Oil-water Interfacial Tension Research Articles

Development of Oil Vehicle Screening Method for Bromo Acid Dye-Based Color-Changing Cosmetic Formulation

Bromo acid dye (Red 21) recently gained attention in the production of color-changing cosmetics. The critical aspect in the development of cosmetic products using this dye group is the compatibility of its oil vehicles. The compatibility of bromo acid dyes with oil vehicles is determined by several parameters such as the dye solubility in the oils, clarity of the mixture, and the ability to change color when the pH of the solution is adjusted to match the skin’s pH. Therefore, this study conducted the compatibility study by examining the ability of 27 oil samples to dissolve Red 21. The ability of a vehicle to dissolve a compound is influenced by the polarity of the vehicle. Hence, a correlation was established between the relative polarity of oils and their ability to dissolve Red 21. The results showed that the water-oil interfacial tension was negatively correlated (r = -0.64) with Red 21 solubility in the oil. From this research, the water-oil interfacial tension represented the relative polarity of the oil and was considered sufficient to predict the compatibility of the oil with Red 21. In addition, hydrocarbon and silicone oils are not compatible with Red 21.

Crude oil displacement enhanced by interfacially active nanoparticles and their coupling effect with low-salinity brines

From the microscopic scale to the petroleum-reservoir scale, the interfacial phenomena of a crude oil–water-rock system crucially control immiscible flow in a porous reservoir. One of the key mechanisms is crude oil droplet displacement dynamics, which can be optimized by manipulating the oil–water interfacial tension and the three-phase contact angle by means of chemical injection. Oil film displacement was enhanced by adding interfacially active nanoparticles, namely poly(N-isopropylacrylamide) or pNIPAM (43–48 nm hydrodynamic diameter and 0.0005–0.0050 wt% concentration range), accelerating the oil droplet receding rate (up to 5.66°/s) and greater degree of oil film dewetting (37.0° contact angle). Such behavior was attributed to nanoparticle-induced structural disjoining pressure between the oil–water and water–solid interfaces. The coupling effect of pNIPAM nanoparticles with low-salinity brines was studied, revealing discrepancy in different valency brines. Coupling with divalent CaCl2 led to much slower oil droplet receding dynamics (2.58°/s, and 58.7° contact angle) since oil-substrate bridging is formulated and promoted by the divalent cation. However, a positive synergy was observed with a monovalent NaCl blend. The crude oil dewetting dynamics were enhanced (9.55°/s) owing to the combined salt-induced hydration and nanoparticle-induced structural forces. The contact angle reduced to 21.5° before eventually detaching from the substrate after a relatively short period (156 s). These findings highlight the coupling effects of nanoparticles and low-salinity brine to enhance dewetting of heavy crude oil. Adding nanoparticles to an ‘optimal’ brine could be an option for faster and greater fluid displacement, which is not limited to oil production applications but several others, such as detergency and other forms of geological storage.

Emulsions stabilized by okra polysaccharides: Physicochemical, interfacial, and emulsification properties

This study provided a comprehensive investigation about the correlation between okra polysaccharide physicochemical characteristics, interfacial behavior, and emulsification properties. Six okra polysaccharides with distinct physicochemical properties were prepared and evaluated for their emulsification performance. The kind of acid used for extraction affected the molecular weight of polysaccharides, while extraction solutions with different pH influenced the molar ratio of monosaccharides and the degree of methyl-esterification (DM), thereby affecting the behavior of polysaccharides at the oil-water interface and emulsification properties. Okra polysaccharides with higher DM and RG-I exhibited lower oil-water interfacial tension and thicker interfacial layers. Compared to the emulsion stabilized by okra polysaccharide extracted using citric acid solution at pH 2.0 (OPC-2), the emulsion stabilized by okra polysaccharide extracted using hydrochloric acid solution at pH 1.0 (OPH-1) exhibited significant advantages of smaller droplet size (0.56 μm) and less malondialdehyde content (6.25 μmol/kg oil). Under pH 2.0, OPH-1 demonstrated the highest viscosity (290.12 mPa S), along with the strongest G' (42.12 Pa) and G" (25.79 Pa), playing crucial roles in sustaining emulsion stability. Moreover, under conditions of high ionic strength, the interaction between ions and okra polysaccharide molecules diminished the emulsifying ability and emulsion storage stability. This study provides significant insights into the performance of okra polysaccharides and polysaccharide-based emulsions, thereby guiding the development of efficient and stable emulsifiers.

