Magnetotelluric Imaging of Electrically Anisotropic Crust Near Fort McMurray, Alberta: Implications for Engineered Geothermal Systems

Abstract

The goal of this thesis is to investigate the character of the basement rocks beneath the oilsands region around Fort McMurray in the context of developing engineered geothermal systems (EGS). Magnetotelluric (MT) data were collected at 94 stations on two profiles near to Fort McMurray and initial inversions showed that while these data exhibited strong 2-D character, an isotropic analysis of the MT data was not possible. Forward modeling of 2-D anisotropy showed that the basement below a depth of 4 - 5 km is electrically anisotropic with a resistivity ratio close to 1000. It was also shown that certain features of MT data commonly interpreted with a 3-D model could be explained with 2-D anisotropic model. The source of the anisotropy was interpreted to be due to interconnected graphite films oriented ~S27E within the metamorphic basement rocks. This direction is reasonably close to the current minimum stress direction of ~S40E, the interaction between the rock MT-interpreted rock fabric and the stress direction will control the propagation of artificial fractures.