Study on Elastoplastic Damage Coupling of Reservoir Mudstone Considering Permeability Change

Mudstone, a common complex medium in oil and gas reservoirs with widely distributed micro-pore micro-fissures, is liable to produce significant damage evolution plastic deformation under high buried depth stress environments. Based on the analysis of physical characteristics, elastoplastic coupling mechanical characteristics mudstone reservoir for engineering are discussed. Firstly, conventional triaxial compression tests different confining pressures were performed calculate variable obtain evolution. The included elastic stage, plastic-dominated stage damage-dominated stage. Secondly, coupled model was proposed, which based degradation stiffness flow caused by internal variables considered during loading process. Thirdly, simulated. simulation results good agreement experimental results, reflects well mudstone, including transition from volume expansion, hardening, softening residual strength, etc. Finally, relevant research permeability secondary development carried out ABAQUS. UMAT USFLD subroutines compiled, seepage–stress verification out. provide reliable basis theory stability deep reservoirs.