Geothermal Exploration North of Mount St. Helens: Washington State Play-Fairway Project
- Temple University, Philadelphia, PA (United States)
- Washington Geological Survey, Olympia, WA (United States)
- Cyrq Energy, Seattle, WA (United States)
Active seismicity within a broad zone in proximity to volcanism in the St. Helens Seismic Zone north of Washington State’s Mount Saint Helens provide key ingredients for hydrothermal circulation at depth. This seismicity extends well north of the volcanic edifice below where several faults and associated fractures in outcrop record repeated slip, dilation and alteration indicative of localized fluid flow. Candidate reservoir rocks include marine metasediments overlain by extrusive volcanics. This study characterizes the faults and fractures in the extrusives which are available in outcrop and sampled along well TGH17-24 and Plate Boundary Observatory strainmeter borehole, B201. Outcrop mapping and borehole image log analysis down to 250 m document abundant volcaniclastic deposits and basalt flows that are highly fractured, although intervening ash layers truncate the vertical extent of many of these structures. However, strike slip faults with well-developed gouge zones and adjacent localized high fracture density provide potential for vertically extensive fracture flow paths. Where these rocks are altered by intrusion, they develop high fracture density that can support heat transfer. Borehole image logs further record breakout that indicate the azimuth of SHmax in the shear zone is approximately 054/234°±23.6°, consistent with seismically active strike slip faults in the seismic zone, faults mapped in outcrop and evident in the borehole image logs, and with of plate convergence data. Furthermore, temperature profiles in two wells indicate isothermal conditions at average groundwater temperatures, consistent with rapidly flowing water localized within fractures.
- Research Organization:
- Washington Division of Geology and Earth Resources, Olympia, WA (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Geothermal Technologies Office
- DOE Contract Number:
- EE0006728
- OSTI ID:
- 1839984
- Journal Information:
- Proceedings - Workshop on Geothermal Reservoir Engineering, Vol. 42, Issue SGP-TR-214; Conference: 44th Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, California, February 11-13, 2019; ISSN 1058-2525
- Publisher:
- Stanford University
- Country of Publication:
- United States
- Language:
- English
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