ABSTRACT

With development dating from the 1800s, the Devonian Berea Sandstone has a long history of oil and gas development in the Appalachian Basin. A new phase of development began in northeastern Kentucky in 2011 with production of high-gravity oil from horizontal wells at depths less than 2200 ft (<671 m). Oil production in areas previously unproductive or primarily gas productive was unexpected because thermal-maturity measures, such as vitrinite reflectance, suggested source rocks should be immature. Moreover, downdip the Berea Sandstone appeared to produce primarily gas within the oil window.

Organic petrography and geochemical analyses were conducted on source rocks overlying (Sunbury Shale) and underlying (Ohio Shale) the Berea Sandstone and produced oil and gas from the Berea Sandstone and Ohio Shale. Samples were collected from southernmost Ohio to southeastern Kentucky along a northwest-to-southeast transect representing increased burial depth. Geochemistry results suggest the Sunbury or Ohio Shales could be sources of oil reservoired in the Berea Sandstone. Migration is necessary to account for oil in the updip parts of the play. Vitrinite reflectance measurements suggest, however, the area mature for oil is larger compared to previous assessments. Consequently, less migration is needed to account for the distribution of oil production. Gas chemistry reflects the thermal-maturity effect of regional dip with additional influence from local structures. Stratigraphic analysis of the Berea Sandstone in core and outcrop shows it to be primarily a siltstone with lateral facies changes, different bedding types, and diagenesis producing a complex reservoir.

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