Application of pigging track approach in gas-exhausting for gas-liquid two-phase flow in undulating pipelines

During the gas-liquid replacement process of the oil undulating pipeline, there are liquid single-phase parts, gas single-phase parts and liquid gas two-phase parts appearing alternately, which pose challenges to the pig tracking and gas-exhaust simulation. In this paper, a novel approach to exhaust the gas from the pipe applying the pigging tech is proposed, and the complicated motion of pig in the undulating pipeline is described by the self-adapting momentum equations based on the hydraulic analysis during operation process. The analysis focuses on the changeable pressure and force condition happen to the pig with its moving along the pipeline and switch the describe-equation to the pigs automatically. The model validation by the field data of a real pipeline in China shows that the relative deviation of pig real time speed is within 0.5%, and the relative deviation of pig position is within 2.2%.