Oil-water Interfacial Tension Research Articles

The role of alginate in starch nanocrystals-stabilized Pickering emulsions: From physical stability and microstructure to rheology behavior

Sodium alginate (SA) was used as a co-stabilizer to improve the Pickering emulsions stabilized by starch nanocrystals (SNC). Compared with pure SNC, SNC/SA complexes possess better neutral wettability with the contact angle approaching to 90°, more surface negative charges, and lower oil–water interfacial tension. These properties of particles make as-prepared emulsion higher stability with the lower creaming index and average droplet size. Furthermore, the emulsion exhibited good stability against salt (0–600 mM) and pH (2.0–6.0) at higher SA concentration (1.0 wt%). Confocal laser scanning microscopy (CLSM) images proved that SNC could be effectively adsorbed at the oil–water interface with the aid of SA. Rheological analysis showed that higher content of SA resulted in improved strength and higher viscosity of emulsion system. Results from this work indicating that SA could be a useful co-stabilizer to fulfill the demands of Pickering emulsions stabilized by SNC with stable characteristics.

Effect of modified γ-Fe2O3 magnetic nanoparticles on the stability of heavy oil-in-water emulsions

The effects of modified γ-Fe2O3 magnetic nanoparticles having various sizes at different mass fractions on the stability of heavy oil-in-water emulsions were compared. The zeta potential, wettability, oil-water interfacial tension, apparent viscosity, and oil droplet distribution of the emulsions were measured. The optimal size of the γ-Fe2O3(-COOH) magnetic nanoparticles was 2–3 μm, and this resulted in the lowest water-separation rate (23.72% at 4 hours), greatest electrostatic repulsion, weakest hydrophilic effect, lowest interfacial tension, greatest migration resistance, and smallest and most uniform oil droplet distribution. In addition, the stability of the emulsions increased and then decreased as the mass fraction of γ-Fe2O3 (-COOH) magnetic nanoparticles increased because of the increased electrostatic repulsion and decreased migration resistance. This in-depth analysis of the effect of modified magnetic nanoparticle size on the stability of oil-in-water emulsions provides comprehensive theoretical support for achieving viscosity and resistance reduction in an environmentally friendly manner.

Simulation research on Jamin effect and oil displacement mechanism of CO2 foam under microscale

CO2 foam can solve the problems of serious water invasion in the later stage of water injection development of conventional reservoirs, fracture channeling in unconventional reservoirs and low production rate of medium and low permeability reservoirs caused by reservoir heterogeneity, and the Jamin effect is the key to its role. In order to investigate the influence of injection rate, liquid phase viscosity, surface tension, pore structure on the resistance of CO2 foam through the pore throat and the influence of CO2 foam Jamin effect on enhancing oil recovery, the micro-scale pore throat models were established, and the interface changes were traced by using the level set and phase field methods. The results show that the greater the injection rate or liquid phase viscosity, the greater the pressure and the foam film strength, the greater the Jamin effect resistance; Jamin effect resistance is positively related to surface tension, the greater the surface tension, the greater the driving force required for difficult deformation; Jamin effect resistance is negatively related to radius of pore throat, the greater the radius of pore throat (the smaller the pore-throat ratio), the smaller the Jamin effect resistance; CO2 foam plays an important role in the oil displacement, and it can displace the oil trapped on the wall, and the oil recovery of CO2 foam flooding is 9% higher than that of water flooding. The smaller the oil–water interfacial tension is, the more CO2 foam displacement is. These research results have certain theoretical significance for the effective use of CO2 foam in oilfield development.

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.

