“FRACure” — A simulation code for forced fluid flow and transport in fractured, porous rock

Köhl, Thomas; Hopkirk, R.J.

doi:10.1016/0375-6505(95)00012-f

Cited by 72 publications

(35 citation statements)

References 6 publications

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“…10. In particular, the upper and lower figures show the effects of groundwater fluxes (0.0, 2.5 · 10 −6 , and 5 · 10 −6 m/s) and aquifer thicknesses (10,20, and 30 m), respectively. At the first inspection, it is evident that both aquifer thicknesses and groundwater fluxes are negatively correlated with the outlet temperatures of the fluid, indicating an increased heat dissipation in soil.…”

Section: Groundwater Effectsmentioning

confidence: 99%

“…While the thickness of the tube is on the order of several millimeters, the tube length and the geological system are usually on the order of a hundred or even several hundred meters. Signorelli et al [19] used the finite-element-based numerical code FRACTure [20] to evaluate the effect of factors not considered by analytical solutions since his code allowed one to use a combination of lower and higher dimension elements. In their analysis, a one-dimensional model was used for heat transport in tubes, while a three-dimensional model was used to simulate heat transfer in the surrounding ground.…”

Section: Introductionmentioning

confidence: 99%

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A computationally efficient pseudo-3D model for the numerical analysis of borehole heat exchangers

Brunetti

Saito

et al. 2017

Applied Energy

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Section: Groundwater Effectsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A computationally efficient pseudo-3D model for the numerical analysis of borehole heat exchangers

Brunetti

Saito

et al. 2017

Applied Energy

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“…FRACTure is a 3-D finite-element code for modeling hydrological, transport and elastic processes. It was developed originally for the study of flow-driven interactions in fractured rock (Kohl & Hopkirk, 1995). CHEMTOUGH2 (White, 1995) is a THC code developed after the TOUGH2 simulator (Pruess, 1991), a 3-D numerical model for simulating the coupled transport of water, vapor, noncondensable gas, and heat in porous and fractured media.…”

Section: Frachemmentioning

confidence: 99%

Modeling brine-rock interactions in an enhanced geothermal systemdeep fractured reservoir at Soultz-Sous-Forets (France): a joint approachusing two geochemical codes: frachem and toughreact

André¹,

Spycher²,

Xu³

et al. 2006

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EXECUTIVE SUMMARYThe modeling of coupled thermal, hydrological, and chemical (THC) processes in geothermal systems is complicated by reservoir conditions such as high temperatures, elevated pressures and sometimes the high salinity of the formation fluid. Coupled THC models have been developed and applied to the study of enhanced geothermal systems (EGS) to forecast the long-term evolution of reservoir properties and to determine how fluid circulation within a fractured reservoir can modify its rock properties. In this study, two simulators, FRACHEM and TOUGHREACT, specifically developed to investigate EGS, were applied to model the same geothermal reservoir and to forecast reservoir evolution using their respective thermodynamic and kinetic input data. First, we report the specifics of each of these two codes regarding the calculation of activity coefficients, equilibrium constants and mineral reaction rates. Comparisons of simulation results are then made for a Soultz-type geothermal fluid (ionic strength ~1.8 molal), with a recent (unreleased) version of TOUGHREACT using either an extended Debye-Hückel or Pitzer model for calculating activity coefficients, and FRACHEM using the Pitzer model as well.Despite somewhat different calculation approaches and methodologies, we observe a reasonably good agreement for most of the investigated factors. Differences in the calculation schemes typically produce less difference in model outputs than differences in input thermodynamic and kinetic data, with model results being particularly sensitive to differences in ion-interaction parameters for activity coefficient models. Differences in input thermodynamic equilibrium constants, activity coefficients, and kinetics data yield differences in calculated pH and in predicted mineral precipitation behavior and reservoir-porosity evolution. When numerically cooling a Soultz-type geothermal fluid from 200°C (initially equilibrated with calcite at pH 4.9) to 20°C and suppressing mineral precipitation, pH values calculated with FRACHEM and TOUGHREACT/ Debye-Hückel decrease by up to half a pH unit, whereas pH values calculated with TOUGHREACT/Pitzer increase by a similar amount. As a result of these differences, calcite solubilities computed using the Pitzer formalism (the more accurate approach) are up to about 1.5 orders of magnitude lower. Because of differences in Pitzer ion-interaction parameters, the calcite solubility computed with TOUGHREACT/Pitzer is also typically about 0.5 orders of magnitude lower than that computed with FRACHEM, with the latter expected to be most accurate.In a second part of this investigation, both models were applied to model the evolution of a Soultz-type geothermal reservoir under high pressure and temperature conditions. By specifying initial conditions reflecting a reservoir fluid saturated with respect to calcite (a reasonable assumption based on field data), we found that THC reservoir simulations with the three models yield similar results, including similar trends and amounts of reservoir po...

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“…Also in periods of strong precipitation or snowmelt, enhanced groundwater flow and infiltration will alter the measured effective thermal conductivity at the site. To date, the increase of the effective thermal conductivity due to groundwater flow cannot be quantified analytically hence numerical tools need to be used [e.g., FRACTURE (Kohl and Hopkirk 1995) or FEFLOW (Diersch 2009)].…”

Section: Introductionmentioning

confidence: 99%

Insights into the reliability of different thermal conductivity measurement techniques: a thermo-geological study in Mære (Norway)

Liebel¹,

Stølen²,

Frengstad

et al. 2011

Bull Eng Geol Environ

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Thermal response tests (TRTs) are used to measure the effective thermal conductivity in boreholes. The results serve as a basis for the dimensioning of commercial ground-source heat pump installations with closed loop systems. The study evaluated the reliability of TRTs performed in winter by comparing two TRTs carried out under very different winter weather conditions. A third TRT elucidated the influence of convection in wells with a higher heat input. Rock cores were analysed for quartz content and these results and the laboratory-measured thermal conductivity data were compared with the TRT results. This highlighted the importance of the distribution and orientation of minerals in the rock, and that a high quartz content does not necessarily give high thermal conductivity values. It is concluded that winter TRTs give useful results if additional temperature loggers are installed in anticipated fracture zones to detect groundwater flow and to survey the effect of infiltrating water.

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“FRACure” — A simulation code for forced fluid flow and transport in fractured, porous rock

Cited by 72 publications

References 6 publications

A computationally efficient pseudo-3D model for the numerical analysis of borehole heat exchangers

A computationally efficient pseudo-3D model for the numerical analysis of borehole heat exchangers

Modeling brine-rock interactions in an enhanced geothermal systemdeep fractured reservoir at Soultz-Sous-Forets (France): a joint approachusing two geochemical codes: frachem and toughreact

Insights into the reliability of different thermal conductivity measurement techniques: a thermo-geological study in Mære (Norway)

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