Experimental study of the pipeline lubrication for heavy oil transport

Heavy oil is accessible in different areas around the world in large amount. Unfortunately its high viscosity makes it difficult to produce and to transport. In this article we focus on transport problems. Pressure drop in the pipes must be lower as possible to limit pump power and to be able to transport in long distance. In the case of heavy oil, the high viscosity leads to huge pressure drop that makes it impossible to simply pump the fluid in single-phase flow, even of large diameter. Different solutions have been developed to transport heavy oil in pipeline like dilution of the crude oil in a lighter one. In this study we experiment a solution that do not modify the viscosity of the oil phase but transform the flow regime of transport: pipeline lubrication. Pipeline lubrication is a technique based on core-annular flow regime and used for pressure drop reduction in the transport of very viscous products. A thin water film adjacent to the internal pipe wall lubricates the internal oil core leading to a longitudinal pressure gradient reduction. An experimental study has been carried out where the influence of the different parameters, which could affect the lubrication process, has been optimised, using water as the annulus and heavy oil as the core of the flow. The tests were conducted in steady laminar flow at moderate flow rates. The results, obtained with annular water injection at the pipe wall, show a pressure drop reduction over than 90% as compared with the same product inflow without lubrication. These results confirm the effectiveness of the lubricating process for heavy oil transport. We also showed that density difference is responsible to particular evolution of the pressure drop with the flow rate.