Title: Strawn Clastic Depositional Systems of the northern Eastern Shelf, with Observations on Regional Petroleum Sourcing, and an Update on JC (Strawn Upper) Field

During the Desmoinesian stage a regional shelf along the northern “Eastern Shelf” had not yet developed. Large scale carbonate buildups, such as the King Platform and Anson Bank, ultimately link together to create the true Eastern Shelf by mid-Missourian time.

Regional sedimentation was controlled by a low angle ramp dipping west-southwest at approximately 1-2 degrees towards the incipient Midland Basin. Ouachita and Muenster-Wichita derived clastics rapidly prograded westward as elongate deltas, depositing fluvio-deltaic, mixed near shore, and deeper marine facies. Deeper deposits, up to 100M water depths, have been observed in atypical restricted depressions, and as suspected submarine channels. The strong cyclicity observed in both clastic and carbonate deposits was likely driven by glacioeustacy. Individual cycles are postulated to represent 200,000-400,000 years of sedimentation.

For Atoka through Strawn reservoirs, there are two primary petroleum source provinces. An eastern, Fort Worth Basin Barnett source, and a western, Midland/Permian Basin source. These two systems are not observed to overlap. There are additional, localized source provinces that can been demonstrated to source Atoka and Cisco-Canyon reservoirs.

This discussion will briefly review the two primary petroleum provinces sourcing Strawn-age reservoirs, analyze specific Strawn cyclical elements studied in King County, and examine the change in depositional vectors for Strawn sandstone cycles through time along the west-southwest pivoting Bend Arch.

Additionally, the NBX operated JC (Strawn Upper) Field, the largest conventional oil field discovered on the Eastern Shelf this century, will be reviewed and discussed.

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