Hibernia Gravity Base Structure

The Hibernia Offshore Platform is an oil-drilling, production and storage facility located in 80 metres of water, 315 kilometres southeast of St. John’s on the Grand Banks of Newfoundland. The platform has a production capacity of 150,000 barrels per day with total recoverable oil reserves estimated to be 615 million barrels.

Kiewit played a crucial role in the construction of this $5.3 billion mega-project, performing the mechanical outfitting (MOF) of utility shafts and, as part of a Kiewit-led partnership, providing construction management services for the gravity base structure (GBS).

The platform has a concrete pedestal, modular topside facilities and a crude oil loading system. The pedestal, or GBS, is a post-tensioned, reinforced concrete structure, consisting of a base raft, roof and a star-shaped caisson 106 metres wide by 85 metres high. The caisson contains four 17-metre-diameter shafts (two drill shafts, one riser shaft and one utility shaft), which extend 26 metres above the roof structure and support the topside modules. The GBS storage capacity is 1.3 million barrels of crude, and it is designed to withstand the impact of icebergs. Construction required 165,000 cubic metres of concrete and 100,000 tonnes of reinforcing steel. The crude oil loading and transport systems include oil lines from the platform to two offshore tanker loading stations.

The MOF contract required fabrication, assembly, ocean shipment and installation of nine modules in the GBS shafts. The cylindrical modules varied from 10 to 12 metres high and weighed 250 to 420 tonnes. Modules included piping, equipment, HVAC, electrical instrumentation and other support systems for storage, pumping and fire suppression.