Study on the imbibition recovery trends in low-permeability cores under high-pressure CO2

Imbibition plays a crucial role in extracting crude oil from low-permeability reservoir matrices. After CO2 is injected into the low-permeability reservoirs for development, both CO2 and surfactants often coexist in the imbibition fluid. While previous studies have mainly focused on the individual presence of CO2 or surfactants, limited research has been conducted on their coexistence. In this paper, the imbibition recovery trends in low-permeability cores under high-pressure CO2 are investigated by measuring the imbibition efficiency, the three-phase contact angle (CA), and the oil-water interfacial tension (IFT). The findings of this research indicate that the surfactant significantly enhances the interface characteristics, substantially increases the imbibition rate, and improves recovery by more than 14 %. Temperature has a greater impact on the interface characteristics compared to pressure, directly influencing the distribution of SDS molecules at the interface. Despite temperature elevation leading to increased IFT and reduced concentration of charged ions, it still enhances the rock hydrophilicity and improves imbibition efficiency. Pressure affects the interface characteristics mainly by modifying CO2 solubility. With increasing pressure, the IFT decreases, the concentration of charged ions increases, and the electrostatic repulsion between ions is enhanced, ultimately enhancing rock hydrophilicity and significantly boosting imbibition efficiency. The coexistence of CO2 and SDS further improves the interface characteristics, exhibiting synergistic effects in reducing IFT and enhancing rock hydrophilicity. These research findings contribute to a deeper understanding of the imbibition mechanism and provide theoretical support for the development and application of CO2 injection in the field.

Influences and mechanisms of imidazolium-based ionic liquids on oil–water interfacial tension and quartz wettability: Experiment and molecular dynamics simulations

Interfacial tension (IFT) and wettability are two key parameters determining pore-scale oil/water distributions and reservoir-scale hydrocarbon production performances. However, how ionic liquid (IL, a green, stable, and efficient chemical) will manipulate IFT and wettability for EOR in sandstone reservoirs has not been sufficiently investigated yet, and the underlying mechanisms at the micro-level are still unknown. In this study, the influences of two typical ILs at various concentrations (i.e., 0.01, 0.1, 1, and 5 mmol/L) on oil–water IFT and alpha-quartz (α-quartz) wettability were investigated. This study shows that low concentrations of ILs can greatly reduce alkane-water IFT, and gemini IL has higher interfacial activity than mono-cationic IL, which is due to the fact that gemini IL with longer alkyl chains is more likely to form conglomerates at lower concentrations. Both the advancing and receding contact angles increase continuously with concentration in ILs solution, which can be given responsibility for the decrease in IFT and the solid–liquid interaction resulting in an increased capacity of alkane droplets to migrate on the α-quartz surface. Additionally, the molecular dynamic simulations examined the micro-wetting process and interaction energy of the IL-alkane-quartz system, and revealed that ILs can effectively reduce interaction energy between octane droplets and α-quartz surface. These insights have promising applications to enhanced oil recovery and oil contamination removal at subsurface.

Experimental investigation to elucidate the hydrate Anti-Agglomerating characteristics of 2-Butoxyethanol

To alleviate the severity of hydrate formation in subsea oil and gas pipelines, the injection of anti-agglomerants (AAs) is one of the promising approaches. In this work, we investigate the hydrate anti-agglomerating characteristics of 2-butoxyethanol, also called butyl glycol ether (BGE), which has been reported in the literature as an effective synergist for kinetic hydrate inhibitors (KHIs), and a solvent for low dosage hydrate inhibitors (LDHIs). In view of its hydrophobic and hydrophilic moieties, we evaluate the adsorption affinity of BGE for the oil–water interface employing the interfacial tensiometer (IFT) apparatus. Moreover, a micromechanical force (MMF) apparatus was used to probe the interfacial behavior of hydrate particles, wherein we measured the cohesive forces between cyclopentane hydrate particles in the presence of BGE at atmospheric pressure and 274.2 K. The kinetics of methane hydrate formation and resistance-to-flow were assessed while measuring the dynamic pressure–temperature data and motor torque signals alongside with visual observations, respectively, employing a high-pressure visual autoclave (HPVA). IFT results reveal the strong surface active properties of BGE with a substantial reduction in oil–water interfacial tension at ambient conditions. However, no considerable change in the cohesive forces between cyclopentane hydrate particles was observed through MMF measurements. In contrast, HPVA results reveal that the addition of BGE enhanced the kinetics of methane hydrate formation; however, the corresponding torque pattern/visual interpretations indicated an anti-agglomerating action of BGE. While synergistically combining the BGE with under-inhibited dosages of mono-ethylene glycol, we further demonstrated a significant improvement in the hydrate transportability, wherein this synergism led to a non-plugging scenario (flowable hydrate slurry). Our findings will offer new insights into the development of new anti-agglomerant chemistries.

