The EGS Collab Project – Stimulations at Two Depths

Abstract

The EGS Collab project, supported by the US Department of Energy, is performing intensively monitored rock stimulation and flow tests at the 10-m scale in an underground research laboratory to address challenges in implementing enhanced geothermal systems (EGS). Data and observations from the field tests are compared to simulations to understand processes and build confidence in numerical modeling of the processes. Experiment 1 examined hydraulic fracturing in a well-characterized fractured phyllite 1.5 km deep at the Sanford Underground Research Facility (SURF). Testbed characterization included fracture mapping, borehole acoustic and optical televiewers, full waveform sonic, conductivity, resistivity, temperature, campaign p- and s-wave investigations and electrical resistance tomography. Borehole geophysical techniques including passive seismic, continuous active source seismic monitoring, electrical resistance tomography, fiber-based distributed strain, distributed temperature, and distributed acoustic monitoring, were used to carefully monitor stimulation events and flow tests. More than a dozen stimulations and nearly one year of flow tests were performed. Quality data and detailed observations were collected and analyzed during stimulation and water flow tests, and these data are available. We achieved adaptive control of the tests using real-time monitoring and rapid dissemination of data and near-real-time simulation. Experiment 2 examines the potential for hydraulic shearing in amphibolite 1.25 km deep at SURF. The testbed consists of nine subhorizontal boreholes, four of which surround the testbed with grouted-in ERT, seismic sensors, CASSM and distributed fiber sensors. The test wells include a “five-spot” set with an injection well and four production/monitoring wells. Like Experiment 1, the testbed was characterized geophysically and hydrologically, and three stimulations have been performed using new tools.

Three‐Dimensional Thermoporoelastic Modeling of Hydrofracturing and Fluid Circulation in Hot Dry Rock

“…The injector, producer, and monitoring wells at the EGS Collab site are depicted as green, red, and yellow lines, respectively. A number of colored circles intersecting the drift (i.e., wide white tubes) represent the mapped fractures (Kneafsey, Dobson, Ajo‐Franklin, et al., 2018).…”

“…The EGS Collab Project was a 3‐year R&D program, funded by the United States Department of Energy in 2017 (White et al., 2019). This project was initiated to provide new knowledge and modeling capabilities, bridging the knowledge gap of EGS between the laboratory scale and the field scale through a meso‐scale stimulation (e.g., hydrofracturing, hydroshearing, acidizing) and circulation experiments (Kneafsey, Dobson, Ajo‐Franklin, et al., 2018; White et al., 2019; White & Fu, 2020). The EGS Collab E1 was performed to investigate the viability of creating hydraulic fractures to connect the injector and producer wells in hot dry rock for geothermal mining.…”

Sanford Underground Research Facility’s approach to school education, community activities, and public outreach

“…The MAJORANA DEMONSTRATOR focusing on neutrinoless double-beta-decay published final results in 2023 [5] and is presently searching for the decay of 180m Ta [6]. The Enhanced Geothermal System (EGS) Collab-SIGMA-V project completed two rock stimulation and flow tests in different rock formations [7], one of which will be repurposed starting late 2023 to conduct research in underground thermal energy storage technologies. The Compact Accelerator System for Performing Astrophysical Research (CASPAR) is concentrating on nuclear astrophysics research ( [8], including recent results [9]).…”

4D Electrical Resistivity Imaging of Stress Perturbations Induced During High‐Pressure Shear Stimulation Tests

“…Experiment #1, which focused on executing and monitoring hydrofracture stimulations, was conducted on the 4,850 Level of the Sanford Underground Research Facility (SURF) in Lead, South Dakota, approximately 1.5 km below ground surface (bgs) (Fu et al, 2021;Heise, 2015). In Experiment #2, shear stimulation testing was conducted on the 4,100 Level of SURF, which lies approximately 1.25 km bgs (Kneafsey, 2022a(Kneafsey, , 2022b. Shear stimulation involves isolating and pressurizing an existing fracture below the minimum principle stress (to avoid hydrofracturing) in an attempt shear-slip the fracture and create a self-propped hydraulic connection between two boreholes.…”