ABSTRACT

An indigenous energy supply for Vancouver Island has been the object of intensive exploration for the past 130 years. More than 1,000 wells have tested the Upper Cretaceous Nanaimo Group of eastern Vancouver Island, resulting in the discovery of numerous shows of natural gas. Most of the gas shows are concentrated in the Comox and Trent River formations, in the central portion of the Comox sub-basin, south of the city of Courtenay.

Natural gas in the Comox sub-basin has been historically regarded as an unwanted by-product of coal mines, and as a severe hazard to exploratory drilling.

Despite a history of blowouts, explosions and fires, production of gas commenced in the 1940's, when farmers near the village of Royston constructed crude wellheads and used gas for light and heat.

In addition to the gas-charged coals of the Comox Formation, several conventional clastic reservoirs contain natural gas in the Comox sub-basin. Trent River Formation reservoirs include fractured marine shales of the Royston Member and submarine-channel conglomerates of the Table Member. Comox Formation reservoirs include shoreface sandstones of the Dunsmuir Member, point-bar sandstones of the Cumberland Member and alluvial-fan conglomerates the Benson Member.

Structural traps probably account for most of the gas shows near Royston village, where long, narrow anticlines overlie northeast dipping listric normal faults. These faults probably flatten within the Comox Formation, thus confining fold closure to the overlying Trent River Formation. Near the outcrop of the reservoirs, groundwater recharge provides a barrier to updip gas migration.

In the course of this study, we have developed a detailed lithostratigraphic framework for the Comox and Trent River formations, which will assist further exploration for energy resources in the Comox sub-basin.

End_of_Record - Last_Page 159-------