Production performance model based on quadruple-porosity medium in shale gas reservoirs considering multi-transport mechanisms

Abstract

ABSTRACT To evaluate the production performance of shale gas wells accurately, a quadruple-porosity medium model based on kerogen, the inorganic matrix, and natural-fracture–hydraulic-fracture network is proposed to simulate shale gas production. This model includes an apparent-kerogen permeability model to characterize the combined effects of gas slippage, Knudsen diffusion, surface diffusion, stress sensitivity, and matrix shrinkage. The fractal theory is used to characterize the non-equidistant distribution of secondary fractures in the hydraulic fracture network quantitatively. In addition, the effect of the stress sensitivity of the hydraulic fracture network on the production is considered, and a numerical method for the quadruple-porosity model is presented. After the validation of the model with field production data, the sensitivity parameters were analyzed to study the effects of the apparent kerogen permeability, Langmuir volume, fractal dimension, primary and secondary fracture conductivities, geomechanical effect, stimulated reservoir volume (SRV), and inorganic-matrix permeability on the gas production. This study provides a theoretical model for a more accurate evaluation of the shale gas production and improves the shale gas seepage theory.