ABSTRACT

From the top of the Precambrian to the top of the Winnipeg formation, faunal studies indicate that Upper Cambrian and late Middle to Upper Ordovician assemblages are present. At the present time only 47 wells penetrate the Precambrian (1 well/2600 square miles). With further drilling it is logical to assume that older Ordovician-Cambrian rocks will eventually be dated in deeper parts of the basin. In the subsurface stratigraphic section, sandstones are predominant ; shales, limestones and dolomites are also present.

Structure contours on top of the Precambrian, Cambrian and Winnipeg show little local structure; isopachs show a suggestion of a Williston Basin in Cambrian time which shifted eastward and became defined during the Ordovician.

No free oil has been recovered on drillstem tests in these rocks to date, and there has been no verified report of appreciable oil-staining in cores or samples. The sandstones usually show porosity and prolific recoveries of salt water suggest favorable permeabilities 1.3.7. In the past two years comparable basal sandstones have proven to be important reservoirs in northern Alberta. A stratigraphic cross-section shows the relationships and similarities between the Alberta basal sands and the Winnipeg and Older Rocks of Saskatchewan.

Although encouragement has been limited, the Winnipeg and Older Rocks represent some 24,000 cubic miles of relatively unexplored sediment in the north Williston Basin and adjoining areas.