Flexible parallel implicit modelling of coupled thermal–hydraulic–mechanical processes in fractured rocks

Abstract

Abstract. Theory and numerical implementation describing groundwater flow and the transport of heat and solute mass in fully saturated fractured rocks with elasto-plastic mechanical feedbacks are developed. In our formulation, fractures are considered as being of lower dimension than the hosting deformable porous rock and we consider their hydraulic and mechanical apertures as scaling parameters to ensure continuous exchange of fluid mass and energy within the fracturesolid matrix system. The coupled system of equations is implemented in a new simulator code that makes use of a Galerkin finite-element technique. The code builds on a flexible, object-oriented numerical framework (MOOSE, Multiphysics Object Oriented Simulation Environment) which provides an extensive scalable parallel and implicit coupling to solve for the multiphysics problem. The governing equations of groundwater flow, heat and mass transport, and rock deformation are solved in a weak sense (either by classical Newton-Raphson or by free Jacobian inexact NewtonKrylow schemes) on an underlying unstructured mesh. Nonlinear feedbacks among the active processes are enforced by considering evolving fluid and rock properties depending on the thermo-hydro-mechanical state of the system and the local structure, i.e. degree of connectivity, of the fracture system. A suite of applications is presented to illustrate the flexibility and capability of the new simulator to address problems of increasing complexity and occurring at different spatial (from centimetres to tens of kilometres) and temporal scales (from minutes to hundreds of years).

Influence of the Main Border Faults on the 3D Hydraulic Field of the Central Upper Rhine Graben

“…To simulate the coupled transport of heat and fluid, we use the open-source software GOLEM [60]. Golem is a flexible, parallel scalable finite elementbased simulator for thermo-hydro-mechanical process modelling in fractured porous rocks as based on the MOOSE framework [61].…”

Evaluating Micro-Seismic Events Triggered by Reservoir Operations at the Geothermal Site of Groß Schönebeck (Germany)

“…In this study we rely on the GOLEM simulator (Cacace and Jacquey, 2017) that builds on the flexible, object oriented MOOSE framework (Gaston et al, 2009). Using this approach, fractures are considered as being of lower dimension (2D structures) than the hosting deformable 3D porous rock and their hydraulic aperture is then used as scaling parameter to ensure continuous exchange of fluid mass and energy within the fracture-solid matrix system (Cacace and Jacquey, 2017). In what follows, the governing equations of groundwater flow, heat transport and rock deformation are briefly described, more information on their numerical implementation is provided in Cacace and Jacquey (2017).…”

A three-dimensional lithospheric-scale thermal model of Germany

“…Sensitivity studies have shown that such effects would influence the absolute values of temperatures but not their regional distribution pattern (Majorowicz and Wybraniec, 2011). Neglecting the influence of coupled fluid and heat transport may also lead to erroneous conclusions as the conductive thermal model that best reproduces the observed heat flow considers an "effective" thermal conductivity that contains the superposed effects of different heat transport processes (Cacace et al, 2010). Again, local studies would be required to better quantify the absolute impact of this simplification.…”

“…For regional exploration, complementary workflows use integrated 3-D structural and physics-based models that help to predict the temperature distribution in the subsurface by taking into account the heterogeneous structural configuration as well as the, often non-linear, causative processes (e.g. Cacace et al, 2010;.…”