How Nord Stream braved the Baltic

October 1, 2011

Gas is due to start flowing through Nord Stream this month following completion of preparatory works on the first of the twin 1224km-long gas pipelines running through the Baltic Sea between Russia and Germany. Formal inauguration of line one commercial operations is scheduled for a November ceremony at the German landfall in Lubmin near Griefswald. Meg Chesshyre and David Morgan check progress on the largest and longest subsea pipeline ever built.

The first of Nord Stream’s 48in diameter trunk lines through the Baltic is 100% complete and in the final stages of pre-commissioning. Following pressure testing, draining and drying, buffer gas filling of line one began in September, keeping Nord Stream’s first leg well inside its 4Q 2011 target for becoming fully operational. The line has already been connected to the OPAL (Ostsee-Pipeline-Anbindungs-Leitung – Baltic Sea Pipeline Link) system, providing a direct link between Siberia’s major gas reserves and the European market.

When line two comes onstream 4Q 2012, Nord Stream – designed by Snamprogetti – will have the capacity to transport 55bcm of Russian gas a year to Europe for at least 50 years.

Saipem is executing the pipelaying operations with three main pipelay vessels (Castoro Sei, Costoro Dieci and Allseas’ Solitaire, the latter under subcontract) plus 20 pipecarriers, survey vessels, tugs and crew boats, 45 shallow draft boats, and a few other ships for ploughing and precommissioning acitivities.

Saipem’s Castoro Sei, extensively revamped for this task, is carrying out the majority of the pipelay work. Having kicked off Nord Stream’s construction in April 2010, the vessel will continue working until 2012. Allseas’ Solitaire was deployed in the Gulf of Finland from September 2010 to August 2011. And between July and October 2010, Saipem’s Castoro Dieci constructed the shore approach of both pipelines in the shallow waters of Germany. The separate stretches of pipeline laid by the three vessels are joined into three continuous sections through the abandonment and recovery process, during which a watertight sealed head of a previously laid stretch of the pipeline is pulled back up from the seabed onto the pipelay vessel’s stinger and new segments added.

Castoro Sei has worked without interruption 24 hours a day, seven days a week, for over a year – in itself a new industry record and no small achievement given this huge, fast-track operation’s substantial mechanical and physical demands on both ship and crew.

Ruurd Hoekstra

Allseas’ Solitaire, the world’s largest pipelay vessel with a 22,000t pipe-carrying capacity, completed work this August on the heaviest section of the second line through the Baltic Sea a few weeks ahead of schedule. The vessel has laid 342.5km of each of the twin pipelines in the Gulf of Finland, comprising 57,000, 24t pipes. Operating with a crew of 405, Solitaire laid pipe 24 hours a day seven days a week for Nord Stream for almost a year.Solitaire’s dynamic positioning was crucial in the Gulf of Finland, with its historic lines of mines and congested sea lanes, and ‘lived up to all our expectations’, says Nord Stream’s construction director Ruurd Hoekstra. ‘Using the Solitaire helped us to minimise the impact on the environment and marine traffic and in this section the safety zone around the pipelaying could be much smaller,’ he explains.

Gert Pellinkoft

Allseas’ project manager Gert Pellinkoft says the company was pleased to contribute to the success of Nord Stream. ‘This project gave Allseas the opportunity to show what we are made of. After overcoming some complicated engineering aspects at the office, both vessel and crew were put to the test during tough weather conditions offshore. It is with pride I can say that our vessel Solitaire and her crew set new standards and continued to lay pipe in truly Arctic conditions. Completing the critical section of line one as part of the Nord Stream project during the first campaign therefore was very satisfying for everyone involved.’

Nord Stream passes through the territorial waters and/or Exclusive Economic Zones of Russia, Finland, Sweden, Denmark and Germany.

