology and distribution in fracturing reservoir has always been an important issue restricting the production and development of shale gas reservoir.In this papper,the Embedded Discrete Fracture Model(EDFM)of shale gas reservoir was firstly established in order to accurately describe the fracture morphology and distribution in the fracturing shale gas reservoirs,improve the accuracy of the productivity prediction.On the basis of accurate description of fracture morphology and distribution in shale gas reservoir and combining with the Ensemble Kalman Filter(EnKF)to update the model parameters,model parameters can be automatic history matching.Stimulated Reservoir Volume(SRV)after inversion was calculated and Stimulated Reservoir capacity simulation was conducted.The main work carried out in this thesis are as follows:(1)Based on the phenomenon of adsorption and desorption,Knudsen diffusion and high velocity non-darcy seepage flow during the flowing process of shale gas reservoirs,an embedded discrete fracture model of shale gas reservoir was established to accurately simulate the production of shale gas reservoirs,EDFM was used to accurately depict the fracture morphology and distribution in shale gas reservoirs.(2)The influence of the main parameters in the reservoir and stimulation design on the productivity of shale gas reservoir was studied by establishing a typical embedded discrete fracture model of shale gas reservoir with a horizontal fracturing well.These parameters can be divided into three categories: primary fracture properties(conductivity,number of main fractures,half length,and inclination),secondary fracture properties(conductivity,number of secondary fractures,half length,and inclination),and matrix permeability.A comprehensive sensitivity analysis was performed to investigate the effects of model parameters on the cumulative shale gas production from strong to weak.It is found that the cumulative gas production of horizontal wells increased with the increase of matrix permeability,number of main fracture sections,conductivity,half length of secondary fractures,dip angle,half length of primary fractures,and number of secondary fractures,while the influence of main fracture inclination and conductivity of secondary fractures on cumulative gas production of horizontal wells was not obvious.According to the analysis results of sensitive factors of production capacity,EnKF algorithm was used to carry out parameter inversion of the main factors affecting the production capacity of typical shale gas reservoir model.The results show that history matching effect after the EnKF update was significantly improved,which reduced the uncertainty of model prediction.Moreover,the estimation accuracy of the updated model parameters was improved,among which the matrix permeability and the conductivity of the main fracture were estimated to be the most accurate,which was consistent with the conclusion of the sensitivity analysis experiment.The EDFM and EnKF method were applied for model parameter inversion according to the production dynamic data of 8 wells in the shale block of feild.The experimental results show that the EDFM and EnKF methods can well describe the fracture morphology and distribution in shale gas reservoirs,and with a great matching consequence on the historical production data of gas wells.In addition,the updated model was used to predict the production status in the next 20 years so as to provide theoretical guidance for field production.