The Rate of Success of Geothermal Wells Drilled in Nevada

Abstract

Numerous assertions have been made regarding the success rates of geothermal well drilling, with difficulties obtaining early-stage financing often attributed to the relatively low drilling success rate. Typically, data intended to evaluate this issue have not been collected in a consistent manner, and “success” depends upon whether one considers exploration, confirmation or production wells. Exploration and confirmation wells in particular are difficult to quantify relative to a success rate, as their purpose is largely data/information gathering. Well permitting records are reported by state agencies and well production is reported monthly (in NV), so one can only determine in retrospect which of the permitted wells actually led to geothermal production and power generation. This paper compiles and evaluates geothermal well records submitted to the Nevada Division of Minerals, and estimates success rates in Nevada from the 1970s and 1980s exploration efforts through construction of the current power plants. The number of wells drilled (all wells including exploration) per MW of production ranges from 0.65 at Dixie Valley to approximately 33.1 at San Emidio. The number of wells drilled per MW of production at eight sites (excluding San Emidio) is 3.1 ± 1.8. The average number of feet drilled per MW of production at the nine sites investigated was 6,644 ± 3,781 ft (including all exploration wells), ranging from 3,528 ft at Bradys to 14,555 ft at San Emidio. If only production, injection, and observation wells required for development are considered, the average ft/MW is 2,093 ± 878 ft, ranging from 1,414 at Bradys to 3,655 at Soda Lake. Production well success rates (percent of those use as production that were drilled for production), following successful exploration and confirmation efforts range from 60-66% at the nine power producing sites investigated in Nevada.