Effect of Anionic Surfactants on the Oil-Water-Rock Interactions by an Improved Washburn Method.

The complex and variable structure of subsurface oil reservoirs as well as the small pore throat size of reservoirs make it extremely important to investigate the effect of oil-water-rock interactions for enhancing oil recovery. In this paper, the powder wettability of oil sand with different polar solvents was investigated using the improved Washburn capillary rise method, and the surface free energy of oil sand was calculated in combination with the OWRK method. In addition, the wettability of anionic surfactants HABS and PS solutions on the surface of oil sand was determined, and it showed that their wetting rates showed different trends after CMC (critical micelle concentration). The C×cosθ value of HABS decreased significantly with increasing concentration, whereas PS showed little changes. This may be related to the aggregate structure formed by HABS on the oil sand surface. Meanwhile, the interfacial free energy between crude oil and oil sand was obtained by crude oil-to-oil sand wetting experiments, and found that the wetting rate of crude oil to oil sand was much lower than that of solvents and surfactants. In combination with the above results and the oil-water interfacial tension (IFT), the oil-water-rock three-phase contact angle and the work of adhesion between the crude oil and the solid were obtained by Young's equation. From the three-phase contact angle results, it can be found that the contact angle values of both HABS and PS are obviously higher than that of the simulated water, and both HABS and PS have the ability to significantly reduce the work of adhesion, which shows a strong ability to strip the oil film on the surface of the solid. The research results of this paper are helpful to understand the oil displacement mechanism of chemical flooding in reservoir pores, which is of great significance for improving oil recovery.

An efficient method for imbibition in asphaltene-adsorbed tight oil-wet reservoirs

Spontaneous imbibition (SI) has been proposed as a crucial approach to enhance oil recovery in unconventional reservoirs. Previous research suggests that wettability alteration rather than oil-water interfacial tension (IFT) reduction is the key mechanism for imbibition oil recovery enhancement. However, our experimental results indicate that for asphaltene-adsorbed oil-wet surfaces it's challenging to substantially modulate wettability. In such oil-wet pores, the negative capillary force cannot function as an imbibition driving force, and hence, the method of altering wettability and maintaining the oil-water IFT at relatively high values to enhance imbibition efficiency is insufficiently applicable. When the capillary cannot work, reducing the IFT to ultra-low levels to induce the transformation of the imbibition pattern may be more effective for imbibition efficiency enhancement. In this paper, low-field nuclear magnetic resonance (NMR) was employed to monitor the SI process. The results suggested that for the asphaltene-adsorbed oil-wet tight sandstone, the surfactants combined system with ultra-low oil-water IFT possessed the highest oil recovery, followed by the medium-IFT systems and high-IFT systems. The spontaneous formation of emulsion was observed when the IFT value was reduced to the ultra-low level. Oil droplets can pass through the small pores easily since the deformability of oil is greatly enhanced. The ultra-low IFT system transforms the imbibition pattern from capillary force-driven to gravity-driven, and exhibits the highest oil utilization rate in micropores, mesopores, and macropores among all imbibition agent systems, thereby having the highest total oil recovery. Consequently, the imbibition-enhancing potential of the ultra-low IFT system is considerable and deserves more attention, especially for the oil-wet pores that can hardly be altered to the water-wet state.

Colloidal and interfacial properties of spray dried pulse protein-blueberry polyphenol particles in model dispersion systems

The phytochemical composition and physicochemical attributes of polyphenol-enriched protein particle ingredients produced with pulse proteins (e.g. chickpea protein, pea protein, and a chickpea-pea protein blend) and polyphenols recovered from wild blueberry pomace were investigated for colloidal and interfacial properties. Anthocyanins were the major polyphenol fraction (27.74–36.47 mg C3G/g) of these polyphenol-rich particles (44.95–62.08 mg GAE/g). Dispersions of pea protein-polyphenol particles showed a superior phase stability before and after heat treatment compared to the chickpea pea protein-polyphenol system. This observation was independent of the added amount of NaCl in the dispersion. In general, at quasi equilibrium state, pulse protein-polyphenol particles and parental pulse protein ingredients showed similar oil-water interfacial tension. However, pea protein-polyphenol particles demonstrated a reduced diffusion-driven oil-water interfacial adsorption rate constant compared to the parental pea protein ingredient. Overall, the obtained results suggest application potential of pea protein-polyphenol particles as a functional food/beverage ingredient.

