Wax deposition has been a problematic issue in flow assurance for the past two decades. In addition to some well-known remediation techniques of wax deposition, field engineers often scour the wax layer by increasing the flow rate to achieve a stripping effect. In previous studies, scholars have typically investigated flow rate as an influencing factor for wax deposition, but the effect of scouring alone on wax layer thickness has rarely been reported. <br/>In this work, the effect of oil scouring on wax deposition was investigated using a self-designed flow loop facility. The indoor scouring experiments were carried out under zero oil-wall temperature difference, thus avoiding molecular diffusion effects. The experimental results found that there is critical shear stress (CSS) for the oil scouring effects. When the shear stress exerted by the oil flow on the wax layer is lower than the CSS, the effect of oil scouring on the wax layer thickness can be negligible. However, the thickness of the wax layer decreases with the increase of the scouring time as the shear stress applied to the wax layer is greater than the CSS. <br/>The mechanism behind this phenomenon is the competition between the wax deposit strength and the non-Newtonian properties of the fluid. The wax deposits are rheomalaxis elasto-viscoplastic in nature. Since the shear stress exerted by oil flow on the wax layer is much lower than the yield stress of the wax layer, the solid nature of the wax deposit is responsible for the low stripping efficiency. But the creep effect makes the wax layer thickness decrease with increasing scouring time when the scouring stress approaches the yield stress of the wax layer. The work provides theoretical guidance for field wax removal operations.

Influence of oil scouring on wax deposition in flow lines

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.