Morphology of paraffin crystals in waxy crude oils cooled in quiescent conditions and under flow

Kané, M.; Djabourov, Madeleine; Volle, Jean-Luc; Lechaire, Jean‐Pierre; Frebourg, Ghislaine

doi:10.1016/s0016-2361(02)00222-3

Cited by 164 publications

(128 citation statements)

References 12 publications

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“…The effect of cooling under shearing over the gel properties was also evaluated in several works (Davenport and Somper 1971;Rønningsen et al 1991;Wardhaugh and Boger 1991a;El-Gamal 1998;Singh et al 1999;Webber 1999;Kané et al 2003;Venkatesan et al 2005;Lin et al 2011). Some authors showed that raising the cooling rate applied during dynamic tests increases not only the gelation temperature, T g , (Singh et al 1999) but also the viscosity at the end of the cooling period (Webber 1999).…”

Section: Introductionmentioning

confidence: 99%

Influence of the initial cooling temperature on the gelation and yield stress of waxy crude oils

et al. 2014

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One of the major problems in waxy crude oil production and transportation is oil gelation that takes place within pipelines as a result of wax crystallization at low temperatures. In such cases, the pressure needed to restart the oil flow in subsea pipelines can be much larger than the usual steady-state pressure, as the temperature in such environment can be as low as 4°C. The literature has shown that not only the temperature itself but also the fluid shear and thermal histories have significant influence on the yield stress of waxy crude oils. This paper investigates the effect of the initial cooling temperature on the waxy crude oil viscosity, gelation temperature, and yield stress. In order to accomplish that, rheological tests were carried out under static and dynamic cooling conditions. The results show that there is a critical range for the initial cooling temperature that provides maximum values for viscosity, gelation temperature, and yield stress. In other words, the highest values of those properties are observed when the cooling started within this temperature range. The effect of a thermal pretreatment usually used to remove light ends was also investigated. In spite of not changing the initial temperature critical range, the yield stress was slightly affected by the thermal treatment. It is worth noting that the yield stress varies from approximately zero to hundreds after dynamic cooling or to thousands after static cooling within the tested range of the initial cooling temperatures.

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Section: Introductionmentioning

confidence: 99%

Influence of the initial cooling temperature on the gelation and yield stress of waxy crude oils

et al. 2014

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“…To span this wide range of length or time scales, we perform dissipative particle dynamics (DPD) [23] simulations on model TEVP fluids consisting of 10 vol % attractive hexagonal solid particles designed to represent the waxy crystalline particles observed in a waxy crude oil [3,24]. The DPD formalism inherently preserves multibody hydrodynamics by conservation of mass and momentum both locally and globally [25,26].…”

mentioning

confidence: 99%

“…Under quiescent conditions these Brownian attractive particles self-assemble into spacespanning networks whose fractal structure was examined via the box-counting method (see Supplemental Material [31], which includes Refs. [3,4,24,25,27,[32][33][34][35][36]). These gel networks were then subject to an imposed shear flow, using Lees-Edwards boundary conditions (constant velocity of the upper and lower boundary cells, induces a linear velocity profile within the calculation box for a simple fluid with _ γ ¼ 2V Wall =L y ) [34,35].…”

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confidence: 99%

Microstructural Rearrangements and their Rheological Implications in a Model Thixotropic Elastoviscoplastic Fluid

2017

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We identify the sequence of microstructural changes that characterize the evolution of an attractive particulate gel under flow and discuss their implications on macroscopic rheology. Dissipative particle dynamics is used to monitor shear-driven evolution of a fabric tensor constructed from the ensemble spatial configuration of individual attractive constituents within the gel. By decomposing this tensor into isotropic and nonisotropic components we show that the average coordination number correlates directly with the flow curve of the shear stress versus shear rate, consistent with theoretical predictions for attractive systems. We show that the evolution in nonisotropic local particle rearrangements are primarily responsible for stress overshoots (strain-hardening) at the inception of steady shear flow and also lead, at larger times and longer scales, to microstructural localization phenomena such as shear banding flow-induced structure formation in the vorticity direction. DOI: 10.1103/PhysRevLett.118.048003 Thixotropic elastoviscoplastic (TEVP) materials are a broad class of structured fluids that include (but are not limited to) most colloidal gels [1], nano emulsions [2], crude oils [3,4], and many biological systems such as blood clots and actin networks [5,6]. As a result of their complex underlying microstructure, TEVPs exhibit a wide range of rich and complex thermo-mechanical properties: Below a critical stress, the microstructural network formed by individual particles remains intact and resists large deformations by external forces. At this stage the macroscopic response of the material is similar to that of a viscoelastic solid. By progressively increasing the applied load, the material reaches its "yield stress" and starts to flow [7]. At this point the particle network that is responsible for solidlike response of the macroscopic sample undergoes plastic rearrangements over an increasingly wide range of length scales [8]. Upon complete yielding of this network, plastic flow results ultimately in a viscouslike response; however, as a result of constant formation and breakage events, the particle-level microstructure continues to evolve giving rise to thixotropic behavior. The many-body nature of the problem means that local forces exerted on a single particle change its energy landscape, which consequently defines its subsequent association or dissociation rate to neighboring particles [9,10]. When combined with multibody hydrodynamic effects in these fluids [11], the resulting microstructure-flow relationship becomes complex and may show long time scale transient behavior and multiple steady states [1,12]. This leads to a wide range of timedependent responses that can also be observed, including microphase separation [13], vorticity aligned structure formation [14][15][16], local rigid plug formation and shear banding [17], plus shear-induced rejuvenation of the particle network [18].Although the general form of the flow curve (relating the shear stress to shear rate) and some transient pheno...

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“…The results indicate that the floccules were effectively separated from KH150BS by employing a method of solvent dilution and filtration at low temperature, and the floccules had high freezing points. Kane et al (2003) found that gel formation appeared for very low amounts of crystals (around 1-2%) when the oil was cooled under quiescent conditions. In such conditions, a colloidal network, which embodies the oil, is formed, and the whole dispersion becomes a gel.…”

Section: Separation Of Floccules From Kh150bsmentioning

confidence: 99%

Causes of Floccules Formation in Hydro-Treated Lubricating Base Oil

Huang¹,

Gao²,

Cheng³

2012

Petrochemicals

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Morphology of paraffin crystals in waxy crude oils cooled in quiescent conditions and under flow

Cited by 164 publications

References 12 publications

Influence of the initial cooling temperature on the gelation and yield stress of waxy crude oils

Influence of the initial cooling temperature on the gelation and yield stress of waxy crude oils

Microstructural Rearrangements and their Rheological Implications in a Model Thixotropic Elastoviscoplastic Fluid

Causes of Floccules Formation in Hydro-Treated Lubricating Base Oil

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