Rheological and Thermal Behavior of Water-Waxy Crude Oil Emulsions and Model Oil Systems

Marinho, Thiago O.; Souza, M.N.; Barbato, Carla Napoli; Oliveira, Márcia

doi:10.4043/26242-ms

Cited by 2 publications

(3 citation statements)

References 13 publications

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“…In this figure, it becomes clear that the all-grooved geometries provide much higher yield stress values for both concentrations, indicating that apparent wall slip occurs in both the stationary and moving geometry parts for these systems. It is worth noting that the yield stress value strongly depends on the total amount of wax in the oil, as expected [6,47]. In particular, the yield stress of the 7.5 wt.…”

Section: Postcooling Rheometric Measurementssupporting

confidence: 62%

Apparent wall slip effects on rheometric measurements of waxy gels

Marinho

Marchesini

Oliveira

et al. 2021

Journal of Rheology

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The effects of apparent wall slip on rheometric measurements of waxy gels are quantified for gels consisting of a macrocrystalline wax added in mineral oil in concentrations of 3.0 and 7.5 wt. %. The waxy gels are formed in situ in a stress-controlled rheometer, and rheological properties are then obtained. Seven different geometry configurations, including parallel plates, concentric cylinders, and vane, are employed. The surface roughness of the different geometries and wax crystals size are assessed to provide insight into the apparent wall slip phenomenon. In the presence of smooth surfaces, a decrease in approximately 80% in the measured yield stress value is observed in oscillatory tests, regardless of system composition. In addition, the storage modulus measurements are substantially different when obtained from smooth or grooved geometries. In creep experiments, the yield stress measurements decrease by 68%. As expected, apparent wall slip markedly affects the shape of the flow curves obtained, causing the appearance of kinks for smooth Couette geometry. Apparent slip velocities are calculated in the regime just above the yield stress, and it is found that for low concentrations apparent slip increases with concentration and decreases with the ratio between the shear stress and dynamic yield stress. The gathered results also demonstrate that the reproducibility of rheological measurements is improved by using geometries with grooved parts. By quantifying the effects of apparent wall slip on rheological measurements of waxy gels for different geometries, this work can provide useful information for the design of pipelines and oil transportation processes.

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Section: Postcooling Rheometric Measurementssupporting

confidence: 62%

Apparent wall slip effects on rheometric measurements of waxy gels

Marinho

Marchesini

Oliveira

et al. 2021

Journal of Rheology

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“…Since the polar fractions in crude oil, such as resins and asphaltenes, may act as natural surfactants, the emulsion tends to be in good stability. As is known to all, the rheological properties of waxy crude oil emulsion are affected significantly by temperature . Once the temperature drops below the wax appearance temperature (WAT), wax molecules in the stable waxy crude oil emulsions will crystallize and precipitate out due to depressed solubility and consequent supersaturation.…”

Section: Introductionmentioning

confidence: 99%

“…As is known to all, the rheological properties of waxy crude oil emulsion are affected significantly by temperature. 1 Once the temperature drops below the wax appearance temperature (WAT), wax molecules in the stable waxy crude oil emulsions will crystallize and precipitate out due to depressed solubility and consequent supersaturation. The precipitated wax crystals will adsorb on the droplet surface, or interlink with each other in liquid oil and further form a spongy network structure, 2,3 inducing poor flowability of the crude oil emulsions, and their gelation ultimately.…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation on the Gelation Process and Gel Structure of Water-in-Waxy Crude Oil Emulsion

Sun

Yang

et al. 2016

Energy Fuels

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The W/O emulsion formed by waxy crude oil tends to gelatinize under low-temperature gathering conditions, which may harm the flow assurance of multiphase transportation. This study mainly focused on the wax-precipitating gelation process of crude oil emulsions, and the structural differences of the emulsions with different water fractions at their gelation temperatures (GTs). First, the changes of wax appearance temperature (WAT) and precipitated wax amount at GT with variable water cut were investigated by DSC. Then, the specific structural properties of these different water cut emulsions at their own GTs were investigated by viscoelastic, yielding behavior, and structural breakdown experiments. On these bases, the gelation mechanism of a waxy crude oil emulsion was deduced. The WAT of a waxy crude oil emulsion was found to rise, evidently with the addition of dispersed water, verifying that water droplets provide necessary nucleation sites for paraffins and thus make them more prone to precipitate. When temperature was cooled down to their respective GTs, the accumulative precipitated wax amount within the emulsions was obviously reduced with increasing water cut. The combination of this phenomenon and further microscopic experiments proved the difference in gelation mechanism. These rheological tests manifested that both storage modulus and yield stress reached their minimum values at about 30% water cut when all emulsions were kept at their respective GTs, while the flow behavior index and the structural breakdown rate came to their maxima at the same water cut. These results are different from what have been known about the rheological properties at the same temperature below the gel point, demonstrating that the structural strength of the emulsion with about 30% water cut is the weakest at the GT. A conclusion could be finally deduced from the above research that, with the dispersed water increasing, the gelation mechanism of a waxy crude oil emulsion is changed, from a spanned wax crystal network structure which traps separated water droplets to an interlinking droplet flocs structure whose interface is adsorbed by a small amount of wax crystals.

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Rheological and Thermal Behavior of Water-Waxy Crude Oil Emulsions and Model Oil Systems

Cited by 2 publications

References 13 publications

Apparent wall slip effects on rheometric measurements of waxy gels

Apparent wall slip effects on rheometric measurements of waxy gels

Experimental Investigation on the Gelation Process and Gel Structure of Water-in-Waxy Crude Oil Emulsion

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