Low Interfacial Tension Research Articles

Synergistic Interaction of Hyperbranched Polyglycerols and Cetyltrimethylammonium Bromide for Oil/Water Interfacial Tension Reduction: A Molecular Dynamics Study.

Applying surfactants to reduce the interfacial tension (IFT) on water/oil interfaces is a proven technique. The search for new surfactants and delivery strategies is an ongoing research area with applications in many fields such as drug delivery through nanoemulsions and enhanced oil recovery. Experimentally, the combination of hyperbranched polyglycerol (HPG) with cetyltrimethylammonium bromide (CTAB) substantially reduced the observed IFT of oil/water interface, 0.9 mN/m, while HPG alone was 5.80 mN/m and CTAB alone IFT was 8.08 mN/m. Previous simulations in an aqueous solution showed that HPG is a surfactant carrier. Complementarily, in this work, we performed classical molecular dynamics simulations on combinations of CTAB and HPG with one aliphatic chain to investigate further the interaction of this pair in oil interfaces and propose the mechanism of IFT decrease. Basically, from our results, one can observe that the IFT reduction comes from a combination of effects that have not been observed for other dual systems: (i) Due to the CTAB-HPG strong interaction, a weakening of their specific and isolated interactions with the water and oil phases occurs. (ii) Aggregates enlarge the interfacial area, turning it into a less ordered interface. (iii) The spread of individual molecules charge profiles leads to the much lower interfacial tension observed with the CTAB+HPG systems.

Development of a Novel High-Temperature Microemulsion for Enhanced Oil Recovery in Tight Oil Reservoirs.

This work focuses on the development of a novel high-temperature microemulsion for enhanced oil recovery in tight oil reservoirs. Microemulsions are a type of mixture that has properties of both liquids and solids; they have shown significant potential for improving oil recovery through spontaneous imbibition. Herein, a high-temperature-tolerant lower-phase microemulsion using a microemulsion dilution method was developed. The properties and morphological characteristics of the microemulsion were evaluated and proposed a mechanism for enhanced spontaneous imbibition oil recovery using imbibition tests and CT scanning technology. The results of the study showed that the optimum concentration of the microemulsion was 0.2 wt% and that it had good thermal stability, small droplet size, lower interfacial tension, good wettability alteration ability, and minimum adsorption loss. The imbibition and CT experiments demonstrated that the reduction in oil/solid adhesion was due to the synergistic effect of IFT reduction and wettability alteration and the ability to increase the imbibition distance through a larger self-driving force. The study concludes that the solubilization coefficient and self-driving force were defined and calculated to quantitatively analyze the imbibition mechanisms and the results showed that the reduction in oil/solid adhesion was due to the synergistic effect of IFT reduction and wettability alteration and the ability to increase the imbibition distance through a larger self-driving force.

Synergistic performance of a Gemini nano ionic liquid and sodium dodecyl sulfate surfactants at the crude oil–water interface

Gemini surface active ionic liquids (GSAILs) are known as effective and environmentally friendly materials. Conventional anionic surfactants like sodium dodecyl sulfate (SDS), on the other hand, can establish desired properties in solutions. This study reports investigation on the influence of the mixtures of an imidazolium cationic GSAIL, [C4im-C6-C4im][Br]2, and the SDS anionic surfactant on the interfacial tension (IFT), emulsification, and wettability alteration of the crude oil–water system. Results demonstrate amazing synergistic effects, resulting in 97.1 % more IFT reductions compared to what could be achieved with the linear contribution of surfactants. Under the GSAIL mole fraction of 0.4 and the mixture concentration of 0.25 molˑdm−3 in aqueous phase, a low IFT of 0.18 mNˑm−1 was attained. This is attributed to the attractive interaction between the involved surfactants. Synergisms of 52.0 and 59.8 % were also achieved in emulsification and wettability alteration with the mixture of surfactants under the optimum GSAIL mole fraction of 0.4. The obtained data for the individual and the mixture of surfactants were analyzed based on, respectively, Frumkin adsorption isotherm and the “non-ideal interactions in binary mixtures” theory. Corresponding consistent parameters were determined and discussed.

