Regional Correlation and Depositional History using Well Log and Core Data of the Middle Devonian Marcellus Poseidon 8M Well, Westmoreland County, Pennsylvania, USA

The Marcellus Shale is the largest natural gas producing formation in the Appalachian basin, and as such, presents a unique opportunity for continued research on an area that is critical to meeting the energy needs of the current society. Although the Marcellus has historically been extensively researched, acquisition of well log and core data from the Marcellus Poseidon 8M well in Westmoreland County, PA, allows for application of a new method of data integration, which was utilized in this project to specifically understand the depositional environment and create a correlation with other study wells throughout the basin. This integration was primarily based on a detailed core study including core description and analysis and fracture characterization. Integration of the core study with log analysis, mineralogy studies from XRD-XRF data, ECS, and log methods, and certain geomechanical properties provided a comprehensive representation of the well data and how the logs responded to changes in lithology. The Marcellus stratigraphy in the Poseidon 8M is characterized by three high-gamma ray intervals (upper, middle, and lower Marcellus) that are likely representative of coarsening-upward sequences as the depositional setting fluctuated between anoxic, sediment-starved accumulation of organic-rich black shale to oxic deposition of calcareous, limestone-rich material. Correlation between the rock’s geomechanical properties and fracture characterization indicate that, at least for the Marcellus, areas of high fracture density correspond with low Poisson’s ratio values, which could be correlated to brittleness. Correlating the Poseidon 8M with the 9 other study wells in the basin shows that the Poseidon 8M is located in an area of the basin, probably toward the center, that experienced larger amounts of (sediment) accumulation, and that the basin regionally thins toward the western peripheral edge