Geophysical Imaging To Enhance Analysis, Design And Drilling Of Large-Scale Geothermal Systems

Improvements in alternative energy sources in the United States have received much attention over these last few years as petroleum-based fuel availability and prices have been tied to concerns about national security and the need to control global warming through reductions in greenhouse gas emissions. Consideration has increased for alternative energy sources, notably wind and solar. Geothermal energy, while considered a ‘mature’ industry, is again being reviewed as a potential<br>alternative for new, large-scale, multi-structure, high-occupancy energy systems. New efforts are now being made to improve the design and installation techniques so that enhanced system efficiency and reduced ‘first costs’ are achieved. This has led to the desire to better understand the impact that the subsurface geologic environment within large geothermal wellfields can have on the thermal conductivity distribution that has been assumed to be present using limited boring information. Geophysical surveys using 2-D Electrical Resistivity Imaging (2-D ERI) and downhole logging, supplementing standard site drilling information, have recently been applied to the largest geothermal heat pump project in the United States. The technique has been shown to yield detailed subsurface characteristics that can be used to improve the analysis, design, and drilling of these large-scale geothermal systems.