Sulfobetaine Zwitterions with Embedded Fluorocarbons: Synthesis and Interfacial Properties.

We describe the preparation of a new set of fluorinated sulfobetaine (FSB) zwitterionic polymers in which fluorocarbon moieties are attached directly to the zwitterionic components. An efficient two-step modification to the conventional sulfobetaine methacrylate monomer synthesis gave access to a series of polymer zwitterions containing varying extents of fluorocarbon character. FSB methacrylates proved amenable to homo- and copolymerizations using reversible addition-fragmentation chain transfer (RAFT) conditions, affording polymers with molecular weights ranging from 5 to 20 kDa and with low molecular weight distributions. Thin films of FSB homopolymers on glass proved stable to aqueous environments and exhibited increasing hydrophobicity with fluorocarbon content, as well as remarkably large water contact angle hysteresis values that enable pinning of water droplets on hydrophobic surfaces, reminiscent of the "petal effect" found in nature. FSB-containing copolymers in aqueous media demonstrated markedly reduced oil-water interfacial tension values, even with moderate (20-50 mol %) FSB incorporation.

The impact of porous structure on oil–water two-phase flow under CO2 environment in continental shale reservoirs

CO2 applications for enhanced oil recovery and storage in continental shale reservoirs are promising, and there is a need to evaluate the impact of porous structure on oil–water two-phase flow under CO2 environment. In this study, first, digital cores of quartz-rich, carbonate-rich, and clay-rich shales are established using Focused Ion Beam Scanning Electron Microscopy scanning data processed through generative adversarial networks. Subsequently, the pore networks generated by digital cores are quantitatively analyzed using the generalized extreme value distribution. Finally, pore network modeling is carried out to elucidate the effect of porous structural differences on oil–water flow considering CO2 dissolution and capillary forces. The results show that quartz-rich shale, characterized by nanopore intergranular dominance and the highest pore network connectivity, demonstrates the highest relative permeability of the oil phase. Carbonate-rich shale exhibits intermediate relative permeability of oil phase, while clay-rich shale exhibits the worst. The dissolution of CO2 reduces oil–water interfacial tension and oil viscosity, enhances oil mobilization within nanopores, and notably increases the relative permeability of the oil phase. The permeability of the oil phase is governed by pore structure, displaying positive correlations with core heterogeneity, pore radius, coordination number, and throat length, and negative correlations with throat radius.

Synergistic collaborations between surfactant and polymer for in-situ emulsification and mobility control to enhance heavy oil recovery

Surfactant-polymer (SP) combined systems is an effective nonthermal method to enhance the heavy oil recovery, through in-situ emulsification and mobility control mechanisms. In this study, a novel SP system was developed using 0.2 wt% anionic surfactant (alkyl naphthol polyoxyethylene ether sulfonate, ANES) and 0.1 wt% polymer (partially hydrolyzed polyacrylamide, HPAM). The SP system had viscosity reduction rate of ∼ 98 %, viscosity ratio of oil to displaced water (μo/μd) of ∼ 3.95 and IFT of ∼ 0.29 mN/m, beneficial for decreasing the mobility ratio of water to heavy oil. Then, the applied performances including emulsion morphologies and stability, wettability alteration ability were systematically characterized. The results showed that the freshly O/W emulsions formed by SP system displayed uniform droplet size distribution, as well as high stability with tight interfacial film. In addition, the SP system exhibited excellent wettability alteration property with low contact angle of 18.3°. The synergistic collaboration mechanisms of surfactant and polymer include heavy oil–water interfacial tension reduction, in-situ emulsification, oil-viscosity reduction and water-viscosity increase. Finally, the static oil washing and dynamic sand-pack flooding experiments showed that the SP system exhibited high oil washing efficiency (62.89 %) and enhanced oil recovery efficiency (56.9 %) with improving the mobility controllability after the primary water-flooding process. This study indicated that the synergistic collaborations between surfactant and polymer had great potential to enhance the heavy oil recovery.

