Organic Content of Devonian Shale in Western Appalachian Basin

In the organic-rich facies of the Devonian shale in the western part of the Appalachian basin, the distribution of organic matter determined from quantitative organic-content data derived from formation-density wire-line logs, provides an indirect measure of both gas in place and the capacity of the shale to supply gas to permeable pathways. Knowledge of organic-matter distribution is important for gas exploration and resource appraisal.

The boundary between organic-rich (“black”) and organic-poor (“gray”) facies is defined here as 2% organic content by volume. The thickness of organic-rich facies ranges from 200 ft (61 m) in central Kentucky to 1,000 ft (305 m) along the Kentucky–West Virginia border. The average organic content of the organic-rich facies increases from 5% by volume on the eastern edge of the study area to 16% in central Kentucky.

The net thickness of organic matter in the organic-rich facies (the product of volume-percent organic content and facies thickness) shows the amount of organic material in the shale, and is the most fundamental of the organic-content characterizations. Net thickness of organic matter ranges between 20 and 80 ft (6.1 and 24.4 m) within the mapped area, with local depositional maxima centered in Martin County, Kentucky, eastern Pike County, Ohio, and northern Ashland County, Ohio. The volume of organic material in the organic-rich facies within the mapped area is about 52 × 10¹² ft³ (1.5 × 10¹² m³).