The EGS Collab project: Outcomes and lessons learned from hydraulic fracture stimulations in crystalline rock at 1.25 and 1.5 km depth

• Three multi-test stimulation and flow experiments were performed in crystalline rock. • Stimulation occurred by hydraulic fracturing, but flow required hydropropping. • Shear stimulation did not occur because of low shear-to-normal force ratio. • Shear stimulation was also impacted by healed fractures having low permeability. • Lessons learned are presented. With the goal of better understanding stimulation in crystalline rock for improving enhanced geothermal systems (EGS), the EGS Collab Project performed a series of stimulations and flow tests at 1.25 and 1.5 km depths. The tests were performed in two well-instrumented testbeds in the Sanford Underground Research Facility in Lead, South Dakota, United States. The testbed for Experiment 1 at 1.5 km depth contained two open wells for injection and production and six instrumented monitoring wells surrounding the targeted stimulation zone. Four multi-step stimulation tests targeting hydraulic fracturing and nearly year-long ambient temperature and chilled water flow tests were performed in Experiment 1. The testbed for Experiments 2 and 3 was at 1.25 km depth and contained five open wells in an outwardly fanning five-spot pattern and two fans of well-instrumented monitoring wells surrounding the targeted stimulation zone. Experiment 2 targeted shear stimulation, and Experiment 3 targeted low-flow, high-flow, and oscillating pressure stimulation strategies. Hydraulic fracturing was successful in Experiments 1 and 3 in generating a connected system wherein injected water could be collected. However, the resulting flow was distributed dynamically, and not entirely collected at the anticipated production well. Thermal breakthrough was not observed in the production well, but that could have been masked by the Joule-Thomson effect. Shear stimulation in Experiment 2 did not occur – despite attempting to pressurize the fractures most likely to shear – because of the inability to inject water into a mostly-healed fracture, and the low shear-to-normal stress ratio. The EGS Collab experiments are described to provide a background for lessons learned on topics including induced seismicity, the correlation between seismicity and permeability, distributed and dynamic flow systems, thermoelastic and pressure effects, shear stimulation, local geology, thermal breakthrough, monitoring stimulation, grouting boreholes, modeling, and system management.

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Publication Details

Journal
Geothermics
Published
2024-11-23
DOI
https://doi.org/10.1016/j.geothermics.2024.103178
Citations
19
Primary Topic
Hydraulic Fracturing and Reservoir Analysis
Type
article
Field-Weighted Citation Impact
4.04

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article

The EGS Collab project: Outcomes and lessons learned from hydraulic fracture stimulations in crystalline rock at 1.25 and 1.5 km depth

Jeffrey Burghardt, Mark D. White, Martin Schoenball, Joseph P. Morris et al.
19 citations
Geothermics
Hydraulic Fracturing and Reservoir Analysis
4.04
article

The EGS Collab project: Outcomes and lessons learned from hydraulic fracture stimulations in crystalline rock at 1.25 and 1.5 km depth

Jeffrey Burghardt, Mark D. White, Martin Schoenball, Joseph P. Morris, Tatiana Pyatina, Chet J. Hopp, Timothy J. Kneafsey, Ghanashyam Neupane, Tom Doe, Ankush Singh, William Roggenthen, Chris Strickland, Paul Schwering, Todd Wood, Verónica Rodrı́guez Tribaldos, Hunter Knox, Jon Weers, Craig Ulrich, Doug Blankenship, Roland N. Horne, Pengcheng Fu, Yves Guglielmi, Earl D. Mattson, Luke Frash, Jonathan Ajo‐Franklin, Mathew Ingraham, George Vandine, Patrick Dobson, Timothy Johnson, Lianjie Huang, Megan M. Smith, Mark McClure, Michelle M. Robertson, Vince R. Vermuel
article en
19 citations

Abstract

• Three multi-test stimulation and flow experiments were performed in crystalline rock. • Stimulation occurred by hydraulic fracturing, but flow required hydropropping. • Shear stimulation did not occur because of low shear-to-normal force ratio. • Shear stimulation was also impacted by healed fractures having low permeability. • Lessons learned are presented. With the goal of better understanding stimulation in crystalline rock for improving enhanced geothermal systems (EGS), the EGS Collab Project performed a series of stimulations and flow tests at 1.25 and 1.5 km depths. The tests were performed in two well-instrumented testbeds in the Sanford Underground Research Facility in Lead, South Dakota, United States. The testbed for Experiment 1 at 1.5 km depth contained two open wells for injection and production and six instrumented monitoring wells surrounding the targeted stimulation zone. Four multi-step stimulation tests targeting hydraulic fracturing and nearly year-long ambient temperature and chilled water flow tests were performed in Experiment 1. The testbed for Experiments 2 and 3 was at 1.25 km depth and contained five open wells in an outwardly fanning five-spot pattern and two fans of well-instrumented monitoring wells surrounding the targeted stimulation zone. Experiment 2 targeted shear stimulation, and Experiment 3 targeted low-flow, high-flow, and oscillating pressure stimulation strategies. Hydraulic fracturing was successful in Experiments 1 and 3 in generating a connected system wherein injected water could be collected. However, the resulting flow was distributed dynamically, and not entirely collected at the anticipated production well. Thermal breakthrough was not observed in the production well, but that could have been masked by the Joule-Thomson effect. Shear stimulation in Experiment 2 did not occur – despite attempting to pressurize the fractures most likely to shear – because of the inability to inject water into a mostly-healed fracture, and the low shear-to-normal stress ratio. The EGS Collab experiments are described to provide a background for lessons learned on topics including induced seismicity, the correlation between seismicity and permeability, distributed and dynamic flow systems, thermoelastic and pressure effects, shear stimulation, local geology, thermal breakthrough, monitoring stimulation, grouting boreholes, modeling, and system management.

GeothermicsVol. 126
Lawrence Livermore National Laboratory (US), National Laboratory of the Rockies (US), Planetary Science Institute (US), Los Alamos National Laboratory (US), Pacific Northwest National Laboratory (US), Lawrence Berkeley National Laboratory (US), The Aerospace Corporation (US), Bellevue College (US), South Dakota School of Mines and Technology (US), Sandia National Laboratories California (US), Brookhaven National Laboratory (US), Victim Support (GB), Idaho National Laboratory (US), Environmental and Water Resources Engineering (IL), Sandia National Laboratories (US), Summit School (US), National Cooperative for the Disposal of Radioactive Waste (Switzerland) (CH), GFZ Helmholtz Centre for Geosciences (DE), Rice University (US), Stanford University (US)
U.S. Department of Energy, Battelle, Colorado School of Mines, Office of Energy Efficiency and Renewable Energy, National Nuclear Security Administration, Geothermal Technologies Office, Office of Energy Efficiency, Lawrence Livermore National Laboratory, National Renewable Energy Laboratory, Sandia National Laboratories, Lawrence Berkeley National Laboratory
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