The location of pipeline blockages continues to be a challenge to pipeline operators at exactly the moment when fast and accurate location of such blockages is fundamental to getting pipelines back in service. Methods currently exist for blockage locations; however, they are generally limited to the conditions in which they can be used or by their accuracy.
This paper discusses a new method for pipeline blockage detection using pressure wave analysis that analyzes the reflections generated by a pressure wave traversing the pipeline to the blockage location and back again. By connecting an ultra high-speed data logger to the pipeline, a pressure wave, generated by the rapid opening and closing of a bleed valve, can be recorded for analysis. The details of the pipeline and the fluid provided by the operator can be used to calculate the system acoustic velocity and, in combination with the recorded data, can, therefore, calculate the distance from the recording location to the blockage.
It can be shown that the theory behind the method is backed by results observed when using it to locate actual blockages within actual pipelines. Case studies are presented to show that the method can be used in both flowing and nonflowing pipelines, both on and offshore, in all fluids to identify where a blockage is located. The theoretical method for calculation of acoustic velocity for known system and fluid parameters can be shown to be accurate within tolerances when compared to the acoustic velocity gained in the field by recording the time of flight between two known points. It can be observed that blockages can be detected to a level of accuracy of up to 0.3% of pipeline length verified by comparison with pipeline features and with odometer data from a stuck intelligent pig.
The method presented in this paper differentiates itself from other pipeline blockage location systems by the use of pressure wave analysis. It has a higher level of accuracy than that claimed by other remote nonintrusive technologies available, therefore, giving pipeline operators the opportunity to target remediation work in a more efficient and cost-effective manner.