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Abstract: Exploring for Hydrocarbons in the Cambro-Ordovician of Newfoundland and Quebec

COOPER, MARK
PanCanadian Petroleum, Calgary, Alberta, Canada

The Humber zone is the most external zone of the Appalachian orogen in western Newfoundland and Quebec. It records multiphase deformation of the Cambro-Ordovician passive margin and of the Ordovician to Devonian foreland basins by the Taconian, Salinian, and Acadian orogenic events.

Recent exploration drilling has provided new evidence for structural and stratigraphic models of western Newfoundland. The first well, Port au Port 1, proved the hypothesis that an earlier extensional fault had been inverted during Acadian compression. The well drilled a small anticline caused by a footwall shortcut fault from this inverted fault. The well tested oil from the Ordovician platform carbonates that were sourced from the basinal equivalent shales now within the Taconic allochthon. The second well, Long Point M-16 was drilled to test a triangle zone. The well demonstrates that the triangle zone is created by a stack of imbricate thrusts of the Taconian allochthon and compressional basement-involved faults that uplifted the Cambro-Ordovician carbonate platform. The structural model developed in the Port au Port area has been extended throughout the Humber zone in western Newfoundland and Quebec. Changes in structural style illustrated by regional cross sections suggest that prospective trap geometries develop only in the southern and central parts of western Newfoundland.

The reservoir model invokes exposure and karsting of the footwalls of extensional faults developed during Middle Ordovician collapse of the carbonate platform. The structurally high fault footwalls became the focii for dolomitizing and mineralizing fluids that utilized major faults as fluid conduits during the Devonian. These fluids deposited sulfides and created zebra and sparry dolomite and some sucrosic hydrothermal dolomites.

Multimillion-barrel oil-pool potential remains in these areas that to date have been only sparsely explored; exploration continues in the search for these pools. 

AAPG Search and Discovery Article #[email protected] AAPG Distinguished Lectures