Structural parameters of bypass pig and movement characteristics of liquid loading in the process of pigging

To ensure pipeline flow safety and carry out pigging operation smoothly, it is of great significance to figure out the effects of structural parameters of bypass pig on its movement laws and cleaning effectiveness. In this paper, pigging simulation was carried out on an actual natural gas condensate pipeline. The effects of the structural parameters (e.g. bypass fraction and friction force) of bypass pig on its movement characteristics and pigging slug were analyzed. Besides, the difference of movement laws between the gas condensate and the liquid water in the process of bypass pigging was studied. It is shown that with the increase of bypass fraction, the average velocity of bypass pig decreases linearly, the pigging slug volume drops remarkably and gas rate fluctuation is flattened. The friction force has a great impact on the simulation results. And the predicted pigging slug will increase greatly if the friction force of the pig before the simulation is underestimated. The movement characteristics of liquid water and gas condensate in the process of bypass pigging differ a lot, and the existence of liquid water can to a certain extent, weaken the effectiveness of bypass pigging.