TY - JOUR
T1 - The EGS Collab Project: Outcomes and Lessons Learned from Hydraulic Fracture Stimulations in Crystalline Rock at 1.25 and 1.5 Km Depth
T2 - Article No. 103178
AU - Kneafsey, Tim
AU - Dobson, Pat
AU - Blankenship, Doug
AU - Schwering, Paul
AU - White, Mark
AU - Morris, Joseph
AU - Huang, Lianjie
AU - Johnson, Tim
AU - Burghardt, Jeff
AU - Mattson, Earl
AU - Neupane, Ghanashyam
AU - Strickland, Chris
AU - Knox, Hunter
AU - Vermuel, Vince
AU - Ajo-Franklin, Jonathan
AU - Fu, Pengcheng
AU - Roggenthen, William
AU - Doe, Tom
AU - Schoenball, Martin
AU - Hopp, Chet
AU - Tribaldos, Veronica
AU - Ingraham, Mathew
AU - Guglielmi, Yves
AU - Ulrich, Craig
AU - Wood, Todd
AU - Frash, Luke
AU - Pyatina, Tatiana
AU - Vandine, George
AU - Smith, Megan
AU - Horne, Roland
AU - McClure, Mark
AU - Singh, Ankush
AU - Weers, Jon
AU - Robertson, Michelle
PY - 2025
Y1 - 2025
N2 - 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.
AB - 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.
KW - coupled process modeling
KW - crystalline rock
KW - EGS Collab
KW - enhanced geothermal systems
KW - experimental
KW - field test
KW - flow test
KW - Sanford Underground Research Facility
KW - stimulation
U2 - 10.1016/j.geothermics.2024.103178
DO - 10.1016/j.geothermics.2024.103178
M3 - Article
SN - 0375-6505
VL - 126
JO - Geothermics
JF - Geothermics
ER -