Application of Magnetotelluric Data to Geothermal Exploration in a Sedimentary Basin Environment: Examples from the Western Canadian Sedimentary Basin

Abstract:

There is a growing consensus that energy production needs to transition to low carbon technologies in order to mitigate greenhouse-gas-emissions and global warming. Geothermal energy has the potential to contribute to this transition both globally and within Canada. Some countries such as have already developed geothermal energy resources by utilizing the hydrothermal systems associated with active volcanoes, while others have been developed in areas where the Earth’s crust is being extended bringing hot material close to the surface. However, since the Earth naturally produces heat everywhere, all parts of Canada have geothermal potential and with appropriate technology it could be extracted.

Recent advancements in geothermal technology have made utilization more efficient at lower temperatures. This allows the geothermal potential in sedimentary basins to be utilized, such as the ongoing development of the Molasse Basin in Germany. This has renewed interest in the geothermal potential of the Western Canada Sedimentary Basin (WCSB). There is extensive geological and geophysical data in the region due to extensive oil and gas exploration. The thermal structure of the WCSB is well known, but the structure of geothermal aquifers away from boreholes remains uncertain. The resistivity structure of the WCSB would give insight into the rock properties relevant to geothermal exploration. The resistivity of a large region can be found using magnetotellurics (MT), but like any surface geophysical method it suffers from non-uniqueness. By combining geophysical measurements of resistivity with well-log data, an enhanced resistivity model can be found.

The University of Alberta acquired MT data in 2013 in the Peace River area, in North West Alberta, which has demand for direct use of heat in community and industrial processing. A near-surface resistivity model was created by smoothing then interpolating resistivity well-logs. This was used to constrain both 2D and 3D MT inversions. The near-surface model has a significant impact on the inversion as the near-surface has a low resistivity, whose lower surface is difficult to resolve without additional information. We will show that this process allows structures in both the sedimentary basin and underlying crystalline basement to be more reliably imaged.