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Saab Seaeye: Little Mothership Solves Big Decommissioning Problem

Saab Seaeye: Little Mothership Solves Big Decommissioning Problem

View all news from: Saab Seaeye Limited
View directory entry for: Saab Seaeye Limited

01 June 2017

An ingenious idea from Saab Seaeye customer, Stinger Technology, has found a way to penetrate the labyrinth inside offshore production tanks in search of environmental contaminates prior to decommissioning.

They managed to squeeze a unique underwater robotic systems configuration loaded with sampling technology  through  a 150  cm  square  hatch  to search  the  tank’s  internal  maze  of baffles,  and navigate along 25.5 cm diameter pipe-runs of curves and bends.

Stinger’s idea turned the already compact Saab Seaeye Falcon into a ‘mother ship’ from which is launched an even smaller fly-out VideoRay and tiny fly-out Stinger Nano.

The Norwegian company dubbed the trio, Mother, Daughter and Little Sister.

With the market expecting 1800 wells to be decommissioned over the next 10 years, in Norway and the UK alone, the new ‘little family’ is set to be busy.

Importantly for offshore operators, is that sampling investigations on installations still in production, but planned for decommissioning, are not interrupted.

Saab Seaeye were pleased to collaborate with Stinger who are known for finding innovative ways to work in confined underwater spaces and chose the Falcon as the smallest and most powerful option on the market.

The Falcon’s five-thruster strong precise manoeuvrability, and the plug and play configurability of its intelligent distributed control system, meant Stinger were confident it would be an ideal mothership for the two fly-off resources.

Measuring just 1 x 0.5 x 0.6 metres in size, Stinger knew the Falcon could pass through the 150cm hatch and into the ‘nose tank’, even when fully configured, ready for launching the daughter and sister from their integrated tether management system on their extended sampling missions.

The entire Falcon mother ship configuration, with its fly-out 120m TMS, its docking station for fly-out daughter and sister, a subsea toolbox, tailor-made subsea interchangeable tools using manipulator, and docking-inclusive cleaning device in its tool basket – all fitted into a total system dimension of

Saab Seaeye engineers were keen to assist in Stinger’s technological achievement, which included Stinger developing their own miniature robotic system in the form of the Nano - the smallest and most advanced plugin fly-out on the market.

Once into the tank and embarking upon the data-gathering mission, two operators work in tandem – one, piloting the Falcon, the other piloting the daughter and sister.

The environmental  sampling  strategy  involved  seeking  out various residues  expected  within the tank from a lifetime of production cycles. These included oil, oil and water emulsion, wax, scale, sediment and sludge, sand, and possibly smaller gas pockets.

The VideoRay and Stinger Nano were fitted out with a range of tools including a deposit depth rule tool for measuring sediment and deposits on base and walls, a scraper tool for measuring the thin layer of hydrocarbon  wax deposits on the tank wall and a scoop sampler. Included was a water quality   sensor   for  measuring   dissolved   oxygen,   temperature,   conductivity,   salinity,   specific
conductance,  resistivity,  pH  and  ORP.  A  bottle  sampler  with  a  manipulator  operated  release mechanism was also included and a camera to verify successful sample taking.