Four of Crowley Maritime Corp.’s ocean class tugboats, Ocean Wind, Ocean Wave, Ocean Sky and Ocean Sun, completed the successful delivery of the offshore oil production and drilling platform, Olympus, to the U.S. Gulf of Mexico. The project was significant because it provided the first opportunity for all four of the company's high-bollard-pull, ocean class tugboats to work together on any single job. The rig, owned by Royal Dutch Shell, is also considered the largest tension-leg platform ever to be developed for the U.S. Gulf of Mexico.
All four Crowley ocean class tugs were required, in both nearshore and offshore waters, to relocate the 120,000-ton, 406-ft. tall tension-leg platform from Ingleside, Texas, 425 miles to its deepwater location in the U.S. Gulf of Mexico. Once in the final position, there was additional support work required to ensure the platform would remain storm-safe during and after installation.
The project was broken into three phases, the nearshore, offshore and positioning phases. During the nearshore phase, the Ocean Wind and Wave provided assistance in pushing the Olympus away from the Keiwit facility dock in Ingleside, Texas, through the Port of Aransas, Texas, and out to deeper waters. During this initial phase, the Ocean Sky was also available and equipped to provide push assistance, if needed.
During this offshore phase, the Ocean Sky took on the role of escort tug, which helped to ensure the towing vessels’ and platform’s safety. Providing additional support was the Crowley-contracted, offshore tugboat Harvey War Horse II. This additional asset was a turnkey solution arranged by the company’s solutions team, a Houston-based project management organization.
In the final stage, called the positioning phase, the Ocean Wind, Ocean Wave and Ocean Sun vessels helped to position the platform in its final location and remained on site in a star pattern to provide support as the platform was attached to tendons and made storm safe. The Ocean Sky remained on site as a stand-by vessel and to provide additional security.
“This successful project is a testament to the capability, station-keeping and power of these vessels,” said Crowley’s John Ara, vice president, solutions. “The design of the ocean class has allowed us to participate in the full scope of marine transportation, including nearshore, offshore and positioning work. From the initial push-off to securing it as storm-safe, these tugs were critical assets in the relocation of the Olympus platform.”
Crowley’s ocean class tugs are modern ocean towing twin-screw vessels with controllable pitch propellers (CPP) in nozzles, high lift rudders and more than 147 MT bollard pull. The first two ocean class vessels, the Ocean Wave and Ocean Wind, are classed as Dynamic Positioning 1 (DP1) tugboats and are twin-screw, steel-hulled tugs with an overall length of 146 ft., beam of 46 ft., hull depth of 25 ft. and design draft of 21 ft. The second two tugs of the class, Ocean Sky and Ocean Sun, are classed as DP2 and are 10 feet longer. All four vessels are capable of rig moves, platform and Floating Production, Storage and Offloading (FPSO) unit tows, emergency response, salvage support and firefighting.