Offshore Pipeline Construction Constructing an underwater pipeline is a major undertaking. Approximately 200,000 pipes have been produced to create Nord Stream 2. Pipelaying began in the summer of 2018. Through a carefully planned and tightly managed process, individual lay vessels have constructed the pipeline at a rate of 3 – 4km per day. The Nord Stream 2 twin pipeline will increase protection and add weight, stretch over 1,230km from Russia’s making the pipeline more stable on Pipe Carrier Vessel Baltic coast, through the Baltic Sea, the seabed. Pipes weighing up to 24 tonnes each reaching landfall at Germany’s coast were shipped to the pipelay vessels from a number of logistics hubs Crane near Greifswald. Once fully operational, Nord Stream 2 has used several strategically located along the route. Pipes are unloaded by crane the pipeline will have the capacity to pipelay vessels to install the pipelines. from the carrier vessel to the Helipad transport 55bcm of natural gas per A number of measures have been pipelay vessel. Personnel are transferred to and from the vessel via helicopter. year – enough to satisfy the needs of taken to minimise disturbance to the 26 million European households. sensitive Baltic Sea environment, Nord Stream 2 will largely run in parallel which has dense shipping traffic to the Nord Stream system in operation. and historic munitions. Nord Stream 2 has worked with some Each pipelay vessel is a floating Pre-Pipelaying Survey Though the seabed was surveyed during of the world’s leading contractors to factory where the pipes are received the route planning phase, a pre-lay survey lay the pipeline through the Baltic Sea. from carrier vessels, welded together performed before pipeline installation confirms Safety and environmental protection into a pipeline in the firing line, and that no significant changes have occurred are foremost considerations throughout finally installed on the seabed. The along the route since the previous survey. the pipeline’s construction. The completed pipeline will undergo individual 12-metre pipes were produced rigorous testing and assessment by at plants in Germany and Russia, an independent certification body. and have a constant internal diameter Once the safety of the pipeline of 1.153mm and a wall thickness of is assured, gas will be able to flow ROV up to 41mm. The pipes were then directly from the world’s largest Stinger coated internally to reduce friction, natural gas reserves into the EU’s The stinger provides support to the pipeline as it is progressively lowered and externally to reduce corrosion, internal energy market. to its designated place on the seabed. Pipelaying Process Post-Lay Survey As it touches down on the seabed, Edge bevel the pipeline is monitored to ensure that it is correctly positioned. Weld Ultrasonic rays S-Curve As the pipeline is lowered to the seabed, it forms an “S” shape, which prevents it The pipes are unloaded from the To prepare the pipes for Here, 12-metre pipe joints are The double-joint is moved to a from being damaged during installation. 1 pipe carrier vessels and stacked 2 welding, the ends are bevelled 3 aligned and welded together 4 non-destructive testing station on the laybarge. Pipe deliveries occur to make them exactly the right shape to create a double-joint segment where every millimetre of the weld regularly to ensure that there is always to be fitted together for welding. The measuring 24 metres. These sections undergoes automatic ultrasonic testing an adequate linepipe buffer on board inside of the pipe is then cleaned using will later be connected to the main (AUT) to detect any unacceptable to keep construction going 24/7. compressed air before it is conveyed pipe string. flaws. If required, the defect will be ROV ROV to the double-joint welding station. removed and the weld rescanned to A remotely operated vehicle (ROV) fitted ensure it meets international standards. with sensors and instruments including cameras transmits information from the Pipe cross-section seabed directly to the survey vessel. Polyurethane Weld Concrete weight coating 60–110mm Heat foam Corrosion protection 4.2mm Ultrasonic rays Rock Placement Former The strategic placement of coarse gravel was necessary in Pipe steel 27–41mm Following AUT, the double-joint The double-joint is now joined Following welding, the weld Once the weld is confirmed some locations along the route is moved in a pipe elevator to to the end of the pipeline using between the double-joint acceptable, a corrosion to create a stable base on 5 6 7 8 which the pipeline could rest. Antifriction coating the central assembly line. There, the a semi-automatic welding process. and the main pipeline undergoes resistant, heat-shrink sleeve is insides are checked for debris and the Qualified welding inspectors oversee automatic ultrasonic testing (AUT). applied over the circumferential double joint is aligned with the main each of the steps to ensure that