Multiple-Porosity and Multiple-Permeability Poroelasticity: Theory and Benchmark Analytical Solution

The linear theory of multiple-porosity and multiple-permeability poroelasticity is presented; a self-consistent extension to Biot’s formulation of a single-porosity, homogenous, isotropic, fluid-saturated, and linearly elastic material is made to obtain the constitutive relations and poroelastic constants of a material with an arbitrary number of N systems or scales of porosity and permeability. Sudden and continued confinement of a spherical sample of porous material while allowing for the pore fluid drainage from the surface boundary is known as Cryer’s problem in the poromechanics literature. The closed-form solution to this problem is developed in Laplace transform domain for the general case of N-porosity and N-permeability poroelasticity with full inter-porosity fluid exchange property. Numerical results in the time domain are presented for single-porosity, double-porosity, triple-porosity, quadruple-porosity, and quintuple-porosity poroelastic models of organic-rich shale.