Effect of composition of emulsifier blends on aerated emulsions: Stability, thermodynamic, interfacial behavior and aeration properties

In this study, we investigated the effect of emulsifier blends with different structures and lipophilic-hydrophilic balance (HLB) on the interfacial composition and crystallization behavior, as well as on the aeration properties of emulsions. The droplet size, physical stability, rheological properties, and partial aggregation rate of the quiescent emulsions were determined. Further, the interfacial protein content, interfacial tension, interfacial rheological properties, and thermodynamic properties were analyzed, and the aeration and texture of the foams were recorded. First, there was a significant difference in emulsion droplet size after compounding with glyceryl monostearate (GM) even though sucrose ester S-1570 (SE) and polysorbate 80 (TW) had the same HLB (p < 0.05), but sorbitan monooleate 80 (SP)-TW performed consistently with GM-TW, having the smallest particle size. Secondly, the addition of GM-SE changed the thermodynamic properties and significantly increased the crystallization temperature of fat (15.79 °C), but had no significant effect on the aeration process. In addition, although GM-SE resulted in emulsions with the lowest interfacial tension, the fat globule surface exhibited viscous behavior (E' < E″) and the worst physical stability of the emulsion, while triglycerol monostearate (TMS)-TW balanced the interfacial tension and strength giving good performance in both emulsion stability and aeration characteristics. In general, the design of compounding emulsifiers should pay more attention to the structural of the emulsifier. These results provide an interesting point of departure for further development of compounding emulsifiers for different needs.

The Stability, Rheological Properties and Interfacial Properties of Oil-in-Water (O/W) Emulsions Prepared from Dielectric Barrier Discharge (DBD) Cold Plasma-Treated Chickpea Protein Isolate and Myofibrillar Protein Complexes.

In order to increase the development and utilization of chickpea protein isolate (CPI) and improve the stability of myofibrillar protein (MP) emulsions, the effect of dielectric barrier discharge (DBD) plasma-modified CPI on the emulsifying properties of MP was investigated. Three different O/W emulsions were prepared using MP, MP + CPI complex, or MP + DBD-treated CPI complex as the emulsifier. Compared with the emulsion prepared from MP, the emulsifying activity index and stability of DBD-treated CPI and MP complex (MP + CPIDBD) were increased (p < 0.05) from 55.17 m2/g to 74.99 m2/g and 66.31% to 99.87%, respectively. MP + CPIDBD produced more stable emulsions with the lowest Turbiscan stability index (TSI) values for a given 3600 s. At shear rates from 0 to 1000-1, MP + CPIDBD-stabilized emulsions had higher viscosities, which helped to reduce the chance of aggregation between oil droplets. The optical microscope and particle size distribution of emulsions showed that MP + CPIDBD emulsions had the lowest droplet size (d4,3) and exhibited more uniform distribution. MP + CPIDBD emulsions had lower interfacial tension. DBD pretreatment increased the adsorbed protein content in the emulsion stabilized by MP + CPIDBD as compared to the MP + CPI complex and promoted the adsorption of CPI by higher ratios of adsorbed proteins as indicated by its intensity in SDS-PAGE. Scanning electron microscopy confirmed that the emulsion prepared from MP + CPIDBD had smaller particle size and more uniform dispersion. Therefore, using DBD-modified CPI could enhance the stability of MP emulsions.

Dynamics of two unequal micron-sized viscous emulsion drops flowing in a two-dimensional constricted microcapillary channel: A numerical study

Emulsions containing unequal-sized droplets are ubiquitous. Compared to the equal-sized emulsion droplet coalescence process in porous media, unequal-sized emulsion droplets show distinctly different dynamics and features when flowing through the capillary channel. In this paper, we numerically studied the flow of two unequal small micron-size emulsion drops flowing in a two-dimensional (2D) half-sine pulse shape constricted tube. The finite element method solves the momentum, continuity, and level set equations. The oil–water interface is tracked using the level set method. Effects of drop size, capillary number (interfacial tension), viscosity ratio, and geometrical shape constriction effects on the droplets' flow behavior across the throat, its flow velocities, and average viscous pressure across the tube were investigated. It is found when there is a significant difference in diameters of the two un-equalized droplets, they will flow separately through the throat, whereas when the two un-equalized droplets’ size is close to each other, they coalescence with each other after passing through the constriction. Higher interfacial tension leads unequal-sized droplets to coalescence more readily while droplets pass without coalescence at low interfacial tension cases. The highest pressure drop is recorded at the critical point where the two unequal-sized droplets begin to merge in the constriction throat. Increasing droplet viscosity reduces the chances of coalescence and increases the average viscous pressure drop hence leading to mobility reduction. In the case of geometrical constrictions, circular-shaped contracted tubes offer the least resistance to fluid flow and are more appropriate for enhanced oil recovery processes. We hope our numerical findings will provide more information to facilitate the enhanced oil recovery process.