Improving the interfacial performance and the adsorption inhibition of an extended-surfactant mixture for enhanced oil recovery using different hydrophobicity nanoparticles

Chemical surfactant injection is one of the Enhanced Oil Recovery (EOR) technologies, revealing a large potential to recover the undisplaced oil into the porous media. Many techniques to improve this methodology have been proposed recently, such as the use of nanoparticles. However, very few studies have focused on the effect of the surface hydrophobicity of nanoparticles on the surfactant efficiency improvement. Furthermore, most studies focus on the use of formulations composed by a single molecule, but in common field applications, the use of surfactant mixtures is recommended since lower Interfacial Tensions (IFT) can be reached. This research work aims to study the use of two different hydrophobicity nanoparticles (Aerosil 308 and Aerosil R812S), to improve the efficiency of an anionic surfactant mix formulation (typically used for EOR processes) from oil/water interfacial reduction and adsorption inhibition. The main purpose is to analyze the resulting interactions between the nanoparticle and the surfactant molecules through IFT measurements and surfactant adsorption inhibition on a solid surface. All systems stability were determined using a Turbiscan, interfacial tensions were measured by a spinning drop tensiometer and, static and dynamic adsorption were calculated to determine the behavior of the main formulations. Results showed the surface nature of nanoparticles has an important effect on the oil–water interfacial tension evolution and on the surfactant adsorption inhibition. Both nanoparticles’ types showed a good performance under specific conditions. However, hydrophilic nanoparticles exhibited a better performance than hydrophobics. The Interfacial performance displayed nonmonotonic trends, especially in adsorption assessments wherein static and dynamic experiments exhibited different behaviors for the same type and concentration of nanoparticle, displaying a different pattern from the literature.

Preparation, Characterization and Antioxidant Activity of Glycosylated Whey Protein Isolate/Proanthocyanidin Compounds.

A glycosylated protein/procyanidin complex was prepared by self-assembly of glycosylated whey protein isolate and proanthocyanidins (PCs). The complex was characterized through endogenous fluorescence spectroscopy, polyacrylamide gel electrophoresis, Fourier infrared spectroscopy, oil-water interfacial tension, and transmission electron microscopy. The results showed that the degree of protein aggregation could be regulated by controlling the added amount of procyanidin, and the main interaction force between glycosylated protein and PCs was hydrogen bonding or hydrophobic interaction. The optimal binding ratio of protein:PCs was 1:1 (w/w), and the solution pH was 6.0. The resulting glycosylated protein/PC compounds had a particle size of about 119 nm. They exhibited excellent antioxidant and free radical-scavenging abilities. Moreover, the thermal denaturation temperature rose to 113.33 °C. Confocal laser scanning microscopy (CLSM) images show that the emulsion maintains a thick interface layer and improves oxidation resistance with the addition of PCs, increasing the application potential in the functional food industry.

