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The AAPG/Datapages Combined Publications Database

CSPG Special Publications

Abstract


Future Petroleum Provinces of Canada, Their Geology and Potential — Memoir 1, 1973
Pages 315-386

Beaufort Sea

Monti Lerand

Abstract

The Beaufort Sea Petroleum Province in extreme northwestern Canada includes the continental shelf and slope under the Beaufort Sea as well as the adjacent Arctic Coastal Plain, altogether totalling about 150,000 square miles. Within this area are two basins, Mackenzie and Banks, with comparable stratigraphy but contrasting structure.

Mackenzie Basin, centred on the Mackenzie River Delta, is bounded on the landward side by positive uplifts including the Romanzof Uplift, the Richardson Mountains, the Aklavik Arch and the Coppermine Arch, and seaward by the Canada Basin. Banks Basin, centred on west-central Banks Island and slightly smaller than the Mackenzie Basin, is bounded by the Coppermine Arch, the Prince Albert Homocline, the Cape Crozier Anticline and the Canada Basin. The Mackenzie Basin is centred on a major downwarp complementary to the adjacent Cordillera, whereas Banks Basin has developed across a largely buried, arch-like structure on the relatively stable margin of the craton. The Mackenzie Basin is bounded on the southeastern and southwestern landward margins by major fault-flexure zones comprised of normal and growth faults. In addition, there are large faults under the Mackenzie Delta and numerous diapirs offshore. Because of the tectonic setting of Banks Basin, structures here seem to be of much less magnitude and of a different character with normal basement faults and broad folds dominating.

Both basins are characterized by a major sub-Mesozoic regional unconformity that truncates all Paleozoic strata and locally Cretaceous beds lie on Proterozoic sediments along their margins. In the Mackenzie Basin, Jurassic, Cretaceous and Tertiary clastic sediments attain an estimated thickness of 30,000 feet under the outer part of Mackenzie Delta, of which about half may consist of Tertiary and Upper Cretaceous deltaic sediments. Along the southeastern margin and eastward towards Banks Basin, progressively younger Mesozoic strata lie on progressively older Paleozoic strata. In Banks Basin, the Mesozoic-Cenozoic clastic section is very much thinner under the onshore part than the corresponding section in the Mackenzie Basin. In both basins a thick marine Cretaceous shale succession underlies the Tertiary deltaic sands. Paleogeographic reconstructions suggest that an almost complete Phanerozoic section could occur offshore, assuming that the Beaufort Sea did not originate through rifting and subsequent continental drift in the Jurassic and Cretaceous.

The post-Middle Cambrian stratigraphic succession can be divided into three tectonic sequences based primarily on source area, but with a fairly close correlation with tectonics and lithology: FRANKLINIAN SEQUENCE (Upper Cambrian to Devonian) — northern source, southern facies dominantly carbonate; ELLESMERIAN SEQUENCE (Mississippian to Jurassic) — northern and southern source, largely carbonate in lower part becoming entirely clastic in upper part; and, BROOKIAN SEQUENCE (Cretaceous to Recent) — southern source, entirely clastic. These sequences, defined merely to provide a capsule summary of Phanerozoic stratigraphy and tectonics, can be traced across the breadth of the Arctic.

Potential reservoir units are thick and numerous in the Mackenzie and Banks Basins and can be conveniently grouped into three divisions corresponding roughly to the three sequences: lower and middle Paleozoic carbonates; Upper Devonian to lower Cretaceous sandstones; and, Uppermost Cretaceous-Tertiary deltaic sands and gravels. All of these possess offshore marine shale fades representing very thick potential source rocks.

Both the Mackenzie and Banks Basins possess excellent potential as sources of hydrocarbons from both onshore and offshore areas, from Paleozoic, Mesozoic and Tertiary reservoirs, and from numerous stratigraphic and structural traps. Hydrocarbons already have been discovered in all three reservoir divisions in the Mackenzie Basin after the completion of thirty-seven onshore wells. No hydrocarbons have yet been discovered in Banks Basin but only three onshore wells have been drilled.

The total Beaufort Sea Petroleum Province probably contains possible reserves at least equivalent to all of the conventional recoverable reserves developed to date in all of the Province of Alberta (11 billion barrels proved), and possibly considerably more.


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