A New Class of Unconventional Hydrocarbon Play in the Lower Paleozoic of the Appalachian Basin and Elsewhere

Loren E. Babcock¹,², Michael Bevis¹, and Peter MacKenzie³
¹School of Earth Sciences, The Ohio State University, Columbus, OH , [email protected] 
²Department of Geology, Lund University, Lund, Sweden, [email protected] 
³Ohio Oil and Gas Association, Granville, OH, [email protected] 

Since 1859, the time that crude oil was first produced from the Venango Sandstone (Devonian) in western Pennsylvania, the Appalachian Basin has been an important region for the testing of sedimentary, stratigraphic, structural/tectonic, and exploration/production models. Currently, this region is experiencing a rebirth of interest as attention is focusing on the production potential of tight, organic-rich Paleozoic siliciclastic deposits, notably the Utica Shale (Ordovician) and the Marcellus Formation or Subgroup (Devonian). Such units, which have long been recognized as source rocks for natural gas and oil, have more recently been recognized as significant, unconventional plays whose resources can be exploited through technological innovations including horizontal drilling and hydraulic fracturing.

The Appalachian Basin offers possibilities for testing new or under-developed unconventional hydrocarbon reservoirs. The Knox Group (Cambrian-Ordovician), which is a proven producer in the region, hints at a greater potential of hydrocarbon reserves in lower Paleozoic strata. The source of the Knox oil and natural gas is uncertain, but by inference with other regions, including other sectors of Laurentia, it was likely sourced from Cambrian, or perhaps even Ediacaran, strata. Such deposits predate foreland basin development in eastern Laurentia.

Dark, organic-rich shales and carbonates are a common and persistent feature of open-shelf and continental slope environments of certain chronostratigraphically delimited intervals of the Cambrian and Ordovician (e.g., Furongian-Tremadocian), notably in regions such as Laurentia, Siberia, and South China, all of which were situated in low latitudes, and in Baltica, which was situated in mid-latitudes. In the Appalachian Basin region, some sub-Knox units have been shown to have hydrocarbon shows and have an obvious but untested potential. Exploitation of potential reserves in analogous lower Paleozoic, organic-rich deposits has taken place on some other paleocontinents, but not all of them.

AAPG Search and Discovery Article #90154©2012 AAPG Eastern Section Meeting, Cleveland, Ohio, 22-26 September 2012