EOR Displacement Characteristics from Cluster Analysis and Fractional Pore Occupation

AbstractThe in situ saponification of crude oil lowers the interfacial tensions of oil–water systems in chemical-enhanced oil recovery (cEOR). When the interfacial tension is sufficiently low, emulsion phases occur, and the fluid phase distribution in the pore space changes, affecting oil displacement efficiency. This change in capillarity allows the injection water to penetrate different classes of pores, which must be reflected in the distribution of fluids in the pore space. This issue still needs to be adequately researched and is not reflected in the classic analyses of oil cluster size. We have performed μCT-based coreflood experiments to study the displacement efficiency of crude oil by alkaline solutions acting as cEOR agents for in situ saponification. The measured fluid distributions were analyzed using oil-cluster size statistics. In addition, the pore classes from which the oil was preferentially displaced and the degree of displacement as a function of alkali concentration were determined. Despite ultralow interfacial tension and emulsion formation, a clear separation of the oil and aqueous phases was observed over a wide range of alkali concentrations, allowing a two-phase analysis of the microscopic fluid distribution. It was found that (a) a Lorentz analysis of the cluster volume distribution is useful to characterize the cEOR displacement efficiency. It shows the tendency of oil clusters toward a more uniform size distribution toward optimal alkali concentration. (b) the additional oil recovery toward optimal displacement conditions comes from the fraction of smaller pores; at optimal conditions, all pore classes are flooded almost equally and to a high degree, equivalent to miscible displacement, i.e., extremely low interfacial tension.

Screening of Chemicals to Enhance Oil Recovery in a Mature Sandstone Oilfield in Kazakhstan: Overcoming Challenges of High Residual Oil

Chemical flooding, such as alkaline-surfactant (AS) or nanoparticles-surfactant (NS) flooding, is an enhanced oil recovery (EOR) technique that has been increasingly utilized to enhance the oil production rate and recovery factor while reducing chemical adsorption. The AS/NS flooding process involves the injection of a mixture of surfactant and alkali/nanoparticles solutions into an oil reservoir to reduce the interfacial tension between the oil and water phases by surfactant and lower surfactant adsorption by alkali or nanoparticles (NPs) to improve the residual oil recovery. In this study, the AS/NS flooding is evaluated for a Kazakhstani oilfield by systematically screening the chemical constituents involved. Field A in Kazakhstan, one of the oldest fields in the country, has been waterflooded for decades and has not produced even 50% of the original oil in place (OOIP). Currently, the water cut of the field is more than 90%, with a high residual oil saturation. Therefore, besides polymer flooding to control mobility, chemical EOR is proposed as a tertiary recovery method to mobilize residual oil. This study aimed to screen chemicals, including surfactant, alkali, and NPs, to design an effective AS/NS flooding program for the target field. The study focused on conducting laboratory experiments to identify the most effective surfactant and further optimize its performance by screening suitable alkaline and NPs based on their compatibility, stability, and adsorption behavior under reservoir conditions. The performance of the screened chemicals in the porous media was analyzed by a set of coreflood experiments. The findings of the study indicated that alkali agents, particularly sodium carbonate, positively affected surfactant performance by reducing its adsorption by 9–21%. The most effective surfactant combination was found, which gave Winsor type III microemulsion and the lowest interfacial tension (IFT) of 0.2 mN/m. The coreflood tests were conducted with the screened surfactant, alkali, and NPs. Both AS and NS tests demonstrated high residual oil recovery and microemulsion production. However, NS flooding performed better as the incremental oil recovery by NS flooding was 5% higher than standalone surfactant flooding and 9% higher than AS flooding. The results of this screening study helped in designing an efficient chemical formulation to improve the remaining oil recovery from Field A. The findings of this study can be used to design EOR projects for oil fields similar to Field A.

