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| Titel |
THM modelling of hydrothermal circulation in deep geothermal reservoirs |
| VerfasserIn |
Vincent Magnenet, Christophe Fond, Jean Schmittbuhl, Albert Genter |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250095626
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| Publikation (Nr.) |
 EGU/EGU2014-11089.pdf |
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| Zusammenfassung |
| Numerous models have been developped for describing deep geothermal reservoirs.
Using the opensource finite element software ASTER developped by EDF R&D, we
carried out 2D simulations of the hydrothermal circulation in the deep geothermal
reservoir of Soultz-sous-Forêts. The model is based on the effective description of
Thermo-Hydro-Mechanical (THM) coupling at large scale. Such a model has a fourfold
interest: a) the physical integration of laboratory measurements (rock physics),
well logging, well head parameters, geological description, and geophysics field
measurements; b) the construction of a direct model mechanically based for geophysical
inversion: fluid flow, fluid pressure, temperature profile, seismicity monitoring,
deformation of the ground surface (INSAR/GPS) related to reservoir modification, gravity
or electromagnetic geophysical measurements; c) the sensitivity analysis of the
parameters involved in the hydrothermal circulation and identification of the dominant
ones; d) the development of a decision tool for drilling planning, stimulation and
exploitation.
In our model, we introduced extended Thermo-Hydro-Mechanical coupling including not
only poro-elastic behavior but also the sensitivity of the fluid density, viscosity, and heat
capacity to temperature and pressure. The behavior of solid rock grains is assumed to be
thermo-elastic and linear. Hydraulic and thermal phenomena are governed by Darcy and
Fourier laws respectively, and most rock properties (like the specific heat at constant stress
csÏă(T), or the thermal conductivity λ(T,Ï)) are assumed to depend on the temperature T
and/or porosity Ï. The radioactivity of the rocks is taken into account through a
heat source term appearing in the balance equation of enthalpy. To characterize as
precisely as possible the convective movement of water and the associated heat flow,
water properties (specific mass Ïw(T,pw), specific enthalpy hmw(T,pw) dynamic
viscosity μw(T), thermal dilation αw(T), and specific heat cwp(T)) are assumed to
depend on pressure and/or temperature. The entire set of material properties is
extracted from references dealing with investigations at Soultz-sous-Forêts when
existing.
The reservoir is described at large scale (about 10 km in width and 5 km in height) and it
is assumed that the medium is homogenous, porous, and saturated with a single-phase fluid
(considering homogenized effective porous and/or fractured layers, neglecting the
details of the fracture networks). We performed a feasability study and show that a
large scale convection regime is possible using realistic parameters. The size of
the convection cell (2.8km) are shown to be compatible with field observations. |
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