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Evaluating petroleum character and charge from different source-rock lithologies in the Woodford Shale and Caney Shale with hydrous pyrolysis


Representative lithologies from the Woodford Shale and Caney Shale exposed in Carter County, OK were sampled for hydrous pyrolysis experiments to determine their influence on petroleum character or charge. The lithologies include shale, siliceous shale, chert, and dolomitic marlstone. These source-rocks range in total organic carbon from 6.5 wt% in chert to 25 wt% in siliceous shale. Hydrous pyrolysis was used because it generates oil that is compositionally similar to natural crude oils and expels it by processes considered operative in sedimentary basins. Characteristics of the expelled oil include API gravity, alkane distribution, biomarker signatures, and C15+ fractions. Characteristics of the generated gas include molecular composition of hydrocarbons and non-hydrocarbons, and stable carbon isotopes of the hydrocarbon gases. Collectively, these analyses provide information on oil-expulsion efficiency, gas potential, transition metal catalysis, oil quality, and gas:oil ratios for each source-rock lithology. This information can be used to better understand variations in petroleum character and quantities generated from the Woodford Shale and Caney Shale. Two different scales of hydrous pyrolysis were used in this study. Small-scale runs were made in 50-mL stainless steel reactors to establish biomarker signatures, and large-scale runs used 1-liter reactors to evaluate character and charge of oil and gas at the end of the oil window for each lithology.