Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Wax deposition model for a new crude oil pipeline in frigid region: Experiments with a laboratory flow
loop
Kaifeng Fana*,b, Si Lia,b, Guangjian Zhanga, Yilinaer Tuerxuna, Kai Chaob, Xuesong Huangb
aCollege of Petroleum Engineering, Liaoning Petrochemical University, Fushun, Liaoning Province, China
bInstitute of Petroleum Engineering Technology, Zhongyuan Oilfield Branch of Sinopec, Puyang, Henan Province, China

the pipe wall. Huang (2011) proposed that molecular diffusion is themain cause of wax deposition. The aging mechanism mainly affects thediffusion process of wax molecules in the porous network structure ofthe deposits, which is reflected in the distribution of wax moleculecarbon number and wax content in the radial direction of the deposits(Fan et al., 2021b, Fan et al., 2022a). The shear stripping mechanism ismainly reflected in the scouring and compaction of deposit by oil flow,which has a significant influence on the wax content and structural
strength of deposit (Fan et al., 2021b, Fan et al., 2022b).
Wax deposition often occurs in the waxy crude oil transporting
pipelines, resulting in the decline of pipeline transportation capacity,
increase of operating pressure and energy consumption. In serious
cases, the pipeline section may even be completely blocked, bringing
huge potential safety hazards to the pipeline system. What’s more, thewax deposition is not only related to its own properties, but also related
to many external factors. Huang et al. (2006) studied the effect of crude
oil temperature on wax deposition rate through experiments. With theincrease of oil temperature, the temperature difference between crude
oil and pipe wall increases and the wax deposition rate gradually
increases. Li et al. (2006) discussed the wax deposition mechanism andthe factors affecting the wax deposition on the pipe wall by simulating
the wax deposition in a certain pipe section during the operation of theoil pipeline. The results showed that when the crude oil temperatureremains unchanged, the increase of oil/wall temperature difference canenhance the wax deposition rate. When the oil/wall temperature
difference remains unchanged and the crude oil temperature increases,
the wax deposition rate also increases. It can be seen that the wax
deposition rate increases with the increase of oil temperature and pipe
wall temperature difference.
In the present work, the newly developed oilfield we focused on is
located in an extremely cold environment, where the temperature isvery low in winter (the extreme low temperature recorded was 36.4 °C). Moreover, the crude oil presented a high wax content. Thus,
the wax deposition risk of the new pipeline is very high. Therefore, thestudies of the wax deposition rule and model can provide a theoreticalbasis for the safe operation of the pipeline and the formulation of wax
removal scheme, and is of great significance to the growth of oilproduction.

ABSTRACTWax deposition prediction is of great significance for the waxy crude
oil pipeline safety. Herein, the wax deposition characteristics of a newcrude oil pipeline was experimentally studied in a laboratory flow loop
device. It was found that the higher oil temperature and pipe/oiltemperature interval could accelerate the wax deposition rate, while theincreases of pipe wall temperature, flow velocity and deposition
duration reduced the wax deposition rate. The wax molecule
concentration gradient and the scouring force played critical roles on
the wax deposition process. Furthermore, a wax deposition model wasdeveloped considering the mechanism of wax molecule diffusion andshear stripping. This work provides an insight into the wax deposition
characteristics and will benefit the pigging maintenance of the newpipeline in the future.

KEY WORDS: Extremely cold environment; Waxy crude oil; Wax
deposition experiment; Prediction model.

INTRODUCTION
Wax deposition has always been the hotspot in petroleum, which is
widely existed in the waxy crude oil pipeline and is affected by manyfactors (Chi et al., 2017, Fan et al., 2021a). More than 80% of the crude
oils in China are waxy crudes with wax content of 2.5%~10%. In thepast few decades, some wax deposition mechanisms, such as molecular
diffusion, shear dispersion, Brownian motion, gravity sedimentation,aging and shear stripping have been proposed (Singh et al., 2000, Singhet al., 2001, Kannan et al., 2018, Yang et al., 2020). Among them,molecular diffusion and aging are the main internal mechanisms
causing wax deposition. Shear stripping, as an external effect, has acertain impact on the deposit, while other mechanisms have little
impact on wax deposition and can be ignored (Xiao et al., 2012). The
molecular diffusion mechanism is mainly due to the temperature
difference between the oil and the pipe wall, resulting in differentsolubility of wax molecules and the concentration difference of wax
molecules, which makes the wax molecules diffuse from the oil flow to1657