Chevron Canada used the Stena Carron to carry out a 106-day drilling program northeast of St. John's. ((CBC))

A drilling program at the deepest offshore site in Canada has concluded, three months after it began under a cloud of controversy.

Chevron Canada started a test drill in the Orphan Basin in May, less than three weeks after the Deepwater Horizon explosion in the Gulf of Mexico triggered international alarm over offshore drilling.

Chevron told CBC News that its work on the Lona O-55 prospect well wrapped up last Thursday after 106 days, without major incident.

Chevron had leased the drill ship Stena Carron for the drill in the largely unexplored area, which is about 250 kilometres north of the Hibernia oil field. Chevron reported that the ship had developed small cracks well above the waterline, but that they did not pose a safety risk.

The Lona O-55 well is about 2.5 kilometres under the surface of the ocean, and about a kilometre deeper than the site of the enormous Gulf of Mexico spill.

Chevron's plans were heavily criticized by environmentalists and some scientists, and prompted regulators to tighten the rules of the drill.

Chevron is now reviewing the results of the drilling, to help determine whether there is a commercially viable reserve of oil. The company must report its results to the Canada-Newfoundland and Labrador Offshore Petroleum Board by 2012. 

Three oil fields off eastern Newfoundland, all in the Jeanne d'Arc Basin, are currently in production. Planning work has started on a fourth field, Hebron. Many in Newfoundland and Labrador's offshore oil business believe the Orphan Basin represents a key frontier in the industry.