Abstract

In the region north of 64° latitude between the Mackenzie River and the Canadian Shield, a wedge of Paleozoic sediments decreases in thickness from a maximum of 10,000 feet at Point Separation in the northwest to zero along the edge of the Shield. These sediments were deposited on a shelf area subject to epeirogenic movements with minor warping. Unconformities are present in the Middle Cambrian, Middle Ordovician, Middle Silurian, Lower Devonian, top of the Middle Devonian and at the top of the Upper Devonian. Sands, shales and evaporitic sediments of the Early and Middle Cambrian were followed by thick marine platform carbonates deposited intermittently from late Middle Cambrian to early Middle Devonian time. A clastic marine succession deposited during late Middle and Late Devonian was interrupted in some areas by the Kee Scarp platform and reef at the end of the Middle Devonian. No beds with ages between Late Devonian and Early Cretaceous are known in the area. Eastern bevelling of the lower Paleozoic sediments occurred in this lacuna. For most of the Cretaceous period, a north-south seaway existed and marine shales with basal sandstones were deposited. During the Laramide Orogeny, the area became land and the Franklin Mountains were formed. Erosion removed much of the Cretaceous rock and subsequent deposition was limited to continental Tertiary beds in a small basin.

There are 102,250 cu. miles and 12,000 cu. miles respectively of Paleozoic and Cretaceous strata. Of this bulk 49,000 cu. miles of marine shales and carbonates are potential source beds, 37,800 cu. miles of shallow water, marine dolomites are of more dubious value as source beds and 12,400 cu. miles of dolomite, limestone and lesser sandstone are potential reservoir beds.

Hydrocarbon shows at the surface and in wells occur in the Cretaceous and Middle and Upper Devonian beds. Norman Wells, with 500 MM bbls. of STO in place in a Kee Scarp reef, is the only oil field.

The area is relatively unexplored. Seventy-six exploratory wells have been drilled but most of these are close to the Mackenzie River.

Because of climatic and geographical factors this is a region in which only very large fields are likely to be economic under present conditions.

Hydrocarbon potential exists in the area, the northeast-trending trough in the Northern Anderson Plains where thick Paleozoic sediments are preserved is the most promising. Cretaceous beds preserved in the downwarp southwest of Great Bear Lake have possibilities for production from the basal sand.