A clever idea has found a way to penetrate the labyrinth inside offshore production tanks in search of environmental contaminates prior to decommissioning.
Saab Seaeye customer Stinger Technology, a Norwegian firm known for finding innovative ways to work in confined underwater spaces, 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 remotely operated underwater vehicle (ROV) Saab Seaeye Falcon into a 'mother ship' for launching an even smaller fly-out VideoRay ROV and tiny fly-out Stinger Nano ROV.
The Norwegian company dubbed the trio, Mother, Daughter and Little Sister.
The full mother, daughter and little sister configuration comprising:
- Saab Seaeye Falcon
- VideoRay Pro4
- Stinger Nano Fly-out TMS with 120m tether
- Docking station
- Subsea toolbox
- Tailor-made interchangeable tools
- Docking cleaning device in tool basket
With the market expecting 1,800 wells to be decommissioned over the next 10 years in Norway and the U.K. 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.
The Falcon's five-thruster strong precise maneuverability, and the plug and play configurability of its intelligent distributed control system, meant Stinger were confident it would be a suitable mother ship for the two fly-off resources, Saab Seaeye said.
Measuring 1 x 0.5 x 0.6 meters 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 1,000 x 1,000 x 850mm.
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.
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.