Investigation of thickness and wax content of wax deposits in polyethylene pipe using a flow loop

Abstract

In this study, the thickness and wax content of wax deposits were found to be thinner and lower in the polyethylene (PE) pipe than in the stainless steel (SS) pipe using a flow loop apparatus. The diffusivity of wax, radial thermal gradient, and wax precipitation rate in the PE and SS pipes were calculated and compared. It was found the diffusivity of wax in the PE pipe was higher and tended to enhance the wax deposition in the PE pipe, while the radial thermal gradient and wax precipitation rate were lower in the PE pipe and had the opposite effects. These factors are shown to be comparable with each other and the effect of the thermal gradient dominates the mass flux of wax from bulk to the oil‐deposit interface and into the deposits finally, thus causing differences in thickness and wax content of deposits between the PE and SS pipes.

Surface Material Effects on Wax Deposition in Noncoated Pipelines

“…Collectively, it seems reasonable to accept that there is a slight difference in deposition, given that the PTFE deposit is marginally larger in all cases. These observed material effects on deposition are much smaller in magnitude compared to those reported in previous work. − Given the fact that none of the previous work attempted to maintain the same surface temperature when different surface materials were used, it is likely that the observed large differences in deposition from previous work were mainly caused by thermal effects rather than material effects.…”

“…Li et al explored surface effects by comparing polyethylene (PE) and steel test sections in a flow loop. , Their initial experiments showed that the PE generated thinner deposits with lower wax content. In their paper presenting these results, they conclude that these results are mainly caused by the lower thermal conductivity of PE as compared to steel, which generates a decreased thermal gradient.…”

“…However, field pipelines might experience constant corrosion, erosion, or aging, causing their surface properties to be very different from those of newly manufactured steel pipes. In addition, nonmetallic pipes such as polyethylene pipes or reinforced thermoplastic pipes are widely used in gathering and transporting crude oils and gas condensates due to their low-cost and anticorrosion properties . According to the current theories of the wax deposition, the deposition process initiates with the formation of a gel layer on a cold pipe wall. , Presumably, the surface properties of pipe walls strongly influence wax deposition rate and the strength of the formed deposits.…”

Effect of polyethylene pipe on wax deposition under different temperature and flow rate conditions

“…Unfortunately, only a few experiments about nonmetallic pipelines influencing wax molecule movement progress, especially PE pipeline, were conducted in the past time 21 . At the beginning period, nonmetallic coated cold finger is one of the widely used approaches to carry out wax deposition experiments.…”

“…Unfortunately, only a few experiments about nonmetallic pipelines influencing wax molecule movement progress, especially PE pipeline, were conducted in the past time. 21 At the beginning period, nonmetallic coated cold finger is one of the widely used approaches to carry out wax deposition experiments. Jorda et al explore the difference between several cold finger devices with two kinds of nonmetallic coated and steel coated respectively during wax deposition experiments.…”