COAL GAS RESOURCE POTENTIAL OF CRETACEOUS AND PALEOGENE COALS OF THE EASTERN GULF OF MEXICO COASTAL PLAIN

Recent investigations conducted by Federal, State, and industry organizations suggest that significant coalbed gas resources may exist in the Trinity (?) (Lower Cretaceous), Midway, and Wilcox Groups (Paleocene-Eocene) in the eastern part of the Gulf of Mexico Coastal Plain. Drill records from Arkansas and Louisiana indicate that there may be Cretaceous coal beds greater than 3 m thick at depths suitable for coalbed gas development (generally 450 – 1,800 m). Available data from conventional oil and gas wells in Louisiana indicate that upper, middle, and lower Wilcox Group coal zones may have potential for coalbed gas accumulations and similar data from Arkansas, Mississippi, and Alabama indicate that gas may be present in coal beds of the lower and middle sections of the Wilcox. In addition, gas accumulations may occur in the coal beds of the upper part of the Midway Group in Mississippi and Alabama. Public data from several wells completed in Wilcox Group coal zones in north-central Louisiana indicate an initial production range from 200 to 3,450 cubic meters of gas per day and 0 to 87 cubic meters of water per day.

In Louisiana, the depth to the targeted Wilcox coal beds range from 300 to 1,500 m, and individual coal beds have a maximum thickness of about 6 m. The thickest coal beds tend to be in the lower Wilcox coal zone and cumulative coal thickness can exceed 30 m. Although geochemical and petrographic data from Wilcox Group coals from across the region indicate that the coal beds are lignite in rank at depths less than 100 m, they reach a rank of subbituminous B, or greater, at depths of approximately 1,500 m. Proximity to salt dome structures or buried Late Cretaceous igneous intrusions and associated geothermal heat flow, may be important exploration tools for finding coal beds with elevated rank and potentially increased gas content. More data are needed to better characterize and assess the coalbed gas potential for the Cretaceous coal beds in this region.