• Economic and Environmental Geology
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• v.43 no.2
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• pp.85-100
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• 2010

Devonian Cairn Formation is one of the important hydrocarbon reservoirs in Alberta, Canada. However, the Cairn Formation, outcropped in the study area, is not prospective reservoir with poor porosity and permeability by some late diagenetic processes. In this study, geochemical characteristics of the Cairn Formation were studied to use these preliminary results for advanced geological and geophysical petroleum explorations in the near future. Rock-Eval pyrolysis showed that total organic carbon content is less than 0.3 wt.%, indicating a minor amount of bitumen and/or other hydrocarbons. The carbonates in the Cairn Formation are mainly composed of subhedral and anhedral dolomites. Pore sizes in the carbonate are various, ranging from nanometer to micrometer. Clastic sediments increase in the upper and lower parts of the Cairn Formation, probably due to changing its depositional conditions. The Cairn Formation can also be divided into several intervals based on Ca/Mg ratio in dolomite and degree of amount of calcite. These could be formed by different sedimentary environment, degree of cementation and recrystallization, different saline/fresh water, etc.

• Economic and Environmental Geology
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• v.45 no.4
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• pp.365-375
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• 2012

The objective of this study is to investigate inorganic characteristics of Devonian bitumen carbonates in Alberta using two drilling cores, Saleski 03-34-88-20w4 and Saleski 08-01-88-20w4, taken from the Core Research Center (CRC) of Canada. The bitumen carbonates are mainly composed of less than 0.2 mm dolomites and some carbonate includes small amount of quartz and calcite. The bitumen carbonates from two cores are interpreted to have formed in similar sedimentary environments and dolomitization processes. Carbonates from Saleski 03-34-88-20w4 core were formed under higher inflow of clastic sediment than those from Saleski 08-01-88-20w4 core. Range of crystallization temperature of dolomites in the both bitumen carbonate cores is about 40~$55^{\circ}C$. Dolomitizing fluid of the bitumen carbonates would be Devonian seawater. Bitumen carbonates from Cairn Formation, compared with the CRC cores, have experienced a similar crystallization temperature, but dolmititizing fluid of the bitumen carbonates from Cairn Formation have been modified from the isotopic exchange with continental crust.