High Interfacial Tension Research Articles

Nonlinear diffusion mechanism of porous media and countercurrent imbibition distance of fracturing fluids

Fracturing fluids countercurrent imbibition is a significant method to enhance recovery during hydraulic fracturing and soaking in shale reservoirs. Most investigations have primarily focused on the fracturing fluids imbibition recovery. In this work, an on-line computed tomography device was employed for the first time to conduct experiments on the imbibition distance of fracturing fluids, quantifying the imbibition distance of fracturing fluids, establishing the model of fracturing fluids imbibition, and clarifying the mechanism of countercurrent imbibition for fracturing fluids. The findings demonstrated that the imbibition distance was 2.625 cm for high mass fraction fracturing fluid and 2.375 cm for low mass fraction fluid. For formation water with viscoelastic fracturing fluids, the imbibition distances were 1.125 and 0.875 cm. Compared to the permeability of 0.082 × 10−3 μm2, the imbibition distance increased by 2.625 times at 0.217 × 10−3μm2 and by 3.25 times at 0.760 × 10−3μm2. At injection pressures of 20 and 15 MPa, the imbibition distance increased by 1.7 and 1.61 times, compared to 5 MPa. Parameter sensitivity analysis demonstrated that crude oil and fracturing fluids viscosity were negatively correlated with imbibition distance. Low interfacial tension boosts imbibition power, extending the imbibition distance. High interfacial tension raises flow resistance, shortening the imbibition distance. Reducing the contact angle improves hydrophilicity and capillary force, extending the imbibition distance. When the permeability is below 1 × 10−3μm2, the imbibition distance increases significantly with rising permeability. When the permeability exceeds 1 × 10−3μm2, the rate of increase diminishes. The investigation in this paper provides guidance for the efficient development of shale oil.

Discrepancy in oil displacement mechanisms at equivalent interfacial tensions: Differentiating contributions from surfactant and nanoparticles on interfacial activities

Discrepancies in oil displacement mechanisms at equivalent interfacial tensions were principally explored in the current study, with a novel emphasis on distinguishing the contributions of surfactants and nanoparticles in interfacial activities. The hypothesis was that if both chemicals exhibit similar interfacial activities, the oil displacement outcomes at the capillary scale should be consistent. Otherwise, differences would indicate distinct interfacial behaviors. Fluid displacement experiments were conducted using a two-dimensional micromodel, where nanofluids and surfactant solutions were tested at equivalent interfacial tensions. In the high interfacial tension pair (20 mN/m), the surfactant solution displaced oil more efficiently and rapidly than nanofluids, achieving greater ultimate oil recovery. This difference was attributed to the effective reinforcement of capillary forces in the surfactant system, which drove the displacement process. In contrast, the nanofluids did not achieve the same level of performance due to their limited ability to modify interfacial forces. This finding highlighted the two chemicals’ fundamentally different interfacial activities and oil displacement mechanisms. Furthermore, in the lowest interfacial tensions pair, where the surfactant achieved 6.5 mN/m and the nanofluids 15.6 mN/m, both systems unexpectedly displayed similar oil displacement efficiencies and fingering-like behaviors. This similarity, however, arose from distinct underlying mechanisms: capillary instability drove fingering in the surfactant system, while expansive layer flow induced fingering-like in the nanofluids. These findings challenge the assumption that reducing interfacial tension with nanoparticles is the primary mechanism in enhanced oil recovery (EOR). The study highlighted the need for a more refined understanding of the action of nanoparticle interfacial activities within EOR processes. To further validate these insights, future research should scale up fluid displacement studies to Darcy’s scale using core-flooding tests, enabling a more comprehensive examination of complex two-phase flow dynamics.

