Leakage detection in a buried gas pipeline based on distributed optical fiber time-domain acoustic wave signal

In long-term operation, buried pipelines are prone to corrosion, deformation, and fracture, resulting in leakage. It will cause serious environmental pollution and economic loss. Distributed temperature sensing (DTS) and location method based on temperature signals have been gradually applied to the pipe network. However, the DTS is difficult to comprehensively monitor pipeline leakage and has blind monitoring areas. In addition, fiber optics are difficult to capture continuous low-temperature changes because of the heat dissipation of soil porous media. Thus, distributed acoustic sensing (DAS) is needed to assist the comprehensive monitoring. The acquisition of acoustic signals caused by the leakage field is of great significance to the study of pipeline leakage monitoring methods. In this paper, the attenuation model of leakage acoustic amplitude is established, and the law of vibration acoustic signal in porous soil is studied. Based on the real natural gas leakage test, the characteristic parameters of the time-domain acoustic wave signal are studied. It is proved that the vibration acoustic signal is a kind of acoustic wave caused by the transient mass loss at the beginning of leakage. The main conclusions are as follows: the time-domain signal amplitude is large and the vibration is obvious when pipeline leakage occurs. Acoustic wave leakage occurs in a very short time and acoustic vibration amplitude reaches its peak. Subsequently, the pipeline is in a stable leakage state, and the waveform continues to expand. When there is no natural gas leakage, the vibration signal intensity is less than 3000, and the amplitude changes little. The difference is that when the pipeline leaks, the vibration test curve signal has obvious bulge and fluctuation, and the vibration signal intensity is basically above 4000. The amplitude of the vibration signal increases with the increase of the leakage hole. The research results provide a theoretical basis for the field application of distributed optical fiber acoustic detection.