Removal of Wax Deposits in Flexible Pipelines by Electrical Heating

Abstract

In offshore oil production, sometimes unexpected situations may occur, resulting in full blockage of a subsea oil pipeline. The blockage is often due to wax freezing in cold sea. In such cases the solution is to remove the blocked oil pipeline from the subsea. In Campos Basin, Brazil, the launcher ship brings the pipelines to the Vitória Harbor, E.S (southern Brazil). The solution adopted there for blockage removal is the application of differential pressure to promote block displacement. The maximum allowed pressure is equal to the rating pressure for the pipeline, but sometimes it is not enough to move the wax core. A new solution has been developed to allow the recovery of those flexible pipes. It consists of an electrical heating process to melt the wax residues. The electrical current circulates through a metallic layer of the flexible pipeline. This solution was accomplished with success and more than 20 km of pipelines have already been recovered. This paper presents the numerical simulation and the experimental results of a flexible pipeline reel electrical heating operation and the method to control it.