Calculation of IFT in porous media in the presence of different gas and normal alkanes using the modified EoS

Gas injection can increase oil recovery because the gas–oil interfacial tension is less than the water–oil interfacial tension (IFT) and tends to zero in the miscibility state. However, little information has been provided on the gas–oil movement and penetration mechanisms in the fracture system at the porosity scale. The IFT of oil and gas in the porous medium changes and can control oil recovery. In this study, the IFT and the minimum miscibility pressure (MMP) are calculated using the cubic Peng-Robinson equation of state that has been modified using the mean pore radius and capillary pressure. The calculated IFT and MMP change with the pore radius and capillary pressure. To investigate the effect of a porous medium on the IFT during the injection of CH4, CO2, and N2 in the presence of n-alkanes and for validation, measured experimental values in references have been used. According to the results of this paper, changes in IFT vary in terms of pressure in the presence of different gases and, the proposed model has good accuracy for measuring the IFT and the MMP during the injection of hydrocarbon gases and CO2. In addition, as the average radius of the pores gets smaller, the interfacial tension tends to lower values. This effect is different with increasing the mean size of interstice in two different intervals. In the first interval, i.e. the Rp from 10 to 5000 nm, the IFT changes from 3 to 10.78 mN/m and in the second interval, i.e. the Rp from 5000 nm to infinity, the IFT changes from 10.78 to 10.85 mN/m. In other words, increasing the diameter of the porous medium to a certain threshold (i.e. 5000 nm) increases the IFT. As a rule, changes in IFT affected by exposure to a porous medium affect the values of the MMP. In general, IFT decreases in very fine porous media, causing miscibility at lower pressures.

Chitosan derivatives as surfactant carriers for enhanced oil recovery – Experimental and molecular dynamic evaluations of polymer-surfactant interactions

Surfactant injections in enhanced oil recovery (EOR) are very efficient, lowering the oil-water interfacial tension (IFT) and altering rocks wettability. Although efficient, surfactant injection during EOR process is economically unfeasible due to the high-cost caused by surfactant losses due to adsorption or precipitation on the rock surface. One strategy to reduce these losses during the flooding process is using surfactant carriers such as nanoparticles, emulsions, and polymers. Polymers are good candidates because they can act in transportation, alter rock wettability, and improve sweeping efficiency. Recently, the potential of chitosan derivatives as wettability modifiers of carbonate rocks was demonstrated. This way, using chitosan derivatives as surfactant carriers is an interesting strategy due to its high storage capacity and environment-friendly product. In this study, cationized (TMC) and hydrophobized (TMC-C14) chitosan derivatives were synthesized, characterized, and evaluated as OADA (oleic acid diethanolamide) surfactant carriers for EOR. Interfacial tension tests evaluated the potential of OADA in low and high salinity medium. Particle size measurements, done by dynamic light scattering, and molecular dynamics simulations (MD), allowed the understanding of the interaction between TMC or TMC-C14 and the surfactant. The controlled surfactant release at the water/oil interface by chitosan derivatives was evaluated by IFT measurements and MD simulations. The results showed that OADA is an excellent surfactant whose IFT reaches 10−2 mN/m, and chitosan derivatives were able to carry the surfactant to the site containing the oil. Thus, chitosan derivatives are an efficient supramolecular surfactant carrier system that can minimize surfactant losses by adsorption on the rock surface, being an interesting alternative for EOR application.

Dynamics of Droplet Coalescence on Hydrophobic Fibers in Oil: Morphology and Liquid Bridge Evolution.

Although droplet self-jumping on hydrophobic fibers is a well-known phenomenon, the influence of viscous bulk fluids on this process is still not fully understood. In this work, two water droplets' coalescence on a single stainless-steel fiber in oil was investigated experimentally. Results showed that lowering the bulk fluid viscosity and increasing the oil-water interfacial tension promoted droplet deformation, reducing the coalescence time of each stage. While the total coalescence time was more influenced by the viscosity and under-oil contact angle than the bulk fluid density. For water droplets coalescing on hydrophobic fibers in oils, the expansion of the liquid bridge can be affected by the bulk fluid, but the expansion dynamics exhibited similar behavior. The drops begin their coalescence in an inertially limited viscous regime and transition to an inertia regime. Larger droplets did accelerate the expansion of the liquid bridge but had no obvious influence on the number of coalescence stages and coalescence time. This study can provide a more profound understanding of the mechanisms underlying the behavior of water droplet coalescence on hydrophobic surfaces in oil.

