Geysers Geothermal Area
Geothermal Area Profile
|Exploration Region:||Holocene Magmatic|
|GEA Development Phase:||Operational"Operational" is not in the list of possible values (Phase I - Resource Procurement and Identification, Phase II - Resource Exploration and Confirmation, Phase III - Permitting and Initial Development, Phase IV - Resource Production and Power Plant Construction) for this property.|
|Mean Reservoir Temp:||278°C551.15 K
|Estimated Reservoir Volume:||157.9 km³157,900,000,000 m³
|Mean Capacity:||1585 MW1,585,000 kW
|USGS Mean Reservoir Temp:||242°C515.15 K
|USGS Estimated Reservoir Volume:||110 km³|||
|USGS Mean Capacity:||520 MW|||
History and Infrastructure
Operating Power Plants: 17
Developing Power Projects: 1
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Power Production Profile
|Gross Production Capacity:|
|Net Production Capacity:|
|Power Purchasers :|
Regulatory and Environmental Issues
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First Discovery Well
|Initial Flow Rate:||
|Flow Test Comment:|
Well Field Description
Well Field Information
|Number of Production Wells:|
|Number of Injection Wells:|
|Number of Replacement Wells:|
|Average Temperature of Geofluid:|| 240 °C513.15 K
|Sanyal Classification (Wellhead):||Steam Field|
|Reservoir Temp (Geothermometry):|
|Reservoir Temp (Measured):|
|Sanyal Classification (Reservoir):|
|Depth to Top of Reservoir:||600m0.6 km
|Depth to Bottom of Reservoir:||3000m3 km
|Average Depth to Reservoir:||1800m1.8 km
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Geology of the Area
|Controlling Structure:||Pull-Apart in Strike-Slip Fault Zone|
|Brophy Model:||Type A: Magma-heated, Dry Steam Resource|
|Moeck-Beardsmore Play Type:||CV-2b: Plutonic - Inactive Volcanism|
|Modern Geothermal Features:||Fumaroles, Geysers, Hot Springs|
|Relict Geothermal Features:|
|Host Rock Age:||Mesozoic|||
|Host Rock Lithology:||metamorphosed sandstone|||
|Cap Rock Age:|
|Cap Rock Lithology:||Hydrothermal alteration layer|
"The Geysers is situated at the southern margin of the Pliocene-Holocene Clear Lake volcanic field, the youngest and northernmost field in a discontinuous chain of these centers extending several hundred kilometers to the southeast. The fields occur at the western edge of the North American plate, along the mantle-rooted, right-lateral, San Andreas transform. Beginning at about 23 Ma, the fields are believed to have formed intermittently above a migrating “slab window” of upwelling and decompression-melting asthenosphere in the wake of the northerly-propagating Mendocino triple junction.
At the latitude of the Clear Lake volcanic field, the San Andreas transform itself is aseismic, with strain instead distributed diffusely across an adjacent, subparallel belt up to 75 km wide along the North American plate edge. Although dominantly a compressional regime, the belt is locally characterized by extensional tectonism. Such an extensional zone is believed to have focused Clear Lake magmatism and accompanying high heat flow. Only a fraction of the magma — about 100 km3 — has been erupted, with most crystallizing as large plutons, including The Geysers felsite.
Host rocks for the felsite and much of The Geysers steam reservoir are tectonically interleaved metaturbidites, metabasalts, metacherts, and serpentinites of the subduction-related, late Mesozoic Franciscan Assemblage. The bulk of the steam reservoir in the lithocap (the entire volume of rock above a pluton, not to be confused with the caprock) of the felsite occurs in brittle metagraywacke and argillite with subordinate metabasalt, variously metamorphosed to greenschist and blueschist grades. The metagraywackes have negligible unfractured permeability, on the order of a few nanodarcies (10−22 m2).
The vapor-dominated system is a two-tiered feature. The so-called “normal” reservoir constituting most of the system had pre-exploitation temperature and pressure of about 240°C and 35 bars. In the northern part of the field, a deep, “high-temperature” (commonly up to 300°C, and reaching 342°C) reservoir underlies and is in apparent pressure communication with the normal reservoir regime. At least the normal reservoir can be represented as a “heat-pipe”, wherein (1) steam is the pressure-controlling phase in intercommunicating fractures; (2) liquid water is tightly held, in part by adsorption and capillary forces, in microfractures of the intervening matrix blocks; and (3) heat is transferred upward by steam while down-flowing steam condensate returns fluid mass to deeper levels of the reservoir."
known or inferred magmatic system
NEPA-Related Analyses (2)
Below is a list of NEPA-related analyses that have been conducted in the area - and logged on OpenEI. To add an additional NEPA-related analysis, see the NEPA Database.
Exploration Activities (6)
Below is a list of Exploration that have been conducted in the area - and cataloged on OpenEI. Add a new Exploration Activity
- Jeffrey W. Adams. 10/2011. The Geysers and Salton Sea Geothermal Fields. Mineral Resources Management Division. California State Lands Commission. 1-3p.
- Geothermex Inc.. 2004. New Geothermal Site Identification and Qualification. Richmond, CA: California Energy Commission. Report No.: P500-04-051. Contract No.: 500-04-051.
- U.S. Geological Survey. 2008. Assessment of Moderate- and High-Temperature Geothermal Resources of the United States. USA: U.S. Geological Survey. Report No.: Fact Sheet 2008-3082.
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List of existing Geothermal Resource Areas.