Apparent Depth to the Wilcox Group, Gulf Coast (wlcxdpthg)

Publication Date

2021-06-11

Time Period

2000

Release Date

2000

United States Geological Survey, 2000, Apparent Depth to the Wilcox Group, Gulf Coast (wlcxdpthg): U.S. Geological Survey data release, https://doi.org/10.5066/P9LB9LVC.

Strong economic controls on the viability of coalbed methane (CBM) prospects makes coal geometry and coal property maps key elements in identifying sweet spots and production fairways. Therefore, this study seeks to identify the apparent prospective areas for CBM exploration in the Wilcox Group (Paleocene-Eocene) lignite and coal beds by mapping net coal thickness, depth to coal, and coal rank (vitrinite reflectance). Economic factors are not considered in this CBM prospects study. Given the comparatively extensive gas pipeline and other production infrastructure development in the Gulf Coast Region, these factors seem less a control compared to other areas. However, open leasable public lands are minimal or non-existent in the Gulf Coast region and access to the CBM prospects could be a problem. Vitrinite reflectance data for the Wilcox Group is sparse. Searches of the AGI Georef, USGS Organic Geochemistry, Pennsylvania State University coal library, and State Geological Survey publications as well as other web data sources has turned up mostly information on shallow, mineable coals. Data from the deeper Wilcox group will mostly require new measurements of vitrinite reflectance from core and cutting samples. What is known about rank is that shallow occurrences of the Wilcox "lignite" ranging in depth from outcrop to <4,000 ft, locally reach a maturity equal to bituminous coal. This rank level is an important benchmark for CBM prospects because it marks the onset of thermogenic gas generation. In conclusion, the data indicate that CBM prospects for the Gulf Coast are better in South Texas (Webb, Dimmitt, LaSalle, and Frio counties) because the coal rank is anomalously high there and the coals occur at shallow depths over an extensive area. There are also local structures and apparent stratigraphic traps in this area that make attractive drilling targets. Finally, these higher rank southern Texas Wilcox coals are also plumbed to an apparently very thick section of Wilcox to the east that is mature with respect to gas generation and could provide significant thermogenic gas to these targets.

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