Computational Mechanics, March, 2010, Vol.45(4), p.263(18)
Byline: Norihiro Watanabe (1,2), Wenqing Wang (1), Christopher I. McDermott (3), Takeo Taniguchi (4), Olaf Kolditz (1,2) Keywords: Geothermal reservoir analysis; Uncertainty assessment; Thermo-hydro-mechanical (THM) coupled processes; Sequential Gaussian simulation; Monte-Carlo simulation 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. Author Affiliation: (1) Department of Environmental Informatics, UFZ-Helmholtz Centre for Environmental Research, Permoserstrasse 15, 04318, Leipzig, Germany (2) Applied Environmental System Analysis, Dresden University of Technology, Helmholtzstrasse 10, 01069, Dresden, Germany (3) Edinburgh Collaborative of Subsurface Science and Engineering (ECOSSE), School of Geoscience, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JW, Scotland, UK (4) Graduate School of Environmental Science, Okayama University, 1-1, Tsushima-Naka, 3-chome, Okayama, 700-8530, Japan Article History: Registration Date: 03/11/2009 Received Date: 30/03/2009 Accepted Date: 30/10/2009 Online Date: 18/11/2009
Monte Carlo Methods ; Geothermal Energy ; Geothermal Resources ; Hydraulic Flow ; Reservoirs (Water) ; Finite Element Method ; Universities And Colleges ; Permeability
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