--> Understanding the Paleoenvironment of Black Shale Resources: Are Depositional Conditions Important Factors in Determining the Economic Success of Unconventional Oil and Gas Resources?

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Understanding the Paleoenvironment of Black Shale Resources: Are Depositional Conditions Important Factors in Determining the Economic Success of Unconventional Oil and Gas Resources?

Abstract

The development of unconventional oil and gas (UOG) resources have become an important facet of the US and global energy portfolio. Currently, UOG resources account for more than one-third of the natural gas production in the US. Despite the success in generating shale gas, there are still questions about maximizing the recovery of hydrocarbons and determining the origin of organic matter in black shales. The Marcellus Formation is one of the largest shale plays in the US. Even though ongoing hydrocarbon exploitation is taking place in this area, there is still significant unknown factors about the original depositional conditions of the Marcellus and other organic-rich black shales. Geochemical techniques that employ major and trace elements, along with carbon and nitrogen stable isotopes are often used to characterize depositional and diagenetic conditions. Lithophilic elements serve as robust proxies for understanding sedimentation and provenance, while the behavior of siderophiles and chalcophiles are suitable in reconstructing redox conditions, and lastly, stable isotopes are employed to describe biogeochemical cycles as well as primary productivity prior to deposition. Here we will present multiple lines of geochemical data used to reconstruct the paleoenvironment that led to formation of the Marcellus shale. Implementing a multiproxy approach that involves major, trace, and rare earth elements, through x-ray fluorescence and inductively coupled plasma mass spectroscopy, along with carbon and nitrogen stable isotope analysis through elemental analyzer isotope mass spectroscopy. Using this multiproxy approach we will characterize the paleoenvironment from the Marcellus locality in Seneca Falls, NY. From our preliminary results, variations in geochemical signatures along with high total organic carbon content suggest that persistent anoxic conditions as a major factor in developing UOG areas.