Exploratory Well At Long Valley Caldera Geothermal Area (McNitt, 1963)

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Exploration Activity: Exploratory Well At Long Valley Caldera Geothermal Area (McNitt, 1963)

Exploration Activity Details
Location Long Valley Caldera Geothermal Area
Exploration Technique Exploratory Well
Activity Date 1959 - 1962

Usefulness useful
DOE-funding Unknown

Exploration Basis
Geothermal exploration in Long Valley started in the late 1950s and early 1960s, when nine wells were drilled and flow tested by Magma Power Company. These wells included:

  • The (Magma) Mammoth No. 1 well drilled in 1959 to approximately 366 m depth (148°C)
  • The Endogenous No. 1-3 wells drilled west of Highway 395 in 1960 in association with Natural Steam Corporation (formerly Endogenous Power Co.) to depths of 192-, 247-, 174-m and temperatures of 178, 174, 172°C, respectively
  • The Endogenous No. 4 and Chance No. 1 (C-1) wells drilled in 1961 to the east of Highway 395 and at Casa Diablo Hot Pool, respectively
  • The Endogenous No. 5-7 wells drilled in 1962 at Casa Diablo to approximately 123-, 230-, 204-m depth, respectively.

Temperature measurements reported above represent equilibrated temperatures, taken after the wells had remained under static conditions for periods ranging from several weeks to six months. Flow testing of (Magma) Mammoth-1 and the Endogenous 1-3 wells in 1960 under production conditions demonstrated the existence of a hot water reservoir at temperatures ranging from 132-181°C at shallow depths of 122-324 m. Total dissolved solids were measured at about 1,500 ppm and with carbon dioxide degassing resulting in calcite formation in the wellbore. At first the tests involved free-flowing the wells for periods varying from a few days to weeks. Later a shaft-driven, downhole pump was used to keep the fluid in single-phase flow eliminating calcite formation in the wells and surface equipment. The downhole pumps also keep the brine at the downhole temperatures, rather than allowing it to cool by flashing during ascent.

Additional References