Offshore Beaufort-Mackenzie Basin and Amauligak Oil Discovery

Robert J. Sharpe, Gerry J. Gurba, Bernhard H. G. Sleumer

A variety of complex structural styles and depositional environments host hydrocarbon accumulations in the offshore Beaufort-Mackenzie basin. At present, only one of these, the Amauligak field, appears large enough to serve as a lead project to spur commercial development of the area.

All offshore Beaufort discoveries to date occur in sandstones ranging from Paleocene to Oligocene in age. All occur in deltaic or delta-derived sediments ranging from delta-plain deposits to submarine fan/turbidites.

In the western Beaufort, sediments are deformed into a series of linear diapiric features interpreted to be thrusted anticlines, possibly associated with strike-slip faulting. Similarly, the Tarsiut area immediately to the east is dominated by diapiric anticlines crosscut by a major east-west-trending fault, also possibly a strike-slip fault.

In contrast, the central and eastern portions of the offshore Beaufort, where Amauligak is located, are characterized by growth faulting in the sand-rich Oligocene depocenter. To the north, in a basinward direction, unfaulted diapiric anticlines are draped by submarine fans. These structures may in part be related to the gravitational faults to the south.

The Amauligak field is located in the growth fault province. It is contained within a large, south-dipping, simple fault-bounded structure in which hydrocarbons are trapped against the north-bounding listric fault. Sediments penetrated at Amauligak include more than 1,500 m of interbedded Oligocene sandstones and shales, the sandstones representing primarily delta-front deposits. Distinctive shale markers are the probable result of the switching of major deltaic lobes.

Reservoir sandstones at Amauligak contain up to 125 m of net oil pay and 50 m of net gas pay in over 30 separate sand units. Porosity averages 0.19 and permeability ranges from 50 to 600 md. Possible oil in place at Amauligak is estimated to be 2.2 billion bbl.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.