Abstract: Stratigraphic Correlation and Petroleum Geology of the Central Maritimes Basin, Eastern Canada

Trent A. Rehill

The Maritimes basin of Atlantic Canada covers an estimated area of 150 000 sq km; however, with 67% of the basin's area lying beneath the Gulf of St. Lawrence, relatively little is known about regional stratigraphy, tectono-stratigraphic history and hydrocarbon potential. The presence of oil seeps in coeval onshore strata, sourced from the Early Carboniferous Horton Group, led to the drilling of twenty exploration wells in the Central Maritimes basin. Most of the wells had gas shows, but all wells, except one gas discovery, were classified dry and abandoned.

The discovery and subsequent mapping of a kilometre-thick Upper Carboniferous coal-bearing package, beneath much of the Gulf of St. Lawrence, has provoked a renewed resource evaluation. The depositional setting for the majority of the offshore strata was thought to be fluviolacustrine, but the recognition of agglutinated foraminifera in the chip samples indicates that sections of the Coal Measures were deposited under marine influence. This enhances the possibility of hydrocarbons sourced from type II and III kerogens originating from the Westphalian section.

Correlations and interpretations of Upper Carboniferous strata in 13 exploration wells drilled in the Gulf of St. Lawrence are presented. Correlations are based on a Westphalian C/ Westphalian B datum, defined by digital well logs and supported by micropaleontological, seismic and representative onshore section data. The detailed stratigraphic correlation suggests that the typical lithologic character of the coal-bearing section changes from being shale-dominated on the flank to sand-dominated towards the depocentre. A depositional model explaining these results is presented.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994