TOUGH-UDEC: A simulator for coupled multiphase fluid flows, heat transfers and discontinuous deformations in fractured porous media

Abstract

A numerical simulator entitled TOUGH-UDEC is introduced for the analysis of coupled thermalhydraulic-mechanical processes in fractured porous media. Two existing well-established codes, TOUGH2 and UDEC, are coupled to model multiphase fluid flows, heat transfers, and discontinuous deformations in fractured porous media by means of discrete fracture representation. TOUGH2 is widely used for the modeling of heat transfers and multiphase multicomponent fluid flows, and UDEC is a well-known distinct element code for rock mechanics. The two codes are solved sequentially, with coupling parameters passed to each equation at specific intervals. After solving thermal-hydraulic equations within the TOUGH2 code, pressure and temperature information is imported into the UDEC model. After solving the mechanical equation within the UDEC code the calculated fracture apertures are converted to the equivalent permeability and porosity values for a TOUGH2 flow analysis. The solution is calculated by iteratively following an explicit sequence for numerical efficiency. Verifications are presented to demonstrate the capabilities of the coupled TOUGH-UDEC simulator. Three application examples of (1) shear dilation due to increased pore pressure, (2) thermal stress and (3) CO 2 injection, show that the new simulator can be an effective tool for geoengineering applications involving shear activation of fractures and faults.

TOUGH-RFPA: Coupled thermal-hydraulic-mechanical Rock Failure Process Analysis with application to deep geothermal wells

“…The combinations of space discretization methods have been developed and widely applied for modeling fracture processes in rock materials. The main types of hybrid models are the hybrid Finite Element Method-Discrete Element Method (FEM-DEM), the hybrid Finite Element Method-Boundary Element Method (FEM-BEM), the hybrid Finite Element-Meshfree Method-Finite Volume Method (FEMM-FVM), the hybrid Finite Volume Method-Discrete Element Method (FVM-DEM), and the hybrid Embedded Discrete Fracture Method-Extended Finite Element Method (XFEM-EDFM) models [31][32][33][34][35]. However, for complex large-scale 3D problems of arbitrary fracturing orientation, the computational efficiency for millions, even billions of elements and the computational accuracy of fracture geometry are challenging at this stage.…”

RHEA v1.0: Enabling fully coupled simulations with hydro-geomechanical heterogeneity

“…For example, sequential coupling solves for the hydraulic and geomechanical variables independently and in sequence. Notable examples are geomechanics models based on TOUGH (Transport Of Unsaturated Groundwater and Heat) (Pruess et al, 1999;Xu et al, 2006;Lei et al, 2015;Lee et al, 2019). These consist of different libraries to solve for coupled thermo-hydro-mechanical (THM) applications relying on the numerical capabilities provided by TOUGH.…”

RHEA v1.0: Enabling fully coupled simulations with hydro-geomechanical heterogeneity

“…For example, sequential coupling solves for the hydraulic and geomechanical variables independently and in sequence. Notable examples are geomechanics models based on TOUGH (Transport Of Unsaturated Groundwater and Heat) (Pruess et al, 1999;Xu et al, 2006;Lei et al, 2015;Lee et al, 2019). These consist of different libraries to solve for coupled thermo-hydro-mechanical (THM) applications relying on the numerical capabilities provided by TOUGH.…”