Petroleum exploration model for the Queen Charlotte Basin area, offshore British Columbia

Abstract

A potential oil-bearing region lies on the west coast of Canada, in the Queen Charlotte Basin area. Upper Triassic – Lower Jurassic source and Cretaceous reservoir rocks are capped by thick Tertiary volcanic and sedimentary strata. The traps are large block structures, and oil generation and migration took place principally in the Tertiary.Previous hypotheses of Queen Charlotte Basin evolution assumed high regional Tertiary heat flow and large tectonic extension; older rocks would have been overheated, and their oil destroyed. New data largely nullify such an interpretation. Miocene positive thermal anomalies were caused by magmatism, hence were local, and Mesozoic rocks may have retained their petroleum prospects. Regional structural style of the area has been dominated by repeated movements of fault-bounded crustal blocks since the Late Jurassic, and the structure of the Cenozoic basin was inherited largely from this older template.The new interpretation of the geologic evolution of the region permits a fresh assessment of its petroleum potential: Cretaceous strata beneath Queen Charlotte Sound are a prime exploration target. Caution is recommended when quantitative basin-formation models are applied to oil exploration; the best exploration model is one that incorporates the maximum geological and geophysical data.