Active Seismics to Determine Reservoir Characteristics of a Hot Dry Rock Geothermal System
Since 1981 three wells have been drilled to depths of between 2.0 and 2.6 km in the Carnmenellis granite, Cornwall, England in order to create a HDR geothermal system. These wells are separated by between 150 and 300 m and have been hydraulically connected by massive injections of both water and viscous gel (50 cpoise). Passive microseismic monitoring of the hydraulic stimulation and circulation experiments has been used since 1982 to determine the size and structure of the reservoir, and monitor its growth. The active seismic survey techniques of cross-hole seismics and vertical seismic profiling (VSP) have been introduced to complement the passive microseismic monitoring in characterizing the reservoir. The cross-hole seismic surveys indicate that the microseismicity defines the area of joint dilation. The attenuation of high frequencies in the region of microseismicity suggests that the reservoir is composed of a complex zone of cracks rather than a single large fracture. VSP surveys also show a good agreement between the microseismically defined reservoir and seismic signal attenuation. Recent improvements in hardware, computer processing and interpretation indicate that active seismics will play an increasingly important part in mapping and understanding geothermal reservoirs. 11 figs., 10 refs.
- Research Organization:
- Camborne School of Mines Geothermal Energy Project, Rosemanowes Quarry, Penryn, Cornwall, England
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AT03-80SF11459; AS07-84ID12529
- OSTI ID:
- 888523
- Report Number(s):
- SGP-TR-109-19
- Resource Relation:
- Conference: Proceedings, Twelfth Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, Calif., January 20-22, 1987
- Country of Publication:
- United States
- Language:
- English
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