Flocculation and coalescence in water-in-oil emulsions stabilized by paraffin wax crystals

The objective of this study was to characterize the flow and rheological behaviour of model wax-stabilized water-in-oil (W/O) emulsions consisting of light mineral oil, paraffin wax and glycerol monooleate as the oil phase and water as the dispersed aqueous phase. An[sic] laboratory-scale benchtop flowloop system was used to explore the flow behaviour of the emulsions' oil phase (oil, paraffin wax and surfactant). The key contribution from this work was that the higher initial temperature gradient (40°C compared to 19°C) experienced by the rapidly-cooled oil led to more initial deposition on the flowloop inner wall. The rheological properties of W/O emulsions with different water cuts (10-50wt%) were also studied. Rotational, oscillatory rheology and creep compliance and recovery were characterized on emulsions aged up to 28 days. Overall, the results demonstrated that emulsion composition, and age could significantly influence an emulsion's flow behaviour and rheological properties.

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Rheological properties and flow behaviour of wax-stabilized water-in-oil emulsions

10.32920/ryerson.14653779 ◽

2021 ◽

Author(s):

Samira Haj-Shafiei

Keyword(s):

Rheological Properties ◽

Initial Temperature ◽

Rheological Behaviour ◽

Flow Behaviour ◽

Paraffin Wax ◽

Oscillatory Rheology ◽

Initial Deposition ◽

Oil Emulsions ◽

Light Mineral ◽

Glycerol Monooleate

The objective of this study was to characterize the flow and rheological behaviour of model wax-stabilized water-in-oil (W/O) emulsions consisting of light mineral oil, paraffin wax and glycerol monooleate as the oil phase and water as the dispersed aqueous phase. An[sic] laboratory-scale benchtop flowloop system was used to explore the flow behaviour of the emulsions' oil phase (oil, paraffin wax and surfactant). The key contribution from this work was that the higher initial temperature gradient (40°C compared to 19°C) experienced by the rapidly-cooled oil led to more initial deposition on the flowloop inner wall. The rheological properties of W/O emulsions with different water cuts (10-50wt%) were also studied. Rotational, oscillatory rheology and creep compliance and recovery were characterized on emulsions aged up to 28 days. Overall, the results demonstrated that emulsion composition, and age could significantly influence an emulsion's flow behaviour and rheological properties.

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Determining Wax Type: Paraffin or Naphthene?

SPE Journal ◽

10.2118/124799-pa ◽

2010 ◽

Vol 15 (04) ◽

pp. 963-968 ◽

Cited By ~ 15

Author(s):

Mark M. Bacon ◽

Laura B. Romero-Zerón ◽

Ken K. Chong

Keyword(s):

Crude Oil ◽

Crystal Morphology ◽

Petroleum Industry ◽

Paraffin Wax ◽

Polarized Microscopy ◽

Wax Deposits ◽

Wax Inhibition ◽

Wax Crystals

Summary Paraffin-wax deposits are known to be a worldwide problem in the upstream petroleum industry. Considerable resources are expended on inhibiting or removing wax deposits every year. Paraffin wax is not the only type of crude-oil-based wax. Microcrystalline waxes, composed of naphthene and iso-paraffin molecules, also exist but are not well studied. The predominance of paraffin (also called macrocrystalline) wax and paraffin-wax-inhibition techniques will likely lead to paraffin-wax treatments being applied to naphthene- based reservoirs. It is unclear how well a paraffin-based treatment will apply to naphthene-based oil. The current study investigates the use of cross-polarized microscopy (CPM) to determine if a crude oil contains macrocrystalline or microcrystalline waxes. The type of wax present in the crude oil can be determined using crystal morphology and size. This study demonstrates that paraffin-wax crystals are elongated structures with statistically larger sizes than the microcrystals. Microcrystalline waxes are shown to be statistically smaller and rounded structures.

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Effect of doped emulsifiers on the morphology of precipitated wax crystals and the gel structure of water-in-model-oil emulsions

Colloids and Surfaces A Physicochemical and Engineering Aspects ◽

10.1016/j.colsurfa.2020.125434 ◽

2020 ◽

Vol 607 ◽

pp. 125434

Author(s):

Xinya Chen ◽

Chuanxian Li ◽

Daiwei Liu ◽

Baoping Li ◽

Hao Zhang ◽

...

