Characterizing the stimulation mode of a fracture is critical to assess the hydraulic efficiency and the seismic risk related to deep fluid manipulations. We have monitored the three-dimensional displacements of a fluid-driven fracture during water injections in a borehole at ~1.5 km depth in the crystalline rock of the Sanford Underground Research Facility (USA). The fracture initiates at 61% of the minimum horizontal stress by micro-shearing of the borehole on a foliation plane. As the fluid pressure increases further, borehole axial and radial displacements increase with injection time highlighting the opening and sliding of a new hydrofracture growing ~10 m away from the borehole, in accordance with the ambient normal stress regime and in alignment with the microseismicity. Our study reveals how fluid-driven fracture stimulation can be facilitated by a mixed-mode process controlled by the complex hydromechanical evolution of the growing fracture. The data presented in this submission refer to the SIMFIP measurements and analyses of the stimulation tests conducted on the 164 ft (50 m) notch of the Sanford Underground Research Facility (SURF), during the EGS-Collab test 1. In addition to the datafiles, there is the draft of a manuscript submitted to Geophysical Research Letters (GRL).

As part of the geophysical characterization suite for the first EGS Collab tesbed, here are the baseline cross-well seismic data and resultant models. The campaign seismic data have been organized, concatenated with geometry and compressional (P-) & and shear (S-) wave picks, and submitted as SGY files. P-wave data were collected and analyzed in both 2D and 3D, while S-wave data were collected and analyzed in 2D only. Inversion models are provided as point volumes; the volumes have been culled to include only the points within source/receiver array coverage. The full models space volumes are also included, if relevant. An AGU 2018 poster by Linneman et al. is included that provides visualizations/descriptions of the cross-well seismic characterization method, elastic moduli calculations, and images of model inversion results.

This package includes data from two days of testing at the Sanford Underground Research Facility (SURF) on the 4100 level. The tests were performed in borehole TV4100 in the battery charging alcove south of the Yates shaft. TV4100 is a vertical borehole ~50 meters deep. A series of hydraulic fracture (mini-frac) and reopening tests were conducted at various depths to investigate the magnitude and direction of the minimum principal stress in that area of the mine. Apparent features of the pressure time/pressure injected volume curves are the onset of fracture, peak pressure, and the initial shut in pressure (ISIP). The raw data files include a Readme with the day, time, and location of each file. The files are organized into 9 columns: time (sec), flow meter (V), Pressure of Return (V), Pressure of Packer (V), Pressure of Injection (V), flow (gpm), Pressure of Return (psi), Pressure of Packer (psi), Pressure of Injection (psi). The shift reports are a short log of how the tests were run in the two-day period. An American Geophysical Union (AGU) 2019 presentation by Ingraham et al. is shown to provide visualization/interpretation of the data. The columns which report voltage (V) show the unscaled voltage value from the transducer, which was recorded in case pressure values needed to be rescaled due to incorrect calibration factors. This was not necessary. Results reported in the AGU poster were filtered with a moving average to remove pump noise before presentation. Note that the logging and impression packer results are included in separate datasets managed by Lawrence Berkeley Laboratory.

The EGS Collab experiment 2 was focused on testing shear stimulation techniques. Shear stimulation, in this case, means using hydraulic pressure to cause shear slip on preexisting fracture or fault planes such that the hydraulic conductivity of the fracture or fault increases. The concept is to create a percolating network of permeable fractures by enhancing the permeability of a primarily preexisting network of fractures. To test this concept the hydraulic pressures for experiment 2 were kept below the the estimated magnitude of the least compressive principal stress based on a set of stress measurements in nearby well TV4100. All tests for experiment 2 were performed by applying hydraulic pressure to well E2-TC. Subsequent stimulations in both E2-TC and E2-TU where the injection pressure was increased above the least compressive principal stress are considered part of experiment 3, which is documented separately. The data are organized in directories labeled by the depth range isolated between packers.

The EGS Collab is conducting experiments in hydraulic fracturing at a depth of 1.5 km in the Sanford Underground Research Facility (SURF) on the 4850 Level. A total of eight ~60m-long subhorizontal boreholes were drilled at that depth on the western rib of the West Access Drift. Six of these holes are used for geophysical monitoring, one is used for hydraulic fracturing and the remaining hole was designed as a production borehole. In addition to these eight boreholes, 4 5-m Jack leg boreholes were drilled for housing geophones. This submission package includes various data type that were assembled to create Earth Models of the testbed. Note: The coordinate system used is local Homestake Mine Coordinate (HMC) system from an old gold mine that was in operation for over 100 years.

The U.S. Department of Energy's Enhanced Geothermal System (EGS) Collab project aims to improve our understanding of hydraulic stimulations in crystalline rock for enhanced geothermal energy production through execution of intensely monitored meso-scale experiments. The first experiment was performed at the 4850 ft level of the Sanford Underground Research Facility (SURF), approximately 1.5 km below the surface at Lead, South Dakota. The data reported here were collected by the continuous active-source seismic monitoring (CASSM) system (Ajo-Franklin et al., 2011). This system was permanently installed in the testbed and consisted of 17 piezoelectric sources that were recorded by 2-12 channel hydrophone arrays, 18 3-C accelerometers, and 4 3-C geophones at a Nyquist frequency of 24kHz. The source array was activated in a repeated sequence of shots (each source fired 16 times and stacked into resultant waveforms) for the duration of the experiment (April 25, 2018 - March 7, 2019) with few exceptions. Please see the attached documents describing the source / receiver geometry. The data are available in both seg2 (.dat extension) and segy (.sgy extension) format. Each segy file contains multiple seg2 files.