Technical Paper: An Investigation of Drilling Success in Geothermal Exploration, Development and Operation

Society: Other
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Presentation Date: 2011


This paper presents a statistical investigation of drilling success in the exploration, development and operation phases of a geothermal power project. Drilling "success rate" is shown to be an awkward concept; it is argued that drilling success is better represented by the average cost per MW capacity secured from a drilling program. The case histories of the Kamojang field in Indonesia and a project at The Geysers field in California are used to illustrate some of the concepts. More than 80 exploration, development and make-up wells have been drilled and commercial power has been produced in the Kamojang field over the last three decades. Fifteen wells were drilled initially at the above-referenced project at The Geysers field, which has been providing commercial geothermal power for three decades now. It is shown that the average drilling success rate improves as more wells are drilled due both to its inherent statistical nature, which becomes better defined with an increasing sample size, as well as due to the "learning curve" effect. For the two case histories presented, the learning curve effect was found to be relatively minor compared to the statistical effect. It is concluded that there is little basis on which to estimate the drilling success rate in exploration, and drilling success rate ranges from 60% to 100%, and typically 70% to 90%, in the development phase, and greater than 90% in the operation phase.

Technical Paper from GRC Transactions, Vol. 35, 2011

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