Research and Development in Geothermal Exploration and Drilling

Geothermal Energy / Exploration

Dan Jennejohn reported in 2009 that a significant amount of the financial risk associated with geothermal power development results from uncertainties encountered in the early stages of resource development; namely geothermal exploration and the drilling of production wells. Costs associated with the exploration and drilling stages of a geothermal project can account for at least 42% of overall project costs. While current exploration and drilling technologies and practices are somewhat effective, opportunities to significantly improve upon conventional technology as well as develop more advanced “revolutionary” exploration and drilling tools exist. Increased research and development (R&D) that is focused on improving current conventional exploration and drilling technologies in the near term as well as bringing “breakthrough” technologies will help to establish a strong geothermal industry base and improve project economics.

Success in initial geothermal exploration directly influences success in geothermal drilling operations. Geothermal developers depend upon exploration of surface features to determine first; whether or not a resource is worth the large amount of investment required to drill a geothermal well, and second; where to place a drill rig so as
to reach an optimal target depth, permeability and resource temperature. Once surface features have been investigated, several techniques are used to help identify drill targets without having to put a drill bit into the ground. These exploration technologies not only need to better locate geothermal resources but they must be able to provide more accurate imaging of the structure of the subsurface reservoir and provide accurate reservoir temperatures at specified depths. In order to better locate geothermal resources improved remote sensing technologies are necessary. The development of more reliable geothermometers with the ability to detect soil/water gases or dissolved minerals and isotopes would improve geochemistry information gleaned in the exploration phase. The increased resolution and reliability of geophysical surveys would provide a much needed improvements in imaging subsurface geothermal reservoirs.

Significant improvements in conventional geothermal drilling and well development techniques are achievable in the near term. Building upon incremental improvements in polycrystalline diamond compact (PDC) technology could result in the implementation of PDC drill bits in geothermal drilling practices. Additional improvements in drilling technology that produce drill bits that will drill for longer periods of time without breaking down are needed. Developing casing techniques and technologies that reduce the number of casing strings needed to line a well merit more R&D. The increased development of geothermal resources will require subsurface development to take place at depths of significant temperature and pressure. The development of drilling materials and tools capable of withstanding higher down-hole temperatures and pressures for long periods of time is an important technological advancement needed to improve drilling success rates.

Geothermal exploration and drilling technologies, while currently adequate, present a unique opportunity. R&D resources, properly allocated to the advancement of
conventional exploration and drilling technologies, will result in important and substantial gains. The same technological issues facing increased enhanced geothermal
systems (EGS) development are typically the same obstacles facing conventional hydrothermal technologies. Therefore, geothermal R&D should be focused on developing
technologies that will help create a robust industry base centered on near-term conventional resource development as well as developing “breakthrough” technologies
that will continue to expand the geothermal resource base beyond conventional hydrothermal.

Original URL: http://www.geo-energy.org/reports/R&D_in_Geothermal_Exploration_and_Drilling.pdf 

Referenced Draft (if still available): 
Department of Energy Geothermal Technologies Program. National Geothermal Action Plan. (Draft).
2009.  http://www1.eere.energy.gov/geothermal/pdfs/ngap.pdf