Permits to construct and operate the pipeline were required from each of these five countries. Environmental impact assessments (EIAs), identifying, predicting and evaluating ways to mitigate the project’s impact on the bio-physical and social environment, had to be completed as a prerequisite for national permits. In all, more than E100 million was invested in detailed environmental studies and project planning to assess and subsequently minimise Nord Stream’s environmental impacts. More than 40,000km of geophysical surveys were conducted, with thousands of objects on the seabed inspected.

Nord Stream’s environmental and social monitoring programme has instituted special precautions to minimise the environmental impact of the pipelaying operations including: monitoring water turbidity, checking the maintenance of the fish population, monitoring the birds patterns and the aquatic fauna, monitoring water flows, and minimising air emissions and light and noise levels throughout the operations.

The giant project has been over 10 years in the planning. The first feasibility studies by the Finnish-Russian joint venture North Transgas in 1997-99 confirmed the technical feasibility and economic efficiency of a pipeline through the Baltic Sea. The company NEGP, which later became Nord Stream AG, was founded in Zug, Switzerland, in 2006. That same year the company began business operations, and started establishing its own organisation. The first logistical plan, which largely corresponded to what would become the definitive features, had been developed by the end of 2006. It was subsequently approved for further planning as early as January 2007.

Castoro Sei set a new industry record by working 24/7 for over a year without interruption.

Project logistics

Nord Stream is currently the longestreaching construction site in Europe. In the course of the project, when all handling operations are taken into account, a total of 90 million tonnes of steel piping and coating materials such as cement and magnetite will have been transported. The project involves the delivery of some 200,000 pipe segments, each one 12.2m long and weighing approximately 25t, along the route. The entire supply chain was optimised to meet the project requirements. Within a span of four years, Nord Stream developed and implemented a customised site logistics solution.

Many new records were achieved on this major logistical challenge. For example, more than 8km of pipeline was laid in a single day, with a typical performance of over 3km or 8-9000t/day – in other words, the weight equivalent to the Eiffel Tower was laid every day on the seabed.

German shore approach dredging and cofferdam construction

The use of existing concrete coating plants, for example in Norway and Scotland, would have incurred additional transport costs of more than E60 million. The investment costs for the construction of two new concrete coating plants (reliability and structure of supply chain already optimised) were about the same, and are cost neutral in the project budget, but make an important contribution toward environmental conservation. Based on this, Nord Stream chose to construct two new concrete coating plants since the use of existing plants would have run contrary to the logistical plan of having short, optimised transport routes.

For capacity and rail access reasons, and to maximise reliability, Nord Stream opted to build two plants, one at either end of the pipeline route. Situated at Mukran in Germany and Kotka in Finland, each has an identical production capacity of 200 pipes per day, making these facilities the largest of their kind for large pipes.

In all, five pipe storage facilities were required (at the two coating yards and at interim sites at Karlskrona, Slite and Hanko), with the nearest pipe storage facility situated less than 100 nautical miles from each point along the route. This ensures that all replenishment sailings with pipes to the pipelay vessel and back again can be completed within 24 hours. Three special pipe carriers are employed for this. If one of the carriers breaks down, the supply chain still remains stable as the next carrier arrives just eight hours later. Additionally, the pipelay vessel carries a contingency surplus, to allow continuous pipe laying.

With the pipes facing outdoor storage for up to 30 months, Nord Stream devised a new quality assurance system to minimise contamination and corrosion. The pipe ends also needed to be protected from mechanical damage, and fitted with an intelligent tracking device. The intelligent end caps developed specifically for the Nord Stream project consist of an inner cap with an integrated gas permeable membrane, an outer cap to protect the end of the pipe, as well as an electronic box with sensors and RFID (radio frequency identification) technology. In addition, a special software tool (ROCOMS) was developed to analyse and document all the data sent. Data transmission is handled by a system of receivers and routers that sends all the data to central control rooms at Mukran and Kotka. There, specialists analyse the incoming signals and arrange inspections of the pipes when required.

