The two 48 inch Nord Stream pipelines run 1,224 km from Portovaya Bay, near Vyborg in Russia, almost parallel through the Baltic Sea to a landfall at Greifswald in Germany. The technical characteristics of the pipeline, together with an applied regime of periodic external and internal inspection surveys and certifying authority technical controls, are the basis for safe and controlled operation of the pipeline system.
As a preventive measure, Nord Stream has implemented a pipeline integrity management System (PIMS), which defines the company’s approach to mitigating risk and maintaining safe and reliable operational integrity of the pipeline. The offshore repair strategy is a key element of the contingency plans.
The Nord Stream repair-preparedness strategy is designed to guarantee a level of preparedness and response capability in the event of an incident. The strategy addresses the bandwidth of potential risks and provides the means to achieve comprehensive repair solutions in a variety of damage scenarios.
Core elements of the repair-preparedness strategy:
- Upfront development of procedures for a spectrum of possible repair cases;
- Proper organisational structure, including internal organisation and agreements with appropriate industry specialist contractors;
- Availability of necessary spares and upfront investment in long-lead items of repair equipment to be stored and maintained for the pipeline’s operational life;
- Availability of qualified and trained personnel with the expertise to implement repairs in accordance with best industry practice; and,
- Maintaining availability of sufficiently skilled and experienced personnel to implement the measures defined in dedicated repair strategy procedures.
Assessment of potential repair types and development of procedures
During the development of the pipeline system, Nord Stream conducted detailed risk assessments for the design, construction, and operation phases. Taking into account such factors as the pipeline’s exact route, characteristics of the construction materials, seabed morphology, number and sizes of vessels crossing over the pipelines, the size and type of anchors or fishing equipment used in the Baltic, and the recommendations of studies on other offshore pipelines, incident scenarios were identified, from which the Nord Stream repair strategy was developed.
Dedicated repair methods and operational procedures have been prepared for a number of services. From the repair methods for the identified incident scenarios, the essential pre-investments in long-lead items, critical repair equipment, and securing of specialised repair contractors, has been determined.
Integration of specialised partners
Nord Stream’s offshore pipeline repair strategy organisation permits a clear assignment of respective responsibilities.
Main repair contractor and membership in the Statoil PRSI Pool
Nord Stream has secured the services of specialised offshore construction company Saipem as its main repair contractor (MRC). As MRC, Saipem will undertake the oversight of the repair operations in the event of an incident necessitating investigation and potential repair.
The MRC, together with Nord Stream’s own in-house technical specialists, has conducted detailed engineering to develop the necessary operational procedures, and definition of equipment needs to ensure that, in the event of an incident, the MRC is “÷ready to act’. The selection of Saipem as MRC has the inherent advantage that, as main contractor in the construction of the offshore pipeline system, the company has familiarity with the project and can also potentially provide the necessary marine vessel spread to undertake recovery and repair of a damaged section of the pipeline.
Another significant element of the Nord Stream repair strategy is its membership of the Statoil-administered Pipeline Repair and Subsea Intervention (PRSI) Pool, allowing access to specialised services and equipment technically suited to performing large-diameter subsea pipeline repairs.
Storage of pipes and spare parts in a “÷ready to mobilise’ condition
In close vicinity to the landfall facilities, a variety of spare parts and an equivalent of approximately 5.5 km of spare pipes are stored. The warehouse facilities allow controlled storage and maintenance of the spare parts for the full operational life of the pipeline system. Nord Stream also maintains long-term storage, preservation, and maintenance agreements for the specialist tooling included within its repair strategy.
Long-lead items: custom-designed tools for potential repair of the pipeline
A milestone to be fully met over 2015 into 2016 is the delivery and system integration testing (SIT) of Nord Stream’s full suite of pipeline repair tools. Partner companies such as TDW Offshore Services AS provide fit-for-purpose subsea tooling solutions.
Specific tooling developed by TDW for Nord Stream AG include its SmartPlug isolation tools, pipeline recovery tool (PRT) with its dewatering and pig-catcher functionality, and its pipeline end sealing plugs (PEPs), all suited to 48 inch diameter.
Other specialist tooling and equipment developments through 2015 into 2016 include a clamp-on pig stopper and SmartPlug launcher (CPS/CSL), an activated sealing pig (ASP), and subsea mechanical tie-in flange assemblies, as well as a liquid/ gas separator.
Pipeline repair clamps and repair clamp installation system
Nord Stream is in the process of developing two structural and pressure containment pipeline repair clamps by Oil States Industries, which can be externally fitted over an area of damage in order to provide a permanent repair solution. Under certain damage scenarios, the clamps can be installed with the pipeline still operational.
To be able to perform installation of the repair clamps, Nord Stream’s MRC has designed a dedicated ROV-operable repair clamp installation system. This system provides a means of ensuring carefully controlled installation of the repair clamp up to the pipeline system’s maximum water depth of 214 m.
Future development of the repair strategy
Nord Stream will move forward in 2015-2016 to assemble the full suite of equipment and tooling that form the core material investments for its offshore pipeline repair strategy.