Current Research in EEPS Seminar – Dr. Jonathan Ajo-Franklin – Lawrence Berkeley National Laboratory
Title: Probing Subsurface Fracture Dynamics Using Continuous Active Source Seismic Monitoring (CASSM)
Abstract: Induced fractures exert a dominant control on the permeability and long-term performance of engineered subsurface systems including enhanced geothermal energy production, unconventional oil & gas fields, and certain classes of environmental remediation problems. Despite this fact, the spatial distribution of fluid-conductive fractures and their behavior over time are poorly constrained by existing methodologies. We present a pair of examples demonstrating the utilization of semi-permanent active-source seismic networks to temporally characterize hydraulic fractures, at an environmental remediation pilot at FE Warren Air Force Base and at a deep hard-rock geothermal analog at the Sanford Underground Research Facility (SURF). This novel approach, which we refer to as Continuous Active Source Seismic Monitoring (CASSM), allows for collection of high temporal resolution tomographic datasets during aseismic fracture evolution, including pore pressure perturbations, shear, and fracture healing. As a result, CASSM can provide both information on fracture network geometry as well as local constraints on stress/velocity relationships, with potential for inversion in terms of fracture permeability.