Determination of organic-matter content of Appalachian Devonian shales from gamma-ray logs

Journal Article · Wed Jul 01 04:00:00 EDT 1981 · Am. Assoc. Pet. Geol., Bull.; (United States)

OSTI ID:5664737

Schmoker, J W

The organic-matter content of the Devonian shale of the Appalachian basin is important for assessing the natural-gas resources of these rocks, and patterns of organic-matter distribution convey information on sedimentary processes and depositional environment. In most of the western part of the Appalachian basin the organic-matter content of the Devonian shale can be estimated from gamma-ray wire-line logs using the equation: phi/sub 0/ = (..gamma../sub B/ - ..gamma..)/1.378A, where phi/sub 0/ is the organic-matter content of the shale (fractional volume), ..gamma.. the gamma-ray intensity (API units), ..gamma../sub B/ the gamma-ray intensity if no organic matter is present (API units), and A the slope of the crossplot of gamma-ray intensity and formation density (API units/(g/cm/sup 3/)). Organic-matter contents estimated using this equation are compared with organic-matter contents determined from direct laboratory analyses of organic carbon for 74 intervals of varying thickness from 12 widely separated wells. The organic-matter content of these intervals ranges from near zero to about 20% by volume. The gamma-ray intensity of the Cleveland Member of the Ohio Shale and the lower part of the Olentangy Shale is anomalously low compared to other Devonian shales of similar richness, so that organic-matter content computed for each of these units from gamma-ray logs is likely to be too low. Wire-line methods for estimating organic-matter content have the advantages of economy, readily available sources of data, and continuous sampling of the vertically heterogenous shale section. The gamma-ray log, in particular, is commonly run in the Devonian shale, its response characteristics are well known, and the cumulative pool of gamma-ray logs forms a large and geographically broad data base. The quantitative computation of organic-matter content from gamma-ray logs should be of practical value in studies of the Appalachian Devonian shale. 16 figures.

• Research Organization: Geological Survey, Denver, CO
• OSTI ID: 5664737
• Journal Information: Am. Assoc. Pet. Geol., Bull.; (United States), Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Vol. 65:7; ISSN AAPGB
• Country of Publication: United States
• Language: English

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47 OTHER INSTRUMENTATION
APPALACHIA
BITUMINOUS MATERIALS
BLACK SHALES
CARBONACEOUS MATERIALS
CHATTANOOGA FORMATION
DEVONIAN PERIOD
ENERGY SOURCES
FLUIDS
FOSSIL FUELS
FUEL GAS
FUELS
GAMMA LOGGING
GAMMA-GAMMA LOGGING
GAS FUELS
GASES
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC FORMATIONS
MATERIALS
MINERAL RESOURCES
NATURAL GAS
NATURAL GAS DEPOSITS
NATURAL GAS WELLS
NORTH AMERICA
OIL SHALES
ORGANIC COMPOUNDS
PALEOZOIC ERA
RADIOACTIVITY LOGGING
RESOURCES
SEDIMENTATION
USA
WELL LOGGING
WELLS