Anchor-damage assessment of subsea pipelines: optimization of design methodology

摘要

The construction and operation of pipelines are known to be challenging and involve certain risks, which have to be at an acceptable level. To mitigate risks and minimize potential causes of pipeline failures, it is necessary to design, construct, and operate the pipelines safely and according to international codes and standards. Statistic shows that high-technology solutions help to decrease the probability of failures. Sometimes, however, even compliance with the necessary rules does not guarantee safe pipeline operations.There are still some undesired events that cannot be completely avoided: for instance, pipeline anchor damage. Mitigation of anchor-damage outcomes could become difficult and expensive. Even in a best-case scenario, when the pipeline only suffers minor damage, the consequences can be serious: extended pipeline shutdown, disruption of the delivery schedule, and financial losses. In the case when a ship's anchor is accidently dragged over a pipeline, the latter may suffer damage, lose its integrity, and leak. Even though the pipeline failures and their causes are discussed frequently (as in databases), there are issues related to this matter that require further study. The extent of the damage strongly depends on a pipe's unique properties, water depth, seabed topography, vessel characteristics, and anchor parameters. In addition, the Automatic Identification System (AIS) ship-traffic database with ships' particulars (identification number, type, gross tonnage, equipment specification, etc.) should also be included in the assessment. A combination of all these factors is important for the analysis and failure-frequency estimation.