The Appalachian basin is referred to as the birthplace of the oil and gas industry. Drilling has occurred since the Drake discovery well in Titusville, Pennsylvania, in 1859. Applying new tricks in an old basin is one way to help meet tomorrow’s energy needs.
An isopach map, cross sections, genetic increment strata (GIS) map, core studies, and subsurface well logs suggest a gas-productive turbidite channel deposit for the Upper Devonian Speechley sandstone in Cherryhill field in west-central Pennsylvania. Isopaching indicates the channel trend, showing the geometry of the sand body perpendicular to basin contouring. Cross sections document a downcutting erosional contact with the underlying marine shales. Using a lithologic time correlator above the sand and the erosional basal contact, a GIS map shows that maximum reservoir development coincides with the central channel axis. Thus, the isopach and GIS maps are essentially identical; both confirm the channel trend.
Bedding characteristics, sedimentary structures, and petrology, from 59 ft (18 m) of conventional core, also suggest a turbidite channel. Bedding is predominately massive, and is comprised of incomplete Bouma sequences. Grain size decreases upward. Porosities which average 8%, and permeabilities, which are generally less than 1 md, were reduced by silica and carbonate cements and clays bridging pore throats. Sedimentary structures include shale clasts, erosional basal contacts, and bioturbation.
The combination of various mapping techniques and core interpretation suggest a turbidite channel origin for the Speechley sandstone. This approach may permit predictions for field development and exploratory drilling.