Experimental Investigation of the Difference in Wax Deposition Aging Rate Between Polyethylene and Steel Pipes

2020 ◽  
Author(s):  
Rongbin Li ◽  
Yaping Li ◽  
Danfu Cao ◽  
Junfang Wang ◽  
Xin Liu
Keyword(s):  
Operating Conditions ◽  
Wax Deposition ◽  
Flow Loop ◽  
Waxy Crude Oil ◽  
Scanning Calorimetry ◽  
Aging Rate ◽  
Wax Content ◽  
The Difference ◽  
Dsc Method ◽  
Wax Deposits

Abstract Wax deposition is an intrinsic problem existing in the production and transportation of waxy crude oil. In the oilfield, non-metallic pipe especially high-density polyethylene pipe (HDPE) has been widely used to solve corrosion problems due to its excellent performance in intensity and corrosion. However, the wax deposition problem in polyethylene (PE) pipe has never been evaluated using dynamic and systemic apparatus. Only a few studies focus on the wax deposition on the coated polyethylene surface by using the cold finger apparatus in recent decades. In this study, the wax deposition experiments were performed using an in-door flow-loop with detachable PE and stainless steel (SS) test sections under the laminar flow regime at the same time to investigate the difference in wax deposition aging rate between the PE and SS pipes. The wax deposits under different operating conditions in both PE and SS pipes were sampled by three layers to study the aging rate at different radial locations during the wax deposition. The wax precipitation characteristics of the wax deposits were determined by using the differential scanning calorimetry (DSC) method. It was found that the wax contents of the wax deposits in PE pipe were lower than that in the SS pipe. And the difference of the wax content between PE pipe and SS pipe decreases with the depositing duration. Eventually, the wax contents of the wax deposits in PE pipe were almost the same as that in the SS pipe. The heat conduction and heat transfer processes in PE pipe and SS pipe were analyzed. The thermal gradient and the concentration gradient at wall were calculated and combined with the heat and mass transfer of wax during the wax deposition to illustrate the difference in wax content. It was found that the variations of the thermal and concentration gradients have significant effects on the diffusion process of wax molecules within the wax deposit layer and thus changing the aging rate. The comparisons and findings of wax deposition between the two kinds of pipes have provided a significant reference for the application of non-metallic pipe in the oilfield.

Experimental Investigation of Wax Deposition at Different Deposit Locations Through a Detachable Flow Loop Apparatus

2014 ◽  
Author(s):  
Si Li ◽  
Qiyu Huang ◽  
Wenda Wang ◽  
Changhui Wang ◽  
Zhenjun Ding
Keyword(s):  
Temperature Interval ◽  
Flow Rate ◽  
Test Section ◽  
Measurement Techniques ◽  
Operating Conditions ◽  
Temperature Fields ◽  
Wax Deposition ◽  
Flow Loop ◽  
Deposit Thickness ◽  
Wax Content

Wax deposition has always been a focus in the research field of flow assurance. Operating conditions are among the predominant factors that control the deposition rate and the nature of the formed deposits. However, the disadvantages of the available wax thickness measurement techniques applied to laboratory flow loops limit deeper studies on this issue. In this work, the effects of operating conditions, including temperature interval and flow rate, on wax deposition at different deposit locations are experimentally studied using a detachable flow loop apparatus. With the detachable test section, it is achievable to obtain the thickness and the wax content profiles of the deposit as functions of axial location and time. The temperature fields in the test section under both temperature intervals are simulated with CFD software FLUENT to provide more information for the analysis of deposition process. As the results manifest, the low temperature interval tends to intensify deposition, relating to the inner temperature field and wax precipitated property of the oil. The larger flow rate leads to a growth in the deposit thickness under the laminar flow regime and brings about a distinct rise in the wax content of deposit at inlet. In addition, the increase in deposit thickness and wax content indicates the phenomenon of deposit aging, and the wax deposit layer is thinner but with higher wax content at the inlet, due to the strong flow scour.

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

2018 ◽  
Vol 3 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Koh Junyi ◽  
Nurul Hasan
Keyword(s):  
Crude Oil ◽  
Residence Time ◽  
Flow Rate ◽  
Temperature Difference ◽  
Wax Deposition ◽  
Flow Loop ◽  
New Models ◽  
Wax Content ◽  
The Difference ◽  
Deep Depth

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.

