Material Constants of Anisotropic Poroelasticity and Its Impacts on Shale Gas Production

Energy & Fuels, 37(23):18722 - 18734, 2023.

• Manuscript

Summary

This study investigates how anisotropic mechanical and hydraulic properties influence shale-gas production. A mixture-theory formulation develops poroelastic material constants for porous solids whose grains and internal structure can be both heterogeneous and direction dependent. The treatment of intrinsic solid density and deformation under unjacketed loading produces a complete parameter set and associated bounds, which are compared with an existing intrinsic-constant formulation. The practical consequences are explored in a three-dimensional shale reservoir model that includes elastic and permeability anisotropy. The horizontal stress component parallel to the wellbore, $\sigma_{xx}$, differs substantially between isotropic and transversely isotropic descriptions. Tilting the plane associated with permeability anisotropy also reduces gas production and changes the orientation of the stress distribution. These comparisons show that an isotropic approximation can miss important stress changes during extraction. The framework therefore connects constitutive characterization at smaller scales with predictions of deformation and production in shale reservoirs.