Enhancing geothermal exploration with electromagnetic geophysics

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Geothermal energy has the potential to produce significant amounts of energy, with minimal emissions of greenhouse gases. Canada has significant geothermal resources, but these resources are currently underutilized. The major barrier to geothermal development in this region is the uncertainty in subsurface structure. This means that drilling exploratory geothermal wells carries a significant economic risk. Electromagnetic (EM) geophysical methods are commonly applied in geothermal exploration and use low-frequency radio waves to measure the electrical resistivity of the subsurface. This parameter is useful in geothermal exploration because it is very sensitive to subsurface temperature and the presence of water within the rock. The magnetotelluric (MT) method, a type of EM method, is widely used in geothermal exploration and uses natural radio signals to probe the Earth. It has the advantage that there is no need to generate a radio signal with a transmitter, but cultural electromagnetic noise from powerlines and other infrastructure can make it impossible to detect these natural radio signals. The proposed research will use MT exploration to investigate the subsurface structure of a geothermal prospect at Lakelse in British Columbia. Hot springs suggest the presence of a geothermal reservoir at depth, but geophysical imaging is required to map the subsurface structure and guide drilling. Borealis GeoPower have collected a range of geophysical datasets at Lakelse as part of their ongoing exploration project. The proposed research will (1) develop new strategies to reduce the effect of cultural noise in the MT data and (2) improve the methods used to convert the measured geophysical data into a model of the subsurface electrical resistivity. This research will help Canada develop an energy source that can contribute to reducing carbon emissions and their resulting impacts on climate.