21 Geology of Marcellus-Utica Shale and How it Relates to Oil and Gas Production

Sunday, 19 March 2017
3:45 PM - 5:30 PM
Monongahela, 17th Floor

STABLE ISOTOPE AND FLUID INCLUSION CONSTRAINTS ON THE BURIAL HISTORY OF THE UTICA FORMATION, NEW YORK STATE

Paper number: 21-3
Program: Theme Sessions
Time: 4:10 PM – 4:30 PM

Authors

Abstract

Thermal maturation and burial history of the Utica Formation and coeval platform facies of the Trenton Group are recorded in widespread carbonate veins. Stable isotope and fluid inclusion data document temporal and geographic variation in fluid composition and burial temperature across the central New York outcrop belt. Near the Taconic structural front, overmature Utica Formation hosts calcite veins with lo-salinity (<4% NaCl equiv.) fluid inclusions derived from shale dewatering with Th >160oC. Fluidized sand-dikes formed contemporaneously with calcite veins. In the central Mohawk Valley, 80 km west of the structural front, relatively lower thermal maturity is recorded in calcite veins containing aromatics and C2-C3 hydrocarbons, and fluid inclusions with Th <140oC. Slightly higher fluid inclusion temperatures (Th >140oC) occur in the western Mohawk Valley. Low-salinity fluid inclusions are generally characteristic of Utica veins across the outcrop belt, and contrast with high-salinity (>15% NaCl equiv.) fluid inclusions in lower Paleozoic and basement-hosted veins of the Adirondack region.

Oxygen and carbon stable isotope data from a wide array of vein systems in the Mohawk Valley generally support derivation of fluids from mud dewatering, with most fluids forming in equilibrium with host sediment at burial temperatures consistent with fluid inclusion data. Late carbonate veins in the eastern Mohawk Valley outcrop belt have unusual positive carbon isotope signatures (δ13C = +8 to +14) indicating contribution of carbonate from residual hydrocarbon degradation. Horizontal calcite veins are present across the outcrop belt, are sometimes associated with minor folds and likely formed during episodic high fluid pressure events. Stable isotope signatures suggest that horizontal veins formed at somewhat lower temperatures than later vertical veins within the same outcrop (horizontal veins at one locality have δ18OPDB of -7 to -9; vertical veins have δ18OPDB of -8 to -12).

Geological Society of America Abstracts with Programs. Vol. 49, No. 2

doi: 10.1130/abs/2017NE-290710

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