Identification of Western Canada Sedimentary Basin Petroleum Systems Using Produced Oil Geochemistry

Abstract

Over 200 oils produced from reservoirs in the Alberta and Saskatchewan portions of the Western Canada Sedimentary Basin and from northern Montana were grouped into six families which share common sources based on genetic-specific biomarkers and stable carbon isotope compositions. Cluster analysis identified a total of 17 subfamilies within this initial family grouping. Principal component analysis of the biomarker and isotope data revealed that the oils were sourced from facies deposited in multiple depositional environments: restricted marl, carbonate-rich, distal shale and a marl source facies with a distinct upwelling signature. Mixing between oil families was also identified. Reservoir and postulated source rock ages range from Devonian to Upper Cretaceous. Oil thermal maturity estimates were made based on biomarker compositions. The estimates are reported as %VRE (Vitrinite Reflectance Equivalent) and show that the oils range from <0.5 to 1.0 %VRE. These values reflect the thermal maturity of source organic matter at time of generation. The most mature oils were generally generated from Upper Devonian marls/shales with a strong upwelling signature and Upper Cretaceous marine shales, while the least mature oils were generally generated from Devonian marls deposited in relatively restricted environments. The maturity trends within each family and between families do not always exhibit regular patterns with geographic position or depth relationships of postulated source-reservoir pairs. These observations, coupled with the geographic and stratigraphic location of mixed oils, provide insight into timing of hydrocarbon generation and extent of migration.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016