Exploring interfacial tension role in the laminar morphology development in reactive compatibilized PP/EVOH

AbstractLaminar-like structures in PP/EVOH (80/20 wt%) blends were developed by in situ reactive compatibilization using a co-rotating intermeshing twin-screw extrusion without the imposition of post-die-forming elongation flows, i.e., draw ratio (DR) = 0. For that, a maleic anhydride-grafted homopolymer polypropylene (PP-g-MA) was added at 1, 1.5, and 3 wt% using a simple mixing protocol. The correlation between the laminar morphology observed via SEM with interfacial parameters was conducted by nonlinear regression of PP/EVOH viscoelastic response (Gʹ and Gʹʹ) applying the Monomodal Palierne Model to estimate interfacial tension. Uncompatibilized PP/EVOH formed a droplet-matrix morphology with high interfacial tension, indicating incompatibility. As PP-g-MA is added, a laminar-like structure is developed. The remaining droplets become smaller at higher content, with lower interfacial tension between the phases. This scenario hampers the stratification of the dispersed phase. At 3 wt% of PP-g-MA, the morphology returns to being a droplet-matrix, although with high adhesion between the phases. Graphical abstract

Material compatibility and processing challenges in droplet deposition modelling additive manufacturing: A study on pharmaceutical excipients Polyvinylpyrrolidone/vinyl acetate (PVP/VA) and Polycaprolactone (PCL)

Additive manufacturing (AM) enables the production of complex, lightweight, and customized components with superior quality. Selecting the right materials considering their thermal properties, printability, and layer adhesion is crucial in melting-based AM techniques. This study investigates Droplet Deposition Modelling (DDM), an innovative material extrusion process that utilizes thermoplastic granules. DDM is distinguished by its shorter manufacturing times and a wider range of materials, setting it apart from traditional material extrusion methods such as fused filament fabrication. We investigated the printability and part quality in DDM using two common pharmaceutical excipients: Polyvinylpyrrolidone/vinyl acetate 6:4 (PVP/VA), which is highly brittle, and Polycaprolactone (PCL), known for its low solubility and role in controlled drug release. Different ratios of PVP/VA and PCL were compounded via hot melt extrusion (HME) and used in DDM to study the impact of ingredient content on printability and part quality, employing geometrical models to assess material compatibility and printability. The study revealed that increasing PVP/VA content leads to higher viscosity, reduced flowability, and uneven deposition, with formulations of 80 % and 100 % PVP/VA showing poor processability. In contrast, formulations with 60 % and 40 % PVP/VA exhibited smooth processing and compatibility with DDM. We identified processing temperature and Drop Aspect Ratio (DAR) as key factors influencing material printability and part quality. Elevated processing temperatures and reduced DAR were found to increase interface temperatures, reduce diffusion, and potentially cause the 'elephant feet' issue. Additionally, smaller droplet sizes and material characteristics, such as higher interfacial tension in PCL, could lead to coalescence. Our findings highlight the complexities in optimizing DDM processing parameters and material blends, underscoring the need for careful formulation design to achieve high-quality 3D printed products.

Experimental Investigation of the Effect of Surfactant–Polymer Flooding on Enhanced Oil Recovery for Medium Crude Oil

High technical and financial risks are involved in exploring and exploiting new fields; hence, greater focus has placed on the development of environmentally friendly, cost-effective, and enhanced oil recovery (EOR) options for existing fields. For reservoirs producing high-density crudes and those with high interfacial tensions, water flooding is usually less effective due to density differences—hence the advent of polymer and surfactant flooding. For cost-effective and eco-friendly EOR solutions, a biopolymer and a surfactant synthesized from Jatropha seeds are used in this study to determine their effectiveness in increasing the oil recovery during core flooding analysis. The experiment involved an initial water flooding that served as the base cases of three weight percentages of polymers and polymeric surfactant solutions. The results for the polymer flooding of 1 wt%, 1.5 wt%, and 2 wt% showed an incremental oil recovery in comparison to water flooding of 16.8%, 17%, and 26%, while the polymeric surfactant mixtures of 5 wt% of surfactant and 1 wt%, 1.5 wt%, and 2 wt% of a polymer recorded 16.5%, 22.3%, and 28.8%, and 10 wt% of surfactant and 1 wt%, 1.5 wt%, and 2 wt% of a polymer recorded incremental oil recoveries of 20%, 32.9%, and 38.8%, respectively.

