Production Evaluation of Fractured Wells in Low Permeability Reservoirs with Nonlinear Flow

The main factors affecting gas flow include start-up pressure gradient,slippage effect and stress sensitivity,etc.According to the characteristic of low permeability gas reservoir,and the change of fluid flow rule after fracturing treatment,a gas well productivity prediction model was established for the finite conductivity vertical fracture wells based on stable seepage theory while taking the influence of the start-up pressure gradient,slippage effect and stress sensitivity into account.The influences of such factors as slippage,start-up pressure gradient,stress sensitivity and formation damage,etc.on productivity were analyzed.Results showed that the gas well productivity would decrease almost linearly with start-up pressure gradient and stress sensitivity,and the major decrease was caused by stress sensitivity.The gas well productivity increased with slippage effect linearly.In the fracturing design of low-permeability gas reservoirs,to increase fracture length would be more important than to increase fracture conductivity,and for a given fracture length,there would be an optimum fracture conductivity.Formation damage would reduce well productivity and the reduction would increase as formation damage radius increase and permeability decrease.