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.

Corrosion Control in CO2 Enhanced Oil Recovery From a Perspective of Multiphase Fluids

“…work from Landry et al (2012) suggested that the settlement of solid particles is much easier onto the pipeline bottom and water may also be accumulated around such solid particles forming a locally water-rich environment. In this condition, corrosion may be preferentially initiated around the solid particle (Han et al, 2013).…”

Comparison of Mono- to Diphosphate Ester Ratio in Inhibitor Formulations for Mitigation of Under Deposit Corrosion

“…Although studies have been conducted to understand how deposits form in order to mitigate deposit formation [1][2] and to experiment with inhibitor packages to understand the risk and mechanisms involved with inhibition of UDC, 3,7-10 no formal attempt has been made to observe the effects of specific chemical components in an inhibitor package on UDC. The objective of this study was to test individual chemical components used in industrial inhibitor packages against localized UDC.…”

“…Experimentation for each inhibitor consisted of 28 d in a 2 L glass cell using API (1) 5L X65 pipeline steel partially covered with 250 μm diameter sand particles. Experimental conditions required purging the specified brine (Table 1) with CO 2 at 1 bar (100 kPa) total pressure while maintaining the solution temperature at 70°C.…”

“…Under deposit corrosion (UDC) is a localized corrosion that occurs where sediments, carried through a production or transmission pipeline, have settled in stagnant or low-flow sections of a pipeline and mitigation strategies are ineffective or impractical. Computational fluid dynamics studies [1][2] have recently been conducted to understand mechanisms of solids deposition in order to mitigate deposit formation. Conclusions from these studies confirmed specific conditions related to flow and pipeline geometry reduce the near-wall velocity at the pipe floor, allowing deposits containing a mixture of water, hydrocarbons, microorganisms, and inorganic compounds to form.…”