A new exploration method is advanced based on the hypothesis that some fractured shale reservoirs are related to a stratigraphic-type trapping mechanism at lithofacies boundaries where gray shales grade laterally into dark, radioactive shales having different physical and chemical characteristics. Hydrocarbons are postulated to move through these indurated, fine-grained shales as they do during late primary migration. Whatever mechanisms are operating at shale lithofacies, facies changes are systematic depositional events that can be mapped using conventional subsurface geologic methods. Shale gas fields associated with the mapped position of shale facies changes are found in all three eastern basins.

Gas occurrences from 139 wells were projected into a stratigraphic test section in Kentucky and West Virginia. Several facies changes and 232 gas occurrences are documented; they show a trend of gas occurrences near shale facies changes. For example, the middle Huron, more than 200 ft (61 m) thick, changes from 88% black to 2% within 17.2 mi (28 km); 87% of reported gas in the unit occurs in that same distance. Of 66 major shows or increases (> 100 mcf or 2,830 m³) in the Ohio Shale, 88% fall within the 17.2 mi (28 km) in which the total unit changes from 86% black to 16%.

Facies changes appear to define trends of shale gas potential within specific beds; thus, a new element has been added to shale gas exploration methodology. The methods developed can be used to test the applicability of the hypothesis to the eastern basins.

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