Simultaneous adjustment on the CO2/oil and CO2/water interface tensions using hydrophilic, lipophilic and CO2-philic surfactants during CO2 flooding to enhance shale oil recovery after hydraulic fracturing

It is an urgent demand to further enhance shale oil recovery after large-scale hydraulic fracturing with a low oil recovery. CO2 flooding technology has been demonstrated to effectively develop shale oil, however, the residual water after hydraulic fracturing can influence the efficiency of CO2 flooding because of the high CO2-water interfacial tension. Here, the hydrophilic, lipophilic and CO2-philic surfactants were investigated to simultaneously adjust the CO2/oil and CO2/water interface tension to accelerate the oil and water flows to enhance shale oil recovery. The results show that the low-carbon alcohol polyoxyethylene polyoxypropylene ether has the hydrophilic, lipophilic and CO2-philic properties. The alkyl chain length and PO groups have great influence on the interfacial tension of CO2-oil, while the presence of EO groups can significantly reduce the interfacial tension of CO2-water. The surfactant of C4EO3PO6 can not only demonstrate the best performance in reducing the interfacial tensions of shale oil-CO2 and water-CO2, but also decrease the minimum miscibility pressure (MMP) of the shale oil-CO2 system to 18.89 MPa from 24.10 MPa. The interfacial tension between water and the CO2 + 1.0 wt% C4EO3PO6 system can be decreased to 6.62 mN/m at 28 MPa and the reduction rate is 56.10 %. The enhancement of surfactants on the extraction effect of CO2 and the mutual diffusion process between CO2 and shale oil or water interface is the major mechanism to decrease the interfacial tensions. Therefore, the addition of surfactant in CO2 can simultaneously decrease the interfacial tensions of CO2-oil and CO2-water and has a potential to enhance shale oil recovery by reducing the capillary resistance of residual water after hydraulic fracturing and increasing the miscibility between CO2 and oil.

Physicochemical and emulsification properties of okara-derived soluble dietary fiber modified by steam explosion

The effective utilization of by-products still poses a challenge in the food industry. In this work, soluble dietary fiber (SDF) extracted from okara was modified by steam explosion (SE) via adjusting steam pressure (1.0, 1.5, and 2.0 MPa) and SE duration (60 and 120 s). The structural and emulsification properties of modified SDF were studied. The untreated SDF exhibited a low yield (5.17%) and poor emulsification properties due to its large molecular weight (162.67 kDa), compact structure, and high interfacial tension (14.27 mN/m). SE increased SDF content by a maximum of 30.31%, 4.86 times higher than that of untreated SDF. Under mild SE conditions (1.0 MPa for 60 s), SDF displayed a loose structure with abundant side chains and a higher glyoxylate content (26.77%). Its near-neutral contact angle (82.0°) and lower interfacial tension (12.69 mN/m) endowed it with higher emulsification capacity, smaller emulsion droplet size, and enhanced emulsifying stability. The molecular weight of SDF decreased and the specific surface area enlarged with increasing SE intensity. Notably, SDF exhibited the best interfacial adsorption characteristics under SE of 2.0 MPa for 120 s, attributed to its low molecular weight (46.99 kDa) and higher protein content (7.58%). Overall, the improved emulsification properties of SDF were attributed to the synergistic effects of amphiphilic equilibrium, electrostatic repulsion, spatial resistance, and enhanced droplet-to-droplet interactions.