Keyword(s):

Gel Structure ◽

Structure Of Water ◽

Oil Emulsions ◽

Model Oil ◽

Wax Crystals

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Relationships Between Fat Crystal Characteristics and Emulsion Stability in Water in Oil Systems

10.32920/ryerson.14652891.v1 ◽

2021 ◽

Author(s):

Shane Mason Hodge

Keyword(s):

Polarized Light ◽

Model System ◽

Paraffin Wax ◽

Crystal Habit ◽

X Ray Diffraction ◽

State Transformation ◽

Solid State Transformation ◽

Experimental Protocols ◽

Oil Emulsions ◽

Light Mineral

Investigations were made into the stabilization of water in oil emulsions using crystalline particles of paraffin wax and fully hydrogenated canola and cottonseed oils. A model system was studied to develop a methodology of study and provide a benchmark for a subsequent study of a real-world system. The model system involved the use of light mineral oil, purified water, paraffin wax and glycerol monooleate emulsifier. The wax was crystallized prior to and following emulsification. Prepared emulsion samples were monitored for sedimentation and flocculation behaviour. Measurements of coalescence were obtained by pulsed field gradient NMR. Formation of the solid crystalline wax phase following emulsification resulted in emulsions more stable to flocculation and coalescence than samples containing the same amount of wax crystallized prior to emulsification. Analysis of emulsion samples with polarized light microscopy showed the wax crystals were associated with the water droplet interfaces rather than dispersed freely within the continuous oil phase. Another investigation employed similar experimental protocols but incorporated food-grade materials. Two different solid fats were used, chosen for their differing polymorphic (crystal habit) behaviour. Solid crystals of canola stearine (ß-tending) and cottonseed stearine (ß-tending) were compared in their abilities to stabilize emulsions at levels of addition between 0 and 2%. Each type of fat was incorporated into the emulsion in a pre-crystallized state, or while melted and crystallized following emulsification. Cottonseed stearine was found to be in the ß polymorph when quickly crystallized following emulsification from 45⁰ to 5⁰C over 6 minutes. Further calorimetric and X-ray diffraction investigations revealed this crystallization behaviour was a result of a solid-state transformation via an imperfectly formed ß̕ intermediate. With respect to the post-crystallized emulsions, where the polymorphism of the two fats were both in the ß-form, the canola stearine provided better stabilization against coalescence than the cottonseed stearine. This observation coincided with a stronger energy of interfacial attachment for crystallized canola than for cottonseed as calculated from measurements of contact angle and interfacial tension. With the pre-crystallized system, incorporation of cottonseed stearine resulted in reduced sedimentation and coalescence compared to samples containing pre-crystallized canola stearine. This difference was attributed to the presence of fine shards of ß̕-form crystals. The system that imparted the highest degree of overall stability incorporated the use of canola stearine srystallized following emulsification.

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Flow behaviour of water-in-oil emulsions stabilized by wax crystals

10.32920/ryerson.14644164 ◽

2021 ◽

Author(s):

Roomana Aafaqi

Keyword(s):

Crude Oil ◽

Pipe Wall ◽

Rheological Behaviour ◽

Flow Behaviour ◽

Large Temperature ◽

Gelation Temperature ◽

Emulsion Flow ◽

Oil Emulsions ◽

Polyglycerol Polyricinoleate ◽

Wax Crystals

The large temperature gradients experienced by crude oil emulsions in pipelines found in colder environments can lead to the precipitation, deposition and build-up of wax-like species from the crude oil onto the pipe wall that result in flow assurance problems. The objective of this thesis was to understand the rheological behaviour of model water-in-oil emulsions stabilized by wax crystals. The microstructure, phase transitions and rheology of model emulsions constisting of water, mineral oil, parrafin wax and the emulsifier polyglycerol polyricinoleate (PgPr) were investigated. Changes in emulsion flow begaviour (steady state and dynamic) as a function of composition, termperature and passage through a laboratory-scale flowloop were investigated, with these parameters significantly affecting shear flow, yield stress and viscoelasticity. The gelation temperature of wax-containing ('waxy') oil was slightly lower than that of its equivalent emulsion due to differences in the structure of the gelled emulsion network. Overall, this study successfully showed that there exist significant differences in the microstructure and flow behaviour of model crude oil emulsions when wax and a dispersed aqueous phase are present.

