Anisotropic dual-continuum representations for multiscale poroelastic materials: Development and numerical modelling

TL;DR

This paper develops an anisotropic dual-continuum poroelastic model for multiscale materials like fractured rock and validates its effectiveness against detailed numerical simulations, highlighting the importance of anisotropy.

Contribution

It introduces an anisotropic poroelastic dual-continuum model incorporating intrinsic stiffness anisotropy and validates it through numerical experiments against explicit fine-scale models.

Findings

Anisotropy significantly affects deformation and flow behaviors.

The dual-continuum model accurately captures global behaviors of anisotropic materials.

Validation shows the model's applicability to complex multiscale poroelastic systems.

Abstract

Dual-continuum (DC) models can be tractable alternatives to explicit approaches for the numerical modelling of multiscale materials with multiphysics behaviours. This work concerns the conceptual and numerical modelling of poroelastically coupled dual-scale materials such as naturally fractured rock. Apart from a few exceptions, previous poroelastic DC models have assumed isotropy of the constituents and the dual-material. Additionally, it is common to assume that only one continuum has intrinsic stiffness properties. Finally, little has been done into validating whether the DC paradigm can capture the global poroelastic behaviours of explicit numerical representations at the DC modelling scale. We address the aforementioned knowledge gaps in two steps. First, we utilise a homogenisation approach based on Levin's theorem to develop a previously derived anisotropic poroelastic constitutive model. Our development incorporates anisotropic intrinsic stiffness properties of both continua. This addition is in analogy to anisotropic fractured rock masses with stiff fractures. Second, we perform numerical modelling to test the dual-continuum model against fine-scale explicit equivalents. In doing, we present our hybrid numerical framework, as well as the conditions required for interpretation of the numerical results. The tests themselves progress from materials with isotropic to anisotropic mechanical and flow properties. The fine-scale simulations show anisotropy can have noticeable effects on deformation and flow behaviour. However, our numerical experiments show the DC approach can capture the global poroelastic behaviours of both isotropic and anisotropic fine-scale representations.