Cellulose nanofibrils-stabilized food-grade Pickering emulsions: Clarifying surface charge's contribution and advancing stabilization mechanism understanding

Pickering emulsions stabilized by cellulose nanofibrils (CN) have sparked significant attention, however the fundamental mechanisms underpinning the stabilization process remain insufficiently elucidated. Focusing on an academic debate of surface charge's contribution to stabilization, this study first explored how the varying carboxyl group contents of TEMPO-oxidized CN (TCNs) impacted Pickering emulsions' formation and stability. TCNs with 662 μmol/g carboxyl groups exhibited distinctive attributes, including larger particle sizes (322 nm in length), improved thermal stability (maximum decomposition temperature of 317 °C), and increased viscosity (1.57 Paִִ⋅s) compared to their counterparts with 963–1011 μmol/g charge density. Notably, the former one, with a larger three-phase contact angle (51.5°), higher interfacial tension, and greater detachment energy (21.69 × 10−18 J), resulted in a homogeneous dispersion of spherical oil droplets and super-stable Pickering emulsions with a consistent emulsifying index of 100% over 30 days. These findings clearly clarified that TCNs with a lower charge density exhibit superior emulsifying properties. In addition, for the first time, a distinct oil droplet-decorated fibrillar structure was observed, probably suggesting that TCNs might be able to serve as anchoring matrixes to guide the distribution of oil droplets. These structures seemed to impeded the migration and accumulation of the oil droplets, consequently enhancing the stability of the resulting Pickering emulsions. To sum, this study clearly elucidated the role of surface charge in stabilizing cellulose-based Pickering emulsions and proposed a new model to expound the cellulose-oil interaction mechanisms, thus providing new theoretical and practical insights on utilization of CN as highly effective emulsifier for super-stable food-grade Pickering emulsions.

High interfacial tension of lipid droplets disrupts the nucleus, cytoskeleton, and motile functions

High interfacial tension of lipid droplets disrupts the nucleus, cytoskeleton, and motile functions

Time evolution of moduli of a polymer-induced liquid precursor (PILP) of calcium carbonate.

In situ AFM observations show that when PILP droplets contact a surface, their initial properties are either a liquid with a high interfacial tension (350 mJ m-2) or a soft gel-like material with a low modulus (less than 0.2 MPa). These findings suggest that PILP may initially be liquid-like to infiltrate collagen fibrils, enabling the production of interpenetrating composites, and/or become viscoelastic, to provide a means for moulding minerals.

Evaluation of the interfacial elasticity of surfactant monolayer at the CO2–water interface by molecular dynamics simulation: Screening surfactants to enhance the CO2 foam stability

Foam stability is adversely affected by the drainage process in the liquid film, which has been a great challenge for CO2 foam flooding in applications. The Gibbs-Marangoni effect, which is induced by the interfacial tension (IFT) gradient, provides a resisting force to the thinning of liquid films in foams under disturbance. Surfactants with higher interfacial elasticity enable rapid recovery to the equilibrium state, thereby improving the stability of the CO2 foam film. However, there is a lack of mechanistic studies aimed at elucidating the correlation between the interfacial elasticity of surfactant monolayers and the molecular structure of surfactants. In this paper, molecular dynamics simulations were employed to investigate the impact of the headgroups and linking groups of sodium polyoxyethylene alkyl ether sulfate (AES), sodium dodecylbenzene sulfonate (SDBS), sodium dodecyl sulfate (SDS), sodium dodecyl sulfonate (SDSn), and sodium laurate (SLA) surfactants on the interfacial morphology, monolayer properties, and surfactant behaviors at the CO2–water interface under reservoir conditions. The results show that the capacity to enhance CO2 foam stability follows the order AES > SDS > SDSn > SDBS > SLA, which is in good agreement with the available experiments. AES monolayers can reach the lowest IFT (∼0.2 mN/m) and the highest interfacial elasticity (30.4 mN/m). We show that the ethylene oxide groups (EO chains) can strongly interact with water molecules via hydrogen bonding and have affinity interactions with CO2 molecules, which is beneficial to the hydrophilic-CO2-philic balance (HCB). SDS monolayers show the second-lowest IFT (3.1 mN/m) and second-highest interfacial elasticity (26.0 mN/m). The linking oxygen atom in SDS facilitates bond rotation and is favorable to film stability. The phenyl group makes SDBS molecules too rigid and has poor HCB, leading to low stability with high IFT (16.0 mN/m) and low interfacial elasticity (13.1 mN/m). SLA has the highest IFT (22.1 mN/m) and lowest interfacial elasticity (6.3 mN/m), and also presents strong aggregation behaviors at the interface owing to interactions between the carboxyl groups. The simulation method and the microscopic insights delivered here are of great significance in screening surfactants to improve CO2 foam performance in oilfields.

