Research On Model Based Leak Detection And Location Method For Oil And Gas Pipelines

Leak detection and location system plays an important role in the management of pipeline systems. In recent years, many kinds of leak detection and location methods have been developed and used, but most of them have limits in real applications, such as the applicability and detect ability. Based on the flow equations of pipeline, the model based leak detection and location method can determine the leak location and size of leakage, and is identified as a promising method in detecting burst, small and sluggish leaks. Recently, the widely used flow meters and Supervisory Control and Data Acquisition systems also provide the basis for applying model based leak detection and location method to oil and gas pipeline. However, the current model based method had difficulties in determining leak location during release transient process, leading to a long location time, and was subjected to severe noise and seldom addressed in gas pipelines. Its accuracy was influenced by the parameters of the model. Therefore, it is of great importance in both theory and application to research on the model based method and to improve the performance of the method.Based on the detailed analysis of current methods, the application of steady-state model based method to oil and gas pipeline has been futher studied, the method to detect and locate leaks during release transients has been researched, and the method to modeling a leaking pipline has been investigated as well.According to the analogous between the pipeline and the circuit, a method to modeling a leaking gas pipeline has been proposed. The simulation model established with the method can provide test data for leak detection and location algorithm. Experiments conducted on a real gas pipeline validate the the simulation model.The application of the steady-state model based method to oil and gas pipelines has been investigated, and the isothermal leak detection method and the variable-step Runge-Kutta method have been proposed for leak location in isothermal and non-isothermal gas pipelines respectively. Simulation research and experiments have been carried on to study the effect of the model simplification on the performance of the two methods. A modification for the steady-state model based method, named the optimal leak location identification based on the least square algorithm, has been presented and experiment results confirm the modification's abability to suppress the noise and to speed up the convergence rate of leak localization. A new method based on the release transient model is proposed to detect and estimate the leakage point during the release transient, leading to a shorter leak location time and facilitating the trouble shooting. Combining the method based on steady-state model and method based on release transient model, an integrated method is constructed to take the advantages of the two methods. Simulation and experimental results showed that the release transient model based method can detect and locate leaks in shortest time after the release and the integrated method not only realized the leak localization in real time, but also ensured the integrity in leak detection.The effect of uneven distribution of pipeline parameter on the precision of leak estimation has been analyzed, a new approach, named equivalent transformation of the pipe length, which transform the uneven parameter distribution to the variation in pipe length, has been presented to compensate for the location error introduced by the uneven distributed parameter, and to improve the accuracy of the model based method. Experiments conducted on real pipelines verified the validation of the compensation method.The isothermal method and the variable-step Runge-Kutta method proposed in this paper enable the application of model based method to gas pipelines, the release transient model based method and the method to compensate for the location error improve the accuracy of the leak estimation and enable leak location in real time, promoting the development and application of model based method to oil and gas pipelines.