Final Technical Report

• Main Authors: Rial, J.A., Lees, J.
• Other Authors: United States. Department of Energy. Office of Geothermal Technologies.
• Format: Report
• Language: English
• Published: J.A. Rial/University of North Carolina at Chapel Hill 2009
• Subjects: Orientation; Fractures; Testing; Geothermal Fields; Iceland; Real-Time Fracture Monitoring; Engineered Geothermal Systems; Shear Wave Splitting; Seismic Waves; Polarization; Detection; Algorithms; 15 Geothermal Energy; Time Delay Real-Time Fracture Monitoring; Shear; Monitoring; Hengill
• Online Access: https://doi.org/10.2172/982094; https://digital.library.unt.edu/ark:/67531/metadc1014268/

As proposed, the main effort in this project is the development of software capable of performing real-time monitoring of micro-seismic activity recorded by an array of sensors deployed around an EGS. The main milestones are defined by the development of software to perform the following tasks: • Real-time micro-earthquake detection and location • Real-time detection of shear-wave splitting • Delayed-time inversion of shear-wave splitting These algorithms, which are discussed in detail in this report, make possible the automatic and real-time monitoring of subsurface fracture systems in geothermal fields from data collected by an array of seismic sensors. Shear wave splitting (SWS) is parameterized in terms of the polarization of the fast shear wave and the time delay between the fast and slow shear waves, which are automatically measured and stored. The measured parameters are then combined with previously measured SWS parameters at the same station and used to invert for the orientation (strike and dip) and intensity of cracks under that station. In addition, this grant allowed the collection of seismic data from several geothermal regions in the US (Coso) and Iceland (Hengill) to use in the development and testing of the software.