Multiple seepage model and gas production simulation of shale with power law fracture distribution

Abstract

Changes in the internal microstructure of shale reservoirs have a significant effect on gas production. In this research, based on the double power law model and the triple medium theory, a triple medium model of shale multi-scale power law fracture distribution is constructed. The accuracy of the model is verified by comparing with the actual test results. Then, the model is used to analyze the relationship between shale stress, permeability, and three kinds of pore media as well as the influence of power law parameters and external force on reservoir microstructure and macroscopic gas production. The findings indicate that (1) the microstructure of shale reservoirs is affected by power law parameters and external forces; (2) gas exchange can cause the evolution of reservoir structure; and (3) the stress change of a single system will cause stress rearrangement of the whole system. This model provides a basic and comprehensive understanding for considering the various transport mechanisms of shale matrix and the microstructure change law of gas production process and proposes a new method for optimizing shale permeability simulation.