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A Waulsortian Mound Case Study

Stark and Dunn Counties, North Dakota

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EDCON-PRJ and Seewald Energy Company (SEC) have acquired a detailed non-exclusive aeromagnetic survey centered in northern Stark County, North Dakota where the Lodgepole play is currently taking place. Waulsortian-type carbonate mud mounds, discovered here by Conoco in 1993, in the Mississippian Lodgepole Formation provide a prolific new oil play with significant regional potential in the Williston Basin.

The primary objective of this aeromagnetic survey was to take a detailed magnetic "look" at the basement configuration where the Lodgepole play is currently centered. A preliminary interpretation of the aeromagnetic data indicates that not only do the data provide analogs for potential Lodgepole mound activity but also provide analogs and prospective areas for older Ordovician Red River and Silurian Interlake reservoirs.

Since the discovery at Dickinson Field in 1993, drilling has expanded to an area approximately 9 miles wide by 15 miles long. By February, 1996, forty wells had been drilled to the Lodgepole with 23 of these (55%) producers. The better wells are capable of producing 1000-2500 bbls/day and per well reserves range from 0.5 to 3.0 million barrels. The largest field to date (Eland) has 15 producers and an estimated total reserve of 12-15 million barrels.

Individual fields are developed in single mound features and in multiple, overlapping mound complexes. Maximum reservoir quality is concentrated in partially fractured, vug-bearing zones located in the upper 100 feet of each buildup. Use of 3-D seismic data has significantly enhanced prospecting but has not eliminated the problems of multiple salt horizons and low velocity contrast with off-mound Lodgepole facies.

Occurrence of similar mounds, both to the west in central Montana and to the north in southern Saskatchewan and Manitoba, suggests a regional distribution for these features. A potential exploration area more than 150 miles long and 15 to 20 miles wide rims the central part of the Williston Basin.


Survey Size: 3,600 line miles

Line Spacing: -mile

Line Direction: East-west

Tie Lines: -mile, north-south

Elevation: Approximately 700 feet, modified drape