The Hibernia Gravity Base Structure is an offshore oil platform located in the Hibernia oilfield southeast of St. John’s, Newfoundland, Canada.
Constructed in the aftermath of the Ocean Ranger accident, the 600-ton gravity base structure (GBS) is situated precisely on the North Atlantic Ocean floor, 80 meters (or 44 fathoms) below the surface, 315 kilometres (or 196 miles) off the coast of St. John’s, Newfoundland, at 46°45′1.57′′N 48°46′58.54′′W.
Read The Scuba News Canada Article on The Ocean Ranger
This GBS can support a topside weighing 39,000 tonnes at towout, rising to 58,000 tonnes when in operation, and is built to withstand iceberg forces. The engineering firms Morrison Hershfield, Mobil Technology, and Doris Development Canada faced many obstacles in their quest to create a structural solution that was both constructible and of sufficient strength. Furthermore, the structural elements and construction techniques employed led to unique design scenarios.
At a location in Bull Arm, Trinity Bay, Newfoundland and Labrador, most of the construction was done. A brand-new neighbourhood with 3,500 worker apartments was built, complete with a gym, cafeteria, and entertainment areas.
While some of the topsides modules were sourced internationally, the majority were built locally. Constructed within a drydock, the 550,000-ton slipform concrete GBS was mated with the topsides at the adjacent deepwater construction site. Kiewit handled the construction management of the gravity base structure as well as the outfitting of machinery within utility shafts.
On May 23, 1997, the assembled GBS was towed out, and on June 5, it was placed in its current location. Four weeks ahead of schedule, on November 17, 1997, the first oil was produced.
As of August 2010, the total oil field production was recorded by the Canada-Newfoundland and Labrador Offshore Petroleum Board at 704 million barrels (111.9 ×106 m3). According to the same update, there are 1,395 million barrels (221.8 × 106 m3) of proven and probable oil reserves.