--> ABSTRACT: Evolution and Hydrocarbon Potential of Queen Charlotte Basin, Canada, by J. Ross McWhae; #91030 (2010)

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Evolution and Hydrocarbon Potential of Queen Charlotte Basin, Canada

J. Ross McWhae

The structural and depositional history of the Queen Charlotte basin, a complex Tertiary rift basin with extensive coeval volcanics, involves regional geology from the Pacific plate west of the Queen Charlotte transform fault to east of the Alexander-Wrangellia terrane, based on geophysics (including newly released seismic lines), revised stratigraphy, and well data. Eight offshore wells were drilled prior to 1970 and nine shallow onshore wells were drilled in or beyond the northwestern margin of the basin. The wells provide data on porosity, seal, maturation (geothermal and vitrinite reflectance data), and oil stains in sidewall cores of the Sockeye B-10 well in the Skonun formation, here 4,500 m thick. The Skonun ranges from early Miocene (17 Ma) to latest Pliocene (2 M ) in age and the lower part is regarded as the primary hydrocarbon objective, especially in the more southern part of the basin where more favorable depositional porosities occur in paralic and shelf sandstones. Higher-than-average geothermal temperatures, locally in the southwest corner of the basin related to oblique subduction of very young oceanic crust, may reach the hydrocarbon-generating threshold in the lower Skonun marine shales.

The middle Cretaceous Haida subarkose appears to be a secondary reservoir--the thickest and cleanest of the post-collision volcaniclastics. Highly organic Lower Jurassic shales provide a second, probably oil-prone, source.

Several right-lateral faults run along and adjacent to the basin. They tend to converge toward the northwest end, causing folded structures. Exotic terrane slivers, emplaced along these faults in Mesozoic and Cenozoic time, developed tensional troughs at the southern trailing edge, such as in the prospective Neogene Queen Charlotte Sound.

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