Coyote Creek is the largest stratigraphically trapped Dakota oil field discovered on the eastern flank of the Powder River basin. The trap is formed by an updip change from clean sand to impermeable sand, siltstone and shale in a pinch-out zone which is only a few hundred yards wide. The trap occurs in an area of homoclinal

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dip slightly modified by small normal faults. The sand body has a relatively flat base, is irregular in shape and loses porosity and permeability from the top downward. It appears to be a near-shore marine deposit. Permeabilities in the sand body are as great as 3,200 md, but more commonly range from 100 to 400 md. The average reservoir thickness is about 46 feet.

Development drilling continues, and to date has resulted in fifty producing wells and nine dry holes. The oil column is about 300 feet thick and recoverable oil will exceed twenty-five million barrels.

The field was discovered between two dry holes one and three-quarters miles apart. This points out the need for closely spaced wildcats to evaluate the productive potential of land in areas of rapid lateral stratigraphic changes. Exploration-wise, the field is significant because its study demonstrates stratigraphic principles which may be used in searching for new oil fields.

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