Construction Begins On New Super-Class Semisubmersible For ODECO

The Ocean Drilling & Exploration Company (ODECO) is adding a new dimension to its drilling fleet with the construction of a heavy-duty, fully winterized, s e l f - p r o p e l l e d semisubmersible with huge deckload capacities, that will be capable of operating in the ice-infested waters of the Bering Sea or anywhere else in the world.

Construction of the rig began recently at Sumitomo Heavy Industries' Oppama Shipyard, located at the mouth of Tokyo Bay.

Delivery is forecast for December 1982. The new semisubmersible will be the 18th semi, and the 41st unit in the ODECO drilling fleet.

Patterned after but slightly smaller than the famed Ocean Ranger, ODECO has endeavored to improve the 'state-of-the-art' of semisubmersibles in all respects.

The Ocean Ranger II, with a fully redundant propulsion system and streamlined lower pontoons, is highly mobile and truly self-propelled. Major improvements in the motion response characteristics have been confirmed in the model basin and are shown to be very favorable, company o f f i c i a l s report. The Ocean Ranger II has been designed to continue in its operating mode in up to 100 knot winds with 4,500 metric tons of variable deckload without reducing deckload or deballasting. All drilling and subsea systems have been critically evaluated against the many rig-years of ODECO experience, and incorporate the most modern rugged equipment available to efficiently drill the deepest of exploratory programs in remote and extremely hostile offshore environments.

This vessel will be a 390-foot long, 226-foot wide, twin-hull design with a 12,450-horsepower propulsion system. The hull consists of two ship-shape parallel pontoons which will enable a calm water transit speed of 12 knots.

The Ocean Ranger II will be a U.S.-flag vessel, fully certified by the Coast Guard and classed AMS + A-l by the American Bureau of Shipping f o r u n r e s t r i c t ed worldwide ocean service. The rig is d e s i g n e d to simultaneously withstand 100-knot winds, a 3- knot current and 110-foot waves.

The helicopter deck will be rated for a Boeing "Chinook" helicopter.

The Ocean Ranger II will accommodate 102 persons in its living quarters, and will drill at the 80-foot draft in water depths up to 1,500 feet. The basic mooring equipment consists of eight windlass units equipped with 4,500 feet of 3.25-inch oil rig quality chain per windlass. Drilling depth capability will be 25,000 feet.

Three revolving cranes service the main deck and peripheral areas. The rig also will have a riser handling system to eliminate the need for cranes to handle the marine riser in extreme wind and sea conditions.

The drilling equipment includes a derrick rated at 1,400,000 pounds static hook load, a fourspeed, 2,400-hp drawworks assembly, a 49.5-inch, 1,200-hp rotary, and two Ceco FB-1600 mud pumps, each driven by a 1,600-hp dc motor. Power will be supplied by six turbocharged 16-cylinder Alco 16-251 (2,950 continuous bhp) main engines with one auxiliary Cummins VTA-1710-GS engine.

The Ocean Ranger II is extensively winterized, and all equipment and systems are designed for service temperatures down to — 35 degrees centigrade. The derrick will be fully enclosed to 115 feet above the heated drill floor, permitting all-weather operations.

Other stories from October 1981 issue

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