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Relationships Between Fat Crystal Characteristics and Emulsion Stability in Water in Oil Systems

10.32920/ryerson.14652891 ◽

2021 ◽

Author(s):

Shane Mason Hodge

Keyword(s):

Polarized Light ◽

Model System ◽

Paraffin Wax ◽

Crystal Habit ◽

X Ray Diffraction ◽

State Transformation ◽

Solid State Transformation ◽

Experimental Protocols ◽

Oil Emulsions ◽

Light Mineral

Investigations were made into the stabilization of water in oil emulsions using crystalline particles of paraffin wax and fully hydrogenated canola and cottonseed oils. A model system was studied to develop a methodology of study and provide a benchmark for a subsequent study of a real-world system. The model system involved the use of light mineral oil, purified water, paraffin wax and glycerol monooleate emulsifier. The wax was crystallized prior to and following emulsification. Prepared emulsion samples were monitored for sedimentation and flocculation behaviour. Measurements of coalescence were obtained by pulsed field gradient NMR. Formation of the solid crystalline wax phase following emulsification resulted in emulsions more stable to flocculation and coalescence than samples containing the same amount of wax crystallized prior to emulsification. Analysis of emulsion samples with polarized light microscopy showed the wax crystals were associated with the water droplet interfaces rather than dispersed freely within the continuous oil phase. Another investigation employed similar experimental protocols but incorporated food-grade materials. Two different solid fats were used, chosen for their differing polymorphic (crystal habit) behaviour. Solid crystals of canola stearine (ß-tending) and cottonseed stearine (ß-tending) were compared in their abilities to stabilize emulsions at levels of addition between 0 and 2%. Each type of fat was incorporated into the emulsion in a pre-crystallized state, or while melted and crystallized following emulsification. Cottonseed stearine was found to be in the ß polymorph when quickly crystallized following emulsification from 45⁰ to 5⁰C over 6 minutes. Further calorimetric and X-ray diffraction investigations revealed this crystallization behaviour was a result of a solid-state transformation via an imperfectly formed ß̕ intermediate. With respect to the post-crystallized emulsions, where the polymorphism of the two fats were both in the ß-form, the canola stearine provided better stabilization against coalescence than the cottonseed stearine. This observation coincided with a stronger energy of interfacial attachment for crystallized canola than for cottonseed as calculated from measurements of contact angle and interfacial tension. With the pre-crystallized system, incorporation of cottonseed stearine resulted in reduced sedimentation and coalescence compared to samples containing pre-crystallized canola stearine. This difference was attributed to the presence of fine shards of ß̕-form crystals. The system that imparted the highest degree of overall stability incorporated the use of canola stearine srystallized following emulsification.

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Flow behaviour of water-in-oil emulsions stabilized by wax crystals

10.32920/ryerson.14644164.v1 ◽

2021 ◽

Author(s):

Roomana Aafaqi

Keyword(s):

Crude Oil ◽

Pipe Wall ◽

Rheological Behaviour ◽

Flow Behaviour ◽

Large Temperature ◽

Gelation Temperature ◽

Emulsion Flow ◽

Oil Emulsions ◽

Polyglycerol Polyricinoleate ◽

Wax Crystals

The large temperature gradients experienced by crude oil emulsions in pipelines found in colder environments can lead to the precipitation, deposition and build-up of wax-like species from the crude oil onto the pipe wall that result in flow assurance problems. The objective of this thesis was to understand the rheological behaviour of model water-in-oil emulsions stabilized by wax crystals. The microstructure, phase transitions and rheology of model emulsions constisting of water, mineral oil, parrafin wax and the emulsifier polyglycerol polyricinoleate (PgPr) were investigated. Changes in emulsion flow begaviour (steady state and dynamic) as a function of composition, termperature and passage through a laboratory-scale flowloop were investigated, with these parameters significantly affecting shear flow, yield stress and viscoelasticity. The gelation temperature of wax-containing ('waxy') oil was slightly lower than that of its equivalent emulsion due to differences in the structure of the gelled emulsion network. Overall, this study successfully showed that there exist significant differences in the microstructure and flow behaviour of model crude oil emulsions when wax and a dispersed aqueous phase are present.

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