Experimental Study on Wax Removal With Real Wax Deposits

2018 ◽  
Author(s):  
Weidong Li ◽  
Qiyu Huang ◽  
Xue Dong ◽  
Xuedong Gao ◽  
Lei Hou
Keyword(s):  
Test Section ◽  
Wax Deposition ◽  
Flow Loop ◽  
Gravity Settling ◽  
Experimental Apparatus ◽  
Field Practice ◽  
Force Profile ◽  
Wax Content ◽  
Wax Deposits ◽  
Wax Removal

Pipeline pigging is one of the most widely used wax remediation techniques in field practice. However, it still depends heavily on “rule-of-thumb” due to the limited understanding of wax deposit properties and wax removal mechanisms. By far, laboratory studies on pipeline pigging generally suffer a gross defect in test materials, i.e., the big discrepancy between the experimental wax samples and real wax deposits. To this end, this paper aims to explore the wax removal in pigging with naturally deposited wax, using a self-designed experimental facility. Wax deposit mass and wax content, two decisive indexes affecting wax removal, were also investigated. The experimental apparatus consists of two parts: a flow loop equipped with a detachable test section to achieve real wax deposits and a wax removal apparatus to perform pigging operations. The test section can be conveniently detached from the flow loop and/or mounted onto the wax removal apparatus for a quick conversion between wax deposition and pigging operation. The results indicate that a higher bulk flow temperature decreases the wax deposit mass and increases the wax content of deposit. Additionally, the distributions of wax content and wax layer thickness suggest that gravity settling plays no role in wax deposition. Moreover, the wax resistive force profile of naturally deposited wax presents four distinct stages, i.e., the build-up phase, the pre-plug phase, the plug phase and the production phase. To the best of the authors’ knowledge, this is the first study on wax removal with real wax deposits. It paves the way for the application of previous artificial-wax-based researches to real wax deposit scenarios.

Effects of the Dispersed Phase on Oil/Water Wax Deposition

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Pengyu Wang ◽  
Wei Wang ◽  
Jing Gong ◽  
Yuanxin Zhou ◽  
Wei Yang
Keyword(s):  
Particle Size ◽  
Crude Oil ◽  
Dispersed Phase ◽  
Wax Deposition ◽  
Waxy Crude Oil ◽  
Water Emulsion ◽  
Oil Emulsion ◽  
Wax Content ◽  
Oil Water ◽  
Water Cut

In the study of the foundation of the oil / water wax deposition experiment, the emulsification characteristics of crude oil emulsion with high wax content have gradually become the hot research area. In the current research of emulsification characteristics of oil/water emulsion, the attention has been focused on the study of the effects of water cut, stirring speed, particle size distribution on the viscosity of waxy crude oil emulsion in the experiment, in which heavy oil and simulated oil are adopted as the working fluids. In this study, the emulsion with different water cut and stirred by different speed was prepared under three different temperature conditions, the temperature above the wax appearance temperature (WAT), near the WAT, and below the WAT. The polarization microscope and rotary viscometer were applied to measure the effects of the particle size of the dispersed phase and waxy crystal distribution on the oil/water emulsion viscosity. The results suggest that preparing the temperature for crude oil emulsion with high wax content has an important influence on the emulsion microstructure. This study lays the foundation for further study of oil/water two phase dynamic wax deposition experiments.

Influence of Hydrostatic Pressure on the Formation of Voids in Gelled Crude Oil

2021 ◽  
Author(s):  
Girma T. Chala ◽  
Shaharin A. Sulaiman ◽  
Azuraien Japper-Jaafar ◽  
Wan Ahmad Kamil Wan Abdullah
Keyword(s):  
Hydrostatic Pressure ◽  
Crude Oil ◽  
Vertical Pipe ◽  
Flow Loop ◽  
Waxy Crude Oil ◽  
Horizontal Pipe ◽  
Waxy Crude ◽  
Oil Transportation ◽  
Wax Content ◽  
Lower Temperature

