02 December, 2013

Green River Shales: Geochemical Basin Study

 

The geochemistry of formation fluids (water and hydrocarbon gases) in the Uinta Basin, Utah, is evaluated at the regional scale based on fluid sampling and compilation of past records.

The geochemistry of formation fluids (water and hydrocarbon gases) in the Uinta Basin, Utah, is evaluated at the regional scale based on fluid sampling and compilation of past records. The focus is on the hydrogeochemistry and gas compositions from the vantage point of a basin-wide view.

Studies suggest that gas composition and water-gas stable isotope characteristics in the central to southeastern basin indicate the presence of a deep, thermogenic, and regionally continuous gas deposit. In particular, gases sampled in this region from the Wasatch Formation and Mesaverde Group indicate a similar source rock (type III kerogen of the deeply buried, thermally mature Mesaverde Group in the central to northern basin) as well as migration from the Natural Buttes gas field toward the southeastern basin.

Evidence for biogenic methane formation is observed only in the upper Green River Formation in the central to northern Uinta Basin. Here, the organic-rich, immature Green River shales experience meteoric water invasions and formation fluid chemistry, and stable isotope compositions are diagnostic of microbial methanogenesis.

This study was co-authored by Carl W. Gable, George A. Zyvoloski, and Lynn M. Walte.

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