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Nanoparticle-stabilized Pickering emulsions have significant application potential in various fields, including enhanced oil recovery. The close relationship between the nanoparticle morphology, size, surface roughness, and interfacial activity is a crucial factor for emulsion stability. In this study, dendritic mesoporous silica nanoparticles (DMSNs) with special mesoporous structure were successfully synthesized, and their ability to stabilize Pickering emulsions for enhanced oil recovery was investigated. Scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction were used to confirm the successful fabrication of DMSNs. In addition, the effects and regulation mechanisms of the reaction time and TEOS addition on the morphology and pore structure of mesoporous nanomaterials were studied, the impact of the synthesis conditions with the results of the structural characterization was linked, the competitive nucleation and growth mechanisms of the dendritic mesoporous nanomaterials were further proposed. The stability of Pickering emulsions under high-temperature and high-salinity conditions was systematically evaluated at different scales by a variety of techniques, such as laser particle size analysis, optical microscopy, and static multiple light scattering. The results showed that the DMSNs-stabilized Pickering emulsions had good stability even at high-mineralization-degree (30,000 mg/L) and high-temperature (80 °C) reservoirs. N 2 physical adsorption–desorption curves and emulsion stability studies suggested that DMSNs with higher specific surface areas and surface roughness values exhibited enhanced surfactant-loading capacities and binding affinities. These properties enable the formation of a mechanical barrier at the oil–water interface and increase the interfacial strength, which are essential for the long-term stability of emulsions. Moreover, the results of core flooding experiments indicated that the DMSNs-stabilized emulsions could significantly enhance oil recovery (by 27.6%). Finally, based on microscopic visualization experiments, a potential enhanced oil recovery mechanism was proposed. These novel findings in this work could extend the knowledge about DMSNs-stabilized Pickering emulsion in EOR. [Display omitted] [ABSTRACT FROM AUTHOR]

The MIL-53Fe@g-C 3 N 4 samples were prepared by solvothermal method and recorded as CM-x. The potocatalytic activity of the MIL-53Fe@g-C 3 N 4 was significantly higher than MIL-53Fe, and it might be due to the successfully constructed heterojunction promoting the migration and separation effciency of photo-generated electron and hole pairs. In order to further enhance the potocatalytic activity of the MIL-53Fe@g-C 3 N 4 , peroxymonosulfate was introduced into the MIL-53Fe@g-C 3 N 4 /Vis system, and the peroxymonosulfate could be simultaneously activated by photogenerated electron and iron to form sulfate radical under visible light irradiation. Therefore, the degradation efficiency of oxytetracycline hydrochloride was enhanced obviously. Meantime, the effects of peroxymonosulfate dosage, oxytetracycline hydrochloride concentration, temperature and pH on the degradation efficiency of oxytetracycline hydrochloride were studied systematically. Meanwhile, the free radical catching experiments and electron spin resonance analysis confirmed that the main active substances were sulfate radical and hole. Finally, the mechanism and possible degradation pathways of MIL-53Fe@g-C 3 N 4 activating peroxymonosulfate to degrade oxytetracycline hydrochloride were proposed. [Display omitted] • MIL-53Fe@g-C 3 N 4 photocatalysts was synthesized by solvothermal method. • Peroxymonosulfate was activated by photogenerated e− and Fe. • The SO 4 •− and •OH mainly contributed to oxytetracycline hydrochloride degradation. [ABSTRACT FROM AUTHOR]