Evaluation of ethanol-based aqueous two-phase systems performance for application in centrifugal partition chromatography (CPC)

Aqueous two-phase systems (ATPS) have recently been proposed for Centrifugal Partition Chromatography (CPC). This type of biphasic system has several advantages over conventional aqueous-organic liquid–liquid systems, namely, high biocompatibility owing to its large water content. The most commonly used ATPS are polymer-based systems. However, owing to their poor phase separation hydrodynamics compared to aqueous-organic systems, the use of short-length water-miscible alcohols has been evaluated as an alternative to polymers. In this study, an ATPS composed of ethanol and dipotassium hydrogen phosphate (K2HPO4) is proposed to overcome the common hydrodynamic drawbacks of polymer-based ATPS. The Ethanol/K2HPO4 system exhibited a very short settling time (ts = 30.85 ± 0.80 s), high interfacial tension (IFT = 6.38 mN/m), significant density differences between the phases (Δρ = 353.40 kg/m3), and low viscosity of the coexisting phases at 25 °C (maximum µ = 3.79 ± 0.11 mPa.s), making it an ideal choice for implementation in CPC apparatus. A comprehensive study of this biphasic system was conducted using CPC equipment by carefully adjusting the operating parameters, specifically, the mobile phase flow rate (F), rotational speed (ω), and mode of operation, that is, ascending (upper phase is mobile) or descending (lower phase is mobile). In this particular CPC equipment, the use of polymers as phase-forming compounds in ATPS resulted in higher CPC pump pressures compared to ethanol or phosphate salt aqueous solutions, thus confirming the superior performance of the ethanol/salt ATPS. The results obtained using this ATPS demonstrated that high F and ω values lead to lower stationary phase retention (SF) and higher backpressures, respectively. SF remained relatively constant and above 50% for F ≤ 6 mL/min but significantly decreased for F > 6 mL/min. This trend confirms that hydrostatically stable conditions can be achieved by employing the Ethanol/K2HPO4 system in the CPC mode by controlling F (i.e., the hydrodynamics of the mobile phase). The partition of the model solutes gallic acid and L-tyrosine was also evaluated using the ethanol/K2HPO4 system. The critical operating CPC parameters were compared, confirming the significant potential of the ethanol/salt ATPS for successful commercial application of this chromatographic technique in the separation of small value-added biomolecules.

Dynamic transformation of bio-inspired single-chain nanoparticles at interfaces.

The interfacial behavior of macromolecules dictates their intermolecular interactions, which can impact the processing and application of polymers for pharmaceutical and synthetic use. Using molecular dynamics simulations, we observe the evolution of a random heteropolymer in the presence of liquid-liquid interfaces. The system of interest forms single-chain nanoparticles through hydrophobic collapse in water, lacking permanent crosslinks and making their morphology mutable in new environments. Complex amphiphilic polymers are shown to be capable of stabilizing high interfacial tension water-hexane interfaces, often unfolding to maximize surface coverage. Despite drastic changes to polymer conformation, monomer presence in the water phase is generally maintained and most changes are due to increased hydrophobic solvent exposure toward the oil phase. These results are then compared to the behavior at the water-graphene interface, where the macromolecules adsorb but do not remodel. The polymer's behavior is shown to depend significantly on both its own amphiphilic character and the deformability of the interface.

