WYOMING – The future of coal is about as black as, well…yeah, you get it. But that hasn’t stopped the Wyoming State Geological Survey (WSGS) from continuing to assess coal resources within the Fort Union Formation in south-central Wyoming.
Report of Investigations 76, Coal Availability of the Fort Union Formation in the Great Divide and Washakie Basins, South-Central Wyoming, estimates the available coal within the Fort Union Formation across the Washakie and Great Divide basins, primarily in Carbon and Sweetwater counties.
“Wyoming coal faces challenges in terms of retiring coal-fired power plants, the current low cost of natural gas, and access to new markets,” said WSGS Director, Dr. Erin Campbell. “However, the WSGS continues to develop an inventory of coal resources in Wyoming to be prepared for future needs.”
The basis for this study is the most comprehensive stratigraphic correlation of Fort Union coal beds in the Greater Green River Basin to date. Coal beds in three historic mining areas—the Little Snake River, Rawlins, and Rock Springs coal fields—were correlated through the adjacent Great Divide and Washakie basins.
Of the 80-plus individual coal beds identified using geophysical logs from subsurface oil and gas wells, the 12 thickest and most continuous coal groups were selected for spatial modeling.
Results from the model include maps of bed thickness, overburden, and areal extent for each of the 12 coal groups. The results from the model were then used to estimate original and available coal resources, as well as the demonstrated reserve base of coal within the Fort Union Formation.
“The most interesting finding of this study is the lateral persistence of some of these rather thin coals,” said coauthor and WSGS geologist Kelsey Kehoe. “We are currently trying to understand how, and when, the Great Divide and Washakie basins formed using the results from the coal correlations. This study will help guide future work into basin history and possibly aid in constraining coal bed natural gas potential in this area.”
Report of Investigations 76 is a regional assessment that is not intended for determining coal resources for detailed planning, rather, it is meant to be a general overview at the basin scale. The stratigraphic data used in this report are available through the U.S. Geological Survey’s National Coal Resources Data System (NCRDS), a federal program that provided partial funding for these coal correlations.
