The thermal regime in a sedimentary basin is one of the main factors affecting the formation and accumulation of energy and mineral resources. The generation of hydrocarbons and the types produced are dependent on the temperature reached by the organic-rich source rocks during their burial history. Also, the processes leading to the formation of metallic mineral deposits of the Mississippi Valley Type are highly dependent on temperature. Thus, knowledge of the geothermal regime and understanding of the factors controlling it are very important in the analysis of sedimentary basins.
Two categories of geothermal information are presented in this chapter: radiogenic heat production by the rocks at the top of the Precambrian, based on the analysis of 424 unweathered core samples, and the geothermal regime in the sedimentary rocks of the Western Canada Sedimentary Basin, based on bottom hole temperature (BHT) measurements. There have been approximately 200,000 wells drilled in the basin, the majority having associated BHT measurements. Processing all the data would have been a task beyond the scope and magnitude of this publication. Also, it should be kept in mind that the wells reach various depths, and an analysis of the geothermal regime by stratigraphic and/or lithological units (e.g., Bachu, 1985, 1988) requires prior knowledge of the stratigraphy, geometry and lithology of the sedimentary rocks, precluding execution of the work and publication of the results within the framework of this Atlas. Thus, the geothermal regime is described at every possible point in the basin by the two most important characteristics: the maximum temperature and the average geothermal gradient. Given the general increase of temperature with depth, the maximum temperature at any location is found at the base of the sedimentary column (top of Precambrian). In addition, knowledge of the geothermal gradient and of the thermal conductivity of rocks allows calculation of basement heat flow. Thus, the geothermal regime in the Western Canada Sedimentary Basin is presented in terms of distributions of radiogenic heat production, heat flow and temperatures at the top of the Precambrian, and of the average geothermal gradient across the basin.
Last modified: August 20, 2008
