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Geochemical and Basin Modeling Evaluation of the Utica/Point Pleasant Unconventional Play, Eastern Ohio


The geochemical analysis of rocks and fluids was a key component in the construction and evaluation of a basin thermal model used to appraise the Utica/Point Pleasant unconventional play in eastern Ohio. The business impact of this work was made in three primary areas: 1) the construction and calibration of a predictive and interactive basin thermal model used to evaluate source rock maturity, 2) the stratigraphic evaluation of oil yield (bbls/acre) to evaluate the oil window portion of the unconventional play, and 3) the measurement and prediction of fluid properties (BTU, CGR, and GOR) to determine the origin of the gas/condensate and to delineate the liquid “sweetspot” of the unconventional play. Modeled source rock thermal maturity, which is a function of burial and temperature history, was compared to vitrinite reflectance equivalent (%Roeq) values derived from aromatic biomarkers in oils, production gas isotopes, graptolite %Roeq measurements, and surface coal vitrinite reflectance. These measured thermal maturity data were used to refine the amount of burial and erosion at the surface unconformity needed to calibrate the modeled thermal maturity of the Point Pleasant Formation. Detailed stratigraphic analysis of the Point Pleasant oil yield (bbls/acre) was evaluated using TOC and Rock-Eval results combined with well log ΔLogR analysis. These results were used to calculate oil yield (bbls/acre) in over fifty wells. The highest oil yields occur in an area defined by the late stage oil to wet gas window ranging from 0.95 to 1.3 %Ro. However, when compared to other unconventional plays such as the Eagle Ford, the cumulative oil yields are much lower making the oil window part of this unconventional play more technically challenged. An expulsion-retention model which considers sorption, pore saturation, inorganic (matrix) and organic (kerogen) porosity was used to predict fluid properties such as the gas-oil ratio (GOR) and the condensate gas ratio (CGR). Calibration of these modeled fluid properties was performed using isotube mud gas analyses, separator gas, and production gas data. Prediction of BTU was also derived from gas wetness derived from both isotube mud gas and production gas data. These data provide insights as to the origin of the gas and condensate (primary versus secondary cracking) and allow for the mapping of the liquid “sweetspot” of this unconventional play.