About This Item

Share This Item

The AAPG/Datapages Combined Publications Database

AAPG Bulletin


AAPG Bulletin, V. 91, No. 4 (April 2007), P. 445-473.

Copyright copy2007. The American Association of Petroleum Geologists. All rights reserved.


Oil and gas geochemistry and petroleum systems of the Fort Worth Basin

Ronald J. Hill,1 Daniel M. Jarvie,2 John Zumberge,3 Mitchell Henry,4 Richard M. Pollastro5

1Central Energy Resources Team, U.S. Geological Survey, Box 25046, MS 939, Denver, Colorado 80225; [email protected]
2Humble Instruments and Services, Inc., Humble Geochemical Services Division, P.O. Box 789, Humble, Texas 77347; [email protected]
3GeoMark Research, Ltd., 9748 Whithorn Drive, Houston, Texas 77095; [email protected]
4Central Energy Resources Team, U.S. Geological Survey, Box 25046, MS 939, Denver, Colorado 80225
5Central Energy Resources Team, U.S. Geological Survey, Box 25046, MS 939, Denver, Colorado 80225; [email protected]


Detailed biomarker and light hydrocarbon geochemistry confirm that the marine Mississippian Barnett Shale is the primary source rock for petroleum in the Fort Worth Basin, north-central Texas, although contributions from other sources are possible. Biomarker data indicate that the main oil-generating Barnett Shale facies is marine and was deposited under dysoxic, strong upwelling, normal salinity conditions. The analysis of two outcrop samples and cuttings from seven wells indicates variability in the Barnett Shale organic facies and a possibility of other oil subfamilies being present. Light hydrocarbon analyses reveal significant terrigenous-sourced condensate input to some reservoirs, resulting in terrigenous and mixed marine-terrigenous light hydrocarbon signatures for many oils. The light hydrocarbon data suggest a secondary, condensate-generating source facies containing terrigenous or mixed terrigenous-marine organic matter. This indication of a secondary source rock that is not revealed by biomarker analysis emphasizes the importance of integrating biomarker and light hydrocarbon data to define petroleum source rocks. Gases in the Fort Worth Basin are thermogenic in origin and appear to be cogenerated with oil from the Barnett Shale, although some gas may also originate by oil cracking. Isotope data indicate minor contribution of biogenic gas. Except for reservoirs in the Pennsylvanian Bend Group, which contain gases spanning the complete range of observed maturities, the gases appear to be stratigraphically segregated, younger reservoirs contain less mature gas, and older reservoirs contain more mature gas. We cannot rule out the possibility that other source units within the Fort Worth Basin, such as the Smithwick Shale, are locally important petroleum sources.

Pay-Per-View Purchase Options

The article is available through a document delivery service. Explain these Purchase Options.

Protected Document: $10
Internal PDF Document: $14
Open PDF Document: $24

AAPG Member?

Please login with your Member username and password.

Members of AAPG receive access to the full AAPG Bulletin Archives as part of their membership. For more information, contact the AAPG Membership Department at [email protected].