The role of shearing effect in evolution of the microscopic behavior of wax crystals

The high-efficient development, storage and transportation of waxy crude oil has a significant meaning for stable supplying of petroleum energy. The variety of complex morphology and microstructure of wax crystals...

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Effect of bio-based flow improver on the microscopic and low-temperature flow properties of waxy crude oil

Journal of Petroleum Exploration and Production Technology ◽

10.1007/s13202-020-01078-x ◽

2021 ◽

Vol 11 (2) ◽

pp. 711-724

Author(s):

William Iheanyi Eke ◽

Sampson Kofi Kyei ◽

Joseph Ajienka ◽

Onyewuchi Akaranta

Keyword(s):

Fractal Dimension ◽

Aspect Ratio ◽

Crude Oil ◽

Flow Properties ◽

Waxy Crude Oil ◽

Waxy Crude ◽

Feret Diameter ◽

Oil Flow ◽

Flow Improver ◽

Wax Crystals

AbstractWax formation creates flow assurance problems in the production and transportation of waxy crude oil. Flow improvers are added to waxy crude in order to reduce handling cost. Bio-based flow improvers derived from cheap renewable resources are attractive as cost-effective, eco-friendly alternatives to the conventional additives. Natural cashew nut shell liquid extracted from waste biomass (Anacardium occidentale shells) was derivatized and applied as flow improver for waxy crude oil. Effect of the additive on wax formation in crude oil was studied by cross-polarized microscopy, while the change in oil flow properties was evaluated using a rotational coaxial cylinder viscometer. Micrographs of the waxy crude were processed and analyzed with image J software. The microscopic properties of the wax crystals were characterized using Feret diameter, crystal area, aspect ratio, circularity, solidity and boundary fractal dimension. The pour point of doped crude oil was depressed by − 18 °C and the wax area fraction reduced by 40% due to wax inhibitive effect of the additive. The presence of the additive resulted in evolution of smaller, rounder and more regular wax crystals with smoother and more even surfaces indicated by reduction in the Feret diameter, aspect ratio and boundary fractal dimension of wax crystals in doped oil, and an increase in crystal circularity and solidity. The shear stress and viscosity of doped oil were reduced by 86.8% and 85.0%, respectively. The flow improvement effect of the CNSL derivative is linked to its effect on morphology and microstructure of wax crystals in the crude oil.

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New Approach for the In Situ Microscopic Observation of Wax Crystals in Waxy Crude Oil during Quiescent and Dynamic Cooling

ACS Omega ◽

10.1021/acsomega.0c00606 ◽

2020 ◽

Vol 5 (20) ◽

pp. 11491-11506

Author(s):

Jian Zhao ◽

Weiqiang Zhao ◽

Hang Dong ◽

Lixin Wei ◽

Yang Liu

Keyword(s):

Crude Oil ◽

Microscopic Observation ◽

Waxy Crude Oil ◽

New Approach ◽

Waxy Crude ◽

Dynamic Cooling ◽

Wax Crystals

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Relationship between Waxy Crude Oil Composition and Change in the Morphology and Structure of Wax Crystals Induced by Pour-Point-Depressant Beneficiation

Energy & Fuels ◽

10.1021/ef200059p ◽

2011 ◽

Vol 25 (4) ◽

pp. 1686-1696 ◽

Cited By ~ 56

Author(s):

Shize Yi ◽

Jinjun Zhang

Keyword(s):

Crude Oil ◽

Pour Point ◽

Oil Composition ◽

Pour Point Depressant ◽

Waxy Crude Oil ◽

Waxy Crude ◽

Point Depressant ◽

Morphology And Structure ◽

Wax Crystals

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The Role of Emulsified Water in the Wax Deposition Path of a Waxy Crude Oil Multiphase Transportation Pipeline

ASME 2019 Asia Pacific Pipeline Conference ◽

10.1115/appc2019-7605 ◽

2019 ◽

Author(s):

Xinyu Lin ◽

Zhihua Wang ◽

Qingshan Feng ◽

Lei Zhang ◽

Yunfei Xu

Keyword(s):

