Geysers Geothermal Area

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Geysers Geothermal Area

Area Overview

Geothermal Area Profile

Location: California

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.

Coordinates: 38.8°, -122.8°

Resource Estimate

Mean Reservoir Temp: 278°C551.15 K
532.4 °F
992.07 °R

Estimated Reservoir Volume: 157.9 km³157,900,000,000 m³
37.882 mi³
5,576,185,875,245.9 ft³
206,525,402,740.1 yd³
157,900,000,000,000 L

Mean Capacity: 1585 MW1,585,000 kW
1,585,000,000 W
1,585,000,000,000 mW
1.585 GW
0.00159 TW

USGS Mean Reservoir Temp: 242°C515.15 K
467.6 °F
927.27 °R

USGS Estimated Reservoir Volume: 110 km³ [3]

USGS Mean Capacity: 520 MW [3]

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History and Infrastructure

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Regulatory and Environmental Issues

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Exploration History

First Discovery Well

Completion Date:

Well Name:



Initial Flow Rate:
  • "d" is not declared as a valid unit of measurement for this property.
  • The given value was not understood.

Flow Test Comment:

Initial Temperature:

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Well Field Description

Well Field Information

Development Area:

Number of Production Wells:

Number of Injection Wells:

Number of Replacement Wells:

Average Temperature of Geofluid: 240 °C513.15 K
464 °F
923.67 °R

Sanyal Classification (Wellhead): Steam Field

Reservoir Temp (Geothermometry):

Reservoir Temp (Measured):

Sanyal Classification (Reservoir):

Depth to Top of Reservoir: 600m0.6 km
0.373 mi
1,968.504 ft
656.166 yd

Depth to Bottom of Reservoir: 3000m3 km
1.864 mi
9,842.52 ft
3,280.83 yd

Average Depth to Reservoir: 1800m1.8 km
1.118 mi
5,905.512 ft
1,968.498 yd

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Geology of the Area

Geologic Setting

Tectonic Setting:

Controlling Structure: Pull-Apart in Strike-Slip Fault Zone

Topographic Features: [10]

Brophy Model: Type A: Magma-heated, Dry Steam Resource

Moeck-Beardsmore Play Type: CV-2b: Plutonic - Inactive Volcanism

Geologic Features

Modern Geothermal Features: Fumaroles, Geysers, Hot Springs

Relict Geothermal Features:

Volcanic Age: Pliocene [12]

Host Rock Age: Mesozoic [14]

Host Rock Lithology: metamorphosed sandstone [15]

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."[16]

Heat Source

known or inferred magmatic system

Geofluid Geochemistry


Salinity (low): 4 [18]

Salinity (high): 430 [19]

Salinity (average): 217

Brine Constituents:

Water Resistivity:

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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.


Document # Analysis
Applicant Application
DOE-EA-1733 EA Calpine 21 June 2010 United States Department of Energy Geothermal/Well Field
DOI-BLM-CA-C050-2009-0005-EA EA AltaRock Energy Inc 11 September 2009 Bureau of Land Management Geothermal/Well Field Development Drilling

Exploration Activities (6)

Below is a list of Exploration that have been conducted in the area - and cataloged on OpenEI. Add.png Add a new Exploration Activity

Page Technique Activity Start Date Activity End Date Reference Material
Cuttings Analysis At Geysers Geothermal Area (1976) Cuttings Analysis 1976 1976

Data Acquisition-Manipulation At Geysers Geothermal Area (1982) Data Acquisition-Manipulation 1982 1982

Fluid Inclusion Analysis At Geysers Geothermal Area (1990) Fluid Inclusion Analysis 1990 1990

Geothermal Literature Review At Geysers Geothermal Area (1984) Geothermal Literature Review 1984 1984

Isotopic Analysis-Fluid At Geysers Geothermal Area (1982) Isotopic Analysis-Fluid 1982 1982

Micro-Earthquake At Geysers Geothermal Area (2011) Micro-Earthquake 2011 2011


  1. Jeffrey W. Adams. 10/2011. The Geysers and Salton Sea Geothermal Fields. Mineral Resources Management Division. California State Lands Commission. 1-3p.
  2. Geothermex Inc.. 2004. New Geothermal Site Identification and Qualification. Richmond, CA: California Energy Commission. Report No.: P500-04-051. Contract No.: 500-04-051.
  3. 3.0 3.1 3.2 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.
  4.  ""Age and thermal history of the Geysers plutonic complex (felsite unit), Geysers geothermal field, California: a 40Ar/39Ar and U–Pb study"
  5. [4]" class="new" title="">[4]
  6. 6.0 6.1  "World geothermal power generation in the period 2001–2005"
  7. [6]" class="new" title="">[6]
  8. [6]" class="new" title="">[6]
  9.  "Research in the Geysers-Clear lake Geothermal Area, Northern California"
  10. [9]" class="new" title="">[9]
  11.  "The Clear Lake Volcanics: Tectonic Setting and Magma Sources"
  12. [11]" class="new" title="">[11]
  13. 13.0 13.1  "Reservoir Response to Injection in the Southeast Geysers"
  14. [13]" class="new" title="">[13]
  15. [13]" class="new" title="">[13]
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  17. 17.0 17.1  "Ethiopian Geothermal Resources and their Characteristics"
  18. [17]" class="new" title="">[17]
  19. [17]" class="new" title="">[17]

List of existing Geothermal Resource Areas.

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