Results of Deep Drilling in the Western Moat of Long Valley California

Abstract

Long Valley caldera has keen explored for its potential geothermal resources for at least two decades. Unocal Geothermal dril-led two deep test wells on the resurgent dome of the caldera during 1979. Neither of these wells encountered a deep, high temperature geothermal reservoir. The results from these wells and other geologic data focused exploration on the western caldera moat. Encouraging temperature q r a d i e n t data in 1982 led to the drilling of a deep test well in 19F5. That well, IDFU 44-16, encountered deep temperature reversal s and a sequence of rocks unlike the previous penet ration s on the resurgent dome. Evidently the well is still within the ring fracture system of the caldera and not within a cent r a l, upwelling, hydrothermal system which supplies the caldera ' s discharge.