Slim Hole Assessment and Geothermal Business Model

Abstract

Drilling costs and risk are major issues influencing the development of geothermal resources. While assessment of competing renewable energy sources (wind and solar) is relatively straight forward and inexpensive, the assessment of geothermal reservoirs (drilling and testing) is expensive and the results are not predictable. Geothermal has the advantage of base-load generation, but this does not command a premium in the market. We have advocated for some time that front-end costs and risk can be reduced through the use of slim hole drilling and testing. Slim hole testing involves a spectrum of options that can extend from measurement of temperatures and analysis of geologic conditions to full flow and injection testing. Although echoed by others, this approach has not been widely adapted. We describe the slim hole assessment of a hidden system at Mountain Home Air Force Base in Idaho, USA to illustrate an intermediate option between temperature gradient and full reservoir testing. Our analysis suggests that subsidies in the form of government or scientific investigations are necessary to mitigate front-end risk, particularly in exploration for buried systems.