Williston Basin Report

Kamerer, Wesley, Williston Basin
This report was prepared at the request of Mr. Tom Moore of Indiana University of Pennsylvania. It presents a concise overview of the Williston Basin’s key aspects including location/extent, tectonic setting, stratigraphy and major oil and gas plays.
The Williston Basin covers a large geographic area stretching west from North Dakota to Montana and north from South Dakota into Saskatchewan and Manitoba provinces of Canada. The boundaries of the basin are defined by the Canadian Shield and the Sioux Uplift to the south and south east and by the Black Hills Uplift, Miles City Arch, Porcupine Dome and Bowdoin Dome to the west and south west. The total extent of the American portion of the basin is upwards of 143,000
Three Archean aged structural provinces under lay the Williston and are responsible for this subsidence. The Superior province underlays to the east while the Churchhill and Wyoming provinces underlay the basin to the west. The Trans-Hudson orogenic suture between this major cratonic basement provinces led to Brockton-Froid fault zone which allowed for structural depression to begin and ultimately the basin being formed. (Anna et. al., 2008)
The first unit above the granitic basement rocks of the Williston basin is the Deadwood Formation. The Deadwood was deposited during the Upper Cambrian Sauk major sequence, which was a major first order transgression. The transgression moved west to east making the Deadwood thicker in the west. It deposited siliciclastic glauconite rich marine sandstones, and shales with very thin carbonate beds throughout.
The Winnipeg Formation overlies the Deadwood Formation and is the lowest formation of Ordovician ages in the Williston. The Winnipeg is divided into two different members. The Black Island member is a quartz-rich sandstone while the Icebox member is mostly shales with few interbedded sandstones. The Black Island has been described as having “excellent reservoir characteristics”. (Nicolas,
This formation consists of fossiliferous limestones and dolomites. The Winnipegosis was deposited in a reef setting and it is a productive hydrocarbon bed in parts of the basin. The Prairie Evaporite overlies the Winnipegosis. The Prairie is a thick stack of salt and anhydrites. Salt dissolution has let to salt collapse and which affects the overlaying units.
Overlying the Prairie Evaporate is the Manitoba Group which is divided into two formations. The lower of which is the Dawson Bay Formation and the higher is the Souris River Formation. The Dawson Bay consists of argillaceous limestones while the Souris River consists of cyclical shale, limestone, anhydrite beds. Both formations are source rocks. The Souris River, however, with its cyclical bedding make it a great structural trap.
Sitting on top of the Souris Formation is the Duperow Formation. The Duperow is much like the Souris accept limestone is more common in the cycles than the shales. It also occasionally has a few sandstone and anhydrite beds.
The Birdbear Formation conformably lays on top of the Duperow. The Birdbear is made up of highly porous and fossiliferous limestone. The Birdbear has a high potential for being a reservoir