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The eNovus. Photo from Oceaneering. |
Permanently stationed underwater vehicles are almost a reality – in Norway, at least. Elaine Maslin reports.
Statoil is working with Oceaneering on a project that could at least achieve a stepping stone towards the goal of having permanently stationed underwater vehicles.
The firms are working on an e-ROV (remote operated vehicle) skid, which could comprise a subsea garage, with a 100kw battery pack and tether management system, with surface communication and control via a buoy with antennae (connected to the skid with a Kevlar and fiber cable), to enable an ROV to work remotely for periods of time on the seafloor. If there is communication available on a nearby subsea template, this could be used instead. It could also link up to a drilling rig, whose activity it could be supporting.
Having ROVs deployed without the need to be attached to a vessel achieves, at least for certain periods of time, the ability to “do away” with the need for a support vessel. ROV operators could be based onshore, communicating with the ROV using the 4G network now installed in the Norwegian North Sea, and operate multiple units at a time.
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“The main reason we can do this now is that we have a 4G mobile network that was placed on the Norwegian Continental Shelf two years ago,” says Pål Atle Solheimsnes, leading advisor – subsea intervention and diving, Statoil, at Subsea Valley in Olso early in April. “That means we can transfer enough data to operate it from shore. The latency is so small. 3G had too much latency. In 2020, 5G is coming. Then the latency will be reduced by 90% again and it will be really, really good. We can use it on all subsea production systems in the North Sea.”
A deployment concept has been developed, involving Subsea 7’s Seven Viking, with several e-ROV skids onboard, almost doing a milk round, deploying the skids via its moon pool to the seabed. Another concept has the Normand Ocean deploying one skid and then going off to do others jobs and returning to collect the e-ROV when it’s completed its work.
Solheimsnes says that the battery pack could be scalable and updated as battery technology improves. A standard buoy will be used.
As of early April, Oceaneering was building a pilot system in Stavanger, Norway, and was due to test it in May at the Troll field. Oceaneering’s eNovus ROV is being used. The garage was already built and the battery pack was being built up.
“We will see if it’s working, what to do better, then make a complete specification for a complete eROV we want to build,” Solheimsnes says. “If successful, it will be in the tool box for an IMR [inspection, maintenance and repair] vessel to use when it wants to.” Solheimsnes says that the idea would be that the system could be rented by Statoil, rather than owned.
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