Atle Gundersen, Gassco AS, Norway, discusses pipeline operation advances and details the company’s pipeline integrity management plan.
Gassco was given a huge opportunity in 2002, when it took over as operator of the world’s largest integrated subsea gas transport network, to combine operating activities and improve pipeline integrity work at reduced cost to the owners. An improvement programme initiated by the company in 2004 has the overall goal of achieving a 20 per cent cut in pipeline operating costs by 2008. Long term budgets so far indicate that this objective is within reach.
Developing a plan
Before Gassco’s creation, the extensive Norwegian subsea gas transport system, comprising approximately 7000 km of pipeline carrying more than 250 million m3/d to Europe, was operated by four different oil and gas companies. These had different inspection philosophies, purchasing strategies and contingency plans.
The first step towards meeting the company’s target was to continue the work already underway, on the basis of risk based pipeline integrity management.
Together with the classification society Det Norske Veritas (DNV) and Norwegian oil company Statoil, Gassco has supported the development of the ORBIT software programme to collect all relevant historical pipeline data.
This solution can analyse the results of annual inspections and suggest new monitoring programmes based both on these findings and on the criticality of the various parts of the system with respect to corrosion, buckling, free spans and pipeline stability.
A crucial requirement is to make more effective use of all the data already gathered through approximately 30 years of operation, rather than spending more money on gathering new information.
Taking a systematic approach when reviewing old data can avoid unnecessary inspections in the future. The in house information Gassco already possesses can provide much information on the behaviour of pipeline and seabed.
Managing the system
Since Gassco has pipeline operations in seven different North Sea countries, one challenge is to get all the different authorities to accept the new approach based on a shift to pipeline integrity management.
Licences to operate and individual national codes and standards could include requirements for inspection types and intervals that are in direct conflict with those recommended in a risk based approach.
To get the full benefit of new technology, it is therefore important to involve the authorities at an early stage and to seek approval for new inspections programmes.
In that context, Gassco has joined forces with DNV to develop a new web based pipeline integrity management console, which will be made available to the different stakeholders through the Internet.
This console will give government agencies and others an up to date image of the risk picture for the total pipeline system. ‘Traffic light’ codes behind each pipeline system will indicate its risk category, and the user can click on individual pipelines to get details on their history, inspection programmes and results, action taken, and general technical data . See the demo below showing the layout of the new Gassco Pipeline Integrity webpage.
This system will also allow Gassco to issue reports and documents to government agencies and other stakeholders, and will be continuously updated as new information is gathered from contractors and technical service providers.
With the system due to be fully operational towards the end of 2005, the next step will be to give the authorities access to the system. This will be preceded by seminars involving relevant government agencies to inform them about using the system and explain why Gassco feels that the risk based management method will provide a better level of safety for the pipeline systems.
Operating such a large system of similar dry gas pipelines also offers benefits with the market for services and in using technical equipment and vessels. Coordinating both internal and external inspection programmes can achieve economies of scale and cost savings.
Contingency measures
Another priority area for Gassco is contingency planning. The importance of this gas transport system for Norway, its overall length and wide geographic distribution, and the fact that part of it has been installed in water depths beyond the reach of divers mean that special arrangements have been put in place to ensure that equipment and vessels are available for emergencies.
A new diverless pipeline welding repair system was recently successfully tested, and will later be extended to include diverless hot taping equipment. The figure below show drivel-less hyperbaric welding of pipeline repair sleeve.
Repair clamps, isolation plugs and mechanical couplings (for smaller diameters up to 30 in.), have been purchased and stored for all pipeline diameters in the system. This pool of equipment is expensive to maintain and keep ready for operation. Access to personnel who are familiar with the equipment and
able to use it at short notice is also important.
Gassco and partners seeks actively to utilise part of the equipment in development projects carried out by contractors or to hire it out to other operators. The cost of maintaining this system is also reduced as each new pipeline system is integrated into the emergency response pool and contributes its membership fee.
Conclusion
Research and development are also important for improving integrity management and reducing operational cost. Gassco participates in a number of industry projects in order to improve pipeline codes and standards and to achieve a better understanding of processes related to pipeline operation.