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The AAPG/Datapages Combined Publications Database

Wyoming Geological Association

Abstract


Oil and Gas and Other Resources of the Wind River Basin, Wyoming; Special Symposium, 1993
Pages 307-317

Surface Vitrinite Reflectance Study of the Wind River Basin, Central Wyoming

Vito F. Nuccio, Thomas M. Finn, Mark J. Pawlewicz

Abstract

Vitrinite reflectance (Rm) analyses indicate that samples from Upper Cretaceous and Paleocene formations collected around the margins of the Wind River Basin are immature to marginally mature with respect to oil and thermogenic gas generation, but have the potential to generate biogenic methane. Rm values for the Upper Cretaceous Frontier Formation are in the 0.40 to 0.60 percent range; the mean is 0.48 percent; Upper Cretaceous Cody Shale samples are in the 0.30 and 0.40 percent Rm range, the mean is 0.41 percent; most Upper Cretaceous Mesaverde Formation samples fall within the range of 0.40 to 0.60 percent Rm the mean Rm value is 0.45 percent; Upper Cretaceous Meeteetse Formation samples have Rm values in the 0.39 to 0.49 percent range, the mean is 0.43 percent; Upper Cretaceous Lance Formation values range from 0.39 to 0.55 percent Rm, the mean is 0.46 percent; and Paleocene Fort Union Formation Rm values, the lowest of all formations analyzed, have a mean Rm of 0.38 percent.

The majority of Rm values from each formation are within a very narrow range and are highly consistent throughout the margins of the basin, especially considering the large areal distribution of samples. This indicates similar burial and thermal histories throughout the area sampled. Additionally, the mean Rm value for each formation generally increases from younger to older, a direct result of greater depth of burial for the older formations. Strata around the periphery of the basin were never buried as deeply as those near the basin center, and these marginal strata probably achieved their measured levels of maturity between the end of Laramide deformation (end of early Eocene; about 52 Ma) and 10 Ma.


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