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

Pipeline Transportation Technology of Blended Hot and Cold Waxy Crude Oils Treated With Pour Point
Depressant
Si Li1,2, Kaifeng Fan1,2, Dingqi Xu1, Kai Liu1
1 College of Petroleum Engineering, Liaoning Petrochemical University, Fushun, Liaoning, China
2 Institute of Petroleum Engineering Technology, Zhongyuan Oilfield Branch of Sinopec, Puyang, Henan, Chinaappearance and distribution of precipitated wax crystals, as studied
previously by Chen et al. (2010), Yi et al. (2011), and Jin et al. (2014).
After treated with proper PPD, the pour point and the apparent viscosity
values under WAT of the treated oils will effectively reduce. Pipelines
applying heating transportation technology with PPD are able to run
with lower temperature and less heat stations, making the transportationsafer and more economical, see Zhang et al. (2013).

ABSTRACTThe transportation technology of waxy crude oil treated with pour point
depressant was investigated in laboratory. Several pour point
depressants were evaluated and the optimal treating conditions weredetermined. Furthermore, the influences of the sudden temperature dropwhen mixing with cold oil and the high-speed shearing exerted bycentrifugal pump were analyzed. In addition, the treating effect in thewhole pipeline was verified by reproducing the cooling rate and shear
rate of the pipe flow with in-door experiment. The blend oil could betransported safely with the treatment technology of pour point
depressant in winter.

The treating effect of PPD on waxy oil may be weakened because of
the reheating, rapid cooling and shear effect in oil pipelinetransportation. Treated crude oil may experience necessary reheatingwhen flowing through intermediate heat stations. If the reheating
temperature was lower than the original treatment temperature, it may
deteriorate the treating effect causing the pour point and viscosity risingagain (Li et al., 2016). The phenomenon of pour point reversion is asevere threat to the pipeline operation safety. In some extremely cold
regions, the temperature difference between the hot treated oil and theambient temperature of pipeline is very significant. When the hottreated oil flows into the cold pipeline, its temperature will drop
suddenly. This rapid cooling may also lead to the deterioration of thetreating effect. In addition, this may happen when treated oilexperiences strong shear from the centrifugal pump or the shear effectcaused by the pipe flow in the temperature range in which amounts ofwax crystals form. Therefore, it is necessary to study the impact ofthermal and shear process to verify the treating effect in the whole
pipeline transportation process.

KEY WORDS: Waxy crude oil; pour point depressant; pipeline;
shear effect; thermal history.

INTRODUCTION
When the temperature of waxy crude oil drops below its wax
appearance temperature (WAT), wax components will precipitate
forming wax crystals. These crystals can gradually develop into a threedimensional network structure, which deteriorates the flow ability ofcrude oil. If the oil temperature was below its pour point, oil will totallylose its flow ability and show up solid-like properties, as described byVisintin et al. (2008) and Fan et al. (2022). As to long-distance oilpipelines exposed to cold surroundings, oil temperature will drop
significantly during transportation. Crudes with high wax fraction tend
to gel at a comparatively high temperature. Once there was oil gelation
incident in a certain pipeline section, oil transportation would beinterrupted and the pipeline might even rupture because of overpressure.

This paper is a study based on an industrial crude oil pipeline. The
transportation technology of waxy crude oil treated with pour point
depressant was investigated in laboratory. Several pour point
depressants were evaluated and the optimal treating conditions weredetermined. The influences of the sudden temperature drop and thehigh-speed shearing from centrifugal pump were analyzed. The treating
effect in the whole pipeline was verified by reproducing the coolingrate and shear rate of the pipe flow with in-door experiment. This study
will offer important theoretical basis for the application of thetransportation technology with PPD in this pipeline.

In waxy crude oil pipelines, heating transport technology is commonlyused to guarantee operating safety. However, as being reported byZhang et al. (2013), the application of this technology spends a hugeamount of energy, as well as the invested capital and manpower of heatstations. For some waxy oils with high pour point or low flow rate, itwould be impossible to maintain oil temperature at a safe level evenwith heating in some cold regions with low soil temperature.

INFORMATION OF OIL PIPELINE

Pour point depressant (PPD) is a kind of macromolecular polymers.
The cocrystallization of wax molecules and PPD can change theZL Crude Oil Pipeline connects ZY Oil Field in the city of Puyang and1760