Uncertainty analysis of thermo-hydro-mechanical coupled processes in heterogeneous porous media

Abstract

In this paper we present an uncertainty analysis of thermo-hydro-mechanical (THM) coupled processes in a typical geothermal reservoir in crystalline rock. Fracture and matrix are treated conceptually as an equivalent porous medium, and the model is applied to available data from the Urach Spa and Falkenberg sites (Germany). The finite element method (FEM) is used for the numerical analysis of fully coupled THM processes, including thermal water flow, advective-diffusive heat transport, and thermoelasticity. Non-linearity in system behavior is introduced via temperature and pressure dependent fluid properties. Reservoir parameters are considered as spatially random variables and their realizations are generated using conditional Gaussian simulation. The related Monte-Carlo analysis of the coupled THM problem is computationally very expensive. To enhance computational efficiency, the parallel FEM based on domain decomposition technology using message passing interface (MPI) is utilized to conduct the numerous simulations. In the numerical analysis we considered two reservoir modes: undisturbed and stimulated. The uncertainty analysis we apply captures both the effects of heterogeneity and hydraulic stimulation near the injection borehole. The results show the influence of parameter ranges on reservoir evolution during long-term heat extraction, taking into account fully coupled thermo-hydro-mechanical processes. We found that the most significant factors in the analysis are permeability and heat capacity. The study demonstrates the importance of taking parameter uncertainties into account for geothermal reservoir evaluation in order to assess the viability of numerical modeling.

Reactive transport codes for subsurface environmental simulation

“…Equations of state (EoS) for several fluids (gases, supercritical fluids) are available to module temperature-driven dynamics [104]. Multicomponent mass transport and (equilibrium and nonequilibrium) heat transport [105] modules are part of OGS.…”

Evaluation of water coning phenomenon in naturally fractured oil reservoirs

“…where q þ and q À are the leakage fluxes across the boundary interfaces, r is the divergence operator in local coordinates system (Watanabe et al 2010), and P f is the pressure inside the fracture. The permeability of the fracture can be expressed by a parallel plate concept (cubic law) as shown in Eq.…”

Application of the geomechanical facies approach and comparison of exploration and evaluation methods used at Soultz-sous-Forêts (France) and Spa Urach (Germany) geothermal sites

“…stress-permeability relationships, Rutqvist et al 2009). A sensitivity analysis of THM parameters for geothermal reservoir simulation can be found in Watanabe et al (2009). Geochemical processes are important to consider in hydrothermal systems (Clauser 2003;Kühn et al 2002).…”

“…This is the concept of a fully coupled thermo-hydro-mechanical (THM) approach to geothermal reservoir modeling (e.g. Kohl and Mégel 2005;McDermott and Kolditz 2006;Watanabe et al 2009). From this comparison significant lessons can be learned and tools developed for designing conceptual models and evaluating the risks involved in the extraction of the heat stored in deep hot rock masses.…”