The Upper Cretaceous Niobrara Formation has yielded natural gas of biogenic origin from structural closures on the gently dipping east flank of the Denver-Julesburg basin and the northern plunge of the Las Animas arch. Present production is from the Smoky Hill Member of the Niobrara Formation. The majority of fields located to date are in Colorado and Kansas; however, several new fields have been discovered in the Nebraska part of the basin. Potential for significant Niobrara gas production exists in the Kennedy and Salina basins of Nebraska, and from parts of South Dakota, North Dakota, Montana, and Canada. The formation has high porosity and low permeability and requires hydraulic fracture stimulation for economic production. Production depths range from 1,000 to 3,200 t (305 to 975 m).

The chalk beds of the Niobrara were deposited in the deep, quiet water of the Cretaceous interior seaway.

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