Construction of the Hibernia Gravity Base Structure (GBS) and assembly of the Topsides and associated Topsides-mounted structures occurred in Bull Arm, Trinity Bay, Newfoundland and Labrador. Prior to the Hibernia project, Bull Arm was a "greenfield" site with little local supporting infrastructure.
Located less than 150 km from St. John's, the site is ideally situated to accommodate construction of a gravity base platform. Steep hills provided excellent protection for drydock construction while a near-shore deepwater construction site accommodated final GBS construction and GBS-to-Topsides mating.
In October of 1990, using owner capital and grants funded by the federal and provincial governments, a world class drydock and fabrication facility were built. Some features of the site include:
- the largest rebar shop in North America
- onshore concrete batch plant
- 150 metre long by 50 metre high assembly hall
- blast/paint shop
- pipe shop
- associated cutting and carpentry shops
permanent office building.
Bull ArmIn this photo, the completed Topsides sits on the assembly pier at Bull Arm. During peak construction in 1995, roughly 5,800 people were employed at the site. To house, feed and entertain the workers, a self-contained community was created that included:
- living accommodations to house a work force of 3,500 people
- a cafeteria large enough to seat 1,000 individuals and serve 2,000 meals per hour
- recreational facilities including a gymnasium, weight room and swimming pool
- a fully-equipped emergency response centre which housed a medical clinic and fire department.
TopsidesOne Topsides supermodule, the Wellhead Module, was fabricated at Bull Arm along with four Topsides-mounted structures: the flareboom, helideck, and main and auxiliary lifeboat stations. The remaining components were fabricated in construction sites located around the world and transported to Newfoundland & Labrador for final assembly and hook-up at Bull Arm.
On February 27, 1997, the 37,000-tonne Topsides was lifted from its assembly pier by two giant barges, then floated to the middle of Bull Arm and mated with the 550,000 tonne Gravity Base Structure (GBS) to form one integrated unit.
Tow-out of the platform began on May 23, 1997. It was installed at its permanent location on the Grand Banks on June 5, to within one metre of the target contact point on the ocean floor. The first well began drilling on July 28, 19 days ahead of schedule, and First Oil was achieved on November 17, 1997, a full four weeks ahead of schedule.
At the end of construction, ownership of the site was transferred to the provincial government.
Gravity Base Structure (GBS)
The Topsides is supported by a massive concete pedestal called the Gravity Base Structure (GBS) which was constructed in Bull Arm, Newfoundland and Labrador. The GBS, which sits on the ocean floor, is 111 meters high and has storage capacity for 1.3 million barrels of crude oil in its 85 meter high caisson. Construction on the GBS began in 1991 and was completed in 1996.The GBS was constructed using high strength concrete reinforced with steel rods (rebar). Slipforming, a continuous process of placing rebar and pouring concrete, was utilized during construction of the GBS.