The synergism of improving interfacial properties between betaine and crude oil for enhanced oil recovery

Betaine, an emerging surfactant for enhanced oil recovery (EOR), has garnered increased attention and recognition. This study focuses on linear alkylbenzene sulfonate betaine (ASB) as the research subject, and different crude oils were utilized to prepare two types of oil–water formulations with high interfacial film strengths but differed interfacial tensions. The interfacial properties were characterized and explored using interfacial dilational rheology, droplet squeeze coalescence, interfacial tension, emulsification, microscopic visualization, and other measuring methods. The actual emphasis in interfacial film properties of betaine as a standalone chemical EOR formulation was clarified. The results indicated that betaine had generally high interfacial film strength with selected crude oils, at this time, the slight difference in film strength had a negligible effect on enhancing the recovery. The main contributing factor was the difference in interfacial tension between the oil and water. Ultra-low interfacial tension could increase the stripping efficiency of oil in pore, reduce the energy required to emulsification or oil droplets initiation, and ensure that droplets were displaced and collected in smaller sizes, thereby avoiding large oil droplets trapped in the pore throat and unable to pass. Making good use of the advantages of improving sweep efficiency brought by high interfacial film strength, at the same time giving the system ultra-low oil–water interfacial tension, ensuring the start-up and migration of porous crude oil, is the core construction principle of betaine surfactant applied to EOR.

Ultra-low interfacial tension Anionic/Cationic surfactants system with excellent emulsification ability for enhanced oil recovery

Droplet size and stability of the O/W emulsion formed by heavy oil determine its fluidity in formation porous media. Hence, an anionic/cationic surfactants system of with excellent emulsification ability, ultra-small droplet size, and reduced oil–water interfacial tension (IFT) to ultra-low level was developed in this study. The AEOSHS/DTAC system can reduce oil–water IFT to ultra-low level within the molar ratio of 4:6 to 6:4. Due to the hydrophilicity of sulfonic acid group and ether group, the precipitation-dissolution balance of AEOSHS/DTAC system is well improved, and its solubility in is enhanced, and transparent solutions can be formed in a molar ratio of 10:0 to 0:10. The droplet size of O/W emulsion formed can as low as 0.6 μm when the molar ratio is 5:5. Moreover, the stability of O/W emulsion is greatly improved. The coalescence and migration process of O/W emulsion is very slow, and the stability is excellent. The dehydration rate after 24 h is only 6%, with the dehydration speed of only 0.25 %·h−1. AEOSHS/DTAC can enhance the heavy oil recovery by 22.05%. Because the droplet size of W/O emulsion is much smaller than porous diameter, the pressure does not increase during the system injection and subsequent water flooding. The AEOSHS/DTAC system is composed by anionic and cationic surfactant, which can attract each other at the interface to form a compound molecular layer. So, the repulsion between molecules on the oil–water interface is greatly reduced, making the arrangement of molecular is tighter, and the adsorption layer is more stable (The occupied area of a single molecule is only 0.06 nm2). The surface activity and interfacial activity are higher, and the droplet size is smaller, and the stability is stronger.

Synthesis and Enhanced Oil Recovery Potential of the Bio-Nano-Oil Displacement System.