Crude Oil ◽

Water Droplets ◽

Wax Deposition ◽

Waxy Crude Oil ◽

Two Phase ◽

Waxy Crude ◽

Oil Water ◽

Emulsified Water ◽

Pipeline Wall ◽

Wax Crystals

Abstract Although the problem of wax deposition in multiphase transportation pipelines have been addressed and some related wax deposition models have been developed in recent years, the complex wax deposition paths derived from the potential variety of flow regimes in multiphase flow have not been well understood. This study presented a method for characterizing wax crystals aggregation behavior and developed a model for describing wax deposition path in oil/water two-phase flows. The impact of the emulsified water droplets on wax crystals aggregation in shearing flows was quantified using polarized light microscopy and image analysis method. The role of the emulsified water droplets in the wax deposition path reaching the upper side and lower side of pipeline wall was discussed by solving the developed model which involves the possible inclination angle of multiphase transportation pipeline. The availability of the mechanistic model was validated by the data and knowledge in the existing literature. The results indicated that wax crystals morphologies and structures tended to be regular with the enhancement of shearing effect, and their aggregation behavior were restrained. The circular degree and particle size of wax crystals showed a characteristic that it firstly increased and then decreased with the accumulation of emulsified water droplets in shearing flow, and this transition appeared to the phase inversion point of the oil/water two-phase. The velocity for wax crystals depositing to pipeline wall decreased and the time for wax crystals depositing to pipeline wall extended with the existence of emulsified water droplets. The wax deposition path became more complex in multiphase transportation, and such effect became remarkable when the dispersity of oil/water two-phase enhanced. Accordingly, the intractable wax deposition of waxy crude oil in cold environment transportation would be mitigated to some extent. This study contributes to comprehending the distinction of wax deposition mechanism in single-phase and multiphase transportation of waxy crude oil, and the proposed method and model are valuable for further predicting wax deposition in waxy crude oil emulsions pipelines. The findings in this study also point out an approach to conducting cost-effective flow assurance operations in crude oil production and transportation.

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A Novel Method for Characterizing the Aggregation of Wax Crystals and An Improvement in Wax Deposition Modeling

Journal of Energy Resources Technology ◽

10.1115/1.4047083 ◽

2020 ◽

Vol 142 (10) ◽

Author(s):

Zhihua Wang ◽

Hankun Wang ◽

Chaoliang Zhu ◽

Zhenhua Rui ◽

Yang Liu

Keyword(s):

Fractal Dimension ◽

Crude Oil ◽

Aggregation Behavior ◽

Wax Deposition ◽

Waxy Crude Oil ◽

Waxy Crude ◽

Wax Crystal ◽

Novel Method ◽

Improved Model ◽

Wax Crystals

Abstract The aggregation behavior and the subsequent deposition behavior of wax crystals own undesirable effects on the production and transportation of waxy crude oil. The understanding and prediction of these behaviors are essential to ensure economic and uninterrupted flow of waxy crude oil when the oil temperature decreases below the wax appearance temperature (WAT). In this paper, a novel method of fractal dimensional analysis was introduced to elucidate the aggregation behavior of wax crystals in different shear flow fields. The fractal methodology for characterizing wax crystal aggregation was then developed, and a blanket algorithm was introduced to compute the fractal dimension of the aggregated wax crystals. Considering the flow characteristics of waxy crude oil in a pipeline can be correlated with the shearing stress work, a modified wax deposition model focusing on shearing energy analysis was established. The results indicate that a quantitative interpretation of the wax crystal aggregation behavior can be realized using the fractal methodology. The aggregation behavior of the wax crystals is closely related to the temperature and shearing experienced by the waxy crude oil. The aggregation behavior will be intensified with decreasing temperature and shearing effect, and a wider fractal dimension distribution appears at lower temperatures when the same shear rate range is used. Furthermore, the improved model provides a method for discussing the effects of the operating conditions on wax deposition. The average relative deviation between the improved model prediction results and experimental results from the literature is 3.01–5.32%.

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