Lowering manifolds, trees, subsea processing equipment, and other items to the sea floor is pretty standard stuff in the subsea installation business, but what isn’t so standard, is subsea trenching.
After pipelines are laid down on the sea floor, either to perhaps connect wells together within a subsea development or a flowline to shore, these pipes are sometimes buried so that they do not extend above the mudline. In areas such as offshore eastern Canada for example, this is important due to the threat of iceberg collisions. Other reasons might include fishing or eliminating the possible hazard to navigation.
To do the work, big and specialized gear is sometimes needed. The following image is via subsea services provider DeepOcean Group and shows the T-3200, the world’s largest trencher:
Handling such a piece of gear from a moving ship requires an equally advanced vessel, such as the 110 meter, DP2 equipped Havyard 858-design Havila Phoenix.
owned on charter to DeepOcean Group and features a 250 ton active heave compensated crane, six Caterpillar 3516 C main engines, and accommodations for up to 140. Since September 2013 however, she has been going through a major conversion project at Havyard’s Leirvik Shipyard where she will be lengthened by 17 meters and have a huge 250 ton active heave compensated A-frame installed from which the T-32oo trencher can be deployed.
The following animation provides an overview of what the new vessel will look like:
In addition the A-frame, the Havila Phoenix will also keep its 250 ton active heave compensated knuckle boom crane and 2500 meter wire capacity, and also have on board a T-1000 trencher.