Investigation of dispersed phase holdup in a Tenova pulsed liquid-liquid extraction column

BackgroundPulsed extraction columns have been designed and studied in different types of internal equipment such as packed, tray, and doughnut discs. In recent years (2017), researchers have turned to research on Tenova columns, which is the newest generation of pulsed columns. Correlations for predicting the hydrodynamics of the Tenova column have not been reported. MethodA pulsed Tenova column with a 7.4 cm diameter and 130 cm height including 30 pairs of modified doughnuts and discs was fabricated and tested. Standard chemical systems with low, medium, and high interfacial tension approved by the European Federation of Liquid-Liquid Extraction are used. Holdup as one of the most important hydrodynamic parameters in designing is studied. The effects of dispersed and continuous phase velocity and pulsation intensity have been taken into account. Significant findingsDimensional analysis used for predicting hold-up and an error about 8% have been obtained. Other experimental relations proposed by researchers in pulsed columns have been studied and the error of about 16% found. First and second critical pulsation intensity, which are the commencement and the end of breaking of drops has been seen in these experiments. The recommended operating pulsation intensity is between these two critical values.

Precise control of aggregation morphology: Effective strategy to tune the properties of ovotransferrin particles

Different aggregation morphologies of ovotransferrin (OVT) aggregates were successfully obtained through precise control, and the effects on structural, physical, liquid–liquid and gas–liquid interfacial characteristics as well as mechanisms were explored for the first time. It was observed that the surface hydrophobicity of OVT fibrils was higher than OVT spheres due to the acid-heat treatment. The exploration of liquid–liquid interface behaviors indicated that OVT fibrils possessed higher adsorption capacity at the interface, revealing the higher surface activity at the oil-water interface. During adsorption process, fibrils exhibited higher diffusion rate, while spheres were easier to penetrate and rearrange at the interface. The interfacial film composed of fibrils possessed more elastic solid-like behaviors owing to the higher surface activity of individual fibrous aggregates and rapid fibril-fibril interactions. The analysis of gas–liquid interface characteristics presented that OVT spheres possessed lower interfacial tension and higher interfacial viscoelasticity, and showed significantly higher FC and FS values in comparation to fibrils. These findings will facilitate the reader's understanding of the relationship between protein aggregate structure and properties, and lay a foundation for broadening the application of OVT and even other proteins.

Experimental investigation on the effect of interfacial properties of chemical flooding for enhanced heavy oil recovery

Chemical compound flooding has demonstrated its efficacy in enhancing light oil recovery through ultra-low interfacial tension (IFT). However, the optimization of chemical systems properties for displacing heavy oil has not been clarified. This research aims to address this problem by designing common polymer and three surfactant-polymer (SP) systems with varying IFT and interfacial viscoelasticity behaviors, and comparing their ability to recover heavy oil. The findings of core flooding tests indicate that the system with low IFT and high interfacial viscoelasticity simultaneously has a better displacement efficiency for heavy oil than other flood systems, which could enhance heavy oil recovery by 21.94%. Micro-model tests reveal the underlying mechanisms driving the enhanced macro-scale oil recovery. The emulsion formation and interface expansion facilitated by low IFT, as well as increased emulsion stability and reduced snap-off of oil droplets due to the presence of an elastic oil-water interfacial film. These phenomena is more capable of driving microscopic heterogeneous remaining oil and film remaining oil than other solution. The comparative experiment analysis shows that the difference in chemical flooding between heavy oil and light oil is caused by the discrepant distributions of surfactants at the oil-water interface. The light oil interface is a monolayer surfactant molecular film, the heavy components and surfactant moleculars exhibit both competitive and cooperative adsorption phenomena at the oil-water interface. The occurrence of viscosity reduction and increased emulsion stability are more influential factors in the process of heavy oil displacement than those of conventional ultra-low IFT systems used for light oil recovery.