Nanoparticles (NPs) have attracted great attention in the tertiary oil recovery process due to their unique properties. As an economical and efficient green synthesis method, biosynthesized nanoparticles have the advantages of low toxicity, fast preparation, and high yield. In this study, with the theme of biotechnology, for the first time, the bio-nanoparticles reduced by iron-reducing bacteria were compounded with the biosurfactant produced by Bacillus to form a stable bio-nano flooding system, revealing the oil flooding mechanism and enhanced oil recovery (EOR) potential of the bio-nano flooding system. The interfacial properties of the bio-nano-oil displacement system were studied by interfacial tension and wettability change experiments. The enhanced oil recovery potential of the bio-nano-oil displacement agent was measured by microscopic oil displacement experiments and core flooding experiments. The bio-nano-oil displacement system with different nanoparticle concentrations can form a stable dispersion system. The oil-water interfacial tension and contact angle decreased with the increase in concentration of the bio-nano flooding system, which also has a high salt tolerance. Microscopic oil displacement experiments proved the efficient oil displacement of the bio-nano-oil displacement system and revealed its main oil displacement mechanism. The effects of concentration and temperature on the recovery of the nano-biological flooding system were investigated by core displacement experiments. The results showed that the recovery rate increased from 4.53 to 15.26% with the increase of the concentration of the system. The optimum experimental temperature was 60 °C, and the maximum recovery rate was 15.63%.

Complexity Model for Predicting Oil Displacement by Imbibition after Fracturing in Tight-Oil Reservoirs

With the increasing difficulty of conventional oil and gas exploration and development, oil and gas resources have developed from conventional to unconventional, and the exploration and development of tight-oil reservoirs are highly valued. In view of the complexity of the influencing factors of oil-water spontaneous seepage after fracturing and the instability of reservoir recovery, this paper takes the tight sandstone reservoir of Yanchang Formation in the southern Ordos Basin as the research object. Based on the micro-nano pore throat characteristics of tight sandstone, the seepage experiment is carried out, and the theoretical model of seepage suction is constructed. The mechanism and influencing factors of suction and oil displacement after fracturing in tight reservoirs are analyzed. Based on the analysis of fluid buoyancy and gravity, a mathematical model of the oil-water spontaneous flow after fracturing was established, and its influencing factors were analyzed. The experimental results show that the pore throats of tight sandstone are mainly in micron- and submicron scale, and the reservoir permeability is related to the pore throat structure, oil-water interfacial tension, and wettability. After fracturing, with the increase of the fracture length, the seepage velocity gradually decreases. With the increase of fracture opening, the influence of buoyancy and gravity on seepage velocity increases. With the increase of the fracture number, seepage velocity also increases. The fracture helps to reduce the adsorption of oil droplets on the core surface and improve the efficiency of spontaneous imbibition and oil displacement of the core. The research results provide theoretical data support for enhancing oil recovery and have important application guiding significance for the operational reliability of manufacturing systems with complex topology and the complexity and operability of production operations in manufacturing systems.

Study on the emulsification characteristics of heavy oil during chemical flooding

Chemical flooding is a very important method to the efficient development of a heavy oil reservoir. A clear understanding of the relationship between emulsification characteristics of heavy oil during chemical flooding and test methods that current used to evaluate the properties of chemical flooding agent can be useful for oilfields development of the heavy oil. In this study, the oil–water interfacial tension (IFT) and oil in water (O/W) emulsion properties (emulsification state, droplet size, viscoelasticity, and stability) formed by six chemical flooding agents at different concentration are tested. Then, combined with the heavy oil flooding dynamics, the emulsification characteristics of heavy oil during the chemical flooding process of are studied and the influence mechanisms of O/W emulsion on oil recovery are clarified. Finally, the emulsification effect of heavy oil on the injection profile turnover is studied by parallel sand-packed tube experiments. Studies show that all six chemical flooding agents can greatly reduce the IFT of heavy oil–water (more than 90%). However, the stronger the emulsification ability, the smaller the droplet size, the better the viscoelasticity, the stronger the stability of O/W emulsion, and the better the heavy oil recovery of the chemical flooding agent. This is mainly because the most effective action stage is the time that before the O/W emulsion front flow reaches the production outlet, chemical flooding agent is injected into the formation. During this period, the amount of emulsified heavy oil, the width of emulsification zone, and the properties of formed O/W emulsion affect the heavy oil flooding efficiency. Therefore, when screening chemical flooding agents, the emulsification speed, the droplet size, and the viscoelasticity of formed O/W emulsion are the primary evaluation factors. In addition, through the parallel sand-packed tube experiment, it is found that the stronger the emulsification ability of chemical flooding agent, the better the performance of formed O/W emulsion, the stronger the profile turnover ability. For reservoirs that the water flow channel has formed, using profile control agents to effectively block dominant flow channels can improve the emulsification ability of chemical flooding agents, thus achieving the purpose of improving the swept area. The research results can provide guidance for the screening of chemical flooding agent with emulsification characteristic and construction process optimizing in the heavy oil reservoirs' development.

