THE PALEOENVIRONMENT OF THE MARCELLUS FORMATION: IMPLICATION FOR UNDERSTANDING THE ORIGIN OF UNCONVENTIONAL OIL AND GAS RESERVIORS

The successful development of unconventional oil and gas (UOG) resources is of paramount importance to the US and global energy portfolios. Currently, UOG reservoirs now accounts for one-third of the total natural gas productions in the US. Despite the success of the shale gas “revolution,” the average recovery from shale play areas is about 25% for gas and less than 10% for tight oil. In order to compensate for this low number, many UOG companies have begun to drill longer horizontal wells that incorporate more hydraulic fracturing stages. This trend has the potential for a bevy of detrimental environmental impacts, such as fugitive gas contamination and fugitive greenhouse gas emissions. One major area of interest for hydrocarbon exploitation is the Marcellus Formation. This formation is one of the largest shale play areas in the US. Despite ongoing interest in hydrocarbon exploitation in this area, there is still a limited scientific understanding of the fundamental factors that control the amount of gas generated and stored in reservoirs as well as total gas production. One deficiency stems from an insufficient understanding of the paleoenvironment of the Marcellus Formation. In this study we present the chemostratigraphy of the Marcellus Formation to better understand the paleoenvironment. We also aim to understand the source, deposition, and significance of total organic carbon (TOC) preserved in the Marcellus Formation. From our analysis, variations in geochemical signatures (e.g., V, Mo, Ni, Sc, Th, U, and REEs) suggest that changes in sedimentation and redox conditions are major components to the source, origin, and preservation of TOC in the Marcellus Formation. In all, this research will provide further insight into the geochemistry of black shale formations and how they can be useful in determining areas for potential UOG reservoirs.