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.

Glycolipopeptide biosurfactant from Bacillus pumilus SG: physicochemical characterization, optimization, antibiofilm and antimicrobial activity evaluation.

The Bacillus pumilus SG isolated from soil samples at the Persian Gulf was analyzed for its ability to produce biosurfactant. Various screening techniques were used for evaluating biosurfactant production and confirming biosurfactant presence in the culture supernatant. Most n-alkanes in the bacterial culture media were effectively degraded in the presence of biosurfactant acquired from the bacteria. The highest interfacial tension (IT) reduction (42 mN/m) was obtained at 24-h fermentation time (exponential phase) and did not change significantly afterwards. The glycolipid structure of the biosurfactant was revealed through NMR and FTIR spectroscopy analysis. Two-level factorial design was then applied for optimization of biosurfactant production, where a maximal reduction of culture broth IT (30mN/m) acquired in the presence of crude oil (0.5%, v/v), NaNO3 (1g/L), yeast extract (1g/L), peptone (2g/L) and temperature of 25°C. The produced biosurfactant that exhibited a critical micelle concentration of 0.1mg/ml was thermally stable. The glycolipid biosurfactant also displayed significant antibacterial activities against both Gram-positive and Gram-negative bacteria. The maximum inhibition of glycolipids biosurfactant was found against Acinetobacter strains (zone of inhibition, 45mm). In addition, antibiofilm activities with a 50-90% biofilm reduction percent were indicated by the glycolipid biosurfactant. In conclusion, the glycolipid biosurfactant produced by B. pumilus SG revealed a wide range of functional properties and was verified as a good candidate for biomedical application. In conclusion, the glycolipid biosurfactant produced by B. pumilus SG showed a wide range of functional properties in this study, and in the case of further in vivo studies, it can be investigated a good candidate for biomedical applications such as use against biofilm or in pharmaceutical formulations.

Effect of the Type and Concentration of Salt on Production Efficiency in Smart Water Injection into Carbonate Oil Reservoir Rocks.

Smart waterflooding is one of the most practical emerging methods of enhanced oil recovery in carbonate reservoirs. In this study, the effect of salt type and its concentration in smart water on oil recovery from a carbonate reservoir rock is investigated. A series of experimental measurements, including zeta potential (ZP), interfacial tension (IFT), and contact angle (CA), were conducted to examine the effect of ions on the oil/brine/rock interaction. IFT, ZP, and CA were also used as screening methods to select effective solutions for flooding experiments. The results of the study show that synthesized brines containing sodium acetate and potassium acetate salts have a significant effect on the reduction of IFT; however, rock surface wettability due to such brines is insignificant. The presence of organic salts in the injected water can alter the properties of the fluid and rock surface, leading to improved oil recovery. The salts can reduce the interfacial tension between the oil and water phases, making it easier for the water to displace and mobilize trapped oil. This effect is particularly beneficial in reservoirs with high oil-water interfacial tension as it enhances the capillary forces and improves the sweep efficiency. Smart water with sodium acetate (MSW.NaOAc) caused a 7% increase in oil production in the tertiary injection process due to IFT and CA reduction. The secondary injection of MSW.NaOAc led to an oil production efficiency of 76%, which is 10% higher than that of the secondary injection of seawater (SW), confirming the effectiveness of acetate ions in enhancing oil recovery. Doubling the concentration of sulfate ions in modified SW (MSW.NaOAc.2S) caused a 19% increase in oil production in tertiary injections after SW flooding. The secondary injection of MSW.NaOAc.2S produced a 13% increase in the recovery factor compared to SW flooding in the secondary mode. The main driving mechanism for oil mobilization was found to be wettability alteration, which is supported by the analyses of CA and ZP. This study confirms that the salt type and concentration present in a brine solution play a vital role in the movement of trapped oil in carbonate reservoirs.

