Anticosti – The Next Albion-Scipio?
Hydro-Québec Pétrole et Gaz, Sainte-Foy, QU
Anticosti is a vast island oriented ESE-WNW, located in the Gulf of St. Lawrence that is essentially composed of rocks of the Cambrian-Silurian carbonate platform.
Oil & gas exploration began on the island in the 1960s and 1970s. A total of 8 wells were drilled on poorly-defined targets or without seismic data. A later period of intense exploration from 1996 to 2001 resulted in the drilling of 5 new wells that have confirmed the hydrocarbon potential of the Anticosti basin.
Hydrothermal dolomites of the Trenton-Black River formation represent one of the targets of Hydro-Québec's exploration program. This target is comparable to the world-class Albion-Scipio oil field, located in the southeastern Michigan basin. The Anticosti platform is the same age (Ordovician) and represents the same depositional setting as this Albion-Scipio. One of the detectable structural expressions of this type of trap is the presence of a minor sag at the top of the Trenton. Trenton dolomitization can also be detected by either the loss or the chaotic nature of the seismic signal. Within the Trenton, this play concept has been established by the Chaloupe well (1999) that penetrated 70 m of porosity (fractures) and good permeability, as evidenced by a loss of 270 m3 of drilling mud while drilling through the Trenton Formation.
Many "sag" targets have been identified on seismic (325 km) and magneto-telluric data acquired by HQ in 2003, and are further supported by seismic inversion and AVO analysis. These are characterized by sags at the top of the Trenton platform associated with seismic signal losses within the Trenton-Black River corresponding to a low acoustic impedance (porosity), zones of conductivity, and class-III AVO anomalies.
AAPG Search and Discovery Article #90031©2004 AAPG Eastern Section Meeting, Columbus, Ohio, October 3-5, 2004