IMPACT OF THE EROSIONAL BOUNDARY ON MIDDLE DEVONIAN STRATIGRAPHY IN SOUTHERN WEST VIRGINIA

The Marcellus Shale spans the region from southern West Virginia to southern New York. It is an organic-rich black shale that was deposited in the Appalachian Basin during the Middle Devonian. In the field area, the unit below the Marcellus Shale is the Onondaga Limestone, and above are the Genesee Formation, the Sonyea Formation, or the West Falls Formation. Each of these contains a basal black shale unit. An erosional event removed a portion of the Marcellus Shale, as well as portions of the overlying units of the Hamilton Group. This is evident in southern West Virginia where the progressively younger units onlap the progressively older units. Well logs, specifically gamma ray and bulk density, are useful indicators of the subsurface lithologies. A wealth of well logs is available for southern West Virginia and an analysis of the logs reveals the nature of the unconformity. In addition to the stratigraphic study, completion information (true vertical depth, new footage, gas before and after treatment, rock pressure before and after treatment, shut-in time before and after treatment, etc.) will reveal the most productive and economically viable regions of the Marcellus Shale.