Geohazards, consisting of geotechnical hazards where ground movements impact pipelines and hydrotechnical hazards where pipelines cross watercourses, can threaten pipeline integrity, causing leaks or ruptures. Given the vast geographies traversed by pipeline infrastructure, geohazard frequency can be high requiring triage of large inventories of identified geohazard sites. Since 2012, field screening probability of failure algorithms have been used to assess and prioritize geohazard threats to pipeline integrity. These algorithms were developed using empirical data from failure case histories, engineering judgement from geohazard professionals, and statistical rates of pipeline impact, exposure, and failure. When combined with consequences, the algorithms provide semi-quantitative risk assessments. The risk assessments are used to compare geohazard threats to other pipeline integrity threats to support cost-benefit decisions for pipeline operation. The algorithms have been applied to 243,000 sites on 440,000 km of oil and gas gathering, transmission, and distribution pipelines primarily in Canada and the United States.
In this paper, lessons learned from applying probability of failure algorithms to geohazard sites over the past 10 years are shared. The algorithms have proved successful in that their use has allowed pipeline operators to focus their integrity management effort on higher probability of failure sites. Use of the algorithms also allows operators to reduce investment on low probability of failure geohazard crossings. For example, the probability of failure assessments provide justification for less frequent reinspection intervals of low probability of failure sites, while providing clear means of advocating for the need to mitigate and monitor high probability of failure geohazard sites. Over the past decade, recalibration of the algorithms has reduced conservatism in earlier versions. As well, advancements in data collection, storage, and quality assurance have been undertaken to improve accuracy.
This paper describes the methods used to assess probability of failure for pipeline landslide and watercourse crossings. The use cases and limitations of the algorithms are also discussed.