Implications of Post-Glacial Warming for Northern Alberta Heat Flow--Correcting for the Underestimate of the Geothermal Potential

Abstract

The research into a geothermal energy option for Northern Alberta basin is currently underway. Correct estimates of heat flow and geothermal gradient for the sedimentary strata (direct heat energy option) and deeper crystalline basement are needed. A series of detailed geophysical logs and boreholes studies have recently been collected in the Hunt well AOC GRANITE 7-32- 89-10. The well was drilled 2.36 km into basement granitic rocks just west of Fort McMurray. A temperature log acquired as part of the University of Alberta Helmholtz-Alberta Initiative (HAI) geothermal energy project in 2010-2011shows that there is a significant increase in thermal gradient in the granites. Inversion of the measured T-z profile between 550 m – 2320 m indicates a temperature increase of 9.6+/- 0.3 oC, at 13.0 +/- 0.6 ka and that the glacial base surface temperature was - 4.4+/- 0.3 oC. This inversion computation accounted for granite heat production of 3 W/m3. We find from the Hunt well study that heat flow in the basin has been underestimated for wells shallower than 2 km due to the paleoclimatic effect. A significant increase in surface temperatures since the end of the last ice age in northern North America causes a perturbation of shallow <2 km heat flows. For this reason, estimates of gradient based on single or numerous data from different depths are not necessarly characteristic of the whole sedimentary column and can lead to spurious predictions of temperature at depth needed for geothermal energy or hydrocarbon models.