The Neogene (formed 24-1.8 million years ago) portion of the Queen Charlotte Basin (Skonun Formation) is expected to contain 80% of region’s total petroleum resource volume and nine of the ten largest fields. Geographically speaking, the most prospective areas are the southern Hecate Strait, followed by the Queen Charlotte Sound, eastern Graham Island, northern Hecate Strait and the Dixon Entrance. The high potential for the southern Hecate Strait is based on abundant Neogene reservoir rocks, numerous large structural features and the underlying presence of Neogene and Jurassic source rocks. Outside the basin margins, western Graham Island and adjacent shelf areas have some potential targets, but very little petroleum potential is expected overall in the onshore/inter-island areas of the southern Queen Charlotte Islands and the adjacent Pacific continental shelf.

The Neogene Targets are divided into:

Miocene Oil and Gas Play – Occurs basinwide as prospects include Skonun sandstones and conglomerates with structural and stratigraphic traps. Structures include tilted fault blocks, fault-related rollovers, drag features and drape anticlines. It is important to note that stratigraphic traps are associated with intra-Tertiary unconformaties and updip pinchouts within half-grabens and against fault scarps. Tertiary plays include areas/structures where reservoir strata are in direct contact with Mesozoic rocks, enabling hydrocarbon charging from a Kunga-Maude source. The main prospect level risks are maturation of source rocks and inadequacy of seals.

Pliocene Oil and Gas Play – The area is restricted to the northern half of the basin, with Skonun sandstones and conglomerates constituting the main targets. It differs from Miocene targets based on structural style and trap development. Pliocene structures include large amplitude folds and faulted anticlines (flower structure) (Rohr and Dietrich, 1992). Pliocene prospects are generally larger in area and involve thicker reservoir sections than Miocene targets. Many prospects are where reservoir strata are in direct contact with Mesozoic sections, which can include Kunga-Maude source rocks. Main exploration risks are the timing of source rock maturation (prior to trap development) and inadequacy of seals. Many prospects are highly faulted making leakage possible along with the high permeability of sandstone units.

Other Targets:

Cretaceous Oil and Gas Play – Traps involve Cretaceous sandstones, mostly within basal units of the Queen Charlotte Group, in fault block or anticlinal structures. Onshore areas where reservoir strata directly overlie Kunga-Maude source rocks have been mapped (Thompson et al., 1991), and it is likely that this stratigraphic relationship also occurs in the subsurface. The most prospective area is a southeast trending fairway from central Graham Island to southwestern Queen Charlotte Sound, where the main reservoir facies was deposited. The play is characterized by single reservoir zones and small structures. The major prospect level risk is maturation conditions of source rocks, coupled with the possible absence of reservoir facies (this is difficult to map seismically in some areas (e.g. Graham Island) due to the overlying thick Masset volcanics). In offshore regions Upper Triassic and Lower Jurassic source strata may have been eroded due to episodic Late Jurassic through Tertiary block faulting.

Some credit from above text to Petroleum resource potential of the Queen Charlotte Basin and environs, west coast Canada by Dietrich, J. R., 1995.

Geological Basins

Oil and Gas Formation

Stratigraphy

Comparison to Other Basins