A Pigging Model for Wax Removal in Pipes

Abstract

Abstract Pigging is widely used in pipelines for wax removal. However, pigging operation relies heavily on "rules-of-thumb." Because of its complexity, rather limited pigging models were presented to predict the wax removal mechanics in past decades. This work aims to develop a pigging model for wax removal in pipelines. A unique experimental facility was designed and constructed for simulating pigging operation for wax removal in pipelines. This facility comprises five main parts: an experiment system, a wax casting system, a motor and control system, a measurement and data acquisition system, and a special designed pig system. The mixture of crude oil and field wax deposit was cast inside the test section to carry out the pigging experiments with disc and cup pigs. It was found that hardness of the scraping element in pig has a profound effect on wax removal, and this effect depends on the wax thickness on the pipe wall tightly. A pigging model, which could well explain the effects of wax thickness, wax hardness, pipe diameter, pig geometry as well as hardness of the scraping element in pig, was established based on the experimental findings. To the best of our knowledge, this is the first time to incorporate the effect of hardness of the scraping element in pig on wax removal into a pigging model. 17 sets of pigging experiments were used to verify the developed pigging model with an average relative error of 10.69%. The pigging model developed in this work could be a practical tool in designing economic and safe pigging programs.