Non-isothermal flow in low permeable porous media: a comparison of Richards’ and two-phase flow approaches
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The present work compares the performance of two alternative flow models for the simulation of thermal-hydraulic coupled processes in low permeable porous media: non-isothermal Richards’ and two-phase flow concepts. Both models take vaporization processes into account: however, the Richards’ model neglects dynamic pressure variations and bulk flow of the gaseous phase. For the comparison of the two approaches first published, data from a laboratory experiment are studied involving thermally driven moisture flow in a partially saturated bentonite sample. Then a benchmark test of longer-term thermal-hydraulic behavior in the engineered barrier system of a geological nuclear waste repository is analyzed (DECOVALEX project). It was found that both models can be used to reproduce the vaporization process if the intrinsic permeability is relative high. However, when a thermal-hydraulic coupled problem has the same low intrinsic permeability, only the two-phase flow approach provides reasonable results.
KeywordsNon-isothermal two-phase flow Richards’ approximation Porous media CTF1 experiment DECOVALEX task D
The development of the numerical models was conducted in the framework of the international DECOVALEX project. The funding from the Federal Institute for Geosciences is highly acknowledged (Dr. Shao). This work is part of the PoF research initiative of the Helmholtz Association within the Environmental Engineering and Geothermal Technology programs. Funding from the Swedish Radiation Safety Authority (SSM) through the US Department of Energy Contract No. DE-AC02-05CH11231 is greatly appreciated.
- Alkan H, Müller W (2008) Approaches for modelling gas flow in clay formations as repository systems. Phys Chem Earth 33(Suppl 1):S260–S268Google Scholar
- Barr D, Birkholzer JT, Rutqvist J, Sonnenthal E (2004) Draft description for DECOVALEX-THMC Task D: long-term permeability/porosity changes in EDZ and near field, due to THM and THC processes in volcanic and crystalline-bentonite systems. Technical report, Earth Sciences Division, Lawrence Berkeley National Laboratory, USAGoogle Scholar
- Bruel D (2002) Impact of induced thermal stresses during circulation tests in an engineered fractured geothermal reservoir: example of the Soultzsous-Forets European hot fractured rock geothermal project, RhineGraben, France. Geothermics 57:459–470Google Scholar
- Freiboth S, Class H, Helmig R, Graf T, Ehlers W, Schwarz V, Vrettos Ch (2009) A model for multiphase flow and transport in porous media including a phenomenological approach to account for deformation-a model concept and its validation within a code intercomparison study. Comput Geosci 13:281-300CrossRefGoogle Scholar
- Lewis RW, Schrefler BA (1998) The finite element method in the static and dynamic deformation and consolidation of porous media, 2nd edn. Wiley, ChichesterGoogle Scholar
- Philip JR, de Vries DA (1957) Moisture movement in porous materials under temperature gradient. Trans Am Geophys Union 38:222–232Google Scholar
- Rutqvist J, Barr D, Birkholzer JT, Chijimatsu M, Kolditz O, Liu Q, Oda Y, Wang W, Zhang C (2008) Results from an international simulation study on coupled thermal, hydrological, and mechanical processes near geological nuclear waste repositories. Nucl Technol 163:101–109Google Scholar
- Villar MV, Fernandez AM, Cuevas J (1997) Caracterización Geoquímica de bentonita compactada: efectos producidos por flujo termohidráulico. Interim Report FEBEX, Informe 70-IMA-M-0-2, CIEMAT, MadridGoogle Scholar