Production of waxy crude oil from offshore fields has increased in the last decade. However, the operation is being challenged with the high wax content of crude oil that tends to precipitate at lower temperature. This paper presents the effects of hydrostatic pressure on the voids formed in waxy crude oil gel. A flow loop rig that simulates offshore waxy crude oil transportation was used to produce the gel. A Magnetic Resonance Imaging of 3-Tesla system was used to scan the gelled samples in horizontal and vertical pipes. The hydrostatic pressure effect was found to be most significant near the pipe wall as a change in percent voids volume of 0.53% was observed at that region. In particular, the voids volume reduction was more pronounced in the lower half side of the pipe. The total volume of voids in the vertical pipe was lower than that in the horizontal pipe, and this suggests that the gel in the vertical pipe became denser due to the effects from the hydrostatic pressure. Conversely, the voids volume around the pipe core in the vertical pipe was higher when compared to that in the horizontal pipe. The change in voids volume near the pipe core and wall shrunk to a minimum and converged to 0.18% voids volume at larger duration of the hydrostatic effect. Further, hydrostatic pressure was observed to have significant influences for higher duration making the void size to be distributed across and along the pipeline; however, it was found to have insignificant effects on voids size distribution for smaller duration. The findings of this study can help for better understanding of voids formation in vertical pipelines that would further assist in developing a model predicting restart pressure accurately.

scholarly journals Experimental and theoretical study on wax deposition and the application on a heat insulated crude oil pipeline in Northeast China

2020 ◽  
Vol 75 ◽  
pp. 3 ◽  
Author(s):  
Dongxu Sun ◽  
Zuoliang Zhu ◽  
Zhiyong Hu ◽  
Ming Wu
Keyword(s):  
Crude Oil ◽  
Northeast China ◽  
Molecular Diffusion ◽  
Operation Time ◽  
Scientific Basis ◽  
Calculation Model ◽  
Wax Deposition ◽  
Waxy Crude Oil ◽  
Oil Pipeline ◽  
Wax Content

An experimental loop apparatus of heat insulated waxy crude oil pipeline was established to study the wax deposition behaviors. The effects of flow rate and ambient temperature on the thickness and wax content of deposition layer were investigated. A kinetic calculation model for the thickness and wax content of deposition layer in heat insulated crude oil pipeline was established based on the principle of molecular diffusion, aging and shear energy. The results calculated by the model are in good agreement with the experimental values. The wax deposition thickness of a heat insulated crude oil pipeline in different seasons and operation time in Northeast China was predicted according to the theoretical model, which was anticipated that can provide a scientific basis for formulating the wax removal cycle of the pipeline. The predicted results showed that the thickness of the wax deposition layer increases first and then decreases along the pipeline.

Effect of operating conditions on wax deposition in a laboratory flow loop characterized with DSC technique

2014 ◽  
Vol 119 (1) ◽  
pp. 471-485 ◽  
Author(s):  
Wenda Wang ◽  
Qiyu Huang ◽  
Changhui Wang ◽  
Si Li ◽  
Wenxing Qu ◽  
...  
Keyword(s):  
Operating Conditions ◽  
Wax Deposition ◽  
Flow Loop

Modeling of Multiphase Wax Deposition

1999 ◽  
Vol 121 (2) ◽  
pp. 81-85 ◽  
Author(s):  
G. M. Elphingstone ◽  
K. L. Greenhill ◽  
J. J. C. Hsu
Keyword(s):  
Single Phase ◽  
Scale Up ◽  
Wax Deposition ◽  
Flow Loop ◽  
Waxy Crude Oil ◽  
Multiphase Transport ◽  
Waxy Crude ◽  
Semi Empirical ◽  
Production Problems ◽  
Deposition Tendency

The environmental conditions typically encountered in deepwater petroleum operations lead to a number of production problems. The cold environment promotes particle formation and deposition of paraffinic compounds in a waxy crude system. These solids can build up inside flowlines and significantly decrease production rates. The wax deposition scale-up technique used for single phase has been applied to multiphase flow conditions. The resulting semi-empirical model is used to simulate multiphase transport of waxy crude oil through integration with a commercial steady-state pipeline simulation package. The wax model is a semi-empirical representation of the wax deposition phenomena. The model incorporates the effects of diffusion and shear through the wax deposition tendency. The key parameters are first measured in a laboratory flow loop.

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

AIChE Journal ◽  
2020 ◽  
Vol 67 (1) ◽  
Author(s):  
Rongbin Li ◽  
Qiyu Huang ◽  
Dongxu Zhang ◽  
Xiangrui Zhu ◽  
Jinxu Shan ◽  
...  
Keyword(s):  
Flow Loop ◽  
Polyethylene Pipe ◽  
Wax Content ◽  
Wax Deposits
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