Long Range Hot Oil Pipeline Leak Detection and Location Technique Based on Negative Pressure Wave

Abstract

Negative pressure wave (NPWs) technique is an effective method for oil leakage detection and location. However, conventional negative pressure wave technology failed to be applied to leakage location in China directly. China’s crude oil has to be transmitted over heating because of its high viscosity, high wax and high solidifying point. In this paper, conventional location method of instantaneous pressure wave was analyzed and techniques were developed to overcome the defects. Since temperature of the oil would drop continuously during transmission, temperature drop influence on physical characteristics of the crude oil and propagation velocity of pressure wave was studied in detail. In order to achieve high precision, wavelet transform algorithm was adopted to define inflexion of negative pressure wave when it propagates along the pipe, and wavelet threshold denoising technique was used to separate the characteristic inflexion of negative pressure wave when calculating the leak position. The problem of false alarms was solved by application of eigenvector indexes method. On the basis of that, a new oil leakage detection and location system was developed for hot oil transmission pipeline. In China, SCADA (supervisory control and data acquisition) system was installed on most oil transmission pipeline to monitor operational parameters for long range crude oil or product oil pipeline. Because it acquires pipeline operational parameters from the existing SCADA system, the cost and complexity of the new system was greatly reduced. The earliest leak detection and location system which installed on a hot oil transmission pipeline in PetroChina 5 years ago is still working well. It responds to leakage (1.5% of the total fluid) within 2 minutes and location error is less than 2% of the pipeline length between the two stations.