Thermal breakthrough calculations to optimize design of a multiple-stage Enhanced Geothermal System

Li, Tianyu; Shiozawa, Sogo; McClure, Mark

doi:10.1016/j.geothermics.2016.06.015

Cited by 79 publications

(19 citation statements)

References 12 publications

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“…Figure 4 shows the schematic of our problem setting. An initial fracture (notch) is located at the center of the two-dimensional domain, Λ = ( − 0.5m, 0.5m) 2 .…”

Section: Selection Of Boundary Conditionsmentioning

confidence: 99%

“…In particular, hydraulic fracturing has been widely employed for extracting hydrocarbons, in which fractures propagate because of the injection of a highly pressurized viscous fluid. Fluid‐driven fracture propagation is also applied to geothermal wells to maximize heat extraction, and used to measure in situ stress state . Other popular applications would include the propagation of magma‐filled cracks and failure phenomena of biological soft tissue …”

Section: Introductionmentioning

confidence: 99%

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The effect of stress boundary conditions on fluid‐driven fracture propagation in porous media using a phase‐field modeling approach

Shiozawa

Lee

Wheeler

2019

Num Anal Meth Geomechanics

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Summary A phase‐field approach for fluid‐driven fracture propagation in porous media with varying constant compatible stress boundary conditions is discussed and implemented. Since crack opening displacement, fracture path, and stress values near the fracture are highly dependent on the given boundary conditions, it is crucial to take into account the impact of in situ stresses on fracturing propagation for realistic applications. We illustrate several numerical examples that include the effects of different boundary conditions on the fracture propagation. In addition, an example using realistic boundary conditions from a reservoir simulator is included to show the capabilities of our computational framework.

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“…Figure 4 shows the schematic of our problem setting. An initial fracture (notch) is located at the center of the two-dimensional domain, Λ = ( − 0.5m, 0.5m) 2 .…”

Section: Selection Of Boundary Conditionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The effect of stress boundary conditions on fluid‐driven fracture propagation in porous media using a phase‐field modeling approach

Shiozawa

Lee

Wheeler

2019

Num Anal Meth Geomechanics

Self Cite

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“…2,4 The key is to create a complex fracture network for fluid circulation between the injection well and the production well by a series of stimulation techniques, such as hydraulic fracturing, waterless fracturing, and chemical treatment. [11][12][13] It is believed that fluid injection can induce fracture shear slip, which contributes to the permeability enhancement of the whole reservoir. [5][6][7] Some mining practices have confirmed that the combination of thermal-chemical-hydraulic (TCH) fracturing technology can induce a more pronounced stimulation effect in geothermal reservoirs than using any single stimulation method.…”

Section: Introductionmentioning

confidence: 99%

“…Numerous studies have demonstrated that the local thermal nonequilibrium (LTNE) theory is more appropriate if there is a rapid heat transport or a large temperature difference between the rock matrix and the flowing fluid. 13 Based on the dual porosity model 37 or the discrete fracture network model, [38][39][40][41][42][43] some studies have been conducted to analyze the heat extraction in 2D or 3D EGS. However, the mechanical effect was not incorporated into the above model.…”

Section: Introductionmentioning

confidence: 99%

Investigation on heat extraction characteristics in randomly fractured geothermal reservoirs considering thermo‐poroelastic effects

Han

Cheng

Gao

et al. 2019

Energy Science & Engineering

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A fully coupled thermal‐hydraulic‐mechanical (THM) model was developed to investigate the underlying response mechanisms during heat extraction in fractured geothermal reservoirs. The random fracture network in the stimulated zone was reproduced based on the fractal theory. The coupled model accounts for the dominant physical phenomena including (a) fluid flow, heat transport, and solid deformation in porous media and fractures; (b) local thermal nonequilibrium (LTNE) between rock matrix and flowing fluid; and (c) temperature‐dependent fluid thermodynamic properties and stress‐dependent pore and fracture permeability. The proposed model was validated by several analytic solutions. Sequentially, the evolution of pore pressure, equivalent temperature, effective stress, and reservoir permeability was analyzed. The sensitivity of the heat extraction performance to fracture network morphology was discussed. Results show that interconnected large‐scale fractures dominate mass and heat transport. Widely distributed small‐scale fractures contribute to the cooling of the heat rock mass along many flow paths in parallel. The change in effective stress associated with fully coupled thermo‐poroelastic effects may induce fracture shear dilation and pore expansion, resulting in an enhancement of the overall reservoir permeability. There is a significant temperature difference between the solid phase and the fluid phase in fractures, but not in porous media. It is more reasonable to use the LTNE theory to analyze the heat extraction of fractured geothermal reservoirs. The fracture network morphology has a profound effect on heat extraction efficiency and injectivity. Undeveloped fracture networks will result in a higher injection pressure, earlier thermal breakthrough, and shorter lifetime, but higher heat extraction ratio. Properly increasing the fracture density can delay the thermal breakthrough time, prolong the service life, and improve the injectivity. Fully connected fracture networks may result in thermal short‐circuiting and earlier thermal breakthrough. Generating a complex and scattered fracture network but without preferential channels is conducive to extracting more heat from geothermal reservoirs.

