The drilling of 2,000 to 3,000 development wells a year for several years into the Clinton Sandstone reservoir in eastern Ohio has provided a data base for distinguishing a number of deltaic sedimentary patterns that are more productive of oil and gas than others. Clinton Sandstone development drilling in Ohio, Pennsylvania,

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and New York is price-driven and tax shelter related. With the designation of almost all of the Clinton reservoir sands as "tight sands" for gas pricing, payout can be expected in many, but not all Clinton wells despite the nearly 90% or higher drilling success ratio.

New regional studies show the upward, deltaic progradation to the west as previously documented, but they also demonstrate new stratigraphic relationships between the upper Cabot Head shales, the sandstone reservoirs of the Clinton, and the overlying Packer Shell Limestone. The upper Cabot Head lies only landward of the progradational edge and the transition westward is from reservoir sands into calcareous sands and carbonate rocks. Within this deltaic system, one which covered much of eastern Ohio, Clinton wells have produced oil and gas from these fluvial, fluvial delta-margin and delta-margin bars, and beach sands for over 50 years.

Both regional and local patterns indicate better areas of Clinton development drilling at various depths. In the fluvial sequences, total sand maps, clean sand maps, porosity maps, and water, oil, and gas saturation maps point to locations of higher oil and gas deliverability. In the delta margin system, sand mapping, cross sections, and porosity maps show multiple bar systems at the edges of deltaic plains and tidal flats where there is higher gas and oil production from the Clinton reservoirs.

Local structural highs and faults affect production in this mainly stratigraphic trap. Locally, structure segregates oil and gas in the same reservoir body, but separate, though laterally equivalent, reservoir sands act differently on the same structure in adjacent wells.

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