Arctic Pipeline Leak Detection using Fiber Optic Cable Distributed Sensing Systems

摘要

Multiple offshore Arctic fields have been developed over the past three decades and the world demand for oil and gas will continue to drive hydrocarbon development in Arctic and sub-Arctic environments. Arctic pipelines are used for the safe and economic transportation of hydrocarbons. While pipelines are designed not to leak, excessive strains due to the effects of ice gouging, strudel scour, frost heave and permafrost thaw settlement along with other loading and failure mechanisms (i.e. corrosion, third party damage) could result in a leak. Failure to detect leaks in a timely manner could have severe safety, environmental, and economic impacts. Large leaks can easily be detected, but small chronic leaks may go undetected for a period of time, especially when pipelines are buried in remote locations or under seasonal ice cover. First, this paper reviews existing Leak Detection System (LDS) technologies for their potential use on Arctic and sub-Arctic pipelines. The technology evaluation based on regulatory requirements and functional criteria suggests that Fiber Optic Cable (FOC) distributed sensing systems have a high potential to be used on Arctic pipelines. Distributed sensing FOC can be used to detect and locate leakages. Pipeline leakage would generate a local change in temperature. These thermal anomalies can be captured by FOC Distributed Temperature Sensing (DTS) systems with good spatial and temporal resolution. Similarly, the acoustic signature generated by leaking fluid can be detected using FOC Distributed Acoustic Sensing (DAS) systems. Inelastic Brillouin and Raman backscattering principles are used for measuring temperature in DTS, whereas the Rayleigh backscattering principle is used for measuring acoustics in DAS. This paper presents information on applicable regulations, operating principles, optical budgets, system integration, sensor positioning, installation and maintenance assessment, technology status, risk analysis using Failure Mode, Effects and Criticality Analysis (FMECA) and field implementation challenges.