Abstract

Reconstruction of burial and thermal-maturation histories of a sedimentary basin provides critical information for delineating hydrocarbon-bearing sections and areas that have been characterized by petroleum generation, expulsion, storage, and/or migration. This paper reports the burial history, thermal maturity, and timing and amount of petroleum generated, expelled, and retained for seven key petroleum source-rock stratigraphic sections at the Cow Creek three-dimensional (3-D) survey area along the Atlantic Rim of the eastern Washakie Basin in south-central Wyoming. The Washakie Basin is within the Greater Green River Basin.

The horizons studied are: (1) the Lower Permian Phosphoria Formation, (2) the Upper Cretaceous Mowry Shale, (3) the Upper Cretaceous Frontier Formation, (4) the Upper Cretaceous Steele Shale (and equivalent rock units), (5) the Upper Cretaceous Mesaverde Group, (6) the Upper Cretaceous Lewis Shale, and (7) the Upper Cretaceous Lance Formation. The maturation level (transformation ratio), thermal gas generated, gas expelled, and gas retained in the source rocks are reported for all of the modeled source rocks at the base of each stratigraphic horizon. Evaluation of these hydrocarbon maturation parameters is an important aspect of exploring for source-rock plays in a petroliferous basin.

The observations made in this study will be useful in evaluating potential Cretaceous shale gas plays in the Washakie Basin. Special emphasis was given to the Mowry Shale in the Cow Creek area because it has significant potential as a source of shale gas.