Surfactant–Polymer Flooding: Chemical Formula Design and Evaluation for High-Temperature and High-Salinity Qinghai Gasi Reservoir

The Gasi reservoir in the Qinghai oilfield is a typical high-temperature and high-salinity reservoir, with an average temperature and average salinity of 70.0 °C and 152,144 mg/L, respectively. For over 30 years since 1990, water flooding has been the primary method for enhancing oil recovery. Recently, the Gasi reservoir has turned into a mature oilfield. It possesses a high water cut of 76% and a high total recovery rate of 47%. However, the main developing enhanced oil recovery (EOR) technology for the development of the Gasi reservoir in the next stage is yet to be determined. Surfactant–polymer (SP) flooding, which can reduce the oil–water interfacial tension and increase the viscosity of the water phase, has been widely applied to low-temperature and low-salinity reservoirs across China in the past few decades, but it has rarely been applied to high-temperature and high-salinity reservoirs such as the Gasi reservoir. In this study, the feasibility of SP flooding for high-temperature and high-salinity reservoirs was established. Thanks to the novel surfactant and polymer products, an SP flooding formula with surfactants ZC-2/B2 and polymer BRH-325 was proposed for Gasi. The formula showed a low interfacial tension of 10−2 mN/m and a high viscosity of 18 MPa·s in simulated reservoir conditions. The oil displacement experiment demonstrated that this formula can enhance the oil recovery rate by 26.95% upon water flooding at 64.64%. This study provides a feasible EOR candidate technology for high-temperature and high-salinity reservoirs, as exemplified by the Qinghai Gasi reservoir.

Comparative study of nanoemulsion and micelle formed by surfactants containing benzene ring for spontaneous imbibition displacement

Nanoemulsion has a wide range of applications in oilfield chemistry due to its unique nanoscale size, excellent kinetic stability and high specific surface area. In this paper, a novel nanoemulsion oil flooding system was prepared using anionic surfactant sodium dodecyl benzene sulfonate (SDBS), the nonionic surfactant alkylphenol ethoxylates (OP-10), kerosene, n-butanol and deionized water. The particle size, Zeta potential, interfacial tension (IFT) and wettability properties were evaluated in the laboratory. The displacement performance of nanoemulsion was evaluated by the spontaneous imbibition experiment. Meanwhile, it compared with the same concentration of SDBS + OP-10 + n-butanol (SOB) system. The results showed that the particle size of the nanoemulsion was 70 ∼ 100 nm. When the concentration of nanoemulsion was 0.10 %, the oil–water IFT could reach 0.091 mN/m. The spontaneous imbibition oil recovery of the nanoemulsion (0.10 wt%) could reach 33.20 %, which was 23.02 % higher than that of SOB system. We also research the spontaneous imbibition displacement mechanism of nanoemulsion and micelle in low-permeability reservoirs. This paper will help to select the best oil displacement agent for the design of enhanced oil recovery (EOR) projects and promote the application of oil displacement agent in oilfield.

Self-Assembled Viscoelastic Surfactant Micelles with pH-Responsive Behavior: A New Fracturing-Displacement Integrated Working Fluid for Unconventional Reservoirs.

The integrated fracturing and oil recovery strategy is a new paradigm for achieving sustainable and cost-effective development of unconventional reservoirs. However, a single type of working fluid cannot simultaneously meet the different needs of fracturing and oil displacement processes. Here, we develop a pH-responsive fracturing-displacement integrated working fluid based on the self-assembled micelles of N,N-dimethyl oleoamine propylamine (DOAPA) and succinic acid (SA). By adjusting the pH of the working fluid, the DOAPA and SA molecules can be switched repeatedly between highly viscoelastic wormlike micelles and aqueous low-viscosity spherical micelles. The zero-shear viscosity of the working fluid enriched the wormlike micelles can reach more than 93,100 mPa·s, showing excellent viscoelasticity and sand-carrying properties. The working fluid is easy to gel-break when it encounters oil, generating a low-viscosity liquid without residue. In addition, the system has strong interfacial activity, which can greatly reduce the oil-water interfacial tension to form emulsions and can achieve reversible demulsification and re-emulsification by adjusting pH. Through the designed and fabricated microfluidic chip, it can be visualized that under the synergistic effect of viscoelasticity and interfacial activity DOAPA/SA can effectively expand the swept volume of tight fractured formations, promote pore wetting reversal and crude oil emulsification, and improve the displacement efficiency. The DOAPA/SA meets the design requirements of the fracturing-displacement integrated working fluids and provides a novel method and idea for constructing the integrated working fluids suitable for fracturing and displacement in unconventional reservoirs.

