Numerical simulation of Fluid-Rock coupling heat transfer in naturally fractured geothermal system

Shaik, Abdul Ravoof; Rahman, Sheik S.; Tran, Nam H.; Tran, Thanh

doi:10.1016/j.applthermaleng.2011.01.038

Cited by 201 publications

(56 citation statements)

References 14 publications

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“…The role of fractures is important in geothermal reservoirs because these are the main flow conduits and water flowing through the fracture collects the heat from the hotter rock matrix. Several previous studies (Randolph and Saar, 2011;Shaik et al, 2011;Ekneligoda and Min Ki-Bok, 2014;Deo et al, 2014) …”

Section: Introductionmentioning

confidence: 98%

Fracture transmissivity evolution due to silica dissolution/precipitation during geothermal heat extraction

et al. 2015

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Section: Introductionmentioning

confidence: 98%

Fracture transmissivity evolution due to silica dissolution/precipitation during geothermal heat extraction

et al. 2015

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“…One example of such approach is presented by Natarajan and Kumar [5]. Review of possible approaches existing in the literature is presented by Shaik et al in the reference [6]. They concluded, that there exists a general lack of understanding the fluid flow through a natural fracture system and heat transfer between rock matrix and flowing fluid.…”

Section: Previous Workmentioning

confidence: 99%

“…(1) to (3) can be solved only numerically. Numerical results presented in the reference [6] shown that for time less than 10-15 years, the rock temperature slightly differs from its initial value under a wide range of conditions, resulting in higher than expected temperature of produced water. For instance, high values of heat transfer coefficients allow the fluid to capture more heat as it is circulated through the fractures, maintaining the high temperature of produced water.…”

Section: Previous Workmentioning

confidence: 99%

“…They concluded, that there exists a general lack of understanding the fluid flow through a natural fracture system and heat transfer between rock matrix and flowing fluid. Shaik et al [6] investigates numerically the role of heat transfer between matrix and circulating fluid on energy production from fractured geothermal systems. In their approach matrix temperature and fracture temperature are treated individually.…”

Section: Previous Workmentioning

confidence: 99%

“…In their approach matrix temperature and fracture temperature are treated individually. The energy balance equations for rock and fluid can be expressed as follows [6]:…”

Section: Previous Workmentioning

confidence: 99%

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Influence of fracture-matrix interaction on thermal front movement in fractured reservoir

Siemek¹,

Stopa²

2015

Bulletin of the Polish Academy of Sciences Technical Sciences

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Abstract. Commercial exploitation of geothermal resources requires the disposal of large volumes of cooled brine in an environmentally acceptable way. Reinjection of cooled (i.e. spent) geothermal water has become a standard reservoir management strategy. Since injected fluids are typically much colder than the reservoir rock, this strategy results in the cooling of the region around the injection wells. Injected cool water may not have sufficient residence time in the reservoir to receive enough heat from surrounding hotter rock, resulting in temperature decrease at producing wells. Usually, the energy transport in geothermal reservoirs is calculated by use of sophisticated numerical simulators. In this paper we present analytical solution of simplified model of mass and heat transfer in fractured porous medium in one dimension, assuming constant rock temperature and neglecting small-scale effect connected with dispersion and heat conduction. The solution presented in this paper is applicable if thermal capacity of rock is high but the specific area is not sufficient for instant thermal equilibrium. This approach allows for better understanding the relation between fluid movement along the fractures and heat transfer between the rock matrix and fluid. Simple numerical experiments reported in the paper have shown the importance of specific surface area of naturally fractured rock, which influences the rate of exchange of heat between the fractures and the rock matrix.Key words: geothermal reservoir, reinjection, thermal front movement.l -specific length [m], Q -heat transfer between rock and fluid per unit of Greek letters

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Thermal drawdown and late‐stage seismic‐slip fault reactivation in enhanced geothermal reservoirs

Gan

Elsworth

2014

JGR Solid Earth

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Late-stage seismic slip in geothermal reservoirs has been shown as a potential mechanism for inducing seismic events of magnitudes to~2.6 as late as two decades into production. We investigate the propagation of fluid pressures and thermal stresses in a prototypical geothermal reservoir containing a centrally located critically stressed fault from a doublet injector and withdrawal well to define the likelihood, timing, and magnitude of events triggered by both fluid pressures and thermal stresses. We define two bounding modes of fluid production from the reservoir. For injection at a given temperature, these bounding modes relate to either low-or high-relative flow rates. At low relative dimensionless flow rates the pressure pulse travels slowly, the pressure-driven changes in effective stress are muted, but thermal drawdown propagates through the reservoir as a distinct front. This results in the lowest likelihood of pressure-triggered events but the largest likelihood of late-stage thermally triggered events. Conversely, at high relative non-dimensional flow rates the propagating pressure pulse is larger and migrates more quickly through the reservoir but the thermal drawdown is uniform across the reservoir and without the presence of a distinct thermal front, and less capable of triggering late-stage seismicity. We evaluate the uniformity of thermal drawdown as a function of a dimensionless flow rate Q D that scales with fracture spacing s (m), injection rate q (kg/s), and the distance between the injector and the target point. This parameter enables the reservoir characteristics to be connected with the thermal drawdown response around the fault and from that the corresponding magnitude and timing of seismicity to be determined. These results illustrate that the dimensionless temperature gradient adjacent to the fault dT D /dx D is exclusively controlled by the factor Q D . More significantly, this temperature gradient correlates directly with both the likelihood and severity of triggered events, enabling the direct scaling of likely magnitudes and timing to be determined a priori and directly related to the characteristics of the reservoir. This dimensionless scaling facilitates design for an optimum Q D value to yield both significant heat recovery and longevity of geothermal reservoirs while minimizing associated induced seismicity.

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Numerical simulation of Fluid-Rock coupling heat transfer in naturally fractured geothermal system

Cited by 201 publications

References 14 publications

Fracture transmissivity evolution due to silica dissolution/precipitation during geothermal heat extraction

Fracture transmissivity evolution due to silica dissolution/precipitation during geothermal heat extraction

Influence of fracture-matrix interaction on thermal front movement in fractured reservoir

Thermal drawdown and late‐stage seismic‐slip fault reactivation in enhanced geothermal reservoirs

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