EXCLUSIVE by Scottish Energy News
A Chinese ship salvage and recovery conglomerate that wants a big slice of the £50 billion N. Sea decommissioning ‘pie’ has appointed a visiting professor at an Aberdeen university as its new UK commercial and business development manager.
Operating from bases in London and Aberdeen, Prof Norman McLennan said that the Shanghai-based China Ocean Engineering Company (COES) said:
“COES has a great recent historical example of why salvage skills are readily transferrable into decommissioning projects in the North Sea.
“And COES is actively looking to move into the UKCS to do business as and when opportunities arise.”
In support, Prof. McLennan cites the successful recovery of the Raising of the Sewol – a ro-ro passenger ferry which sank off the southwest coast of Korea in April 2014 – in Spring 2017. He said:
“The Raising of the Sewol was arguably one of most difficult offshore single lift wreck recoveries ever attempted. It was extremely complex and sensitive and by way of achievement it was a:
World first – single piece, intact wreck removal 7,900 MT from 45m water depth in extreme sea and seabed conditions, lifting a load that was bigger than the Eiffel Tower in Paris (7,300 MT)
- World record trailer load in operation – at 17,000 MT weight
- Health, Safety & Environmental focus with zero casualties during the operation – which included 12,000 hours under water!”
The water depth at the wreck site was around 45m (at the limit of normal diving capabilities without saturation). The sinking of this vessel was widely reported in the international media owing to the number of fatalities at the time.
COES (Shanghai Salvage) was appointed by the South Korean Government Ministry of Fisheries (MOF) to recover the vessel from the seabed and transport it to port and for ultimate onshore dismantling.
Following a competitive process – COES was chosen owing to its innovative proposal to raise the wreak in a single piece with optimal safety features. Key objectives for the project were:
- Single-piece recovery (pictured)
- Prevent the loss of remains from the wreck.
- Wreck to be landed ashore at a safe Korean port
- Certainty over final out turn cost with COES executed the work for a fixed price all-inclusive lump sum, thereby accepting and assuming significant risk in an area renowned for its adverse weather conditions and typhoons.
In terms of overall project activity, COES spent around 600 days on the work and successfully recovered the Sewol integrally.
The whole weight of the Sewol (including lifting beams and mud) was in the region of 17,000 MT once recovered onto the deck of the semi-submerged vessel.
Although 97 divers were deployed by COES working in subsea conditions where visibility was at times down to less than three-ft, no workforce injuries were recorded on this most difficult of projects.
The project progressed by adopting an approach of side lifting with lifting beams thereby minimizing drilling and cutting operations for the hull which in turn minimized the damage to the hull.
The Sewol salvage project was divided into the following key stages:
- Pre‐Survey & Mobilisation
- Oil Recovery & Removal
- Netting / blanking of windows & doors
- Buoyancy added
- Bow lifting and 18 middle lifting beams installation
- Stern lifting beams installation
- Tandem lift by two barges to surface
- Final float on semi-submersible barge
- Load-in by SPMT trailer system – Delivery onshore.
Stage 2. Oil Recovery & Removal
The total recovered oil mixture was 954 cubic meters, including 131 cubic meters of fuel. Obviously – this early work was crucial to minimize contamination to the sea environment during the future refloating stage of the project
COES utlised a self-made underwater drilling machine to drill holes on the surface of the oil tanks. The advantage of this special machine was that it has a connection flange installed following the drilling of the holes. The flange can then be connected with the oil pump to pump oil away with the resultant gain of having no oil spilled. This was a significant risk with the Sewol project which was managed and avoided.
Stage 3 Netting / blanking of windows & doors
A further highly sensitive consideration was the request made by the families of those who lost their lives to try and recover any relics and personal effects which might float away during the recovery operation.
In order to respect this wish – Shanghai Salvage installed a 200m x 160m x 3m surrounding net all-round the ferry, which was trialed for the first time in salvage operations. This net was installed to good effect thereby minimising the risk.
To prevent the remains of nine missing bodies floating out of wreck during re-floating operation, COES divers installed over 300 wire meshes to the doors and windows.
Because the hull structure of the Sewol vessel was weak, to have used traditional lifting methods would have damaged the wreck.
Accordingly; COES applied 33 lifting beams with 28m x 1.8 m x 0.9m each under the wreck. COES determined that the large contact area would protect the hull from deformation. The middle 18 lifting beams as a whole – were installed under the wreck immediately after the bow lifted.
Stage 8. Final float on semi-submersible barge
COES deployed a semi-submersible barge (72,146MT) sunk at site with main deck 13.5m under water surface.
Tugs assisted the fleet (ie the two barges with Sewol together) move just above semi-submersible barge, while the whole weight of Sewol was transferred to the semi-submersible barge, re-floated the semi-submersible barge with main deck finally 3.5m above water surface.
Prof. McLennan added; “At 1735 hrs on 9 April 2017, the ferry Sewol slowly rolled down from semi-submersible ship deck onto the yard, successfully completing the Sewol salvage project.
“The relatives’ wishes to “Let Sewol go home” had been granted and COES / Shanghai Salvage made good on its promise to fulfil this mission.
“It was truly an emotional and historical moment – and COES / Shanghai Salvage was highly commended by the South Korean Government for completing one of the most difficult offshore single lift wreck recoveries ever attempted.”
Meanwhile, a former Labour Scottish Minister from the pre-devolution era yesterday described the minority SNP-led Scot-Govt failure to bring N. Sea decommissioning work to Dundee as ‘one of the biggest scandals’ of the last decade.
Speaking in Dundee – which largely lost out on the North Sea oil exploration bonanza last century – Brian Wilson said the lack of government support for a potential £100 billion industry is seeing work ‘lost to England’.
He added: “Not only have Norway and other countries prepared for it, but the east coast of England has prepared for it far better and that is where many of these installations are going <for decommissioning>.
“They don’t have to go to the other side of the world, they just go down to Humberside. Why is none of that, virtually none of that, coming to Scotland?”
Decommissioning involves breaking up North Sea oil and gas installations and it has been estimated the industry could bring 5,000 jobs to Dundee alone.
13 Mar 2018