Micro-Earthquake At Fenton Hill HDR Geothermal Area (Brown, 2009)
From Open Energy Information
Exploration Activity: Micro-Earthquake At Fenton Hill HDR Geothermal Area (Brown, 2009)
A geophone sonde was placed in the EE-1 well bore in order to detect and locate microearthquakes triggered during hydraulic fracturing of the reservoir. Additional sensors were also placed at 3,444 m depth in the EE-2 wellbore, at 750 m depth in GT-1, at 2,438 m depth in GT-2, at 655 m depth in PC-1. Nine surface seismic stations were also operated during the MHF Test to aid in environmental monitoring. Fehler et al. (1987) developed a three point statistical method for identifying fault or joint planes within 3 dimensions in what may otherwise appear to be an amorphous microearthquake location set, based on a 2-D procedure contributed by Lutz (1986). The method was applied to the microseismic data collected during the 1983 Massive Hydraulic Fracturing (MHF)Test, and was able to resolve five statistically significant planes along which most of the microearthquakes occurred. Correlation of these planes where they intersect fluid injection zones (as determined from temperature logs) and/or zones of weakness (as determined from caliper log breakout zones) confirmed that the planes identified coincide with the major fluid paths during hydraulic injection. Microseismic data were also used to determine the seismic volume of the reservoir, defined by an envelope-shaped region containing the majority of the measured microseismic events. The initial seismic volume of the Phase II reservoir created during the MHF Test was 130 million m^3, produced at a joint extension pressure of 38 MPa, however significant growth of the seismic volume occurred at the southern end of the reservoir during the Initial Closed-Loop Flow Test (ICFT) conducted in 1986.
- John T. Whetten, Bert R. Dennis, Donald S. Dreesen, Leigh S. House, Hugh D. Murphy, Bruce A. Robinson, Morton C. Smith (1987) The US Hot Dry Rock Project
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