Simulation And Application Research On Pigging Process Of Long Distance Oil And Gas Pipeline

With the rapid development of China’s pipeline industry,the transport distance and freight volume of long-distance pipeline are continuously increasing.Pigging,as an important means to ensure the efficient and safe operation of pipeline,has been widely used.Pig as the core tool of pigging operation,it is very important to master its movement rule to reduce the risk of pigging operation and ensure the safe implementation of pigging operation.However,due to the tightness of the pipeline,the complexity of medium flow and the diversity of topography and landform along the pipeline,the static model can no longer accurately describe the dynamic change trend of each parameter in the pigging process.Therefore,it is necessary to study the dynamic simulation technology of pigging process of long-distance pipeline,so as to provide reliable technical guidance for the formulation and implementation of pigging operation plan,so as to improve pigging effect and reduce pipeline energy consumption.Aiming at the above problems,this paper studies the dynamic simulation technology of pigging process of long-distance pipeline,and formulates the simulation program of pigging process.Firstly,the stress and deformation of the pig in the pipeline were analyzed,and the effective contact length between the pig and the inner wall of the pipeline was calculated by the equivalent volume method.the launche process of the pig was studied,which laid a foundation for the establishment of its motion model.Then,the influencing factors of pigging process in long-distance pipeline were analyzed and summarized to provide reference for the research on the movement rule of the pig.Secondly,the dynamic simulation model of pigging process,including a nonlinear partial differential equation group and a second order ordinary differential equation group,is proposed by taking into account the terrain fluctuation,gas reality and the force of the pig in a comprehensive way.The characteristics(MOC)method was used to solve the pipeline flow equation,and the runge-kutta method was used to solve the dynamic simulation initial value and the pig movement model.Assuming that the pig completely separates the pipeline into upstream and downstream fluids,linear interpolation and left and right characteristic lines are used to process the moving boundary conditions of the pig,and the movement equation andpipeline flow equation of the pig are connected with the pressure difference at the head and end of the pig as the key parameters to realize the coupling solution of the dynamic simulation model of the pigging process.The simulation program of pigging process was written with Java language,and the maximum relative error between the calculation result and the literature data was 5.19%,and the minimum relative error was 0.37%,which verified the rationality of the dynamic simulation model and the accuracy of the program.Finally,the pigging examples of JF and HW pipelines are analyzed.The pigging process of JF pipeline sending diameter pig,magnetic steel brush pig and heavy pig was respectively simulated,and the average relative error between the pigging time and 18 groups of field data was 5.34%,which once again verified the accuracy of the pigging process simulation program.It was determined that the minimum pigging flow of JF pipeline and HW pipeline were 6.9×106m3/d and 8940.24t/d,respectively.The pipeline inclination has a great influence on the speed of the pig in the gas pipeline,but has no influence on the liquid pipeline.