Interfacial tension of smart water and various crude oils

The utilization of smart water in EOR (enhanced oil recovery) operations has drawn increased attention in recent years. Nevertheless, the variety and complexity of mechanisms during smart water injection require more research endeavors. In this study, interfacial tension (IFT) for the smart water/crude oil interacting system has been investigated. The investigated parameters included various salts with different salinity, pH, asphaltene type, and aged smart water with two crude oil samples. The results showed that the hydration of ions in smart water would play a key role to discern the primary mechanism of smart water. The interaction of acidic and basic asphaltene with hydration shell of different ions can be considered as primary mechanism for efficacy of smart water. Acidic and basic asphaltenes serve as intrinsic surfactants due to their interaction with OH− in the anion hydration shell and H+ in the cation hydration shell, respectively. The propensity of acidic asphaltene to interact with anions with high hydration energy and the tendency of basic asphaltene to interact with cations with high hydration energy led to an IFT of 0.2 mN/m and 11.3 mN/m for acidic and basic oils, respectively. The impact of pH also revealed that acidic and basic asphaltenes would have lower IFT in alkaline and acidic environments. Finally, it was found that changes in IFT for the aged smart water with crude oil depend on the asphaltene type as well as salt and salinity.

Structure and functionality of cinnamaldehyde/chitosan/gum Arabic complex particles

The work aims to study the effects of the mixing order of chitosan, gum Arabic and cinnamaldehyde and the concentration of cinnamaldehyde on the structure and functionality of complex particles. The results showed that non-covalent and Schiff base reactions occurred between cinnamaldehyde, chitosan and gum Arabic. When chitosan and gum Arabic (CS-GA-1:0.3) were mixed first, the complex particles were flat spherical and more compact and existed in aggregate state, with higher particle size, Zeta potential and wettability, and lower interfacial tension. When mixing cinnamaldehyde with chitosan or gum Arabic first (CS-CA-1:0.3 and GA-CA-1:0.3) and adding high concentration of cinnamaldehyde (CS-GA-1:0.9 and CS-GA-1:1.2), the structural compactness and morphological regularity of the complex particles got weakened, leading to the decrease in contact angle and increase in interfacial tension. All complex particles could be effectively used as Pickering emulsion stabilizers. When chitosan:cinnamaldehyde mass ratio reached 1:0.6 and below, the complex particles showed obvious antibacterial properties. The above results laid a foundation for the application of chitosan-based complex particles in the food and medical field.

Synergistic Effect of Salt and Anionic Surfactants on Interfacial Tension Reduction: Insights from Molecular Dynamics Simulations.

Surfactants are commonly utilized in chemical flooding processes alongside salt to effectively decrease interfacial tension (IFT). However, the underlying microscopic mechanism for the synergistic effect of salt and surfactants on oil displacement remains ambiguous. Herein, the structure and properties of the interface between water and n-dodecane are studied by means of molecular dynamics simulations, considering three types of anionic surfactants and two types of salts. As the salt concentration (ρsalt) increases, the IFT first decreases to a minimum value, followed by a subsequent increase to higher values. The salt ions reduce the IFT only at low ρsalt due to the salt screening effect and ion bridging effect, both of which contribute to a decrease in the nearest head-to-head distance of surfactants. By incorporating salt doping, the IFTs can be reduced by at most 5%. Notably, the IFTs of different surfactants are mainly determined by the hydrogen bond interactions between oxygen atoms in the headgroup and water molecules. The presence of a greater number of oxygen atoms corresponds to lower IFT values. Specifically, for alkyl ethoxylate sulfate, the ethoxy groups play a crucial role in reducing the IFTs. This study provides valuable insights into formulating anionic surfactants that are applicable to oil recovery processes in petroleum reservoirs using saline water.

