Wabek and Plaza Fields: Carbonate Shoreline Traps in the Williston Basin of North Dakota
SPERR, THOMAS, Presidio Oil Company, Denver, CO, STEVEN G. STANCEL, Independent, Denver, CO, and MICHAEL L. HENDRICKS, Hendricks and Associates, Inc., Denver, CO
Wabek and Plaza fields in Mountrail and Ward counties, North Dakota, will ultimately produce 8 million and 3 million bbl of oil, respectively, from reservoirs in the Sherwood and Bluell intervals of the Mississippian Mission Canyon Formation. Both fields produce from porous, oolitic, and pisolitic lime packstones and grainstones deposited as shoals along a low-energy shoreline. A facies change to impermeable dolomitic and salina/sabkha environments to the east provides the updip trap.
The Sherwood at Wabek has more than 100 ft of oil column driven by solution gas and water influx. Effective porosity consists of interparticle, vuggy, and minor dolomitic intercrystalline porosity. Log porosities range from 6 to 26%, averaging about 10%, and net pay averages about 26 ft.
One mile west of Wabek, Plaza field produces from the Bluell, stratigraphically overlying the Sherwood. Log porosities range from 6 to 16%, averaging about 9%. Net pay averages about 6 ft. An oil-water contact is not yet defined, but at least 120 ft of oil column are present.
Regional depositional slope and local depositional topography were major controls on Mission Canyon shoreline trends and the development of reservoir facies. In the Wabek-Plaza complex, the position and trend of the Sherwood and Bluell shorelines can be related to structural trends identified in the crystalline basement from aeromagnetic data. Locally, thickness variations in the underlying Mohall interval amplified relief on the Wabek-Plaza structure and influenced the deposition of shoreline reservoirs.
AAPG Search and Discovery Article #91010©1991 AAPG Rocky Mountain Section Meeting, Billings, Montana, July 28-31, 1991 (2009)