Computational Fluid Dynamics Study of Solids Deposition in Heavy Oil Transmission Pipeline

Abstract

Previous studies have shown that transmission-quality heavy crude oil carries water-wetted solid particles, that these particles can accumulate on the pipe floor and cause under-deposit corrosion, and that the incidence of accumulation is strongly correlated to locations downstream of over-bends. This paper describes a computational fluid dynamics (CFD) analysis of light and heavy oil flow in a representative segment of a real transmission pipeline in which corrosion has been observed. The purpose was to gain insight into the key processes affecting deposition in heavy oil that do not occur for light oil and to offer suggestions for mitigation. The analysis suggests that the key effect in determining whether particles become trapped is the near-wall velocity of the flow, which is found to be significantly lower for heavy oil compared to light oil, especially downstream of over-bends. This causes particles near the pipe floor to move slowly and makes them susceptible to becoming trapped. It is interesting that the key process affecting deposition is not the tendency of particles to fall to the pipe floor, which occurs more readily in light oil than heavy oil, but, rather, the ability of the flow to keep particles moving along the pipe floor.