Study Of The Coupling Model Between Fracture And Multi-fractured Horizontal Wells Of Shale Gas

Shale reservoirs belong to low porosity and low permeability reservoirs.In the process of development,multi-stage fracturing technology is usually used to improve the productivity of gas well.Different from the conventional gas reservoirs,shale reservoirs have many natural micro cracks,which forms a complex network system after artificial fracturing.As the continuation of production,interference among fractures become more and more serious.What's more,the production is always accompanied by adsorption and desorption.In the existing production forecast models of horizontal well with staged fracturing,respectively for shale gas adsorption,gas diffusion and slippage phenomena have meticulous research.But the model that covers all the factors is few.The model often ignored the pressure drop in the horizontal wellbore.After research shale gas horizontal well staged fracturing production prediction models,based on the shale gas flow characteristics,this paper completed the productivity prediction research.The mainly completed work is as follows:(1)After research shale gas reservoir characteristics,development characteristics and seepage characteristics,respectively get the influence of gas diffusion,slippage and desorption to the development of shale gas,which lay the theoretical foundation for the prediction model.(2)Based on the percolation of shale gas reservoir,this paper build the model that the shale gas flow through the matrix-natural fracture-artificial fracture-horizontal wellbore.In the model,take the apparent permeability of shale gas,which take the slippage into consideration,as the matrix permeability.The desorption equation is added into the mass conservation equation,which also considered the interference between the artificial fractures.(3)The pressure drop in horizontal wellbore is obtained based on the momentum theorem and mass conservation,which considering the frictional pressure drop and the acceleration pressure drop.(4)Coupling the model according to the continuity of pressure and production.Finished the programming of the model with MATLAB and give the iterative solution of the model.(5)The model,which consider the desorption process,the artificial fracture pattern and the interference among fractures,is suitable for describing the unsteady flow of shale gas.(6)The pressure decreases gradually along the direction of the horizontal well and the considered bottom hole flowing pressure is not constant.(7)The gas production of shale gas horizontal well is positively correlated with the gas reservoir thickness,shale matrix porosity and natural fracture permeability and negatively correlated with the bottom hole flow pressure.(8)The gas production of shale gas horizontal well is positively correlated with the number,the length,the width,the spacing and the permeability of artificial fractures.(9)The fracture distribution patterns have influence on production.The dumbbell pattern corresponds to the high production,then is the rectangular pattern and the spindle pattern is corresponds to the lowest production.