Following the concrete coating, the cleaned pipes are fitted with inner and outer caps at both ends, and remain protected until delivery. All pipes are delivered with a barcode that is later transferred electronically to the RFID chip. Classic pipe tracking takes place in the pipe tracking system (realtime image of all storage sites). Unlike traditional area surveillance systems, the ROCOMS security system allows users to monitor the condition of each individual pipe. The system is fully functional, and more than 200,000 intelligent end caps are in use. Incoming warnings are analysed, and Saipem reports that all the pipes leaving the storage facilities for the pipelay vessel are in perfect condition. ‘Not a single pipe coming from interim storage has been rejected so far due to damage,’ notes the company.

Daslav Brkic

‘Thanks to an outstanding effort from all parties involved, this enormous project is actually ahead of schedule,’ says Saipem vice president, E&C business development, Daslav Brkic. ‘Through extensive planning and project preparation, excellent team work and lots of hard work from the client, main contractor and subcontractors alike, this gigantic effort is turning into a major success.’ MC

Landfall challenge

Technically, operationally and logistically, Boskalis operations manager Jan Paulsen rates the Nord Stream German landfall as the most complex project he has ever encountered. Under subcontract to Saipem, the Dutch dredging contractor completed the project last year with joint venture partner Rohde Nielsen from Denmark. It brought more than 40 vessels into play in the shallow waters of the environmentally sensitive Bay of Greifswald, a noted nature reserve on the northeast German coast.

Paulsen looks back in awe at the numerous challenges that faced the BORN joint venture landfall team as they prepared this 28km trenched section of the twin pipeline route in readiness for Saipem’s flat-bottomed barge Castoro Dieci to complete the nearshore pipelay. ‘You won’t find a challenge like this anywhere else,’ says Paulsen. ‘A 1.5km pull of 48in pipe, requiring the rigging up of a 500t winch – this technically is not something you do every day!’

Shore pull of the first 48in pipeline at Germany's Bay of Greifswald landfall and (right) completion of both pulls.

For the pipelay operations a new channel needed to be dredged in just a couple of metres of water through the sand barrier that shelters the Greifswalder Bodden from the Baltic Sea. But the shallow draft conditions ruled out deployment of heavy sea-going dredging equipment, requiring the contractors to mobilise instead an armada of smaller backhoes and bucket line dredgers along with a fleet of split hopper barges to deposit the soils in their various dedicated locations.

In May 2010, with onshore cofferdam construction complete, the end of the herring spawning season permitting offshore work in the area, and Castoro Dieci expected to arrive in just six weeks, the assembled dredging fleet was just two days away from start-up when its tough schedule became even tougher. Unexploded ordnance from a Second World War firing range had been discovered in the trench.

‘We sat back and scratched our heads, and the decision was made to conduct a full new magnetometer survey to identify other anomalies,’ recalls Paulsen. ‘This took quite a while and we had to reconsider all our dredging schedules as it meant the fleet could only work in specified areas as they were checked and cleared, rather than across the whole site as originally planned. We also had to execute the work in close liaison with the client and its specialist UXO advisers.

‘That was quite a challenging start to the project,’ he adds. ‘However, we managed to keep to all the original key milestones, notably of course being ready for the Castoro Dieci, and once the barge arrived the fleet continued dredging all around it. Under the circumstances, the job went very well.’

With the crews of the 40-odd vessels all requiring accommodation onshore, and their dredging locations spread over a working area with a circumference greater than 100km, offshore logistics clearly required close attention. In addition to dredging a near 30km trench, the various dredged soils had to be deposited at a number of different locations. The main deposit location, where sand or other suitable materials would be dumped for reuse later, was 50km to the east. Peaty (organic) material had to be pumped ashore 60km to the west, while unsuitable materials were dumped beneficially to assist in the construction of a ferry harbour 50km to the north. And any significant deviation from the planners’ theoretical soil model also required time-consuming redirection of the dredged material to another location.

The final line one weld took place on 19 August at the Russian Portovaya Bay landfall.

