Families of oils and their sources in southeastern Saskatchewan

Four compositionally distinct families of oils are characterized by gross geochemical and C/sub 15+/ saturated hydrocarbon fraction compositions obtained by gas chromatography and mass spectrometry-gas chromatography. Family A oils (two pools) are characterized by low pristane/nC/sub 17/ and phytane/nC/sub 18/ ratios, high diasterane/regular sterane ratios, and low C/sub 23//C/sub 30/ terpane ratios. This family of oils is restricted to Ordovician pools and is identical to the oils from Ordovician reservoirs in the US portion of the Williston basin. Family R oils (two pools) are characterized by low pristane/phytane and high diasterane/regular sterane ratios. This family of oils is restricted to Winnipegosis Formation pinnacle-reef reservoirs. Family B oils (nine pools) are characterized by crossplots of the ratio of diasteranes/regular steranes against either the ratio of saturate/aromatic hydrocarbons or the ratio of pristane/phytane. Within family B, a group of oils (four pools) with low C/sub 23//C/sub 30/ terpane ratios may represent a mixture of oils from families B and A. Family B oils are restricted to pools in the Birdbear Formation, the Bakken Formation, and the Madison Group. The most abundant family of oils, family C(22 pools), is identified by the same criteria used to characterize family B oils, although they have more » low diasterane/regular sterane ratios and low pristane/phytane ratios in comparison to family B. Family C occurs in the Madison Group and younger reservoirs. A distinctive subgroup of oils in family C has high saturate/aromatic hydrocarbons ratios. One oil with an intermediate diasterane/regular sterane ratio may represent a mix of oils from families B and C. Oils occur in reservoirs lying stratigraphically close to their sources. Family A is sourced from Ordovician kukersites in the Big Horn Group and family R is derived from organic-rich laminites of the Elk Point Group. « less