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The Surface Geochemical Expression of Carbonate-Hosted Hydrocarbon Reservoirs and Faults in New York, Ohio, Nevada and Utah

David M. Seneshen, James H. Viellenave, and John V. Fontana
Direct Geochemical, Golden, CO

The innovative application of both organic and inorganic surface geochemical tools and non-seismic geophysical methods facilitates hydrocarbon exploration and structural mapping in the Appalachian Basin of New York and Ohio and the Great Basin of Nevada and Utah. The interrelationship of C1-C8 hydrocarbons in soils is used to discriminate between gas-prone, oil-prone and dry areas. Soils over the Appalachian Basin gas fields are characterized by anomalous C1/C2, light alkenes (i.e. ethylene and propylene), Ba and K. Soils over faults in proximity to these gas reservoirs are anomalous in C2/ethylene, Ca, Mg, Li, Pb, Zn, Mn, and Cu, and U. In comparison, miocroseepage over the Grant Canyon oil field in Nevada also has a unique multivariate hydrocarbon signature (i.e. C1+ethylene/C3). In contrast, soils over high-angle, normal faults proximal to Grant Canyon are anomalous in C2/ethylene, C5, C6 and CO2, CO, Ca, Mg, Li, Br, U, As, and S. The same geochemical signatures are evident over an oil prospect and adjacent faults in western Utah. Gravity and well data indicate the same Paleozoic stratigraphy as Grant Canyon. The magnetic data suggest the presence of a proximal pluton (i.e. similar to the Troy Pluton at Grant Canyon) and resistivity anomalies could reflect an underlying oil accumulation. The main conclusion from these case studies is that soils over reservoirs and faults are geochemically distinct, and this must taken into account when interpreting geochemical, geological and geophysical data to define targets for follow-up.