Oxygen isotope systematics and reservoir evolution of the Northwest Geysers, CA
- Geothermal Consultant, Santa Rosa, CA (United States)
- Univ. of Utah, Salt Lake City, UT (United States); and others
Whole-rock oxygen isotope values ({delta}{sup 18}O) for metagraywacke from the Northwest Geysers reservoir show systematic variations with respect to depth, location and reservoir characteristics. Whole-rock {delta}{sup 18}O values for metagraywacke decrease from approximately +15 per mil near the present surface (+750 m msl) to +2 to +4 per mil deep within the present steam reservoir (-2600 m msl). Deep portions of the metagraywacke reservoir (-2000 to -2750 m msl) are recrystallized to a biotite-rich hornfels and have {delta}{sup 18}O values ranging from approximately +5 to +12 per mil. A fault-bounded compartment has been identified within the central Northwest Geysers area where the statistics and systematics of the reservoir geochemistry are distinct from both the adjacent areas and the remainder of The Geysers. Within the reservoir portion of the fault-bounded compartment, the {delta}{sup 18}O values decrease from an average of about +12 per mil near the top of the steam reservoir, to a minimum of +8 per mil in the deepest portion of the drilled reservoir (-2164 m msl). Median and mean 8180 values from the metagraywacke reservoir indicate that the fault-bounded reservoir compartment is about 2 per mil less isotopically exchanged than any other producing section of The Geysers reservoir.
- DOE Contract Number:
- AC07-95ID13274
- OSTI ID:
- 495307
- Report Number(s):
- CONF-960913-; TRN: 97:002642-0061
- Resource Relation:
- Conference: Annual meeting of the Geothermal Resources Council, Portland, OR (United States), 29 Sep - 2 Oct 1996; Other Information: PBD: 1996; Related Information: Is Part Of Geothermal development in the Pacific rim. Transactions, Volume 20; PB: 886 p.
- Country of Publication:
- United States
- Language:
- English
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