A quadruple-porosity model for transient production analysis of multiple-fractured horizontal wells in shale gas reservoirs

Multiple types of pores are present in shale gas reservoirs, including organic pores of nano scale, non-organic pores, natural and hydraulic fractures. Gas flow in different types of pores is controlled by different mechanisms, and Darcy's law is not able to describe all these processes adequately. This paper presents a "quadruple-porosity'' model and corresponding analytical solutions to describe the different permeable media and simulate transient production behavior of multiple-fractured horizontal wells in shale gas reservoirs. Dimensionless transient production decline curves are plotted, and characteristic bi-linear flow and linear flow periods are identified based on the analysis of type curves. Sensitivity analysis of transient production dynamics suggests that desorption of absorbed gas, Knudsen diffusive flow, gas slippage and parameters related to hydraulic fractures have significant influence on the production dynamics of a multiple-fractured horizontal well in shale gas reservoirs. The model provides insights into multiple shale gas flow mechanisms and production prediction of shale gas reservoirs.