A thermo‐hydro‐mechanical coupled model in local thermal non‐equilibrium for fractured HDR reservoir with double porosity

Abstract

The constitutive thermo‐hydro‐mechanical equations of fractured media are embodied in the theory of mixtures applied to three‐phase poroelastic media. The solid skeleton contains two distinct cavities filled with the same fluid. Each of the three phases is endowed with its own temperature. The constitutive relations governing the thermomechanical behavior, generalized diffusion and transfer are structured by, and satisfy, the dissipation inequality. The cavities exchange both mass and energy. Mass exchanges are driven by the jump in scaled chemical potential, and energy exchanges by the jump in coldness. The finite element approximation uses the displacement vector, the two fluid pressures and the three temperatures as primary variables. It is used to analyze a generic hot dry rock geothermal reservoir. Three parameters of the model are calibrated from the thermal outputs of Fenton Hill and Rosemanowes HDR reservoirs. The calibrated model is next applied to simulate circulation tests at the Fenton Hill HDR reservoir. The finer thermo‐hydro‐mechanical response provided by the dual porosity model with respect to a single porosity model is highlighted in a parameter analysis. Emphasis is put on the influence of the fracture spacing, on the effective stress response and on the permeation of the fluid into the porous blocks. The dual porosity model yields a thermally induced effective stress that is less tensile compared with the single porosity response. This effect becomes significant for large fracture spacings. In agreement with field data, fluid loss is observed to be high initially and to decrease with time.

Mechanical Properties of Sandstones Exposed to High Temperature

“…Modern rock engineering applications such as deep geological disposal of nuclear waste (Ringwood 1985;Gibb 1999;Hökmark and Claesson 2005;Gibb et al 2008;Sanchez et al 2012), geothermal heat (especially of hot dry rock) extraction (Zhao 2000;Ghassemi and Zhou 2011;Feng et al 2012;Gelet et al 2012;Cherubini et al 2013), and underground coal gasification (Burton et al 2007;Luo et al 2011;Kempka et al 2011;Younger 2011;Nakaten et al 2014) experience high-temperature environments, where rocks generally experience high temperatures up to several hundred degrees Celsius. Consequently, rock behaviors under and after high-temperature conditions are of high interest and still a challenge to scientists and engineers of different disciplines.…”

A review on heat transfer and energy conversion in the enhanced geothermal systems with water/CO2as working fluid

“…Recently, a few researchers have focused on the subsurface heat exchange in EGS using the LTNE model [66][67][68][69][70][71]. Recently, a few researchers have focused on the subsurface heat exchange in EGS using the LTNE model [66][67][68][69][70][71].…”

“…Recently, a few researchers have focused on the subsurface heat exchange in EGS using the LTNE model [66][67][68][69][70][71]. Gelet et al considered hydraulic diffusion, thermal diffusion, forced convection, and deformation in a two-phase framework with a focus on the LTNE model and determined solid-to-fracture heat transfer coefficients by fitting the results of the LTNE model to data collected from the Fenton Hill HDR reservoirs, as shown in Figure 3(b) [70,71]. Zhang et al presented an LTNE model to simulate heat transfer and fluid flow of supercritical CO 2 under conditions at the European EGS site at Groβ Schönebeck, considering the heterogeneity of permeability of different layers and the fracture zone.…”

Two-dimensional THM modelling of the large scale natural hydrothermal circulation at Soultz-sous-Forêts

“…Some numerical models have also been developed to account for mechanical, thermal and hydraulic couplings at the same time, with a simplified geometry of the fault network, see, e.g. Kohl et al (1995) or Gelet et al (2012). In addition, other thermodynamical aspects have been addressed like chemical couplings in Bächler and Kohl (2005).…”