Combining analysis of random elastic polycrystals with poroelasticity for granular composites having orthotropic porous grains and fluid-filled pores

Abstract

Analysis of random polycrystals has typically been applied to solid grains of anisotropic elastic materials. Poroelastic analysis has similarly been applied to otherwise isotropic systems with pores having a variety of shapes and filled with fluids. Present effort is focused on combining these two types of geomechanical analyses by treating anisotropic (specifically orthotropic) poroelastic grains jumbled together to form an overall isotropic polycrystalline poroelastic material. The resulting problem is approximately twice as difficult to solve as the typical elastic polycrystal problem because the polycrystal analysis must be carried through twice: once for the drained (pore-fluid free to escape) poroelastic constants, and again for the undrained (pore-fluid trapped) poroelastic constants. As should be anticipated, poroelastic effects induced by trapped fluid are significantly stronger for the effective bulk modulus than for the effective shear modulus.