Numerical models of HDR geothermal reservoirs—a review of current thinking and progress

SUMMARYIn the study of heat extraction by circulating water in a fracture embedded in geothermal reservoir, the heat conduction in the reservoir is typically assumed to be one dimensional and perpendicular to the fracture. In this paper, we demonstrate that by an integral equation formulation utilizing Green's function, the multi-dimensional heat #ow in the reservoir can be modelled. In the resulting numerical solution system, the discretization of reservoir geometry is entirely eliminated, leading to a much more e$cient scheme. The multi-dimensional heat conduction e!ect as compared to its one-dimensional simpli"cation is studied.

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“…The above solution can be further simpli"ed by neglecting the fracture heat storage term, *¹(x, 0, t)/*t, in (1). In this case, (9) reduces to…”

Section: Analytical Solutionmentioning

confidence: 99%

Integral equation solution of heat extraction from a fracture in hot dry rock

Cheng

Ghassemi

Detournay

2001

Num Anal Meth Geomechanics

133

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“…The concept involves drilling two or more wells into the reservoir to intersect permeable fractures, injecting cold water into one part of the well system and recovering hot water from the other ( Figure 1). A comprehensive review of this concept, alternatively called the Hot Dry Rock, may be found in Reference [1].…”

Section: Introductionmentioning

confidence: 99%

Integral equation solution of heat extraction‐induced thermal stress in enhanced geothermal reservoirs

Ghassemi

Tarasovs

Cheng

2005

Num Anal Meth Geomechanics

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SUMMARYDuring fluid injection in enhanced geothermal systems, thermo-mechanical processes can play an important role. In fact, the phenomena of reservoir seismicity and the variation of injectivity with respect to injection water temperature can be attributed to the induced thermal stresses. In this paper, a threedimensional integral equation formulation is presented for calculating thermally induced stresses associated with the cooling of a fracture in a geothermal reservoir. By utilizing Green's function in the integral equation, the three-dimensional heat flow and stresses in the reservoir are modelled without discretizing the reservoir. The formulation is implemented in a computer program for the solution of injection into an infinite fracture as well as for the injection/extraction in an arbitrarily shaped fracture.

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“…As stated above, two aspects must be considered in numerical simulation of EGS reservoirs: fracture representation and hydrologic-thermal-mechanical-chemical processes simplification [28,29]. In the aspect of fracture representation, in this study we employed the EPM method and this method is reasonable only when the fracture spacing is lower than 2~3 m. For fracture spacing larger than 2~3 m, the MINC method or the MINC method should be employed.…”

Section: Limitation Of This Researchmentioning

confidence: 99%

Orthogonal Test Analysis on Conditions Affecting Electricity Generation Performance of an Enhanced Geothermal System at Yangbajing Geothermal Field

Zeng

Tang

et al. 2017

Energies

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Abstract:The main conditions affecting electricity generation performance of an enhanced geothermal system (EGS) include reservoir porosity, reservoir permeability, rock heat conductivity, water production rate and injection temperature. Presently there is lack of systematic research the relative importance of the five aforementioned conditions. The orthogonal test method is a statistical approach to analyze multi-factor and multi-level influence on system performance. In this work, based on the geological data at Yangbajing geothermal field, we analyzed the five conditions affecting the electricity generation performance of EGS, and ranked the relative importance of the five factors. The results show that the order of the relative importance of the conditions on electric power is water production rate > injection temperature > reservoir porosity > rock heat conductivity > reservoir permeability; the order of the relative importance of the conditions on reservoir impedance is reservoir permeability > injection temperature > water production rate > reservoir porosity > rock heat conductivity; the order of the relative importance of the conditions on pump power is water production rate > reservoir permeability > injection temperature > reservoir porosity > rock heat conductivity, and; the order of the relative importance of the conditions on energy efficiency is water production rate > reservoir permeability > reservoir porosity > injection temperature > rock heat conductivity. The construction of an EGS reservoir should be located at a formation with higher reservoir porosity or rock heat conductivity, while the determination of reservoir permeability, water production rate and injection temperature should be based on the comprehensive target.

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Numerical models of HDR geothermal reservoirs—a review of current thinking and progress

Cited by 61 publications

References 23 publications

Integral equation solution of heat extraction from a fracture in hot dry rock

Integral equation solution of heat extraction from a fracture in hot dry rock

Integral equation solution of heat extraction‐induced thermal stress in enhanced geothermal reservoirs

Orthogonal Test Analysis on Conditions Affecting Electricity Generation Performance of an Enhanced Geothermal System at Yangbajing Geothermal Field

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