Abstract

The Beaufort-Mackenzie Basin has been a depocentre since early Jurassic time, when extensional tectonics initiated the structural depression. Normal faults involving Paleozoic, Mesozoic and lowermost Tertiary sediments occur on the southeast flank of the basin in the vicinity of Tuktoyaktuk Peninsula. Here, Lower Cretaceous sands are the prime target for petroleum exploration. Flanking the southwest margin of the basin are the British and Barn Mountains and the northern Richardson Mountains, derived from Columbian and Laramide orogenic events. Fluvial-deltaic sediments of Mesozoic and Paleogene age, provided from those highlands, are involved in compressional and extensional structures, and are the focus of petroleum exploration activity in the Mackenzie Delta and adjacent offshore areas.

Hydrocarbons discovered in the Beaufort-Mackenzie Basin have been predominantly gas, but oil has been recovered from both Tertiary and Cretaceous sediments. On the basis of oil — source rock correlation studies, two oil families have been suggested, one Cretaceous-generated, the other Tertiary. The Beaufort Basin has been classified into three regional geochemical provinces which coincide with the geologic provinces. The West Coastal Plan area is a dry-gas province, as the sedimentary section has been subjected to high heat flow. The Tertiary of the northern part of the Mackenzie Delta and adjacent offshore area is likely to be gas- and gas/condensate-prone with some oil, based on the predominance of terrestrial organic matter. However, some oil-source zones have been identified within the Tertiary. Low heat flow in the region results in the present-day depth to maturation being as much as 4 300 m. The Tuktoyaktuk Peninsula region is considered an oil-prone province because of the occurrence of organic-rich, bituminous zones in the Cretaceous.

Currently accepted source-rock concepts indicate that both Cretaceous and Tertiary sediments rate as generally fair to good sources in the Beaufort. Examination of known discoveries strongly suggests that there has been significant hydrocarbon migration.