Numerical modelling of convection-driven cooling, deformation and fracturing of thermo-poroelastic media

Convection-driven cooling in porous media influences thermo-poro-mechanical stresses, thereby causing deformation. These processes are strongly influenced by the presence of fractures, which dominate flow and heat transfer. At the same time, the fractures deform and propagate in response to changes in the stress state. Mathematically, the model governing the physics is tightly coupled and must account for the strong discontinuities introduced by the fractures. Over the last decade, and motivated by a number of porous media applications, research into such coupled models has advanced modelling of processes in porous media substantially. Building on this effort, this work presents a novel model that couples flow, heat transfer, deformation, and propagation of fractures with flow, heat transfer, and thermo-poroelasticity in the matrix. The model is based on explicit representation of fractures in the porous medium, and discretised using multi-point finite volume methods. Frictional contact and non-penetration conditions for the fractures are handled through active set methods, while a propagation criterion based on stress intensity factors governs fracture extension. Considering both forced and natural convection processes, the numerical results show the intricate nature of thermo-poromechanical fracture deformation and propagation.