Application Research Of Distributed Optical Fiber Sensing Technology Used In Deformation Monitoring Of Long Distance Pipelines

Oil and gas pipelines are being laid over long distances and serve in harsh environment; the security issue has been widely concerned. Excessive deformation is one of the main failure modes of oil and gas pipelines, and traditional pipeline monitoring methods are mostly regular and offline detection, while Brillouin distributed optical fiber sensing technology will become the new method of pipeline health monitoring for the advantages of long-distance, continuous, real-time and online monitoring. The main contents of this thesis are as follows:(1) Failure modes of pipelines and the existing pipeline monitoring methods are investigated; the problems of pipeline monitoring methods are pointed out, then the application of Brillouin distributed optical fiber sensing technology to pipeline deformation monitoring is studied.(2) The basic theory of distributed optical fiber sensing technology is presented. Various types of pipeline deformation failure cases are analyzed and discussed. And then, the feasibility of the application of technology in the pipelines is analyzed.(3) Deformation types and failure assessment of the pipeline for deformation are summarized. Behaviors of pipe buckling based on ABAQUS are analyzed and the strain distributions with the changes of external loads are presented, then the critical buckling strain of pipe is determined and is regarded as a threshold to monitor the pipeline bucking occurrence.(4) Strain monitoring of pipelines based on Brillouin optical fiber sensing technology is carried out to verify the feasibility and effectiveness of the technology in the pipeline deformation monitoring, and optical fiber sensing ability of strain and temperature, the methods of sensing fiber fixation to the pipe and the factors affecting the measurement accuracy are investigated.(5) Pipeline deformation health monitoring system based on strain sensing by Brillouin distributed fiber sensor is constructed and the deformation assessment software based on LABVIEW by strain analysis to monitor and track positions of pipe large deformation is developed.