Crude oil and shale samples from the Denver basin of Colorado, Wyoming, and Nebraska were analyzed by organic geochemical techniques to determine the stratigraphic occurrence and regional distribution of petroleum source beds.
The study demonstrates that the oils produced from Cretaceous Sussex, Shannon, ?D? and 'J' sandstone reservoirs are genetically related and have probably been derived from Cretaceous source beds in the Carlile, Greenhorn, Graneros, and Mowry interval. Oils produced from fractured Niobrara and Lower Pierre formations are geochemically dissimilar to other Cretaceous oils and may have been generated in place. The Permian Lyons oils distinctly different from all of the Cretaceous oils and its source has not been identified.
Samples of the Cretaceous Carlile-Greenhorn-Graneros-Mowry interval that contain hydrocarbon distributions similar to the Cretaceous oils examined are restricted to the basin axis area between Denver and Fort Collins, Colo. This limited geographic distribution of effective source beds and the occurrence of petroleum in thermally immature areas of the basin suggest that extensive lateral migration has occurred.
Organic geochemical studies can identify oil source-bed relationships and areas of favorable source-bed potential and can, therefore, provide valuable input to oil exploration decisions.