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Detailed Characterization of Hydrocarbons in Source Rocks and Mud Rock Reservoirs by Thermal Extraction-Evolved Product GC-MS and GC-MS/MS Analysis

Abstract

Methods have been developed to measure and characterize mobile components in hydrocarbon-bearing rocks using a Frontier thermal vaporization/multishot pyrolyzer in tandem with Agilent GC-FID-MSD or GC-QQQ. On the one hand, simple RockEval parameters from the bulk evolved products (S1, S2, S3 and Tmax) are obtained by substituting the regular column in the GC by a deactivated metal capillary. On the other hand, with the GC column in place, evolved gases from different temperature cuts are cryo-trapped and chromatograms from GC-MS (SIM/SCAN) FID or GC-MS/MS are obtained for detailed, high-resolution molecular characterization of the volatilized components in the rock samples. Diverse sample sets from the Eagle Ford, Wolfcamp, Woodford, Monterey, Green River, and Tuwaiq Mountain formations were used as test sets. Comparisons between results from the regular Rock-Eval 6 analysis and the yields from the thermo-vaporization process indicated very good correspondence. In this mode, several different temperature programs appropriate for unconventional reservoirs have been investigated giving information useful for mobility assessment. In the molecular characterization mode, information was obtained on the distribution of diverse species, including not only the simple alkanes, but also trace saturated and aromatic biomarkers, sulfur compounds, and diamondoids. Interfacing the multi-shot vaporizer/pyrolyzer with the GC/MSMS triple quad enabled complete characterization of the equivalent of the entire solvent-extractable organic matter from whole-rock samples. We believe that this approach of thermal extraction of whole rock volatiles into a GC-MS/MS system has the potential of eliminating the need for pre-analysis solvent extraction and SARA separation in source-rock and mud-rock reservoir characterization efforts.