MARCELLUS SHALE AT THE EROSIONAL BOUNDARY IN SOUTHERN WEST VIRGINIA: REEXAMINATION AND FURTHER INTERPRETATION

The Marcellus Shale is an organic-rich unconventional shale-gas reservoir that was deposited in a shallow, epicontinental sea that covered the Appalachian Basin during the Middle Devonian. Southern West Virginia contains progressively younger beds on top of progressively older beds with an unconformity separating the Middle and Late Devonian rocks. In comparison, northern West Virginia saw erosional truncation as a result of the Late Devonian transgression. The unconformity that was identified in southern West Virginia represents a boundary that should be the zero-isopach line. However, well logs produced from the western region of this unconformity reveal the possibility that the Marcellus Shale exists past this limit. Reviewing well logs, constructing cross sections, and examining well field data helps show where the Marcellus occurs and how its production potential varies compared to production in the north. The unit generally increases in thickness and depth to the northeast and production totals follow this trend. Although some wells in northern West Virginia have only been active for a few years, they have yielded almost 8 times the amount of natural gas of some 33-year-old wells in the south. Determining the extent of the Marcellus Shale in southern West Virginia and examining production at the erosional boundary will contribute to the maximized future exploitation of these resources.