Protein modified cellulose nanocrystals on reinforcement and self-driven biodegradation of aliphatic polyester

Due to the highly environment-dependent biodegradation and uncontrolled degradation period, the long-run feasibility and effectiveness of biodegradable polymers are extensively questioned to solve plastics waste accumulation and pollution problems. This work physically incorporated lipase PS from Burkholderia cepacian on cellulose nanocrystals (CNC) and embedded it in polycaprolactone (PCL) to construct stable and controllable interfacial microenvironment between CNC and PCL for the reinforcement and controllable self-driven biodegradation. The physical adsorption of lipase PS on CNC was studied by monitoring the surface charge and particle size. FT-IR spectra confirmed the successful incorporation of lipase PS and CNC. Compared with CNC, protein-modified CNC had a higher maximum thermal decomposition temperature of 345 °C and lower interfacial tension of 11 mN/m with PCL which provided PCL composites with higher nucleation efficiency and tensile elongation of 1086 % at break. In addition, only 0.67 % embedded lipase PS completely hydrolyzed PCL membranes in <140 h. The post-compression molding at 80–100 °C had negligible influence on the lipase activity, which indicated that CNC could protect the lipase from inactivation in polymer extrusion and compression. This work also highlighted protein-modified CNC as a new technology for polymer reinforcement.

Prismatic Block Copolymer Hexosomes.

Cubosomes and hexosomes are recent solution morphologies with an ordered porous structure and are observed for lipids and amphiphilic block copolymers (BCPs) with high hydrophobic fractions. Whereas lipid hexosomes typically exhibit a prismatic shape, BCP hexosomes have so far only been observed as closed microspheres where inner channels are not connected to the surrounding medium. Here, we describe the formation of flat, prismatic BCP hexosomes with pronounced faceting and a highly ordered lattice of hexagonally packed channels. We assemble polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP or SV) into the hexosome framework using polystyrene-block-poly(4-vinylpyridine)-block-poly(tert-butyl methacrylate) (PS-b-P4VP-b-PT or SVT) as a macromolecular surfactant in low-χ solvents. During solvent exchange, SV-rich domains form through liquid-liquid phase separation, followed by solidification and confined assembly within these domains. Since the final solvent (acetone) has a very low χ parameter toward PS and P4VP (equaling low interfacial tension), solidification of the hexosome occurs under confinement conditions that we term "supersoft". The low interfacial tension allows the stabilization of the hexagonal-prismatic shape, which originates from the hexagonal lattice of channels. Increasing the interfacial tension with polar cosolvents at some point dominates the particle shape, resulting in deformation of prismatic BCP hexosomes into spinning-top structures. The use of low-χ solvents for confined assembly of BCPs may allow the formation of unusual particle shapes simply by tuning the polymer-solvent interaction.

Interfacial Rheological and Emulsion Properties of Self-Assembled Cyclodextrin-Oil Inclusion Complexes.

To investigate the effect of the molecular size of alkanes and the cavity size of cyclodextrins (CDs) on the formation of interfacial host-guest inclusion complexes, the interfacial tension (IFT) of CD (α-CD, β-CD, γ-CD) solutions against oils (hexadecane, dodecylbenzene) was determined by interfacial dilational rheology measurements. The results show that the "space compatibility" between CDs and oil molecules is crucial for the formation of interface host-guest inclusion complexes. Hexadecane with a smaller molecular size can form host-guest inclusion complexes with small cavities of α-CD and β-CD, dodecylbenzene with a larger molecular size can form interfacial aggregates with the medium-sized cavity of β-CD easily, and the polycyclic aromatic hydrocarbon molecules in kerosene can form inclusion complexes with the large cavity of γ-CD. The formation of interfacial inclusion complexes leads to lower IFT values, higher interfacial dilational modulus, nonlinear IFT responses to the interface area oscillating, and skin-like films at the oil-water interface. What's more, the phase behavior of Pickering emulsions formed by CDs with different oils is explored, and the phenomena in alkane-CD emulsions are in line with the results in dilatation rheology. The interfacial active host-guest structure in the kerosene-γ-CD system improves the stability of the Pickering emulsion, which results in smaller emulsion droplets. This unique space compatibility characteristic is of great significance for the application of CDs in selective host-guest recognition, sensors, enhanced oil recovery, food industries, and local drug delivery.

