Use of pressure surge for unblocking hydrocarbon pipelines

Large pressure surges in pipelines are rarely generated intentionally. Small surges have practical use in condition monitoring such as leak-detection, but large surges are more likely to be consequences of actions that would be avoided if possible. This paper describes an exception to the norm in which large pulses are generated intentionally and have positive purposes, namely the location and removal of blockages in pipelines in the hydrocarbon industry. A huge variety of pipelines exists in this industry and they are used for diverse purposes. It is common for them to be multi-purpose and to be used to convey a wide range of fluids with a colourful range of chemical properties. One consequence of this diversity is that deposits sometimes build up on the walls of pipes and, when not treated in time, this can result in the complete blockage of a line. Effective techniques exist for estimating the locations of blockages and so do techniques for removing them. However, neither task can be undertaken with certainty and, in particular, it is sometimes impossible to remove blockages by existing means at acceptable cost. The paper describes a recently-developed method of removing certain types of blockage by means of pressure surges "fired" along a fluid line in rapid succession. The method is not universally applicable, but it is far less costly than replacing long sections of pipe so it can be worth trying even though success is not guaranteed. Although the fluid mechanics of the methodology is quite well understood, much uncertainty remains about the physical mechanisms that excite blockages themselves. Accordingly, the method inevitably relies on empiricism and experience as well as on rigorous science. It is hoped that its presentation in this paper will stimulate discussion and trigger new ideas that can be developed in future partnerships.