Mechanical Behaviors of Low-Permeability Sandstone under the Coupled Elastoplastic Damage and Evolved Gas Permeability

Low-permeability sandstone generally exists in oil and gas reservoirs. During oil and gas exploitation, reservoir pressure depletion causes significant plastic deformation and damage evolution. In reservoir history matching, it is vital to study the mechanical behaviors of sandstone considering both the coupled elastoplastic damage and permeability evolution. In this paper, a series of triaxial compression tests were performed to study the coupled elastoplastic damage mechanical behaviors of low-permeability sandstone. The permeability changes during the tests were obtained by using gas as a permeability-measuring medium. The results showed that due to the coupled effects of plastic deformation and damage evolution, the stress-strain presented obvious nonlinear and softening characteristics. A coupled elastoplastic damage model was first proposed to study the elastoplastic behaviors and damage evolution of low-permeability sandstone. Furthermore, a coupled elastoplastic damage mechanical model of low-permeability sandstone considering permeability evolution was put forward. The model can effectively describe the mechanical behaviors of low-permeability sandstone, which are in good agreement with the experimental results.