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Survey: Allseas makes major investment in Sonardyne acoustics for deep water operations

Posted on 31.07.2007 - 10:00 EDT in SURVEY NEWS by Rons_ROV_Links

Allseas makes major investment in Sonardyne acoustics for deep water operationsThe Swiss-based pipelay specialist Allseas Group S.A. has placed a major order with Sonardyne International Ltd, Yateley, UK, for the supply of its Wideband deepwater Long BaseLine (LBL) acoustic positioning technology. The order includes two of the company's recently launched Lodestar AHRS (Attitude Heading and Reference System) units which makes Allseas the first commercial customer to benefit from this advanced new technology.

The complete order includes a substantial quantity of Sonardyne's latest Wideband Compatt 5 acoustic transponders and five Data Fusion Engines that will be used to undertake both LBL and Ultra-Short BaseLine (USBL) subsea positioning operations. The two Lodestar units ordered are the subsea variants and will be used to aid the high accuracy installation of structures on the seabed.

Allseas has specified that all of the subsea equipment be rated to 5,000 metres operating depth. This is reported to reflect Allseas' belief that future contracts will find them operating in increasingly deeper waters. By investing in appropriate acoustic positioning technology now, the company believes that they can future-proof their investment offering them a competitive advantage when bidding for complex deepwater operations.

The new equipment will initially be used by Allseas to provide field wide positioning for the Allseas fleet mobilised on the KG-D6 project for Reliance offshore India. Although this work is expected to take place in water depths averaging 1,000 metres, Allseas surveyors anticipate that the size of the project will result in considerable acoustic congestion brought about by multiple vessels operating within close proximity to each other. This factor was a major driver in the choice of the Sonardyne Wideband solution as the technology enables users to overcome this difficulty through the availability of over 200 non-interfering navigation channels.

The use of Sonardyne's unique ‘ping stacking' acoustic interrogation technique also provides an advantage when working in deepwater by enabling USBL system users to transmit acoustic interrogations to subsea transponders before the last reply was received. This provides a vessel's dynamic positioning system with a position update every second regardless of water depth. Sonardyne Wideband also provides a ten-fold improvement in measurement repeatability and faster position update rates when structures are being lowered onto the seabed.

The Sonardyne equipment is scheduled for delivery to Gibraltar at the end of August where mobilisation of the Allseas fleet will begin. The vessels involved include Allseas' new vessel Audacia, deepwater pipelay vessel Lorelay and Highland Fortress pipeline survey vessel. Solitaire, the World's largest pipelay vessel, was also upgraded to Fusion Wideband USBL earlier in the year.
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