Defining organic-rich facies in the Devonian shale in the western part of the Appalachian basin

Technical Report · Tue Jan 01 04:00:00 EST 1980

OSTI ID:5358234

Schmoker, J W

The Devonian shale section is often divided into organic-rich (black) and organic-poor (gray) subdivisions. In some instances, coarser grained gray shale may act as a reservoir and produce gas, but in the western part of the Appalachian basin the organic-rich shale facies are believed to contain the bulk of the producible gas resource. Therefore, Devonian-shale studies usually emphasize the organic-rich facies. If drill cuttings are available for the Devonian shale sequence, the boundary between organic-rich and organic-poor facies is commonly based on the color of the shale. Other boundary definitions are based on gamma-ray wireline logs, with the assumption that natural gamma radiation and organic content correlate. A gamma-ray intensity of 20 API units above the gray-shale baseline has been used to define the boundary between organic-rich and organic-poor facies (20-API method); a gamma-ray intensity of 230 API units has been used as the threshold value for shale of high gas content and could thus be regarded as another definition of the organic-rich, organic-poor boundary (230-API method). An organic-matter content of 2% by volume (0.8% by weight) is favored by the author as the best definition of the organic-rich, organic-poor boundary (2% method).

• Research Organization: Geological Survey, Washington, DC (USA)
• OSTI ID: 5358234
• Report Number(s): USGS-OFR-80-707
• Country of Publication: United States
• Language: English

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ORGANOLEPTIC PROPERTIES
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YIELDS