The paleogeothermal and present thermal regimes of the Alberta Basin and their significance for petroleum occurrences

Detailed heat-flow studies in the Alberta part of the Western Canadian Sedimentary Basin show that the hydrodynamically controlled geothermal pattern and the depth-temperature distribution of the Mississippian and Devonian oil and gas pools are related. Cooling below the Rocky Mountain Foothills and the deep part of the basin, caused by gravity-imposed downward water movement, results in low geothermal gradient values and deep burial of the oil-generation 'window'. An increase in geothermal gradients in the shallower eastern part of the basin, caused by rising fluid flow, brings the oil-generation 'window' closer to the surface. It can be shown that the heat-flow regime in southern Alberta during the time of maximum burial of the sediments, which was the most important time for oil and dry gas generation, was not very different from that at present. This means that when burial and erosional history are known, present heat-flow data can be used to study hydrocarbon generation and the condition of preservation of the oil and gas pools.