Luncheon – October 16, 2009

Title: 3D Interpretation of a Metorite Impact Field, Red Wing Creek Field, Williston
Basin, Western North Dakota

Speakers: Benjamin Herber, Paul Weimer, (University of Colorado, Boulder, CO), Roger Barton (True Oil, Casper, WY), William S. Hammon III (Terra Spark, Boulder, CO), Chunju Huang, Shu Jiang (University of Colorado, Boulder, CO)

Date: October 16, 2009

Publication: The Outcrop, October 2009, p. 25

The Red Wing Creek Field in the Williston Basin of western North Dakota is one of a handful of oil and gas fields in the world that is known to produce from a structure that formed associated with a meteorite impact. Discovered in 1972, this field has produced 17 millions barrels of oil and 25 BCF of gas from 26 wells, of which 22 are still producing. Ultimate recovery is estimated to be at least 60 million barrels of oil. The impact crater consists of a structurally high central core, with two surrounding structurally high areas; an inner and an outer rim. The total deformed area is about 65 square km; the central core area is 2.6 square km. Production is primarily from reservoirs in the central core that consist of highly deformed carbonate strata of the Upper Mississippian Madison/Mission Canyon Formation. Production occurs from highly fractured strata with less than 1 mD of permeability. Geochemical analyses of the oil indicate the source rock as the underlying Devonian Bakken Shale.

Regionally, the Upper Mississippian Madison Group consists, at the base, of the Lodgepole Formation, overlain by Mission Canyon, overlain by anhydrite and salt of the Charles Formation, overlain by the Kibbey Formation (sandstones, shales, and carbonates). However, within the crater, these strata are of variable thickness and not present everywhere.

At the peak of the central core, the steeply dipping vertical Mission Canyon strata are overlain by sub-horizontal Jurassic strata. The remainder of central core consists of steeply dipping Mission Canyon strata overlain by salt and anhydrite of the Charles Formation that flowed after deformation. In the inner rim, the Mission Canyon Formation varies from gentle to steep dips (up to 22 degrees) and is overlain by the Charles Formation. The Mission Canyon strata in the outer rim are gently dipping (4-5 degrees), and are also overlain by the Charles Formation.

Interpretation of a 3-D seismic data set using select attributes allows for the detailed mapping of the faults and deformed strata within the impact feature. A combination of coherency, curvature, edge stacking, and dip azimuth attributes were used iteratively to determine the best interpretation. These attributes indicate that faults deform primarily the outer and inner rims, and the central core. The outer rim has a radius of 3.3 to 5 km (2 to 2.5 miles), and is defined by a series of arcuate normal faults, which are, in essence, an updip slide escarpment. Individual faults are up to 2.5 km (1.55 miles) in length with offsets up to 110 m (350 feet). The inner rim has a radius of 2 km (1.25 miles). Along the inner rim, faults have normal to high angle reverse motion with offsets up to 135 m (440 feet). Faults are up to 1.6 km (1 mile) in length. Faulting density is greatest in the central core. Faults are up to 0.8 km (0.5 mile) in length, and have a radial to crosscutting pattern within the core. The decollement for the deformed Upper Mississippian interval appears to be the Lodgepole Limestone, directly underlying the Mission Canyon Formation. Attribute analyses also show fracturing/faulting of the Lower Paleozoic strata (about 1220 m, 4000 feet) underlying the impact feature into the upper portions of the Precambrian basement.