In 1981 Chevron's board came to the conclusion that Chevron had no natural advantage in building or operating electrical generating plants, even though Chevron had developed expertise in locating geothermal resources. The analogy was that Chevron provides oil and gas for electrical generation, but does not build or operate the power gas/oil power plant except in rare cases where they don't have a choice.
As a consequence, Chevron's Heber, and Brawley projects in California and the project near Fernley Nevada had to become joint-ventures with power generation companies. When Unocal, which operated power plants at Geysers CA, Hawaii, and other locations around the world, became part of Chevron these power plants and the geothermal sources to power them were sold off. As in this example:
64.233.167.104
Below is a recent list (May 2007) of the operating geothermal plants in the United States, from the Geothermal Energy Association. Many of these resources were originally developed by Chevron or Unocal.
geo-energy.org
The Chevron/Unocal geothermal groups continued to locate and develop geothermal resources, occasionally building and operating a power plant themselves when no reliable partner could be found to operate the plant. As a result, Chevron is the world's largest producer of geothermal resources, and is also reluctantly the world's largest producer of geothermal electrical power. Chevron's current portfolio of geothermal properties are located primarily in Indonesia and the Philippines.
In my opinion, both Chevron and Unocal were hampered in the early years by an over-reliance on geologists whose sole stock in the geothermal trade consisted of little more than drilling shallow 500 ft temperature gradient holes, over geophysicists who mapped the deep fractures which are the source of each high-temperature geothermal resource. Geophysicists have largely won out in geothermal prospecting.
In the coming years, the largest utilization of geothermal will be shallow low-temperature wells combined with a heat-pump to heat buildings, such as the system installed in Buckingham Palace. This heat resource is widely available and avoids the problems of silica-deposition which increases costs in high-temperature sources used for electrical power generation.
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