Study On The Key Problems In The Pipeline Security Monitoring And Pre-warning Technique Based On Multi-Seismic Sensors

The sustained high-speed national economic development in China makes the demand of energy supplies especially oil resources increase rapidly. The oil Pipeline transportation plays an extremely important role in the national economy. Because of the dangers and pollution of the pipeline transported medium, the leakage accidents may cause huge loss of life and properties along with the environmental pollution. In recent years, the national oil transportation pipeline networks were seriously damaged; and ninety five percent of them were caused by the artificial invasions. Presently the prevalent methods to judge leakage are evaluation of parameters, such as pressure in pipeline, flow rate and temperate obtained by common oil and gas pipeline leakage detecting devices to infer whether a leakage has occurred. The monitoring sensitivities of these methods are low and the warning of leakage exclusively arrives after the leakage. The serious problem which urgently needs to be solved is to detect the pipeline invasion actions and avoid them before the pipeline security was threatened or the damages were occurring caused by the invasions but the loss doesn't cause. Therefore it is necessary to study the pipeline security monitoring and pre-warning technology.This dissertation involves the in-depth study on the pipeline security monitoring and pre-warning technique based on seismic signals. The seismic signals generated by the different targets around the pipeline were gathered. These signals were pre-processed and the targets features were extracted. The pattern recognition was done to identify the targets. The next work is to judge whether the targets belongs to the invading class and the localization is finished.The major study of this dissertation covers the following aspects:1. It studies the monitoring principle which utilizes the seismic signals to detecting the motion targets and also elaborates a variety of seismic waves in the stratum and the dissemination mechanism. It confirmed the method which makes use of the Rayleigh wave to detecting the ground moving targets. The experiments were designed to gather the several different target signals.2. The seismic signals are typically non-stationary. It analyzed the characteristics and analyzing methods of non-stationary signals. It applies the energy spectrum signal feature extraction method based on the wavelet package decomposition, the EMD (Empirical Mode Decomposition) based signal feature extraction method, and the signal feature extraction method based on the higher-order statistics to extracting the eigenvectors of the detected signals along the pipelines.3. It studies the target signals acquiring and detecting methods based on multi-sensors in the pipeline security monitoring and pre-warning technique. On the basis of researching the multi-sensor data fusion methods, it proposed the evidence reasoning theory to dispose the single recognition results. The fashioned outcomes are better than these single recognition results.4. It investigated the targets localization principles and the method based on the time difference of arrival (TDOA). On the basis of TDOA and In view of the seismic signals'non-stationary characteristics, it proposed a new method: a new localization method based on HHT (Hilbert-Huang Transform) characteristic frequency and time difference of arrival. The experiment verifies the new method is effective.