Influence of carbon nanodots on the Carbonate/CO2/Brine wettability and CO2-Brine interfacial Tension: Implications for CO2 geo-storage

Understanding the interfacial and wettability phenomena of the CO2-brine and rock-CO2-brine system plays a key role in the geo-storage of CO2 and in their security containment. Carbon nanodots (CNDs) have been identified as a promising surface-active agent for altering the wettability from strongly oil-wet into water-wet in the carbonate reservoirs, thus it contributed for the oil recovery increment in the carbonate formations. However, no consideration was given to the application of CNDs for the enhancement of CO2 geological storage and containment security in the carbonate formations. In the current study, we assessed the impact of CNDs on the residual and structural trapping of CO2 in the carbonate reservoir. The contact angles (θ) of the CO2-brine-carbonate rock system were studied before and after the treatment of CNDs for both the clean and crude oil-aged samples. Subsequently, we also investigated the CO2-seawater interfacial tensions (IFT) with and without CNDs addition. All these measurements were performed as a function of CNDs concentration (0–1000 ppm), temperature (20–80 °C) and pressure (14.7–3000 psi). The results showed that the clean carbonate rock remained strongly water-wet before and after CNDs-treatment. The oil-wet carbonate sample was turned into CO2-wet at all investigated temperatures when the pressures increased to 1000 psi, however, it turns to be weakly water-wet upon treatment with CNDs at the highest pressure (3000 psi). Specifically, at 3000 psia and 20 °C, the contact angle of oil-wet carbonate reduced from 122° to 86° with the addition of CNDs at the increased concentration of 1000 ppm. Such wettability modifications in carbonate formations will enhance the efficacy of CO2 storage potential, and eventually, this will help to de-risk their security containment. The θ generally demonstrated a declining trend with the increase of CNDs concentration but it slightly increased with the rise in temperature and pressure. These results suggest that warmer reservoirs and increased storage depth could be unfavorable for CO2 storage in carbonate formations. Thus, the pre-injection of a minimal concentration of CNDs in the formation would improve CO2 storage effectively. Also, no significant change was observed in the CO2-seawater IFT in the presence of CNDs, which indicates that the capillary trapping of CO2 could be favorable due to their lower contact angle and high CO2-brine IFT as the most suitable condition to maintain the high capillarity. The study demonstrates that the highly stable, freely soluble, easy detectable, scalable, and economically viable CNDs has the potency to enhance the containment security of CO2 in carbonate formation.

The Influence of Solvent Selection upon the Crystallizability and Nucleation Kinetics of Tolfenamic Acid Form II.

The influence of the solution environment on the solution thermodynamics, crystallizability, and nucleation of tolfenamic acid (TFA) in five different solvents (isopropanol, ethanol, methanol, toluene, and acetonitrile) is examined using an integrated workflow encompassing both experimental studies and intermolecular modeling. The solubility of TFA in isopropanol is found to be the highest, consistent with the strongest solvent-solute interactions, and a concomitantly higher than ideal solubility. The crystallizability is found to be highly dependent on the solvent type with the overall order being isopropanol < ethanol < methanol < toluene < acetonitrile with the widest solution metastable zone width in isopropanol (24.49 to 47.41 °C) and the narrowest in acetonitrile (8.23 to 16.17 °C). Nucleation is found to occur via progressive mechanism in all the solvents studied. The calculated nucleation parameters reveal a considerably higher interfacial tension and larger critical nucleus radius in the isopropanol solutions, indicating the higher energy barrier hindering nucleation and hence lowering the nucleation rate. This is supported by diffusion coefficient measurements which are lowest in isopropanol, highlighting the lower molecular diffusion in the bulk of solution compared to the other solutions. The TFA concentration and critical supersaturation at the crystallization onset is found to be directly correlated with TFA/isopropanol solutions having the highest values of solubility and critical supersaturation. Intermolecular modeling of solute-solvent interactions supports the experimental observations of the solubility and crystallizability, highlighting the importance of understanding solvent selection and solution state structure at the molecular level in directing the solubility, solute mass transfer, crystallizability, and nucleation kinetics.

