Warwick, P. D.1, F. C. Breland2, A. W. Karlsen1,
(1) U.S. Geological Survey, Reston, VA
(2) Basin Research Energy Section, Baton Rouge, LA
ABSTRACT: Regional Correlation and Character of Coal-bearing Zones, Wilcox Group, North-central Louisiana: Implications for Coalbed Gas Exploration
Recent exploration and production of coalbed gas in the Wilcox Group (Paleocene-Eocene) of north-central Louisiana has prompted a re-evaluation of coal character and the structural/statigraphic setting of the coal-bearing rocks in this region. Cross sections constructed from well logs that transect the region indicate that the Wilcox Group is about 125 m thick and the top of the Group is at about 330 m depth in the shallowest part of the basin overlying the Monroe Uplift in Morehouse and Ouachita Parishes. Wilcox strata thicken and dip toward the south, as illustrated in Concordia Parish, where the Wilcox is greater than 700 m thick and the top of the Group has been mapped at depths greater than 1,500 m. In general, Wilcox coal beds can be grouped into upper, middle and lower coal zones. Individual coal beds reach a maximum thickness of about 6 m, and the thickest coal beds tend to be in the lower coal zone. Cumulative coal thickness can exceed 30 m. Coal-bearing strata of the Wilcox Group extend southward, and eastward into neighboring western Mississippi, and westward into northwestern Louisiana and northeastern Texas.
New and published vitrinite reflectance (Ro) data from Wilcox Group coals, in northeast Texas, north Louisiana, and central Mississippi, indicate that the coal beds are lignite in rank (Ro <0.37) at depths less than 100 m, but reach a rank of subbituminous B or greater (Ro >0.42%) at depths of approximately 1,500 m. Although several coalbed gas exploration wells have been drilled in north Louisiana, detailed data on coal-gas content and coal character currently are confidential. Regional coal zone mapping in north Louisiana and preliminary characterization studies, combined with preliminary production data, indicate that the basin is underlain by extensive coal zones that may contain valuable coal-gas resources.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.