Oil families in Mannville Group reservoirs of southwestern Alberta, Western Canada sedimentary basin

Abstract

Lower Cretaceous oils in southern Alberta have been assessed using column chromatography, sulphur analysis, gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). These oils can be divided into four oil families, E, Q, EQ and F, on the basis of biomarker characteristics. Family E oils are characterized by low pristane/phytane ratios and a C 35 homohopane prominence. Family Q oils are identified by the presence of so-called “Q compounds” (Q/R ratio > 0.5) and have high C 27 diasterane to regular sterane ratios. Family EQ oils are a mixture of Family E and Family Q oils, with biomarker characteristics intermediate between these two families and low abundance of “Q compounds” (Q/R ratio < 0.5). Family F oils have high saturate/aromatic ratios, high pristane/phytane ratios (> 1.2) and no C 35 homohopane prominence. Oil-source rock correlation to available source rock data suggest that Family E oils are derived from the Upper Devonian-Mississippian Exshaw Formation and Family Q oils correlate to the Lower Cretaceous Ostracode Zone. Family F oils are likely derived from shales of the Upper Jurassic Rierdon Formation, however additional geochemistry data from this potential source rock are required to confirm this interpretation.