Oil And Gas Pipeline Safety Monitoring Based On Distributed Optical Fiber Sensing Basic Research

Pipeline transportation as one of the most efficient way in the petroleum and gas transportation has been widely used. However, in recent years, pipeline leakage, due to drill stolen, natural disasters, aging pipes and other reasons, occurred frequently, it caused a very high price to the economy and the environment. Therefore, the safety monitoring of petroleum and gas pipelines becomes increasingly important. Existing petroleum and gas pipeline safety monitoring methods mainly have the negative pressure wave method, the acoustic method and the stress wave method, although they have been used in certain degree, they commonly have the shortcomings of high maintenance costs, monitoring is difficult and high rate of false positives and other shortcomings. In recent years, fiber sensing technology, which has the advantage of anti-electromagnetic interference, high sensitivity, large dynamic range, has experienced a rapid development, and it has got certain degree of commercial use in bridge security monitoring and temperature monitoring. Optical fiber sensing technology can also be applied to the field of petroleum and gas pipeline safety monitoring, When vibration or stress events caused by the petroleum and gas pipeline leakage have some influence on the fiber, phase and polarization state of light signal transmitted by the fiber will change, therefore, petroleum and gas pipeline safety monitoring can be achieved by monitoring the optical signal changes. Therefore, optical fiber sensing technology as a novel sensing technology is a very competitive and promising pipeline safety monitoring method. The main work of this dissertation has the following content:1. A distributed linear optical fiber sensor based on Sagnac interferometer is designed, and the principle of position determination of this sensor is analyzed, position determination simulation and experiments are carried out.2. The polarization induced signal fading phenomenon commonly existing in fiber optic interferometer is analyzed, the optical transmission model of the optical fiber sensor is built by using the Jones matrix, and the power transmission coefficient is theoretically analyzed when the light reflector, the fiber ring and the Faraday rotator mirror (FRM) respectively as the reflection devices for the sensor. The results show that the FRM have a significant effect for the elimination of the polarization induced signal fading phenomenon.3. A signal processing software based on Matlab and VC mixed programming is made by taking full advantage of the rich library of Matlab, the signal is de-noised by wavelet transform, and the spectrum of the signal is further analyzed by Fast Fourier Transform (FFT). Interference signals on two different vibration position are processed, and after that, clear "zero frequency" distribution that has a good consistence with the theoretical simulation results can be seen, it shows that the sensor can locate the position of the vibration point.