Simulation and experimental study on amphiphilic modified graphene oxide for EOR

The application of nanosheet in enhanced oil recovery (EOR) offers a practical approach to resolving some surface-related problems. In this study, theoretical calculation and experiment were combined to study the interfacial behavior and mechanism of amphiphilic modified graphene oxide. Octadecyl amine and aspartic acid were successfully grafted onto graphene oxide nanosheets by starch template method. The stability of the modified structure was verified by IR, XRD and SEM. The change of microstructure in molecular simulation can enhance the understanding of the structure of amphiphilic modified nanosheets under SEM. The contact angle experiment directly shows its amphiphilicity, which shows that the contact angle of hydrophilic surface is 34.6° and that of hydrophobic surface is 103.5°. The interfacial elasticity experiment shows that the interfacial film formed by synthetic GOTA has certain elasticity. When the concentration increases, the interfacial film formed in the adsorption process can effectively separate the oil and water phases. Based on the interfacial tension value, the ability of graphene oxide and modified graphene oxide with different concentrations to reduce the interfacial tension between distilled water and diesel oil was investigated successively. The mechanism of GOTA action was explained from the aspects of molecular structure and energy by molecular simulation. The results show that the interfacial tension fluctuates around 16 mN/m when the GOTA concentration is 0.005%, and the average interfacial tension is 17.48 mN/m when the GOTA concentration (molecular number percentage) is 0.004% in the simulation process, which is highly consistent. Further studies have shown that the interface formation energy of the system is significantly reduced after the addition of zwitterionic surfactants, and the interfacial tension can be reduced to 11.95 mN/m. With the help of molecular simulation, the adsorption mechanism of GOTA on the interface is explained from the aspects of microstructure change, interaction energy, cohesion energy, interface density and conformation. The adjustment of these interactions will directly affect the oil-water interface morphology and interfacial tension.

Development of 1 Month Sustained-Release Microspheres Containing Liraglutide for Type 2 Diabetes Treatment.

Liraglutide has been extensively applied in the treatment of type 2 diabetes mellitus (T2DM), but its 11-15 h half-life resulted in daily administration, which led to poor patient compliance. This study aimed to solve this problem by developing liraglutide-loaded microspheres with a 1 month sustained release prepared by the W1/O/W2 method combined with the premix membrane emulsification technique to improve therapeutic efficacy. Remarkably, we found that the amphiphilic properties of liraglutide successfully reduced the oil-water interfacial tension, resulting in a stable primary emulsion and decreasing the level of drug leakage into the external water phase. As a result, exceptional drug loading (>8%) and encapsulation efficiency (>85%) of microspheres were achieved. Furthermore, the uniformity in microsphere size facilitated an in-depth exploration of the structural characteristics of liraglutide-loaded microspheres. The results indicated that the dimensions of the internal cavities of the microspheres were significantly influenced by the size of the inner water droplets in the primary emulsion. A denser and more uniform cavity structure decreased the initial burst release, improving the release process of liraglutide from the microspheres. To evaluate the release behavior of liraglutide from microspheres, a set of in vitro release assays and in vivo pharmacodynamics were performed. The liraglutide-loaded microspheres effectively decreased fasting blood glucose (FBG) levels and hemoglobin A1c (HbA1c) levels while enhancing the pancreatic and hepatic functions in db/db mice. In conclusion, liraglutide sustained-release microspheres showed the potential for future clinical applications in the management of T2DM and provided an effective therapeutic approach to overcoming patient compliance issues.

Performance and mechanism of organic solid-phase sediment composite plugging agent

The surface pipeline sediments of the Yingmai and Hade oil fields mainly contain substances such as asphalt and paraffin. The formation of sediment can increase the backpressure during pipeline transportation, and in severe cases, it can also lead to pipeline blockage. In order to solve this on-site situation, indoor experiments were conducted in the early stage, and an efficient organic unblocking system LXW was optimized and formulated. Based on this system, this article selects the wire mesh filtration method to evaluate the unblocking performance of LXW and on-site unblocking agents in the study and comparison of three evaluation methods. At the same time, based on the analysis of the chemical composition, microstructure, and melting point of organic sediments, from the perspectives of safety, environmental protection, and economic factors, further compares the performance and universality of the three unblocking systems, optimizes the process parameters of the LXW unblocking system, explores its stability and impact on the demulsification and dehydration of crude oil emulsions, and evaluates its safety performance. The LXW unblocking system has a more efficient unblocking effect and better universality, which can solve the problem of multiple block blockages on site. In addition, compared with existing unblocking agents, it has better economic benefits and is in line with the characteristics of low cost on site. On this basis, the dissolution and dispersion mechanism of the blockage system on sediment was studied through laser scattering system and fluorescence microscope, and its microscopic mechanism was further verified. At the same time, the oil-water interfacial tension under the action of the unblocking system was studied, and it was found that adding the agent can significantly reduce the equilibrium interfacial tension, which is of great significance for increasing production and injection.

