THE FINAL NORTH AMERICA CONVENTIONAL OIL FRONTIER: THE INTRACRATONIC HUDSON BAY BAIN IN NORTHERN CANADA

The Hudson Bay Basin covers ~820,000 km² and is the largest intracratonic basin in North America. The succession of the Hudson Platform consists mainly of Paleozoic strata, with a maximum preserved thickness of about 2500 m. The Paleozoic succession includes Ordovician to Devonian marine carbonates, reefs and shales with locally thick Devonian evaporites. Paleozoic strata are unconformably overlain by erosional remnants of Jurassic, Cretaceous and Cenozoic non-marine and marine strata. In a first phase of exploration (1973-1985), over 46,000 line-km of seismic reflection data were acquired and 5 offshore exploration wells drilled. Most of the seismic profiles and all of the exploration wells are located in a relatively small area in the central part of Hudson Bay.

Re-evaluation of the available seismic indicates that syn-tectonic sedimentation occurred in Late Ordovician(?), Silurian and Early Devonian with significant depocentre migration with time. New biostratigraphic data, supported by the seismic evidence, suggest 3 major unconformities, with the most important one at the Silurian-Devonian boundary. AFT data suggest that maximum burial occurred in Late Devonian and in agreement with organic matter reflectance data, imply that the Ordovician interval went through the oil window. Various hydrocarbon generation models are tested and from available data, hydrocarbons were generated in the deepest part of the basin with peak oil generation in Late Devonian. Available hydrocarbon system data are synthesized in 5 prospective petroleum plays, including recently recognized porous hydrothermal dolomites and Ordovician, Silurian and Devonian reefs. Type II-S Upper Ordovician oil shales are recognized at several locations in the basin with TOC values up to 35% and thickness up to 15 metres. Lower Silurian shales may also have local potential (TOC values up to 2%). Offshore high-resolution bathymetric surveys led to the recognition of circular sea-floor depressions similar to fluid-escape pockmarks and interpretations of RADARSAT images suggest possible oil slicks at sea surface. Some direct hydrocarbon indicators are interpreted from the vintage seismic information. Taken together, these new hydrocarbon systems data suggest that large areas of the Hudson Platform are prospective for oil accumulations.