With the increasing depth of reservoir development, the temperature and shear resistance of fracturing fluids needs to be further improved. In comparison with traditional crosslinking agents, nano-crosslinkers have superior crosslinking properties and can enhance the temperature and shear resistance of fracturing fluids. However, the synthesis of nano-crosslinkers is complicated and not sufficiently explained to elucidate the crosslinking mechanism. In this study, a nanosilica colloidal crosslinker with a larger size and more crosslinking sites was synthesized by a simplified method using nanosilica. The structure and crosslinking mechanism of nanosilica crosslinkers were explored using FTIR, XPS, TGA, and SEM. The results indicated that the nanosilica and organoboron were bonded through B-N bonds. The nanosilica crosslinker has good dispersion and excellent thermal stability. The thermal and shear stability of nano-crosslinked fracturing fluids was better than that of fracturing fluids formed with organoboron crosslinkers. Specifically, temperature resistance is enhanced by 7–18 °C and shear resistance by 5–20 mPa s. In addition, the gel-breaking fluid changes the wettability of the core surface and enhances the flow capacity of the oil. The results of FTIR showed the synergistic effect of hydrogen and covalent bonding between the crosslinker and guar gum molecules. The results of SEM indicated that the guar gum molecules are transformed from a linear structure to a membrane structure during the transformation of the fracturing fluid from a base fluid to a gel, which gave the gel water retention capacity and good proppant-carrying capacity. Furthermore, the nanosilica crosslinker is distributed on the surface of the membrane or located in the membrane by binding to the membrane. The interaction between the nanoparticles and the membrane structure enhances the strength of the membrane structure, which allows for better shear stability of the nano-crosslinked fracturing fluid at high temperatures. [Display omitted] • A nanosilica colloidal crosslinker is developed to improve the performance of hydroxypropyl guar gum fracturing fluid. • This product can increase the residual viscosity of the fracturing fluid gel by 5–20 mPa s. • The continuous membrane structure in HPG fracturing fluid is observed using vacuum freeze-drying and SEM. • The combination of chemical bonds and hydrogen bonds enhances the performance of the fracturing fluid. • The modified nanosilica enhances the structural strength and water retention capacity of the continuous membrane. [ABSTRACT FROM AUTHOR]

With the increasing depth of reservoir development, the temperature and shear resistance of fracturing fluids needs to be further improved. In comparison with traditional crosslinking agents, nano-crosslinkers have superior crosslinking properties and can enhance the temperature and shear resistance of fracturing fluids. However, the synthesis of nano-crosslinkers is complicated and not sufficiently explained to elucidate the crosslinking mechanism. In this study, a nanosilica colloidal crosslinker with a larger size and more crosslinking sites was synthesized by a simplified method using nanosilica. The structure and crosslinking mechanism of nanosilica crosslinkers were explored using FTIR, XPS, TGA, and SEM. The results indicated that the nanosilica and organoboron were bonded through B-N bonds. The nanosilica crosslinker has good dispersion and excellent thermal stability. The thermal and shear stability of nano-crosslinked fracturing fluids was better than that of fracturing fluids formed with organoboron crosslinkers. Specifically, temperature resistance is enhanced by 7–18 °C and shear resistance by 5–20 mPa s. In addition, the gel-breaking fluid changes the wettability of the core surface and enhances the flow capacity of the oil. The results of FTIR showed the synergistic effect of hydrogen and covalent bonding between the crosslinker and guar gum molecules. The results of SEM indicated that the guar gum molecules are transformed from a linear structure to a membrane structure during the transformation of the fracturing fluid from a base fluid to a gel, which gave the gel water retention capacity and good proppant-carrying capacity. Furthermore, the nanosilica crosslinker is distributed on the surface of the membrane or located in the membrane by binding to the membrane. The interaction between the nanoparticles and the membrane structure enhances the strength of the membrane structure, which allows for better shear stability of the nano-crosslinked fracturing fluid at high temperatures. [Display omitted] • A nanosilica colloidal crosslinker is developed to improve the performance of hydroxypropyl guar gum fracturing fluid. • This product can increase the residual viscosity of the fracturing fluid gel by 5–20 mPa s. • The continuous membrane structure in HPG fracturing fluid is observed using vacuum freeze-drying and SEM. • The combination of chemical bonds and hydrogen bonds enhances the performance of the fracturing fluid. • The modified nanosilica enhances the structural strength and water retention capacity of the continuous membrane. [ABSTRACT FROM AUTHOR]