Any unacceptable flaws will be girth weld. Then, polyurethane foam pipe string in preparation for welding. welding is performed in accordance removed, and the weld rescanned is poured into a former surrounding Pipes shown in yellow for clarity. with Nord Stream 2’s and authority to ensure it meets international the weld area. This foam hardens, Pipelay vessel design is for illustration only. approved welding procedures. standards. providing further protection. Solid Foundations A Strong Team from Solitaire Coast to Coast Allseas’ Solitaire was deployed for offshore construction FINLAND of the pipeline’s deep-water sections. Nord Stream 2 has worked with several pipelay contractors Narva to build its twin pipeline through the Baltic Sea. Of these, NORWAY Bay Allseas has been the main contractor, with three vessels As one of the world’s largest pipelay Key figures vessels, it has laid numerous offshore > Length: 300 metres ESTONIA mobilised for the project. pipelines, including the twin 48-inch > Width: 41 metres SWEDEN > RUSSIA Nord Stream pipelines. Its long length Maximum speed: 13.5 knots and ship shape make it particularly > Installed power: 51.5 megawatts Allseas Group MRTS JSC workable, and full dynamic positioning > Dynamic positioning and propulsion: LATVIA Allseas is a global contractor for pipeline MRTS is a Russian company which allows the vessel to manoeuvre precisely 10 azimuth thrusters DENMARK installation, heavy lift and subsea operates in the field of subsea pipeline and safely in areas with historic mine > Accommodation: 420 people construction. The group operates a fleet of construction. The company installed the lines and congestion in the Baltic Sea. > Work stations: 2 double-joint factories LITHUANIA state-of-the-art ships. To date, Allseas has starting section of the twin pipeline in Thanks to the vessel working without with 3 welding stations each, 5 welding already laid more than 21,500 kilometres the shallow waters off the Russian coast, anchors, only the pipeline touched stations for double joints, 1 NDT station, RUSSIA of pipeline in offshore projects. As the including the two above-water tie-ins close the seabed along the pipeline route. 4 coating stations chief pipelay partner, the company was to the Russian landfall. This helped to minimise the impact on Lubmin near Greifswald POLAND responsible for installing the majority of the environment and marine traffic. GERMANY the two pipeline strings. It used three of Saipem its vessels – Solitaire, Pioneering Spirit Saipem, headquartered in Milan, Italy is a and Audacia – to lay a total of about global company that provides onshore and Design, construction and operation of 3.5 and 50 kilometres respectively to bury 2,200 kilometres of 48-inch pipeline. While offshore services to the oil and gas sector. the new twin pipeline system draw on the pipelines for their stability, protection the first two ships are dynamically positioned, Saipem pulled ashore the final section of Nord Stream experience. However, and the security of marine traffic and Audacia was converted into an anchored the pipeline and connected it to the landfall thorough preparation was key. By the fishing activities. To ensure safe installation Sea Baltic the through vessel for its work in German waters. of Nord Stream 2 in Germany. It also end of the project, 71,000 line kilometres and operation of the pipeline, potential Pipeline Twin the Constructing performed three above-water tie-ins in of seabed will have been surveyed to munitions from the World Wars were German waters. define the optimum route for the twin avoided where possible, and cleared where 2 Stream Nord pipeline. The varying topography of the necessary. After pipelaying began, post- Baltic seabed meant that in certain places, lay surveys were performed to determine preparatory works had to be performed where additional support, stabilisation before pipelaying began. To avoid or protection was needed once the excessive freespans in the two pipeline pipelines rested on the seabed. As much strings, among others, rocks between as 90 percent of all rock placement has 60 and 100 millimetres in size were placed taken place post-lay, using only new, clean on the seabed at dedicated locations to and crushed granite. At some locations create supporting berms. In the shallow along the route where this was deemed waters near the Russian and German impractical, post-lay ploughing was carried landfalls, dredging took place over out to stabilise the pipelines. What Does it Take to Install Facts and Figures Pioneering Spirit Audacia an Offshore Pipeline? The largest construction vessel in the world was used to To build the shallow water section of the pipeline in Germany, 360 pipes install parts of the offshore section of the twin pipeline system. the smaller and more versatile Audacia was used. Andrew Turnbull, Deputy Manager have been delivered to each Offshore Construction, explains how the pipelay vessel every day.