An investigation of stimulation mechanisms in Enhanced Geothermal Systems

McClure, Mark; Horne, Roland N.

doi:10.1016/j.ijrmms.2014.07.011

Cited by 287 publications

(120 citation statements)

References 77 publications

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“…Therefore, hydraulic fracturing is often only considered relevant in the near field of a wellbore, where it improves the linkage between the borehole and the natural fracture system. Rutledge et al (2004) showed that shear activation of existing fractures and creation of new fractures can occur concomitantly, dependent on the in situ stress conditions, injection pressure, initial fracture transmissivity, fracture network connectivity and fracture orientation (e.g., McClure and Horne, 2014). Regardless of which process is dominant, the direction of reservoir growth, and therefore the geometry of the stimulated volume, depends to a considerable degree on the in situ stress gradient, stress orientation and the natural fracture network.…”

Section: Stimulation By Hydraulic Shearingmentioning

confidence: 99%

“…Injection of fluid into a rock mass invariably leads to the deformation of the surrounding rock mass due to poroelasticity (Biot, 1941) or slip-related stress changes (McClure and Horne, 2014). Numerical studies have suggested that stress interaction between adjacent fractures can have a significant impact on the stimulation results (e.g., Gischig and Preisig, 2015).…”

Section: Rock Mass Deformation and Stress Interactionmentioning

confidence: 99%

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The seismo-hydromechanical behavior during deep geothermal reservoir stimulations: open questions tackled in a decameter-scale in situ stimulation experiment

et al. 2018

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Abstract. In this contribution, we present a review of scientific research results that address seismo-hydromechanically coupled processes relevant for the development of a sustainable heat exchanger in low-permeability crystalline rock and introduce the design of the In situ Stimulation and Circulation (ISC) experiment at the Grimsel Test Site dedicated to studying such processes under controlled conditions. The review shows that research on reservoir stimulation for deep geothermal energy exploitation has been largely based on laboratory observations, large-scale projects and numerical models. Observations of full-scale reservoir stimulations have yielded important results. However, the limited access to the reservoir and limitations in the control on the experimental conditions during deep reservoir stimulations is insufficient to resolve the details of the hydromechanical processes that would enhance process understanding in a way that aids future stimulation design. Small-scale laboratory experiments provide fundamental insights into various processes relevant for enhanced geothermal energy, but suffer from (1) difficulties and uncertainties in upscaling the results to the field scale and (2) relatively homogeneous material and stress conditions that lead to an oversimplistic fracture flow and/or hydraulic fracture propagation behavior that is not representative of a heterogeneous reservoir. Thus, there is a need for intermediate-scale hydraulic stimulation experiments with high experimental control that bridge the various scales and for which access to the target rock mass with a comprehensive monitoring system is possible. The ISC experiment is designed to address open research questions in a naturally fractured and faulted crystalline rock mass at the Grimsel Test Site (Switzerland). Two hydraulic injection phases were executed to enhance the permeability of the rock mass. During the injection phases the rock mass deformation across fractures and within intact rock, the pore pressure distribution and propagation, and the microseismic response were monitored at a high spatial and temporal resolution.

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Section: Stimulation By Hydraulic Shearingmentioning

confidence: 99%

Section: Rock Mass Deformation and Stress Interactionmentioning

confidence: 99%

The seismo-hydromechanical behavior during deep geothermal reservoir stimulations: open questions tackled in a decameter-scale in situ stimulation experiment

et al. 2018

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“…In case of the single-fracture model only one wing of the fracture is simulated, whereas the complex fracture interaction due to stress shadowing in the multi-fracture simulation required the full model. Due to the high stress anisotropy fracture propagation is expected to be perpendicular to 3 [12,13]. Therefore, predefined fracture planes are introduced to the models with their normal parallel to 3.…”

Section: Dec Software Descriptionmentioning

confidence: 99%

Simulating the Hydraulic Stimulation of Multiple Fractures in an Anisotropic Stress Field Applying the Discrete Element Method

Zeeb

Konietzky

2015

Energy Procedia

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The current study investigates hydraulic fracture stimulation for an Enhanced Geothermal System (EGS) in a petrothermal environment to evaluate stress shadowing and fracture interaction in a multi-fracture setup. Previous studies investigated the geothermal potential of the area around Freiberg (Saxony, Germany), which is therefore used as a case example. The commercial discrete element code 3DEC™ is applied to conduct the numerical simulations. The simulation results show that hydraulic fracture stimulation results in a strong stress field alteration, which significantly influences the propagation of subsequently stimulated fractures. The resulting deflection of fractures can be minimized applying an optimized stimulation concept.

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“…In addition, the boundary element method (BEM) was also used for modelling similar problems. For example, Ding [46], Ghassemi et al [47], Kumar and Gutierrez [48], and McClure and Horne [49] used the BEM or displacement discontinuity element method (DDM) to simulate the heat and mass transfer in geothermal reservoir with single fracture or fracture networks.…”

Section: Introductionmentioning

confidence: 99%

An Approximate Solution for Predicting the Heat Extraction and Preventing Heat Loss from a Closed-Loop Geothermal Reservoir

Feng

et al. 2017

Geofluids

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Approximate solutions are found for a mathematical model developed to predict the heat extraction from a closed-loop geothermal system which consists of two vertical wells (one for injection and the other for production) and one horizontal well which connects the two vertical wells. Based on the feature of slow heat conduction in rock formation, the fluid flow in the well is divided into three stages, that is, in the injection, horizontal, and production wells. The output temperature of each stage is regarded as the input of the next stage. The results from the present model are compared with those obtained from numerical simulator TOUGH2 and show first-order agreement with a temperature difference less than 4 ∘ C for the case where the fluid circulated for 2.74 years. In the end, a parametric study shows that (1) the injection rate plays dominant role in affecting the output performance, (2) higher injection temperature produces larger output temperature but decreases the total heat extracted given a specific time, (3) the output performance of geothermal reservoir is insensitive to fluid viscosity, and (4) there exists a critical point that indicates if the fluid releases heat into or absorbs heat from the surrounding formation.

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An investigation of stimulation mechanisms in Enhanced Geothermal Systems

Cited by 287 publications

References 77 publications

The seismo-hydromechanical behavior during deep geothermal reservoir stimulations: open questions tackled in a decameter-scale in situ stimulation experiment

The seismo-hydromechanical behavior during deep geothermal reservoir stimulations: open questions tackled in a decameter-scale in situ stimulation experiment

Simulating the Hydraulic Stimulation of Multiple Fractures in an Anisotropic Stress Field Applying the Discrete Element Method

An Approximate Solution for Predicting the Heat Extraction and Preventing Heat Loss from a Closed-Loop Geothermal Reservoir

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