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“…These numerical models allow us to define well's system design, fracture paths, extraction rates, and temperature of injected and produced thermal waters, to interpret hydraulic tests or stimulation processes, and to predict reservoir behavior during geothermal power production. Therefore, they are mandatory to optimize the productive capacity and the thermal breakthrough occurrence [1,44].…”

Section: Introductionmentioning

confidence: 99%

Modeling Highly Buoyant Flows in the Castel Giorgio: Torre Alfina Deep Geothermal Reservoir

et al. 2018

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The Castel Giorgio-Torre Alfina (CG-TA, central Italy) is a geothermal reservoir whose fluids are hosted in a carbonate formation at temperatures ranging between 120 ∘ C and 210 ∘ C. Data from deep wells suggest the existence of convective flow. We present the 3D numerical model of the CG-TA to simulate the undisturbed natural geothermal field and investigate the impacts of the exploitation process. The open source finite-element code OpenGeoSys is applied to solve the coupled systems of partial differential equations. The commercial software FEFLOW5 is also used as additional numerical constraint. Calculated pressure and temperature have been calibrated against data from geothermal wells. The flow field displays multicellular convective patterns that cover the entire geothermal reservoir. The resulting thermal plumes protrude vertically over 3 km at Darcy velocity of about 7 * 10 −8 m/s. The analysis of the exploitation process demonstrated the sustainability of a geothermal doublet for the development of a 5 MW pilot plant. The buoyant circulation within the geothermal system allows the reservoir to sustain a 50-year production at a flow rate of 1050 t/h. The distance of 2 km, between the production and reinjection wells, is sufficient to prevent any thermal breakthrough within the estimated operational lifetime. OGS and FELFOW results are qualitatively very similar with differences in peak velocities and temperatures. The case study provides valuable guidelines for future exploitation of the CG-TA deep geothermal reservoir. IntroductionSince the 1970s, the increasing threat of a worldwide energy crisis has prompted many governments to reduce their dependence on traditional nonrenewable energy sources focusing on renewable ones (e.g., geothermal energy, hydroelectric, wind-energy, and several forms of solar energy, such as bioenergy, biofuel, photovoltaic, and solar-thermal energy [1]). Geothermal energy is expected to play an increasing role to meet future power demand. This is related to its enormous exploiting potential, which is capturing the attention of industries also due to technological advances in the exploration of promising geothermal fields [2,3].Most of the world famous geothermal energy sources exploited today are associated with volcanic and/or recent tectonically active areas. Important examples are the geothermal areas of Yellowstone [4][5][6] northern California [7], the Pannonic Basin [8], and the Rhine Graben [9][10][11]. Italy strongly contributes to the development of geothermal power generation. In 1904, the world first electrical power was produced from a geothermal energy source in the Larderello site (Tuscany, central Italy) [1,[12][13][14][15][16][17][18].Beyond the world famous Larderello system, fossil and active hydrothermal manifestations are distributed all along the Preappennine belt of central Italy, facing the Tyrrhenian coast. This area has undergone both lithospheric extension and upper mantle doming. Such processes have been active since the Miocene [19,20] and are likely...

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Thermal breakthrough calculations to optimize design of a multiple-stage Enhanced Geothermal System

Cited by 79 publications

References 12 publications

The effect of stress boundary conditions on fluid‐driven fracture propagation in porous media using a phase‐field modeling approach

The effect of stress boundary conditions on fluid‐driven fracture propagation in porous media using a phase‐field modeling approach

Investigation on heat extraction characteristics in randomly fractured geothermal reservoirs considering thermo‐poroelastic effects

Modeling Highly Buoyant Flows in the Castel Giorgio: Torre Alfina Deep Geothermal Reservoir

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