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Drilling (Mobile Drilling Units)

First & Second Generation Semi Submersible Drilling Rigs

Deepwater drilling dictates that operations be carried out from a floating vessel. Drillships heave, pitch and yaw with each passing wave, and the industry needed more stable drilling platforms. A semi submersible obtains its buoyancy from ballasted, watertight, pontoons located below the ocean surface and wave action. The operating deck is located above the tops of the passing waves. Structural columns connect the pontoons and operating deck. When the rig moves its location, the pontoons are de-ballasted so that the rig can float on the ocean surface.

In 1961, Shell Oil successfully converted an existing submersible rig into the first semi submersible drilling unit for operation in the Gulf of Mexico. The industry quickly accepted the semi concept and the fleet increased rapidly to 30 units by 1972. At present, there are about 160 semi submersibles in service. First generation semis are generally limited to water depths of less than 600 feet, and second generation are usually intended for water depths up to 1000 feet. Most of these early semis have been retired.

Year Rig Name Features Designer No. Built
1961 Bluewater I First semi submersible, converted from existing 4 column submersible Shell Oil 1
1963 Ocean Driller First new build; 3 col. Vee shaped structure ODECO 2
1965 Sedco 135 3 footed columns; arranged in a triangular shape Friede & Goldman 12
1969 Pentagone 81 5 footed columns arranged in pentagon shape Neptune 11
1971 Ocean Prospector First self-propelled, 12 columns; 2 main tubular hulls; Ocean Victory class ODECO 11
1973 Sedco 700 Twin pontoon hulls; 8 columns
thruster propulsion
Earl & Wright 15
1973 Western Pacesetter Twin pontoon hulls; 6 columns
design licensed to all
Friede & Goldman 39
1974 Deap Sea Driller Twin pontoon hulls, 8 columns (known as Aker H-3 Design) Aker Mek Verksted 29

Recognizing the pioneering efforts of the following people and companies who contributed to the development of this technology:

Bruce Collipp, Jerome Goldman, Alden J. "Doc" Laborde,
Bill Martinovich, Fred Olsen, Andre Rey-Grange,
Aker Mek Verksted,
Earl & Wright, a Sedco Company (Transocean Inc.),
Friede & Goldman (Friede Goldman Halter),
Neptune (Transocean Inc.),
ODECO (Diamond Offshore Drilling), Shell


2011 Call for Nominations
2011 Industry Pioneer Nomination Form 
2011 Technology Pioneer Nomination Form

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