Macasty Shale of the Anticosti Basin, Developing a New Ordovician Shale Oil Resource Play in Eastern Canada
Located in the Gulf of St. Lawrence in Quebec, Anticosti Island extends over a length of 220 km with a maximum width of 56 km and covers an area of 7,943 sq-km (3000 sq-mi). Anticosti is a large ESE-WNW oriented structure situated along the Laurentia passive margin of Ordovician carbonates that extends from western Texas to Newfoundland. The geological units forming the island are of Paleozoic age, ranging from Cambrian to the end of the Silurian. Past exploration efforts included the drilling of about 20 wells, of which most of the activity over the past 15 years was focused on conventional (TBR Hydrothermal) targets. This paper will present how an exhaustive review of vintage data, combined with new rock analysis and seismic data, led to a major update of the oil and gas potential for the entire Anticosti sedimentary basin.
The current exploration phase recognizes the potential of the Macasty Shale as a liquid-rich resource play (potential for light oil/condensate production). The Macasty has good to excellent organic richness with an average Total Organic Carbon content of 2.6%. The organic matter/kerogen type of the Macasty is Type II. More porous than the Utica Shale, the mineralogy of the Macasty is similar to the producing Barnett Shale. The Macasty has an average porosity of 6.3%, which compares favourably with other North American shale resource plays. In 1970, ARCO drilled a stratigraphic well at the deepest point of the Island (3,838.2 m), providing a major opportunity to geoscientists to study the petroleum system of the area. The Ordovician shale in the Arco Anticosti #1 well is between 2,399 and 2,487 metres in depth, where it has attained its full thermal maturity for Oil Generation and is in the Late Oil Window to Early Condensate – Wet Gas Window of thermal maturity (Rock-Eval/Tmax data). 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 in Ohio and the Eagle Ford Shale in Texas.
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. For the Macasty Shale only, current estimations established the potential oil initially in-place (OIIP) to be over 40 billion barrels.
AAPG Datapages/Search and Discovery Article #90195 © 2014 Eastern Section Meeting, London, Ontario, Canada, September 27-30, 2014