ABSTRACT

Most oil production on the Fort Peck Reservation occurs along the Wolf Creek nose, which is a positive tectonic element protruding into the Williston Basin. Nisku exploration has recently seen a revival with the advancement of 3D seismic technology. Abandoned Mississippian production at Bredette and recent discoveries in the north-central part of the Reservation, confirm that a structural and stratigraphic shelf flanks the Central Reservation Block. Numerous Devonian salt dissolution events have likely created other fractured reservoirs that have not been tested by the drill.

The Mississippian Bakken Formation is a mature source rock, if not a potential reservoir, over much of the Reservation. Fracture enhancement is likely along the entire length of the Smoke Creek syncline and coincident. Prairie salt dissolution edge.

Basinward of the syncline lie more typical, multipay, Williston Basin oil fields. The Reservation's eastern area has seen only a few frontier discoveries, where as many as 5 or 6 pay zones are likely, each having million barrel potential at depths varying from 7,500 to 11,000 ft (2,286-3,353 m).The Smoke Creek anticlines are focal points for new exploration on the eastern side of the Reservation.

Fort Peck Reservation wells have recovered 83 million barrels of oil, and proven reserves exceed 18 million barrels. Probable Devonian Nisku reserves in the central Reservation fields are 10 million barrels. Deeper pay potential on Poplar dome is significant; a solitary Nisku well, not committed to the unit, produced 285,000 barrels. The transition shelf has undiscovered resource potential of at least 10 million barrels. Reservation reservoirs in the east contain perhaps 10 million barrels. Horizontal drilling is proposed by at least one active operator on the Reservation and should greatly enhance the transition zone and other fractured reservoir recoveries. Renewed leasing and drilling activity is noted between the Volt and Lustre oil fields within the Central Reservation Block.