Oil and gas exploration to date in the Mackenzie Delta/Beaufort Sea Region of Arctic Canada has included 174 exploratory wells and close to 160,000 km of reflection seismic data. The results of this exploration effort are very encouraging. Approximately 1.4 billion barrels of oil and 12.3 Tcf of natural gas have been found in 50 separate significant discoveries, for an overall success rate of 29 per cent. Development of the largest discoveries is within sight now, likely starting with the development of the large onshore gas discoveries at the Taglu, Parsons Lake and Niglintgak fields. companies examining world-wide exploration opportunities will find the Mackenzie Delta/Beaufort Sea region of immediate interest for a number of reasons. Analysis indicates that large undiscovered potential resources of oil and gas remain to be found, totalling 5.7 billion barrels of oil and 55 Tcf of gas. Second, proven custom drilling systems have been developed to handle the ice and storm conditions of the Arctic environment. Third, for the first time in close to 20 years, issuance of new exploration rights is underway. Clearly, the Mackenzie Delta/Beaufort Sea has all the ingredients to develop as an important oil and gas province in the early 1990s.
The Mackenzie Delta/Beaufort Sea exploration are covers an area of over 140,000 km2 in the northwestern corner of Arctic Canada, extending from'the southern edge of the modern delta of the Mackenzie River to the summer limit of the polar pack ice. (Figure 1).
From a geological perspective, the sedimentary section of interest to petroleum exploration, as summarized by Dixon et al(1), differs markedly from onshore to offshore (Figures 2 and 3). In the onshore areas underlying the TUktoyaktuk Peninsula, southern Richards Island and the Yukon Coastal Plain, reservoirs occur chiefly in Lower Cretaceous sandstones, with older Jurassic sandstones and Paleozoic carbonates of lesser significance.
In northern Richards Island and in the offshore, sequences of Cenozoic and Mesozoic sandstones and shale were deposited, first in prograding sandstone and shale wedges, and later in thick deltaic sequences. In all, nine major depositional sequences have been recognized, including five deltaic packages. Incursions of the sea between the deltaic cycles resulted in deposition of intervening marine shales. Reservoirs are developed in the deltaic sandstones themselves, in the shelf sands adjacent and seaward of the deltas, and in mounded deposits of deeper water clastics deposited in submarine fans north of the paleoshelf edge. The thickness of the Mesozoic-Cenozoic sedimentary section exceeds 11 km in the depocentre beneath the central Beaufort Shelf.
A variety of structural styles results in the creation of prospective closures for hydrocarbon entrapment. On the Tuk peninsula, southern Richards Island, and the adjacent shallow offshore, down-to-the-basin faulting and basement faulting have created fault-bounded closures involving Mesozoic sandstones and Paleozoic carbonates. On Richards Island and the central Beaufort Shelf, large scale, sedimentary listric faults and shale-cored diapiric structures have developed as a result of basin subsidence and rapid deposition of thick, under-compacted clastics during the Cenozoic. In the west Beaufort, elongated, high-relief anticlinal closures are prevalent, created by compressional forces directed from the southwest.
