Managing Integrity of Underground Fiberglass Pipelines

The majority of Husky’s fiberglass pipelines in Canada have been used in upstream oil gathering systems to carry corrosive substances. When properly designed and installed, fiberglass pipelines can be maintenance-free (i.e., no requirements for corrosion inhibition and cathodic protection, etc.) However, similar to many other upstream producers, Husky has experienced frequent fiberglass pipeline failures. A pipeline risk assessment was conducted using a load-resistance methodology for the likelihood assessment. Major threats and resistance-to-failure attributes were identified. The significance of each threat and resistance attribute, such as type and grade of pipe, and construction methods (e.g., joining, backfill, and riser connection) were analyzed based on failure statistical correlations. The risk assessment concluded that the most significant threat is construction activity interfering with the existing fiberglass pipe zone embedment. The most important resistance attribute to a fiberglass pipeline failure is appropriate bedding, backfill and compaction, especially at tie-in points. Proper backfilling provides most resistance to ground settlement, frost-heaving, thaw-unstable soil, or pipe movement due to residual stress or thermal, and pressure shocks. A technical analysis to identify risk mitigation options with the support of fiberglass pipe supplier and distributors was conducted. To reduce the risk of fiberglass pipeline failures, a formal backfill review process was adopted; and a general pipeline tie-in/repair procedure checklist was developed and incorporated into the maintenance procedure manual to improve the workmanship quality. Proactive mitigation options were also investigated to prevent failures on high risk fiberglass pipelines.