An Experimental Study on Wax Removal in Pipes With Oil Flow

Pigging is recognized as one of the most used techniques for removing wax deposits in pipelines. In an earlier paper, the mechanics of the wax removal was studied using an experimental setup under dry conditions, i.e., no oil presence. In this study, the pigging experiments are conducted for both regular disc and by-pass disc pigs under flowing conditions. A new test facility was designed and constructed. The test section is 6.1 m (20-ft) long Schedule 40 steel pipe with an inner diameter of 0.0762 m (3-in.). A mixture of a commercial wax and a mineral oil is cast inside the spool pieces for different wax thicknesses and wax oil contents. The wax breaking and plug transportation forces are investigated separately. The results indicated that the wax breaking force increases as wax thickness increases, and the wax plug transportation force gradient is independent of the wax plug length. In comparison to previous test results, presence of oil reduced the wax plug transportation force. Experimental results also showed that the wax transport behavior of the by-pass pig is significantly different than that of the regular pig. The by-pass pig allows the oil to flow through the by-pass holes and mobilizes the removed wax in front of the pig resulting in no discernible wax accumulation in front of the pig. Therefore, no measurable transportation force was observed for the by-pass pig tests.