Probabilistic methodology for the assessment of original and recoverable coal resources, illustrated with an application to a coal bed in the Fort Union Formation, Wyoming

First posted June 23, 2021 For additional information, contact: Geology, Energy & Minerals Science CenterU.S. Geological Survey12201 Sunrise Valley Drive, MS 954Reston, VA 20192Contact Pubs Warehouse The U.S. Survey (USGS) has been using its Circular 891 for evaluating uncertainty in coal resource assessments more than 35 years. Calculated cell tonnages are assigned to four qualitative reliability classes depending exclusively on distance the nearest drill hole. main appeal of this methodology, simplicity, is also drawback. Reliability may depend so marginally hole that, over time, it become evident that inadequate modeling and limited by other shortcomings. present publication describes use geostatistics as an approach allowing a satisfactory performance which achieved following 891. Geostatistics takes advantage partly random organized fluctuations attributes such thickness, density, elevation top bed, borrowing concepts tools have standard features statistics risk analysis decades. Considering readers interested study not background go directly into details we start explaining geostatistical techniques. remainder devoted formulating assessment applying data from Fillmore Ranch bed Fort Union Formation Wyoming, computer software applied performing calculations displays. methodology designed report three different forms resources: place, mineable surface mining methods, underground methods. These types resources reported graphically displaying both magnitude total at scale. In case example, there 90-percent probability place 9.687 ± 0.383 billion short tons (bst), while available 2.279 0.160 bst, only 0.240 0.025 bst because steep dip west away outcrop. magnitudes derived numerical distributions any specific form.