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

Experimental Study and Molecular Dynamics Simulation of Oil Displacement Using Different Microemulsions in the Fang2 Block of Songfangtun Oilfield

After many years of mining in the Fang2 block of the Songfangtun oilfield, the conventional water drive development method can no longer meet the requirement of greatly improving the recovery rate, and ternary composite drive (TCD) technology is adopted for this purpose. TCD is one of the most important methods to further improve crude oil recovery, and it has entered the industrialization and promotion stage, but there are still problems of fouling in the injection and extraction system and high production and maintenance costs. In order to reduce formation damage and improve recovery in the Songfangtun oilfield, an alkali-free microemulsion system was developed by replacing the weak base sodium carbonate with sodium chloride, but its emulsification capacity was weak and the recovery enhancement value was lower than that of the weak base TCD. In order to improve the emulsification performance of the alkali-free microemulsion and enhance the effect of oil repulsion, an alkali-free microemulsion oil-repellent system was developed on the basis of the alkali-free ternary system by using the compounding of surfactant, alcohol, and sodium chloride. Through indoor physical modeling experiments, it was concluded that the SDBS alkali-free microemulsion system had the best effect on improving crude oil rheology and viscosity reduction, and the lowest interfacial tension of 9.4 × 10-4 mN/m in the solution system when the mass fraction was 4%, with the maximum recovery rate of 47.03%, and the decrease in water content of 9.3%. Through molecular dynamics simulation and microemulsion oil-repellent coefficient, it is concluded that the alkali-free SDBS microemulsion system can greatly reduce the interaction force between crude oil and rock, with the lowest peak value of radial distribution function of 4.21, and the oil-repellent coefficient of F p of 5.85; CMG reservoir numerical simulation software is adopted to verify the chemical repellent numerical simulation of Fang2 block, which shows that the recovery degree of SDBS alkali-free microemulsion system is 24.8% higher than that of water repellent, with the cumulative increase of 213.6 thousand tons of oil. The developed alkali-free microemulsion system not only realizes the goal of ternary composite alkalinity-free but also achieves the purpose of greatly improving the recovery rate and reducing the cost and increasing efficiency. It has a broad application prospect and can also provide a technical reference for the efficient development of other old oilfields with land-phase sandstone.

Unlocking the potential of rice bran oil body as fat replacement in cookies: single and double crosslinked binary emulsion-filled gels based on lutein-loaded rice bran oil body emulsion

BACKGROUND

Rice bran oil body is rich in nutritional value, which is a byproduct of rice processing. The aim of this study is to develop a novel emulsion-filled gel with lutein-loaded rice bran oil body and investigate its functionality as a fat replacer in cookies. The effects of incorporating structured oil body in the form of emulsion-filled gel instead of butter in cookies with a ratio of 0, 10, 20 and 50 wt% formulation were determined by measuring appearance, texture, thermodynamic properties, moisture distribution and microstructure.

RESULTS

The results demonstrated the relationship between geometry, moisture and structure. The 20 wt% emulsion-filled gel substitution ratio yielded mobility and distribution abilities of melted fat and sugar in the cookies that were closest to those of butter. The addition of emulsion-filled gel increased the L* value and decreased the a* value, while the b* value of the cookie increased due to the advanced delivery of lutein by oil body. By controlling the addition ratio, the texture of the cookies can be adjusted. Starch granules were separated due to colloidal particles, reducing saturated fat content and decreasing cookie gelatinization enthalpy. The fat coating on starch particles enhanced the binding capacity of free water, improving air entrapment and forming a constrained gluten network structure.

CONCLUSION

These findings provide a theoretical basis for rice bran oil body as a novel substitute for butter in the development of healthy, high-quality cookies. © 2024 Society of Chemical Industry.

Synergistic Effect of Asphaltene, Resin, and Wax Improving the Emulsification and Interfacial Properties of a High-Phase-Inversion Thin Oil

Nowadays, high-phase-inversion in situ emulsification technology has shown great potential in enhancing oil recovery from high-water-cut thin-oil reservoirs. However, emulsification characteristics, interfacial properties, and the mechanism of high phase inversion have not been systematically described. In this study, an emulsification experiment was conducted to investigate the effects of shear time, shear rate, and temperature on the phase inversion of thin oil. Furthermore, the influence of resin and wax on the dispersion of asphaltene was studied through microscopic morphology analysis. Interfacial tension measurement and interfacial viscoelasticity analysis were carried out to determine the interaction characteristics of asphaltene, resin, and wax at the interface. The results showed that, at 50 °C, the phase-inversion point of thin oil reached as high as 75%, and even at 60 °C, it remained at 70%. The shear time and shear rate did not affect the phase-inversion point of thin oil, while an increase in temperature led to a decrease in the phase-inversion point. Moreover, compared to the 20% phase-inversion point of base oil, the phase-inversion point increased with different proportions of asphaltene, resin, and wax. Particularly, at the ratio of asphaltene/resin/wax = 1:5:9, the phase-inversion point reached as high as 80%, indicating the optimal state. In this proportion, asphaltene aggregates exhibited the smallest and most uniform size, best dispersion, lower interfacial tension, and higher interfacial modulus. These findings provide reference and guidance for further enhancing oil recovery in medium-to-high-water-cut thin-oil reservoirs.

