Review of the Factors that Influence the Condition of Wax Deposition in Subsea Pipelines

Abstract

When crude oil is transported via sub-sea pipeline, the temperature of the pipeline decreases at a deep depth which causes a difference in temperature with the crude oil inside. This causes the crude oil to dissipate its heat to the surrounding until thermal equilibrium is achieved. This is also known as the cloud point where wax begins to precipitate and solidifies at the walls of the pipeline which obstruct the flow of fluid. The main objective of this review is to quantify the factors that influence wax deposition such as temperature difference between the wall of the pipeline and the fluid flowing within, the flow rate of the fluid in the pipeline and residence time of the fluid in the pipeline. It is found the main factor that causes wax deposition in the pipeline is the difference in temperature between the petroleum pipeline and the fluid flowing within. Most Literature deduces that decreasing temperature difference results in lower wax content deposited on the wall of the pipeline. The wax content increases with rising flow rate. As for the residence time, the amount of deposited wax initially increases when residence time increases until it reaches a peak value and gradually decreases. Flow-loop system and cold finger apparatus were used in literature investigations to determine the trends above. Three new models are generated through a regression analysis based on the results from other authors. These new models form a relationship between temperature difference, flow rate, residence time and Reynolds number with wax deposition. These models have high values of R-square and adjusted R-square which demonstrate the reliability of these models.

Application of full factorial design to screen the factors influencing the wax deposition of Malaysian crude oil

“…Similar results have been obtained further to confirm this obtained finding, (Ridzuan et al 2016) even though their experiments were performed at a longer time value. These results are in agreement with other researchers (Junyi and Hasan 2018;Lim et al 2018;Salam et al 2014). However, it should be remembered that this scenario may not be implemented in a realistic oil field pipeline since the reservoir provides fresh crude oil constantly due to the fluid's shorter residence period.…”

“…The deposition of the wax layer on the inner curved surface area and the maintenance of oil pipelines or distribution networks alone is a tedious task. It is considered a complex and costly problem (Junyi and Hasan 2018;Sun et al 2016). In Malaysia, the oil wells reportedly contained as high as 20 wt.% of solid wax content and temperature of pour point as high as 36 °C.…”

“…The solubility of wax is influenced over time, and the rate of deposition rises, causing the operative flow area or pipeline cross-section area to decrease. This can also trigger a full pipe blockage that affects the supply (Chala et al 2014;Junyi and Hasan 2018).…”

Occurrence and Characterization of Paraffin Wax Formed in Developing Wells and Pipelines

“…The variance between the cold temperature at sub-sea level and the warmer temperature of the internal pipeline fluid is the main cause of wax formation [96]. WAT is considered as the freezing point where the fluids begins to solidify [131], which causes a decrease in pipeline flow as precipitated wax becomes heavier and thicker. Exposure of pipelines to cold surroundings causes accumulation, gathering, and solidification of droplets, giving a cloudy appearance [127].…”

Geological modeling and upscaling of the Ronier 4 block in Bongor basin, Chad

“…From Fig. 1, Bongor Basin is designed by the extensional movement of the Central African Shear Zone (CASZ); more information on shear zone can be found here (Khan et al 2003;Junyi and Hasan 2018. This is detached from the Doba-Doseo Basin to the south by a basement high, and this is a huge scale of domain (Sern et al 2012) for modeling.…”