Preparation and performance of graphene oxide-polyacrylamide based nanoscale microsphere emulsion for profile control

A new kind of in-depth profile control and displacement graphene oxide-polyacrylamide (GO-PAM) based nanoscale microsphere emulsion for enhancing oil recovery was designed by the inverse microemulsion polymerization technology, which simultaneously plays the multifunction roles of plugging pore throat, reducing water-oil interfacial tension and oil viscosity benefiting from the synergistic effect of nanoscale microsphere and GO sheets. The emulsion shows superior suspension properties, thermal stability, hydration swelling, and the excellent emulsifying ability for crude oil. The average particle size of PAM microspheres is about 40 nm, and the size of GO sheets is about 1–10 µm. Only 0.1% dispersion of GO-PAM emulsion reduces the water-oil interfacial tension by 63%, and reduces the viscosity of thick oil by 10%. And with increasing emulsion dosage to 5%, the viscosity can be reduced by more than 50%. For low permeability simulated cores, the plugging efficiency of the GO-PAM emulsion system increases from 80% to 88% compared with PAM emulsion. The microscopic oil displacement experiment shows that our designed emulsion enhanced oil recovery by 6–7%. The GO-PAM composite microsphere emulsion is expected to be a competitive candidate for in-depth profile control and heavy crude recovery.

New Insight into Temperature Effects on Low-Rank Coal Flotation Using Diesel as a Collector.

Efficient flotation of low-rank coal is of great significance for the development of green and low-carbon cycles. Temperature is a crucial parameter of flotation, but the mechanism of its effect on flotation lacks understanding. In this paper, the mechanism was studied by kinetic flotation, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, low-temperature liquid-nitrogen adsorption (LP-N2A), X-ray photoelectron spectroscopy (XPS), and molecular dynamics simulation. The flotation combustible recovery gradually decreases as temperature rises. Compared with 60 °C, the combustible recovery at 5 °C increases by 18.13%. The desorption energy for oil droplets decreases as the temperature rises. As a result, the oil droplets are easier to desorb at high temperatures. The SEM and LP-N2A results demonstrate that the pores and fractures of the coal sample are well developed. Also, the oil-water interfacial tension and viscosity of oil droplets decrease as the temperature rises, while the diffusion ability increases. These increase the volume of oil droplets that penetrate into the pores, resulting in poor spreadability of oil droplets on the coal surface. The average volume of bubbles gradually increases as temperature rises, which renders the flotation foam unstable and worsens the flotation. Therefore, the flotation performance is better at low temperatures.

Preparation of Multifunctional Surfactants Derived from Sodium Dodecylbenzene Sulfonate and Their Use in Oil-Field Chemistry.

Four products were obtained from sodium dodecylbenzene sulfonate (SDBS) and formaldehyde (40% solution) using a simple reaction. The products were characterized by TGA, IR, UV and MS to confirm the major chemicals in each sample. The new products could reduce the interfacial tension between oil and water in the experimental temperature range further compared to SDBS. The emulsion ability was also enhanced by SDBS-1 to SDBS-4. The oil-displacement efficiencies of SDBS-1 to SDBS-4 were obviously higher than that of SDBS, and the oil-displacement efficiency of SDBS-2 was the best, with an efficiency of 25%. The experimental results all indicate that these products have an excellent ability to reduce oil-water interfacial tension and that they can be used in the oil and petrochemical industry for oil production and have certain practical uses.