Differences of wax-based emulsion gel in 3D printing performance: Crystal distribution and droplet stability

Six kinds of natural waxes were used for emulsion gels preparation. The differences in printing performance were explored based on the crystal distribution and droplet stability. Firstly, the effect of crystal distribution was investigated through microstructures and rheological properties. It was found that the dense crystal network/interfacial crystallization could stabilize the droplet and provide modulus to ensure the self-supporting behavior after printing, whereas excessive crystal could lead to droplet rupture and coalescence. Furthermore, all emulsion gels could recrystallize by heating, which could enhance the performance of 3D printing. Then, the droplet stability was investigated after storing/freeze-thawing. It was found that emulsion gels with dense crystal networks/interfacial crystallization had more stable droplets, which ensure the continuous extrusion during printing. Finally, printing performance was investigated comprehensively. Three emulsion gels with denser crystal networks/interfacial crystallization had higher recovery rates (16.17-21.15%) and more stable droplets, which perform better in 3D printing correspondingly.

Comparative study of natural wax-based W/O emulsion gels: Microstructure and macroscopic properties

In this paper, six kinds of natural wax, including sunflower wax (SFX), rice bran wax (RBX), carnauba Brazilian wax (CBX), beeswax (BWX), candelilla wax (CDX), and sugarcane wax (SGX) were used to prepare water-in-oil (W/O) emulsion gels. Microstructures and rheological properties of all emulsion gels were investigated by microscopy, confocal laser scanning microscope (CLSM), scanning electron microscopy (SEM), and rheometer, respectively. By comparing polarized light images of wax-based emulsion gels and corresponding wax-based oleogels, it could be found that dispersed water droplets greatly affected the crystal distribution and hindered crystal growth. Polarized light microscopy and CLSM images proved that natural wax could perform a dual-stabilization mechanism by interfacial crystallization and crystal networks. SEM images illustrated all waxes except SGX were platelets and formed networks by stacking on top of each other, while flocs-like SGX was easier to adsorb on the interface and formed a "crystalline shell". The surface area and pore formed by different wax varied wildly, which accounted for their differences in the gelation ability, oil binding capacity, and strength of the crystal network. The rheological study showed that all wax had solid-like properties and wax-based oleogels with denser crystal networks correspond to emulsion gels with higher modules. The dense crystal network and interfacial crystallization could improve the stability of W/O emulsion gels proved by recovery rates and critical strain. All the above proved that natural wax-based emulsion gels can be used as stable, low-fat, and thermal-sensitive fat mimics.

Water Droplets Tailored as Wax Crystal Carriers to Mitigate Wax Deposition of Emulsion

This study explores how the micro-distribution change of wax crystals from the continuous oil phase to the oil-water interface mitigates the macro wax deposition of an emulsion. Two types of interfacial actions between wax crystals and water droplets, interfacial adsorption and interfacial crystallization, which were induced by two different emulsifiers, sorbitan monooleate (Span 80) and sorbitan monostearate (Span 60), respectively, were detected by differential scanning calorimetry and microscopy observation. The wax interfacial crystallization promoted by Span 60 resulted in the wax being nucleated directly at the oil-water interface prior to the continuous oil phase, conferring the nascent wax crystals and water droplets to be combined as coupled particles. The utilization of the wax interfacial crystallization behavior to hinder wax deposition of an emulsion was further explored. When the coupled wax crystal-water droplet particles were formed during the wax deposition process, water droplets acted as wax crystal carriers, entraining these nascent wax crystals to disperse in the emulsion, which significantly reduced the amount of wax crystals available to form the network of the deposit. In addition, this change also led to the basic structural units in the wax deposit evolving from wax crystal clusters/networks to water droplet flocs. The study elucidates that through adjusting the dispersion of wax crystals from the oil phase to the oil-water interface, water droplets could act as a functional component to tailor the properties of the emulsion or resolve related flow and deposition problems in pipeline transportation.

Effects of Asphaltene Concentration and Test Temperature on the Stability of Water-in-Model Waxy Crude Oil Emulsions

In oil fields, the formation of water-in-waxy crude oil emulsion is inevitable. The dissolved/crystallized state wax can interact with asphaltenes and then greatly affect the emulsion stability. However, studies on this aspect are still insufficient. In this work, the effects of the test temperature (30 °C well above the wax appearance temperature (WAT) and 15 °C well below the WAT) and asphaltene concentration (0∼1.5 wt %) on the stability of the water-in-model waxy crude oil emulsions containing 10 wt % wax were systematically investigated. When the model crude oils contain no wax, the flowability of the oils is good and the asphaltene concentration has little influence on the oil rheology. Increasing the asphaltene concentration facilitates the adsorption of asphaltenes to the oil-water interface, thus reducing the interfacial tension and water droplet size while enhancing the interfacial dilatational modulus. The stability of the emulsions improves with the increase in the asphaltene concentration, but the emulsions are still unstable. When the model crude oils contain 10 wt % wax, the WAT slightly decreases from the initial 25 to 24 °C after the addition of asphaltenes. The oil rheology is greatly improved by the addition of 0.05 wt % asphaltenes. With the further increase of the asphaltene concentration, the improved rheological ability of the asphaltenes deteriorates rapidly. At the asphaltene concentration of 1.5 wt %, the oil rheology is dramatically aggravated. The stability of the emulsion containing 10 wt % wax is mainly controlled by two aspects: on the one hand, the dissolved-state wax (30 °C) could facilitate the adsorption of asphaltenes to the interface, further reduce the interfacial tension and the water droplet size, and enhance the interfacial dilatational modulus; on the other hand, the wax crystals precipitated in the oil phase (15 °C) can form a stronger network structure at relatively high asphaltene concentrations (0.5∼1.5 wt %) and then immobilize the water droplets. The above two aspects greatly improve the sedimentation and coalescence stabilities of the emulsions at 15 °C. In addition, we did not find persuasive evidence showing that the wax could crystallize around the water droplets and strengthen the oil-water interfacial films.