Most exploratory and development drilling for oil and gas in Hocking and Perry Counties, Ohio, prior to the 1950s was based on completion results of the nearest well. Economically profitable wells have become increasingly more difficult to obtain, requiring more detailed geologic knowledge of the reservoir rock.

The Silurian "Clinton" sandstone reservoir has received most of the recent attention. The "Clinton" is divided into three units within this area--the "Stray Clinton," "First Clinton," and "Second Clinton."

"Clinton" sandstones belong to a deltaic complex of Medinan age. Studies of mineralogy, texture, sedimentary structures, and geometry indicate a variety of possible terrestrial-transitional and marginal marine subenvironments.

Oil and gas accumulation is dependent on stratigraphic variation rather than structure. Apparent reservoir-controlling parameters important to exploration and secondary recovery are (1) interstitial clay content, (2) shale stringers and laminations, (3) degree of cementing, (4) grain size, (5) pore geometry, and (6) thickness.

The best producing oil wells are those which have been completed in thick, shale-free distributary channel deposits and delta-platform tidal channels. The best secondary-recovery method appears to be gas repressuring, although waterflooding may have limited application. The orientation of natural and induced fractures should be considered in setting up drilling operations for secondary- and primary-recovery operations.