Analysis of heat transfer processes and geothermal pattern in the Alberta Basin, Canada

The transfer of heat from the crystalline basement of sedimentary basins to the atmosphere can be influenced to different degrees by the movement of formation waters within the complex structure of aquifers and aquitards in the basin. Past studies of the geothermal regime in the Western Canada Sedimentary Basin have shown the existence of a low geothermal gradient (low heat flux area) in the foothills region of southwestern Alberta, and of a high geothermal gradient (high heat flux area) in the lowlands in northeastern Alberta, close to the Precambrian Shield. These distributions of geothermal gradients and heat fluxes were attributed to the effects of basin wide groundwater flow. Hydrogeological studies in selected parts of the basin, and dimensional analysis applied to heat transfer processes show that the permeability of the sediments, and indeed the fluid velocities, are too low to play a significant role in the transport of terrestrial heat in the Alberta part of the Western Canada Sedimentary Basin. On a regional scale, the actual distributions of the heat flux and geothermal gradients are probably due to crustal thickening and/or increased radiogenic heat generation in the basement. Thermal anomalies, which may be due to granitic intrusions, are superimposed over this trend. At an intermediate scale, the geothermal field is controlled by topography, stratigraphy, and lithology of the sediments. Only on a local scale is the convection of heat important.