Impacts of Cooling Rates on Voids in Waxy Crude Oil under Quiescent Cooling Mode

Chala, Girma T.; Sulaiman, Shaharin Anwar; Japper-Jaafar, Azuraien; Abdullah, Wan Ahmad Kamil Wan

doi:10.4028/www.scientific.net/amm.799-800.62

Cited by 9 publications

(3 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Remarkably, thermal analysis could help to understand and develop control strategies alleviating flow problems [25][26][27]. Thermal shrinkage experienced during cooling of waxy crude oil produces an intra-gel void, and this reduces the strength of the gel structure [28][29][30]. On the other hand, flow assurance could be maintained by injecting non-reacting gas into production pipelines to ease the restarting of the pumping of waxy crude oil.…”

Section: Introductionmentioning

confidence: 99%

Artificial Neural Network and Regression Models for Predicting Intrusion of Non-Reacting Gases into Production Pipelines

Chala¹,

Negash

2022

Energies

View full text Add to dashboard Cite

Wax deposition and gelation of waxy crude oil in production pipelines are detrimental to crude oil transportation from offshore fields. A waxy crude oil forms intra-gel voids in pipelines under cooling mode, particularly below the pour point temperature. Consequently, intrusion of non-reacting gas into production pipelines has become a promising method to lessen the restart pressure required and clear the clogged gel. A trial-and-error method is currently employed to determine the required restart pressure and restart time in response to injected gas volume. However, this method is not always accurate and requires expert knowledge. In this study, predictive models based on an Artificial Neural Network (ANN) and multilinear regression are developed to predict restart pressure and time as a function of seabed temperature and non-reacting gas injected volume. The models’ outcomes are compared against experimental results available from the literature. The empirical models predicted the response variables with an absolute error of below 5% compared to the experimental studies. Thus, such models would allow accurate estimation of restart pressure, thereby improving transportation efficiency in offshore fields.

show abstract

Section: Introductionmentioning

confidence: 99%

Artificial Neural Network and Regression Models for Predicting Intrusion of Non-Reacting Gases into Production Pipelines

Chala¹,

Negash

2022

Energies

View full text Add to dashboard Cite

show abstract

“…Waxy crude oil behaves as a Newtonian fluid above the wax appearance temperature, over which a viscosity is not a function of temperature [4][5][6]. As the temperature further drops, the wax within the waxy crude oil starts precipitating, forming gelled crude oil below the pour point temperature.…”

Section: Introductionmentioning

confidence: 99%

Study on influence of flow rates on voids in waxy crude oil subjected to dynamic and static cooling

Chala¹,

Sulaiman²,

Japper-Jaafar³

et al. 2015

J. Mech. Eng. Sci.

Self Cite

View full text Add to dashboard Cite

The assumption of constant yield stress in the conventional restart pressure equation neglects the effects of thermal shrinkage and gas voids formation, which in turn resulted in an over-designed production piping systems. This paper presents a study on the effects of flow rates on the formation of voids in gelled waxy crude oil. A flow loop rig simulating offshore waxy crude oil transportation was used to produce a gel. A Magnetic Resonance Imaging (MRI) was used to scan the gelled crude oil over the three planes. Waxy crude oil underwent both dynamic and static cooling to observe the effects of volume flow rates on the voids formed in wax-oil gel. Volume flow rate was found to have different influences on the intra-gel voids in the pipeline. A volume flow rate of 5 L/min resulted in a maximum total voids volume of 6.98% while 20 L/min produced a minimum total voids volume of 5.67% in the entire pipe. Slow flow rates resulted in a larger voids volume near the pipe wall. In contrast, faster flow rates produced insignificantly higher voids volume around pipe core. Generally, slower flow rates favoured the formation of higher total voids volume following sufficient steady time of wax crystal formation, producing larger voids areas in gelled waxy crude oil.

show abstract

“…As a result of thermal shrinkage of waxy crude oil during cooling, the formation of intra-gel voids is eminent [8][9][10]. Many research papers also recommended the understating of thermal shrinkage and the resulting gas voids formation to predict the restart pressure as accurately as possible [11]. Xiaokai et al [12] illustrated the importance of considering the heat transfer calculation in the process of restarting, including physical properties of gelled crude oil during phase changes while cooling.…”

Section: Introductionmentioning

confidence: 99%

Investigation of convective heat transfer coefficient and initial temperature of waxy crude oil on the formation of voids

Chala¹,

Sulaiman²,

Japper-Jaafar³

et al. 2016

Int. J. Automot. Mech. Eng.

Self Cite

View full text Add to dashboard Cite

This paper presents the convective heat transfer coefficient of waxy crude oil while undergoing cooling and reports the influence of initial temperature on the intra-gel void formation. A flow loop rig was used to cool down waxy crude oil to the same end temperature while varying the initial temperature to observe the effects of initial temperature on the voids formed. The convective heat transfer coefficient and heat transfer rate of waxy crude oil subjected to cooling were calculated. It was observed that the heat transfer rate and the convective heat transfer coefficient of waxy crude oil below the wax appearance temperature were much lower than that of the Newtonian liquid crude oil owing to the wax crystal formation entrapping some liquid crude oil within it, below which the formation of voids is eminent. In addition, it was found that lower initial temperatures tend to form higher void volumes near pipe walls and in the entire pipe with a maximum change in void volume of 0.9% observed between the maximum and the minimum initial temperature tested. The insignificant influence of initial temperature on intra-gel void formation was also observed as the waxes are liquid above the wax appearance temperature.

show abstract

Impacts of Cooling Rates on Voids in Waxy Crude Oil under Quiescent Cooling Mode

Cited by 9 publications

References 8 publications

Artificial Neural Network and Regression Models for Predicting Intrusion of Non-Reacting Gases into Production Pipelines

Artificial Neural Network and Regression Models for Predicting Intrusion of Non-Reacting Gases into Production Pipelines

Study on influence of flow rates on voids in waxy crude oil subjected to dynamic and static cooling

Investigation of convective heat transfer coefficient and initial temperature of waxy crude oil on the formation of voids

Contact Info

Product

Resources

About