Ordovician-Aged Liquid-Rich Shales and Hydrothermal Dolomites Plays: An Updated Review of the Eastern Canada Anticosti Basin Hydrocarbon Potential

Marcil, Jean-Sebastien; Lavoie, Jeremie; Mechti, Nabila; Dorrins, Peter K.; Marcotte, Bertrand; Lavoie, Jean-Yves

Located in the Gulf of St. Lawrence in Quebec, Anticosti Island extends over a length of 220 km and a maximum width of 56 km and covers an area of 7,943 sq-km (3,103 sq-mi). Anticosti is a large ESE-WNW oriented rhombohedra shaped structure situated along the Laurentia passive margin that extends from western Texas to Newfoundland. The geological units are of Paleozoic age, ranging from the Cambrian to the end of Silurian.

In 1970, ARCO drilled a stratigraphic well at the deepest point of the Island (3,838.2 m). It leads to the clear identification of a major source-rock, the middle Ordovician-aged Macasty Shale. Hydrocarbon expulsion from Macasty Shale reach 75 billion bbl over the island with 2/3 generated in the "deep fairway". A second exploration phase targeted dolomitized carbonates located on the upper side of the Jupiter Fault zone. Shell Canada wells, drilled in the 90s, demonstrate the occurrence of HTD reservoir in Romaine and Mingan carbonates formation. The current exploration phase recognized the potential of the Macasty Shale as a liquid-rich resource play (potential for light oil/condensate production). Technical evaluation indicates that the level of thermal maturity observed thus far in the Macasty in the Deep Macasty Fairway compares favourably with published findings for the oil-rich Utica/Point Pleasant Shale and the Eagle Ford.

Resources assessment studies (P50 - Best Estimate) recently published by different groups corroborate the analytical results and the interpretation of the authors concerning the high hydrocarbon potential of the Anticosti Basin. In October 2009, a multidisciplinary team attached to the Geological Survey of Canada published a Petroleum Resource Assessment for the Paleozoic Succession of the St. Lawrence Platform. This report estimate the Resource in-place in the hydrothermally dolomitize carbonate at 957 million boe, mainly located in the Anticosti Basin. In July 2011, Corridor Resources published a Resource assessment report of the Macasty Shale. This report established the Total Resource Potential over an area of 1,550,000 acres at 33.9 billion boe, mainly located in the Shallow Macasty Zone. In September 2011, Junex inc. published a Resource assessment report of the Macasty Shale situated in the Deep Fairway. This report established the Total Resource Potential over an area of 233,275 acres at 12.2 billion barrels.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013