Electrical dehydration performance of shale oil: From emulsification characteristics to dehydration mechanisms

Shale oil, as a successor to ordinary crude oil, has received extensive attention. However, the high-stability shale oil emulsions are still challenging for electrical dehydration systems. In this work, the differences between shale oil and ordinary crude oil were compared in terms of emulsion droplet size, physical properties and components to clarify the emulsification characteristics of shale oil and reveal its electrical dehydration mechanism. To this end, comprehensive electrical dehydration experiments were carried out under different parameters and transformers. The results showed droplet diameters of shale oil emulsions less than 10 µm, a value much smaller than that of crude oil. Shale oils with high viscous contained lots of natural emulsifiers, promoting the formation of the rigid asphalt film and wax crystal network structure. The synergistic adsorption of surfactant and paraffin molecules and the film formation of asphaltenes promoted by resins make shale oil display lower interfacial tension and higher interfacial film pressure. The above characteristics were the main reasons behind the formation of shale oil stable emulsions. Factors, such as electric field frequency, dehydration temperature, dehydration time, and demulsifier concentration influenced the emulsification characteristics and dehydration performance of shale oils at variable degrees. The dehydration performances of high-frequency transformer (Transformer B) and ultra-high-frequency transformer (Transformer C) on shale oil emulsion SH-1 were better than that of low-frequency transformer (Transformer A) due to tensile breakup or oscillatory coalescence of droplets under different electric field conditions. Considering energy consumption and economy comprehensively, Transformer C has excellent application potential. The analyses also show that high-frequency, heating and adding demulsifier are the key and necessary factors in the electric dewatering treatment of shale oil. In sum, these results look useful for future design optimization of shale electrical dehydration devices.

Numerical analysis of pore-scale CO2-EOR at near-miscible flow condition to perceive the displacement mechanism

Gas flooding through the injection of text{CO}_{2} is generally performed to achieve optimum oil recovery from underground hydrocarbon reservoirs. However, miscible flooding, which is the most efficient way to achieve maximum oil recovery, is not suitable for all reservoirs due to challenge in maintaining pressure conditions. In this circumstances, a near-miscible process may be more practical. This study focuses on pore-scale near-miscible text{CO}_{2}–Oil displacement, using available literature criteria to determine the effective near-miscible region. For the first time, two separate numerical approaches are coupled to examine the behavior of text{CO}_{2}–oil at the lower-pressure boundary of the specified region. The first one, the Phase-field module, was implemented to trace the movement of fluids in the displacement text{CO}_{2}–Oil process by applying the Navier–Stokes equation. Next is the TDS module which incorporates the effect of text{CO}_{2} mass transfer into the oil phase by coupling classical Fick’s law to the fluids interface to track the variation of text{CO}_{2} diffusion coefficient. To better recognize the oil recovery mechanism in pore-scale, qualitative analysis indicates that interface is moved into the by-passed oil due to low interfacial tension in the near-miscible region. Moreover, behind the front ahead of the main flow stream, the text{CO}_{2} phase can significantly displace almost all the bypassed oil in normal pores and effectively decrease the large amounts in small pores. The results show that by incorporating mass transfer and capillary cross-flow mechanisms in the simulations, the displacement of by-passed oil in pores can be significantly improved, leading to an increase in oil recovery from 92 to over 98%, which is comparable to the result of miscible gas injection. The outcome of this research emphasizes the significance of applying the text{CO}_{2}-EOR process under near-miscible operating conditions.

A Double-Emulsion Method for the Fabrication of PLA Single-Hole Hollow Particles

Background: Polymeric hollow particles with a single-hole structure have attracted broad interest due to their combined advantages of a hollow cavity and an opening hole in the shell. Aim: In the past decades, much progress has been made in the fabrication of such particles with various strategies. However, there is a lack of research on the easy fabrication of biodegradable polylactide (PLA) single hole particles (PLA SHHPs). Methods: In this work, we reported a simple double emulsion method for the fabrication of PLA SHHPs. The W/O/W double emulsion was formed by homogenizing PLA chloroform and brilliant blue G (BBG) solution. Scanning electron microscopy and confocal laser scanning microscopy were used for the characterization. It was found that the concentrations of PLA chloroform and BBG solution both had a significant influence on the emulsion structure. Result: PLA SHHPs with a percentage &gt;85% were obtained from the emulsion composed of PLA chloroform (10.0 w%) and BBG solution (4 mM). The particle formation mechanism was also proposed based on the result of the low interfacial tension between PLA chloroform/BBG solution. Conclusion: The results may inspire new development of PLA particles with unique structures, which are promising to be used in drug delivery, catalysis, microreaction and micromotors.