The Midwest Regional Carbon Sequestration Partnership recognizes that both the Devonian Oriskany Sandstone and the Silurian Salina Group offer potential for subsurface carbon dioxide storage in northern West Virginia. The Silurian–Devonian Helderberg Group lies stratigraphically between these two units, and consequently, its potential as a geologic seal must be evaluated. Predominantly a carbonate interval with minor interbedded siliciclastics and chert, the Helderberg Group was deposited in an ancient epeiric sea. Although most previous investigations of this unit have concentrated on outcrops in eastern West Virginia, new information is available from an injection well drilled along the Ohio River at First Energy's R. E. Burger electric power plant near Shadyside, Ohio. Geophysical, seismic, and core data from this well have been combined with existing outcrop information to evaluate the Helderberg Group's potential as a seal. The data collected suggest that only secondary porosity remains, and permeability, if it exists, most likely occurs along faults or within fractures.