Deep sea stability

An advanced maritime vessel design being developed by QinetiQ and Norway’s OTG will allow oil companies to conduct operations in a stable environment, regardless of harsh weather conditions.

Harsh environmental conditions make the complex tasks associated with oil recovery and well maintenance from certain oilfields in the North Sea extremely challenging

QinetiQ is working with Norwegian exploration and production technology company, OTG (Oilfield Technology Group), to develop a new type of vessel which will allow oil companies to conduct operations in a stable environment while weathering some of the world’s stormiest seas.

The agreement between the two companies follows a two-year joint development programme and the establishment of OTG Interventions, a wholly owned subsidiary of OTG, which will build and own the vessel. OTG Interventions is currently evaluating several ship operators and will soon announce who will be selected to operate the Tri/SWATH vessel in the Norwegian sector of the North Sea.

A SWATH (Small Waterplane Area Twin Hull) vessel normally consists of two parallel torpedo-like hulls attached to which are two or more streamlined struts, which pierce the water surface and support an above water platform. The advantage to such a design is that they are more stable, less prone to pitching and rolling and requiring less power for propulsion than conventional designs.

QinetiQ’s approach to SWATH design is to develop vessels with a tri hull configuration, which provides even greater stability, a vitally important feature for vessels commanding complex work in often very stormy seas.

Currently, oil companies have 15 to 20 percent lower oil recovery rates from subsea wells compared to platform wells in the North Sea and other offshore basins. This is because there is currently no cost-effective solution to performing subsea repair and maintenance on the growing number of subsea wells.

The Tri/SWATH vessel should allow this work to be performed at one fifth the cost of traditional approaches such as (anchored) semi-submersible vessels, and less than half of the cost of dynamically positioned semi-submersibles.

OTG Interventions and QinetiQ expect to complete the final stages of vessel design early in 2005 for operation in mid 2007. QinetiQ’s role will be to assist in achieving type approval from the necessary classification societies and to support the owner to ensure the vessel is built to the required design specifications.

The two companies have also started to evaluate this concept for other oil and gas applications, including an ultra optimised drilling vessel that can operate at a lower day rate than conventional drillships and drilling rigs.

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