A comparison of geothermometers for the Geysers Coring Project, California - implications for paleotemperature mapping and evolution of the Geysers hydrothermal system
Conference
·
OSTI ID:494372
- Univ. of Utah, Salt Lake City, UT (United States)
Altered and mineralized core from The Geysers Coring Project contains multiple organic- and mineral-based paleotemperature indicators which in combination (1) furnish new details of the The Geysers thermal evolution and (2) suggest new ways to map peak paleotemperature distributions throughout the steam field. Of particular interest in this regard, maximum temperatures recorded by fluid inclusions in the core commonly correspond to those indicated by vitrinite reflectance (roughly 280-300{degrees}C). Similarly, minimum fluid-inclusion paleotemperatures are close to those calculated from the interlayer smectite content of late-stage, mixed-layer illite/smectite (< 5 micron fraction) in hydrothermal veins. These geothermometers clearly document a cooling trend - in the steam-reservoir portion of the core (417.3-488.3 m depth) to the current temperature (about 235{degrees}C), but in the caprock (243.8-417.3 m) to as low as about 180{degrees}C. We suggest that vitrinite reflectance would be very useful for accurate (and inexpensive) mapping of peak paleotemperatures; elsewhere in The Geysers, where the typical small-diameter air-drilled cuttings make fluid-inclusion microthermometry impractical. In the northwest Geysers, vitrinite geothermometry could be utilized to help constrain the timing of formation of the deep {open_quotes}high-temperature{close_quotes} steam reservoir.
- DOE Contract Number:
- AC07-95ID13274
- OSTI ID:
- 494372
- Report Number(s):
- CONF-960913--
- Country of Publication:
- United States
- Language:
- English
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OSTI ID:6762468