Abstract
Abstract The deposition of wax on the inner surface of subsea pipelines is a prevalent problem during the production and transportation of waxy crude oil. It can reduce effective diameter and restrict fluid flow through the pipeline. In this study, we evaluated the effect of Steel pipe, Polyvinyl Chloride (PVC) pipe and Ethylene-Tetra-Fluoro-Ethylene (ETFE) – coated – pipe on wax deposition at different temperatures and flow rates. A flow loop facility was designed to investigate the effect of different pipe surfaces on wax deposition or inhibition. Increasing temperature differential between crude oil and pipe wall, generally increased the aggregates in the three pipes. However, the amount of deposited wax gradually reduces as deposition thickness increases due to increasing trapped oil within the wax aggregates. Thus, the volume of the trapped oil increases with temperature differential. Conversely, as flow rate increases, the deposition thickness reduces, indicating less trapping of the oil as the concentration of the deposited wax increases. The least amount of deposition was observed for the ETFE – coated – pipe and a higher wax deposition reduction efficiency (70 % in average) obtained compared to steel pipe and PVC pipes. The ETFE – coated – pipe reduces wax deposition by modifying the wetting properties of the inner walls of the pipe and reducing the free surface energy of the pipe wall. ETFE has low thermal conductivity which prevents heat loss thereby making it more effective in reducing wax deposition.