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ABSTRACT: Coal-Bed Methane Potential of Vancouver Island Coalfields

Candace Kenyon, D. Keith Murray

Commercially attractive quantities of coal-bed methane gas on Vancouver Island, British Columbia, are indicated from recent studies by the provincial Geological Survey Branch and independent consultants. Coal mining activity began in 1847, which provides large amounts of data concerning drilling, mining, quality, and reserves. Presence of methane is corroborated by documented accounts of coal mine disasters. Coal measures are part of the Upper Cretaceous Nanaimo Group, which covers approximately 800 mi2, and are divided into two subbasins. Cretaceous strata rest unconformably on predominantly volcanic basement rocks and are controlled in their distribution by paleotopography. Maximum aggregate coal thickness in the Nanairno subbasin is 30-60 ft; in the Comox su basin, greater than 40 ft. Post-Cretaceous faulting strongly influences the area. Tertiary intrusives have effected coal quality to some extent. Sampling of coal seams is currently underway to determine levels of thermal maturation. Vitrinite reflectance ranges from 0.59 to 3.21 (Ro max). The majority of coals are of high-volatile B to A bituminous rank, with local variations near Tertiary intrusions. Test-well desorption data have indicated that coals can contain as much as 380 ft3 of methane per ton of coal. Gas samples taken were pipeline quality, about 95% methane, 4.5% heavier hydrocarbons, and 0.5% carbon dioxide. A conservative estimate of in-place methane resource is 800 bcf. Plans are currently underway to construct a natural gas pipeline from the mainland o service Vancouver Island. This would provide the necessary infrastructure to make extraction of the methane resource economic.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990