loading page

Creation of a mixed-mode fracture network at meso-scale through hydraulic fracturing and shear stimulation
  • +12
  • Martin Schoenball,
  • Jonathan Blair Ajo-Franklin,
  • Doug Blankenship,
  • Chengping Chai,
  • Patrick Dobson,
  • Timothy J Kneafsey,
  • Hunter A Knox,
  • Monica Maceira,
  • Michelle Robertson,
  • Parker Sprinkle,
  • Christopher Strickland,
  • Dennise Templeton,
  • Paul C Schwering,
  • Craig Ulrich,
  • Todd J Wood
Martin Schoenball
Lawrence Berkeley National Laboratory

Corresponding Author:[email protected]

Author Profile
Jonathan Blair Ajo-Franklin
Lawrence Berkeley National Laboratory (DOE)
Author Profile
Doug Blankenship
Sandia National Laboratories
Author Profile
Chengping Chai
Oak Ridge National Laboratory
Author Profile
Patrick Dobson
Lawrence Berkeley National Laboratory (DOE)
Author Profile
Timothy J Kneafsey
Lawrence Berkeley Laboratory
Author Profile
Hunter A Knox
Pacific Northwest National Laboratory
Author Profile
Monica Maceira
Oak Ridge National Laboratory (DOE)
Author Profile
Michelle Robertson
Lawrence Berkeley National Laboratory
Author Profile
Parker Sprinkle
Pacific Northwest National Laboratory
Author Profile
Christopher Strickland
Pacific Northwest National Laboratory (DOE)
Author Profile
Dennise Templeton
Lawrence Livermore National Laboratory
Author Profile
Paul C Schwering
Sandia National Laboratories
Author Profile
Craig Ulrich
Lawerence Berkeley National Laboratory
Author Profile
Todd J Wood
Lawrence Berkeley National Laboratory (DOE)
Author Profile

Abstract

Enhanced Geothermal Systems could provide a substantial contribution to the global energy demand if their implementation could overcome inherent challenges. Examples are insufficient created permeability, early thermal breakthrough, and unacceptable induced seismicity. Here we report on the seismic response of a meso-scale hydraulic fracturing experiment performed at 1.5 km depth at the Sanford Underground Research Facility. We have measured the seismic activity by utilizing a novel 100 kHz, continuous seismic monitoring system deployed in six 60 m-length monitoring boreholes surrounding the experimental domain in 3-D. The achieved location uncertainty was on the order of 1 m, and limited by the signal-to-noise ratio of detected events. These uncertainties were corroborated by detections of fracture intersections at the monitoring boreholes. Three intervals of the dedicated injection borehole were hydraulically stimulated by water injection at pressures up to 33 MPa and flow rates up to 5 L/min. We located 1933 seismic events during several injection periods. The recorded seismicity delineates a complex fracture network comprised of multi-strand hydraulic fractures and shear-reactivated, pre-existing planes of weakness that grew unilaterally from the point of initiation. We find that heterogeneity of stress dictates the outcome of hydraulic stimulations, even when relying on theoretically well-behaved hydraulic fractures. Once hydraulic fractures intersected boreholes, the boreholes acted as a pressure relief and fracture propagation ceased. In order to create an efficient sub-surface heat exchanger, production boreholes should not be drilled before the end of hydraulic stimulations.
Dec 2020Published in Journal of Geophysical Research: Solid Earth volume 125 issue 12. 10.1029/2020JB019807