The first deep heat flow determination in crystalline basement rocks beneath the Western Canadian Sedimentary Basin

• Published in: Geophysical Journal International
• Main Authors: Majorowicz, Jacek, Chan, Judith, Crowell, James, Gosnold, Will, Heaman, Larry M., Kück, Jochem, Nieuwenhuis, Greg, Schmitt, Douglas R., Unsworth, Martyn, Walsh, Nathaniel, Weides, Simon
• Format: Text
• Language: English
• Published: Oxford University Press 2014
• Subjects: Geodynamics and tectonics; Fort McMurray
• Online Access: http://gji.oxfordjournals.org/cgi/content/short/197/2/731; https://doi.org/10.1093/gji/ggu065

Heat flow ( Q ) determined from bottom-hole temperatures measured in oil and gas wells in Alberta show a large scatter with values ranging from 40 to 90 mW m−2. Only two precise measurements of heat flow were previously reported in Alberta, and were made more than half a century ago. These were made in wells located near Edmonton, Alberta, and penetrated the upper kilometre of clastic sedimentary rocks yielding heat flows values of 61 and 67 mW m−2 (Garland & Lennox). Here, we report a new precise heat flow determination from a 2363-m deep well drilled into basement granite rocks just west of Fort McMurray, Alberta (the Hunt Well). Temperature logs acquired in 2010–2011 show a significant increase in the thermal gradient in the granite due to palaeoclimatic effects. In the case of the Hunt Well, heat flow at depths >2200 m is beyond the influence of the glacial–interglacial surface temperatures. Thermal conductivity and temperature measurements in the Hunt Well have shown that the heat flow below 2.2 km is 51 mW m−2 (±3 mW m−2), thermal conductivity measured by the divided bar method under bottom of the well in situ like condition is 2.5 W m−1 K−1, and 2.7 W m−1 K−1 in ambient conditions), and the geothermal gradient was measured as 20.4 mK m−1. The palaeoclimatic effect causes an underestimate of heat flow derived from measurements collected at depths shallower than 2200 m, meaning other heat flow estimates calculated from basin measurements have likely been underestimated. Heat production ( A ) was calculated from spectral gamma recorded in the Hunt Well granites to a depth of 1880 m and give an average A of 3.4 and 2.9 μW m−3 for the whole depth range of granites down to 2263 m, based on both gamma and spectral logs. This high A explains the relatively high heat flow measured within the Precambrian basement intersected by the Hunt Well; the Taltson Magmatic Zone. Heat flow and related heat generation from the Hunt Well fits the heat flow–heat generation relationship determined for other provinces of ...