ABSTRACT

A suite of 27 oils from predominantly Nisku reservoirs of the Western Canada Sedimentary Basin (WCSB), in central and southern Alberta, can be classified into six groups or families based on stable carbon isotope ratios of individual gasoline range (C₅-C₁₀) compounds. A novel analytical technique combining Solid Phase MicroExtraction (SPME) and Continuous Flow Isotope Ratio Mass Spectrometry (CF-IRMS) is employed to measure the ¹³C/¹²C ratios. The majority of oils show characteristics of generation from a common source rock, the Upper Devonian Duvernay Formation. Systematic isotope distributions in straight chain and branched alkanes can help to delineate a common source rock along with the influence of secondary alteration processes such as biodegradation, evaporation, and thermochemical sulfate reduction. A 1-2‰ enrichment in ¹³C between groups can distinguish different levels of thermal maturity during oil genesis. Numerous analytical challenges are inherent in obtaining accurate ¹³C measurements for gasoline range analytes, but when utilized in conjunction with biomarkers and other compound specific geochemical techniques, the isotopic composition of these compounds exhibits good potential as a correlation tool.

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