CASIM Used Off Crane Barge To Set Tree Down On Wellhead

Flexible solution - Taking subsea tree installation off the critical path.

An advanced system designed to safely and economically lower subsea equipment continues to prove that complex installation procedures can be taken off the critical path and performed from small, easily available vessels instead of costly drilling rigs and construction vessels.

The compensated anchor-handler subsea installation method, or CASIM, was developed by deepwater mooring systems specialist InterMoor. It can be used to install equipment such as suction-embedded plate anchors, suction piles, subsea trees and manifolds.

Equipment such as suction piles can weigh anything up to 200 t, while subsea trees can typically weigh between 40 and 80 t (although InterMoor is also in discussions with clients regarding the deployment of trees that weigh around 110 t with the running tool). To date, subsea trees sized up to 3 m x 3 m x 4.5 m (and weighing between 45 and 57 t) and suction piles up to 23.7 m long by 5.5 m diameter (and weighing up to 182 t dry weight and 152 t wet weight) have been successfully deployed using CASIM, in water depths between 450 and 1706 m.

By way of a specific example, it was CASIM’s flexibility that was key during a recent project for US-based Newfield Exploration Company, an independent oil and gas exploration and production company. In November 2006, Newfield was bringing a well into production in the Gulf of Mexico’s Mississippi Canyon and had already chartered a vessel to run the well’s umbilical. This provided an opportunity to transport the 57-t horizontal production tree to the location. However, although the Intrepid (a dynamically positioned crane barge) had a 400-t crane, it did not have any heave compensation to facilitate accurate placement of the tree on the seabed.

Brent Boyce, project manager, InterMoor, explains that InterMoor was able to lower the tree from the Intrepid using its crane by deploying the CASIM heavecompensation system. “We used CASIM to safely set the tree down on the wellhead. However, this was only to wet store it, and we did not lock the tree because the plugs still needed to be drilled out,” he says.

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