The remote nature of long-distance pipelines can expose them to a range of external loads.
Earthquakes, landslides, sea bed movement, ship anchor drags, permafrost, flooding, third party damage, construction and backfill all have the potential to locally deflect a pipeline from its as-built position.
While the incidence of natural force damage is comparatively low, the consequences are far greater.
Natural force damage only equates to 8 per cent of significant incidents but causes 34 per cent of all property damage.
This is because these incidents tend to result in pipeline rupture rather than leakage (hence greater spill volumes), longer downtime and increased property and environmental damage.
It is possible to identify ground conditions and locations where pipelines may be at risk of damage from bending deformation and where mapping should be considered as a matter of course.
Subsea pipelines in areas of known or suspected seabed movement or areas of spanning, as well as subsea pipelines in areas of known marine activity where there is a chance of anchor drag or trawling should also be assessed routinely.
Pipeline mapping can be carried out as part of a wider integrity monitoring program where defects and metal loss can also be identified in a single run using smart pigs.
PII Pipeline Solutions’ (PII) MagneScanâ„¢ high-resolution metal-loss inspection for advanced length and width sizing of pitting and Narrow Axial External Corrosion (NAEC) or CalScanâ„¢ EP (Caliper) tools can locate and measure dents and other geometric deviations.
PII has first-hand experience of inspecting undersea pipelines that have been subjected to considerable external force.
PII was engaged by a European customer who has a number of large diameter offshore lines in its infrastructure portfolio.
The mapping data provided by the Inertial Mapping Unit (IMU) is used to provide a 3D model of the pipeline’s actual centerline co-ordinates so that any areas of significant curvature and the associated bending strain magnitude can be identified and investigated.
When repairs are required for defects reported by an inspection, highly accurate IMU coordinates enable the pipeline operator too quickly and reliably locate them via a precise GPS location prior to excavation, significantly reducing digging costs and in-field time.
As well as helping to assess bending strain, IMU mapping can help pipeline operators to satisfy regulatory demands.
Increasingly, regulations demand that pipeline operators document the precise location of pipeline assets.
Pipeline mapping can also benefit operators by determining the precise location of each girthweld and pipe feature.
Strain measurement is an excellent indicator of where unknown or unexpected pipeline movement may have occurred.
By identifying change of shape of a pipeline and any potential movement since the last inspection run it offers enhanced integrity monitoring and early warning of ground instability.
Strain measurement also helps prevention of failures through identification of strain events and coincident features throughout the pipeline.
Combined with PII’s IMU technology, it provides an invaluable integrity monitoring tool for oil and gas pipeline operators.
To find out more about PII Pipeline Solutions products and services visit www.ge-energy.com/products_and_services/services/pipeline_integrity_services.