Impact mechanism of active nanofluid on oil–water two-phase seepage during and after fracturing fluid invasion in tight oil reservoirs

Due to damage caused by fracturing fluid invasion, tight oil reservoirs exhibit slow post-hydraulic fracturing production recovery and low productivity. This study investigates the impact of a nanoclay-based active agent system on oil–water two-phase flow during and after fracturing fluid invasion, emphasizing its potential for enhancing recovery in tight oil reservoirs. Laboratory experiments using crude oil and natural core samples analyze the mechanism of how nanofluids affect oil–water distribution and flow characteristics during fracturing fluid invasion and oil recovery stages. Results show that nanofluids rapidly disrupt the emulsified state of “water-in-oil” emulsions, reducing emulsion viscosity by 84.19% and oil–water interfacial tension by two orders of magnitude, facilitating oil droplet dispersion and deformation and altering the wettability of oil-wet rock surfaces to aid crude oil detachment. Nanofluids increase the accessible volume of the water phase in pores and throats, enlarging flow paths for fracturing fluid flowback and oil recovery. The oil recovery process post-fracturing fluid invasion is delineated into three stages: substantial fracturing fluid flowback in the first stage, with nanofluids reducing the fluid return rate by 11.08% upon crude oil breakthrough; emulsion droplets occupying pores and throats in the second stage, with nanofluids reducing additional resistance during emulsion flow; and continuous oil production in the third stage, with nanofluids consistently and stably altering rock surface wettability to reduce invaded rock matrix resistance to oil flow. The findings of this study hold potential value in mitigating damage from fracturing fluid invasion in tight oil reservoirs.

Numerical Investigation on Alkaline-Surfactant-Polymer Alternating CO2 Flooding

For over four decades, carbon dioxide (CO2) has been instrumental in enhancing oil extraction through advanced recovery techniques. One such method, water alternating gas (WAG) injection, while effective, grapples with limitations like gas channeling and gravity segregation. To tackle the aforementioned issues, this paper proposes an upgrade coupling method named alkaline-surfactant-polymer alternating gas (ASPAG). ASP flooding and CO2 are injected alternately into the reservoir to enhance the recovery of the WAG process. The uniqueness of this method lies in the fact that polymers could help profile modification, CO2 would miscible mix with oil, and alkaline surfactant would reduce oil–water interfacial tension (IFT). To analyze the feasibility of ASPAG, a couples model considering both gas flooding and ASP flooding processes is established by using the CMG-STARS (Version 2021) to study the performance of ASPAG and compare the recovery among ASPAG, WAG, and ASP flooding. Our research delved into the ASPAG’s adaptability across reservoirs varying in average permeability, interlayer heterogeneity, formation rhythmicity, and fluid properties. Key findings include that ASPAG surpasses the conventional WAG in sweep and displacement efficiency, elevating oil recovery by 12–17%, and in comparison to ASP, ASPAG bolsters displacement efficiency, leading to a 9–11% increase in oil recovery. The primary flooding mechanism of ASPAG stems from the ASP slug’s ability to diminish the interfacial tension, enhancing the oil and water mobility ratio, which is particularly efficient in medium-high permeability layers. Through sensitivity analysis, ASPAG is best suited for mid-high-permeability reservoirs characterized by low crude oil viscosity and a composite reverse sedimentary rhythm. This study offers invaluable insights into the underlying mechanisms and critical parameters that influence the alkaline-surfactant-polymer alternating gas method’s success for enhanced oil recovery. Furthermore, it unveils an innovative strategy to boost oil recovery in medium-to-high-permeability reservoirs.

