Petroleum product pipeline monitoring by optical frequency domain reflectometry

Large natural gas and product transmission pipelines exist throughout the United States. These pipelines are susceptible to failure through corrosion and cracking due to internal and external factors. As these transmission pipelines age, the likelihood of a catastrophic failure increases. The ability to the monitor corrosion and wall thickness of these pipelines is paramount to reduce the risk of disastrous failure and increase reliability as well as safety. Optical frequency domain reflectometry (OFDR) can monitor distributed temperature and strain measurements along the fiber optic cable mounted on natural gas and product pipelines. This measurement technique can provide valuable information of pipe structural health conditions through hoop strain changes due to pipe wall thinning, and temperature changes due to gas leaks based on the Joule-Thomson effect. Since these pipelines are typically buried, the depth of the pipeline results in a potential loss in the sensing range where the fiber is not physically monitoring the hoop strain of the pipeline. A different configuration of the interferometer will allow for the distributed fiber measurement to start atop the pipeline itself. This configuration results in no loss of sensing range and maintains the sensing resolution of a typical interferometer for an OFDR measurement. The quasi-extended range distributed hoop strain measurements were demonstrated on an active transmission pipeline.