A BRIEF OVERVIEW OF UPPER DEVONIAN AND MIDDLE DEVONIAN BLACK SHALES NATURAL GAS PRODUCTION ON PENNSYLVANIA STATE FOREST LANDS

Much attention is being given to the Ordovician-age Utica shale as the next big natural gas shale play in the mid-Atlantic region following the success of the Marcellus shale development. In most of Pennsylvania, the Utica shale lies several thousand feet deeper than the Marcellus shale. This greater depth could be cost-prohibitive for Utica natural gas development across much of Pennsylvania except in those westernmost counties of the state where the Utica is located at much shallower depths.

In contrast, shallower Upper Devonian-age black shales (in particular, the Geneseo and Burket shales) lying immediately above the Tully limestone are being tested by some natural gas operators as the units are penetrated by drilling targeting the Middle Devonian-age Marcellus shale. Favorable results have subsequently led to the development of and production from some Upper Devonian black shale unconventional wells within Pennsylvania; at least a dozen of these wells are located on Pennsylvania state forest lands.

The cumulative volume reported from the Burket and Geneseo Upper Devonian black shales producing on PA state forest Lands between June 2011 and June 2013 was approximately 5.6 million Mcf, enough to meet the domestic needs of more than 62,000 average U.S. households (space and water heating, cooking, etc.) for one year. Cumulative royalties generated by these shale gas wells has amounted to approximately $3 million over the same time period.

Production decline curves using monthly data compiled from both Upper Devonian black shales and Marcellus wells located on state forest lands were compared, including some curves derived from wells producing from both shale intervals drilled off the same well pad. Preliminary analysis suggests that that decline rates for the Upper Devonian black shales resemble those of lower quality Marcellus wells, which might be explained, in part, by the lower pressures in the shallower interval black shales.