Chevron USA Inc. as operator, with Mobil as a partner, decided to drill an offshore well near Prudhoe Bay, Alaska using a grounded ice island as the drilling structure.
The island was designed and built by Ice Construction and Engineering (I.C.E.), a joint venture between CATCO (a division of Crowley Marine) and Ausenco. The construction and monitoring were conducted by I.C.E. under a turnkey, fixed price contract valued at over $4.5 million US, the first time this type of contractual relationship had been attempted for an ice island project.
The island was located in 6 m (21 ft) of water and was built by spraying sea water using 20 m3/min (5000 gpm), 1400 kPa (200 psi) pressure pumps equipped with nozzles and swivels. An island with a total thickness of 14 m (46 ft) and a diameter of 270 m (890 ft) was successfully completed. Ice loading was the dominant design force which determined the island size.
The design included a mechanical cooling system at the well conductor to protect against thawing of the ice by heat generated by the drilling activity.
Construction of the island required 40 days. Drilling on the completed island began February 20 1989 and the rig was released on April 71989, after drilling to a depth of 3350 m.