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The AAPG/Datapages Combined Publications Database

Williston Basin Symposium

Abstract

MTGS-AAPG

Seventh International Williston Basin Symposium, July 23, 1995 (SP12)

Pages 89 - 102

Lithofacies and Petroleum Potential of the Birdbear Formation (Upper Devonian), Southwestern Manitoba and North-Central North Dakota

C.D. Martiniuk, Manitoba Energy and Mines, Winnipeg, Manitoba, Canada R3C 4E3
H.R. Young, Department of Geology, Brandon University, Brandon, Manitoba, Canada R7A 6A9
J.A. LeFever, North Dakota Geological Survey, University Station, Grand Forks, North Dakota 58202 USA

ABSTRACT

The Birdbear Formation is a widespread carbonate-evaporite unit that was deposited over a broad, shallow Upper Devonian shelf extending from central Alberta to eastern North Dakota. The formation can be subdivided into a lower, carbonate member composed predominantly of non-argillaceous limestones and dolostones and an upper, evaporite-carbonate member of mainly dolostones with interbedded evaporites. It is conformably underlain by the Duperow Formation. Contact with the overlying Three Forks Formation is conformable throughout most of Manitoba and North Dakota.

The Birdbear Formation represents one cycle in the Devonian marine transgressive-regressive sequence. Depositional environments recognized within the Lower and Upper members of the Birdbear Formation range from low energy subtidal to higher energy intertidal, lagoonal and supratidal. Lithofacies that represent these environments can be identified and correlated in southwestern Manitoba and north-central North Dakota.

The Birdbear Formation has produced in excess of 823,527 m3 (5,182,373 bbls) of oil in the Williston Basin mostly from stromatoporoid banks and biostromes that border the basin in northeastern Montana and from facies associated with basement-related faulting and Late Devonian salt collapse structures in Saskatchewan and northeastern Montana.

Correlative facies within the Birdbear Formation in Manitoba and North Dakota suggests a potential for the exploitation of several different types of stratigraphic traps. Exploration for hydrocarbons also may be directed toward areas of basement-related and multiple stage salt collapse structures. The current edge of the Prairie Formation salt is definable within the study area and may serve as a control on the distribution of reservoir facies, the enhancement of porosity and entrapment of hydrocarbons. Secondary dolomitization, a major control in stratigraphic trapping in other areas of the basin, may also serve the same role in the study area.

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