Influence of nanoparticle addition to Winsor surfactant microemulsion systems

Study on Formation and Migration Law of Foam in Fractures and Its Influencing Factors

This study focuses on the characteristics of foam generation, flow, and plugging in different reservoir fracture environments. Through visual physical model experiments and stone core displacement experiments, we analyze the flow regeneration of foam in a simulated reservoir fracture environment as well as its sealing and sweeping mechanisms. The findings reveal that low permeability reservoirs, with their smaller and more intricate fracture structures, are conducive to the generation of high-strength foam. This is due to the stronger shear effect of these fracture structures on the injected surfactant and gas mixture system, resulting in a denser foam system. Consequently, low permeability reservoirs facilitate a series of mechanisms that enhance the fluid sweep efficiency. Furthermore, the experiments demonstrate that higher reservoir fracture roughness intensifies the shear disturbance effect on the injected fluid. This disturbance aids in foam regeneration, increases the flow resistance of the foam, and helps to plug high permeability channels. As a result, the foam optimizes the injection-production profile and improves the fluid sweep efficiency. Stone core displacement experiments further illustrate that during foam flooding, the foam liquid film encapsulates the gas phase, thereby obstructing fluid channeling through the Jamin effect. This forces the subsequently injected fluid into other low-permeability fractures, overcoming the shielding effect of high-permeability fractures on low-permeability fractures. Consequently, this improves the fluid diversion rate of low permeability fractures, effectively inhibiting fluid cross-flow and enhancing sweep efficiency. These experimental results highlight the advantages of foam flooding in the development of complex reservoirs with low permeability fracture structures, demonstrating its efficacy in inhibiting fluid cross-flow and optimizing the injection-production profile.

Construction of asymmetric dual-layer polysaccharide-based porous structure on multiple sources for potential application in biomedicine

Biomedical materials can produce high efficiency and special behavior with an integrated internal structure. It is possible that changing the structure of biomedical materials could extend and promote the application of eco-friendly and multifunctional biomaterials. However, the instantaneous formation of complex structures between tannic acid (TA) and polysaccharides is disrupted, and the reconstruction of the new porous structure becomes a key issue. Here, we present an innovative one-step forming method for an asymmetric dual-layer porous structure of carboxymethyl chitosan (CC)/sodium alginate (SA)/TA, which can be utilized in various biomedical applications. Even after 6 months of storage, it still demonstrates a range of desirable properties including tailorable performance, efficient antibacterial activity, ultrarapid antioxidant activity, low differential blood clotting index and cytotoxicity. This suggests its potential for regulating and controlling wound bleeding, providing flexible possibilities for potential applications in biomedicine.

Multiple phase inversion of emulsions stabilized by in situ surface activation of CaCO3 nanoparticles via adsorption of fatty acids

The in situ surface activation of raw CaCO(3) nanoparticles by interaction with a series of sodium carboxylates of chain length between 6 and 12 as well as sodium 2-ethylhexylsulfosuccinate (AOT) was studied, and the impact of this on the stabilization and phase inversion of toluene-water emulsions was assessed. By using complementary experiments including measurement of particle zeta potentials, adsorption isotherms of amphiphile, and relevant contact angles, the mechanism of this activation was revealed. The results show that hydrophilic CaCO(3) nanoparticles can be surface activated by interaction with sodium carboxylates and AOT even if they are not surface-active themselves. Both the electrostatic interaction between the positive charges on particle surfaces and the negative charges of anionic amphiphile headgroups and the chain-chain interactions of the amphiphile result in monolayer adsorption of the amphiphile at the particle-water interface. This transforms the particles from hydrophilic to partially hydrophobic such that they become surface-active and stabilize oil-in-water O/W(1) emulsions and induce O/W(1) → water-in-oil W/O phase inversion, depending on the chain length of the carboxylate molecules. At high amphiphile concentration, bilayer or hemimicelle adsorption may occur at the particle-water surface, rendering particles hydrophilic again and causing their desorption from the oil-water interface. A second phase inversion, W/O → O/W(2), may occur depending on the surface activity of the amphiphile. CaCO(3) nanoparticles can therefore be made good stabilizers of both O/W and W/O emulsions once surface activated by mixing with traces of suitable anionic amphiphile.