Seismic Interpretation and Well Logging Results of a Deep Borehole into the Canadian Shield in Northeastern Alberta: Preliminary Results

With the increasing awareness of the need for the reduction of carbon emissions globally, geothermal energy, which offers a potential for cleaner energy generation, is one potential new source. In Alberta, these geothermal resources are likely to be found in the sedimentary basin, or in the deeper crystalline basement rocks. Alberta exhibits a very low geothermal gradient compared to other existing geothermal fields located in areas of volcanic and tectonic activity. To mitigate this effect, the focus in Alberta will involve the development of engineered geothermal systems (EGS) in the target resource. This project is part of the Helmholtz-Alberta Initiative (HAI), which is a research collaboration between scientists in Germany and Canada on energy projects for cleaner energy production. The first goal for EGS research and development is to develop a detailed geological-geophysical characterization of selected sites to delineate potential geothermal reservoirs in Northern Alberta. One of the selected sites is in the Fort McMurray area. Using an existing deep borehole that reaches a depth of 2.3 km into the crystalline basement, our aim is to identify geological features such as zones of fractures in the basin and/or basement that could provide an indication of enhanced fluid flow potential - a necessary component for any geothermal systems to be viable. The earlier stage of our research involves re-processing of surface seismic data. This helps to improve the signal-to-noise ratio for the geological interpretation of the subsurface, such as the locations of saline aquifers and faults that allow heat flow in the rocks, and zones of fractures that may indicate elevated porosity. Current re-processing of the seismic data displays sets of dipping reflectors which may intersect the borehole. Zero offset and walkaway vertical seismic profiles (VSP) were conducted at the borehole for direct comparison with the surface seismic sections. They are also useful in obtaining information about the reflectivity and the velocity structure of the subsurface. The full integration of surface seismic data, VSP data, and well logs are expected to provide a detailed characterization of the sedimentary basin and crystalline basement rocks of the Canadian Shield in Northeastern Alberta. In particular, the unusually low fluid pressures in the well may be related to states of stress that are likely still influenced by post-glacial rebound.