The bile salt/phospholipid ratio determines the extent of in vitro intestinal lipolysis of triglycerides: Interfacial and emulsion studies

This study focused on the protein-stabilised triglyceride (TG)/water interfaces and oil-in-water emulsions, and explored the influence of varying molar ratios of bile salts (BSs) and phospholipids (PLs) on the intestinal lipolysis of TGs. The presence of these two major groups of biosurfactants delivered with human bile to the physiological environment of intestinal digestion was replicated in our experiments by using mixtures of individual BSs and PLs under in vitro small intestinal lipolysis conditions. Conducted initially, retrospective analysis of available scientific literature revealed that an average molar ratio of 9:4 for BSs to PLs (BS/PL) can be considered physiological in the postprandial adult human small intestine. Our experimental data showed that combining BSs and PLs synergistically enhanced interfacial activity, substantially reducing oil–water interfacial tension (IFT) during interfacial lipolysis experiments with pancreatic lipase, especially at the BS/PL–9:4 ratio. Other BS/PL molar proportions (BS/PL–6.5:6.5 and BS/PL–4:9) and an equimolar amount of BSs (BS–13) followed in IFT reduction efficiency, while using PLs alone as biosurfactants was the least efficient. In the following emulsion lipolysis experiments, BS/PL–9:4 outperformed other BS/PL mixtures in terms of enhancing the TG digestion extent. The degree of TG conversion and the desorption efficiency of interfacial material post-lipolysis correlated directly with the BS/PL ratio, decreasing as the PL proportion increased. In conclusion, this study highlights the crucial role of biliary PLs, alongside BSs, in replicating the physiological function of bile in intestinal lipolysis of emulsified TGs. Our results showed different contributions of PLs and BSs to lipolysis, strongly suggesting that any future in vitro studies aiming to simulate the human digestion conditions should take into account the impact of biliary PLs – not just BSs – to accurately mimic the physiological role of bile in intestinal lipolysis. This is particularly crucial given the fact that existing in vitro digestion protocols typically focus solely on applying specific concentrations and/or compositions of BSs to simulate the action of human bile during intestinal digestion, while overlooking the presence and concentration of biliary PLs under physiological gut conditions.

Flooding Performance and Optimization of Injection Parameters of Nanosized Oil Displacement Agents in Extra-Low-Permeability Reservoirs.

There have been few studies on the role of nanofluids in oil displacement and injection parameters, despite their significant impact on the oil displacement effect. To enhance oil recovery in an ultralow-permeability reservoir, the nanosized oil-displacement agent with nano-SiO2 modified by a silane coupling agent as a main component was selected for the first time in the Changqing oilfield. To assess the performance of the nanofluid, various factors such as particle size, contact angle, interfacial tension, and emulsion stability were taken into consideration. The oil displacement effect of nanofluids was evaluated by a microscopic model and ultralow-permeability core displacement experiment, and its optimal injection parameters were determined. The average particle size of the nano-oil displacement agent is 22-30 nm. It can change the wetting condition of the rock from oil-wet to water-wet and reduce the oil-water interfacial tension. Even at 80 °C, the emulsion formed by the agent remained stable. The oil displacement experiment shows that the nano-oil displacement agent whose injection pressure increases can displace the residual oil trapped in small pores that cannot be affected by conventional water flooding. The injection mode of "nanoflooding agent drive + water drive + nanoflooding agent drive", injection rate of 0.1 mL/min, injection concentration of 0.5%, and injection volume of 0.5 PV (0.25 PV per segment), which can effectively guide the injection of the oil displacement agent, achieve the best oil displacement effect.

Correlation between emulsification and butyryl group distribution in various butyrylated starches

Butyrylated starch, a modified starch with significant applications in the food and pharmaceutical industries, lacks sufficient research on its emulsification. In this study, butyrylation was performed using waxy corn starch, tapioca starch and corn starch as raw materials, and their group distribution were determined. X-ray photoelectron spectroscopy (XPS), Raman microscopy and water contact angle measurements showed that the distribution of butyryl group in B-WCS was highly uniform. The results of the emulsification assay illustrated that B-WCS exhibited significant emulsifying potential at similar degrees of substitution. Analysis of the interface behavior demonstrated that B-WCS reduced the oil-water interfacial tension and formed a rigid interface film that resisted external deformation, thereby maintaining emulsion stability. This indicates that B-WCS exhibiting a highly uniform group distribution has significant emulsification potential. This study revealed the emulsification mechanism of butyrylated starch from an interface perspective and analyzed the relationship between the butyryl group distribution and emulsifiability.