‘Every morning we needed 100 people on the water and 100 people off the water, and in the evening the same thing,’ explains Paulsen. ‘But at any given moment any of the barges could be sailing anywhere, making the planning of crew changes extremely problematic.’ The BORN joint venture responded by making one person solely responsible for the offshore logistics of people and equipment and day-to-day management of the four vessels dedicated to that purpose. ‘Sometimes there was a slight delay due to the huge sailing distances involved, but overall that system worked well,’ notes Paulsen.

Germany's line one 'Golden weld' was completed on 25 August.

Rock installation

Meanwhile, having completed prelay works for Nord Stream lines one and two last year, Boskalis – this time in a 50:50 joint venture with Tideway – is continuing postlay work under what has been hailed as one of the largest pipeline rock protection contracts ever awarded. The E100 million contract from Saipem calls for installation of rock berms for stress/freespan corrections, in-service buckling mitigation and on-bottom stability.

Fallpipe vessel Seahorse loading quarried material at Kotka in Finland

To date, three fallpipe vessels have been deployed on Nord Stream – Sandpiper, Seahorse and Rollingstone – with two of these vessels occasionally having to work in tandem to stay ahead of Saipem’s Castoro Sei and Allseas’ Solitaire pipelay barges.

The water depths en route (up to 225m) presented no difficulty for these vessels; the bigger enemies to progress were unexpected soil conditions along the way and the harsh Baltic Sea winter’s encroachment on available time at location. Boskalis Offshore project manager Dirkjan van den Boom explains: ‘Prelay started well enough, but to avoid delaying the barges we needed to complete a foundation at KP674 – the starting point for pipelaying – by April 2010.

‘That pushed us into the winter season. To complicate things even more we encountered soil conditions that we just did not expect, requiring us to almost double the size of that berm and putting us under additional pressure time-wise and operationally because we had to secure sufficient quantities of rock from our Baltic supply ports at Oskarshamn [Sweden] and Kotka [Finland].

‘Fortunately, we were still able to complete prelay by August 2010, well ahead of schedule. We then switched to postlay for line one until bad winter weather stopped us in December. Normally things start to freeze around late January, early February, but our last vessel had to leave the area on Christmas Day.

‘We remobilised in late March and followed the ice back into the Gulf of Finland. With the Nord Stream lines divided into three sections due to the pressure drop between its two landfalls – from 220bar in Russia, to 200bar at KP600 and then to 180bar on the final stretch into north Germany – the next challenge was meeting a pressure test schedule which first required postlay of each section to be completed to avoid overstressing the line.

‘The harsh winter had already delayed our start, and despite some additional work, we just managed to complete everything in time,’ says van den Boom. ‘All of line one was tested without delay. And on 28 August we completed the whole scope for line one, enabling Nord Stream to start production on schedule.’

Now the project’s focus is on getting line two ready for pressure testing next spring. Although obviously depending on what other assignments may come along in the meantime, on present reckoning there is a ‘good chance’ that the Rockpiper, Boskalis’ 25,000t capacity newbuild fallpipe vessel (OE August 2010), will join Nord Stream’s final stages when it comes into service next January – the Arctic winter willing of course! DM



Current News

Incident Reported During Construction of Seaway 7's Alfa Lift Vessel in China

Incident Reported During Construction of Seaway 7's Alfa Lift Vessel in China

Equinor, BP JV Picks Vestas' Giant 15MW Turbines for New York Offshore Wind Projects

Equinor, BP JV Picks Vestas' Giant 15MW Turbines for New York Offshore Wind Projects

U.S. Coast Guard Boards Containership in Connection to California Pipeline Oil Spill

U.S. Coast Guard Boards Containership in Connection to California Pipeline Oil Spill

Aker BP Gets Drilling Permit for Lyderhorn East Offshore Well

Aker BP Gets Drilling Permit for Lyderhorn East Offshore Well

Subscribe for OE Digital E‑News

Offshore Engineer Magazine