Insights into Enhanced Oil Recovery by Coupling Branched-Preformed Particle Gel and Viscosity Reducer Flooding in Ordinary Heavy Oil Reservoir

Viscosity reducer flooding has been successfully applied in tertiary oil recovery of ordinary heavy oil reservoirs. However, lowering interfacial tension or reducing oil viscosity, which is more critical for viscosity reducer to improve oil recovery of ordinary heavy oil, has not yet formed a unified understanding, which restricts the further large-scale application of viscosity reducer flooding for ordinary heavy oil reservoir. Moreover, when the dominant water flow channel is formed in the reservoir, the sweep efficiency decreases sharply and can affect oil recovery efficiency of viscosity reducer. Therefore, in this study, the concept of branched-preformed particle gel (B-PPG) coupling viscosity reducer flooding is proposed. The oil-water interfacial tension performance, emulsification ability, and viscosity reduction performance of three different viscosity reducers were evaluated. The enhanced oil recovery ability of viscosity reducers, B-PPG, and viscosity reducer/B-PPG composite systems was investigated by performing sand pack flooding experiments. The results show that the oil-water interfacial tensions of the three viscosity reducers S1, S2, and S3 are 0.432 mN·m-1, 0.0112 mN·m-1, and 0.0031 mN·m-1, respectively. S1 with the highest interfacial tension has the best emulsification and viscosity reduction performance, S2 is the second, and S3 is the worst. The lower the interfacial tension, the worse the emulsification stability. The sand pack flooding results show that the incremental oil recovery of viscosity reducer S2 flooding is the largest, 7.5%, followed by S1, 7.3%, and S3, 5.6%. The viscosity reducer S2 with moderate interfacial tension and emulsifying capacity has the best ability to improve the recovery of ordinary heavy oil. The incremental oil recovery of B-PPG is 12.7%, which is significantly higher than that of viscosity reducer flooding. Compared with viscosity reducing flooding, the viscosity reducer/B-PPG composite systems have better enhanced oil recovery capacity. The findings of this study can help for better understanding of enhancing oil recovery for ordinary heavy oil reservoir.

Biophysical function of pulmonary surfactant in liquid ventilation

Liquid ventilation is a mechanical ventilation technique in which the entire or part of the lung is filled with oxygenated perfluorocarbon (PFC) liquids rather than air in conventional mechanical ventilation. Despite its many ideal biophysicochemical properties for assisting liquid breathing, a general misconception about PFC is to use it as a replacement for pulmonary surfactant. Because of the high PFC-water interfacial tension (59 mN/m), pulmonary surfactant is indispensable in liquid ventilation to increase lung compliance. However, the biophysical function of pulmonary surfactant in liquid ventilation is still unknown. Here, we have studied the adsorption and dynamic surface activity of a natural surfactant preparation, Infasurf, at the PFC-water interface using constrained drop surfactometry. The constrained drop surfactometry is capable of simulating the intra-alveolar microenvironment of liquid ventilation under physiologically relevant conditions. It was found that Infasurf adsorbed to the PFC-water interface reduces the PFC-water interfacial tension from 59 mN/m to an equilibrium value of 9 mN/m within seconds. Atomic force microscopy revealed that after de novo adsorption, Infasurf forms multilayered structures at the PFC-water interface with an average thickness of 10–20 nm, depending on the adsorbing surfactant concentration. It was found that the adsorbed Infasurf film is capable of regulating the interfacial tension of the PFC-water interface within a narrow range, between ∼12 and ∼1 mN/m, during dynamic compression-expansion cycles that mimic liquid ventilation. These findings have novel implications in understanding the physiological and biophysical functions of the pulmonary surfactant film at the PFC-water interface, and may offer new translational insights into the development of liquid ventilation and liquid breathing techniques.