Smart wormlike micelles with stimuli-tunable rheological properties may be useful in a variety of applications, such as in molecular devices and sensors. The formation of triplestimuli-responsive systems so far has been a challenging and important issue. In this work, a novel triplestimuli (photo-, pH-, and thermoresponsive) wormlike micelle is constructed with N-cetyl-N-methylmorpholinium bromide and trans-cinnamic acid (CA). The corresponding multiresponsive behaviors of wormlike micellar system were revealed using cryogenic transmission electron microscopy, a rheometer, and H NMR. The rheological properties of wormlike micellar system under different temperatures, pH conditions, and UV irradiation times are measured. As confirmed byH NMR, chemical structure of a CA molecule can be altered by the multiple stimulation from an exotic environment. We expect it to be a good model for triple-responsive wormlike micelles, which is helpful to understand the mechanism of triple-responsiveness and widen their applications.
This work aims at studying the effect of electrostatic interactions between cationic surfactants and silica nanoparticles (NPs) on foam stability in porous media. The physio-chemical property of NPs, the gas-liquid interface properties, the foam flow characteristics, together with the stability under different concentrations of surfactant and NPs were investigated and compared. It was found that the affinity of silica NPs to the surface is tunable by variation of surfactant concentrations. NPs and surfactants as a whole assembling at the surface substantially improve the foam stability in static and dynamic tests. These surfactant-modified NPs accumulate at the bubble surface and remain stable under dilution of brine, providing a barrier effectively preventing coalescence. In addition, foam stability is enhanced since the layer of NPs significantly reduces the mass transfer rate, consequently mitigating the Ostwald ripening.
The adsorption and viscoelastic properties of a micellar solution of 2-hydroxyl-propanediyl-1,3-bis(hexadecyldimethylammonium bromide), abbreviated as 16-3OH-16, have been investigated by surface tension and rheological measurements. Meanwhile, an aqueous solution of propanediyl-1,3-bis(hexadecyldimethylammonium bromide), abbreviated as 16-3-16, was also examined. From the steady state and oscillatory rheological results, a notable difference in shear viscosities between the two systems was observed. Zeta potentials and size distributions confirm the change in the potentials and hydrodynamic diameters, and these results are in good agreement with the rheological results. The differences of the two solutions were attributed to the effect of the hydroxyl group on the spacer of 16-3OH-16. Molecular dynamic simulations and density functional theory (DFT) calculations were performed to investigate the non-covalent interactions in the solution and the difference between the molecular orbitals and the electrostatic potentials. Our research shows that a more uniform distribution of positive charges around the spacer could result in a more effective electrostatic screening effect between the charged headgroups, and promote the formation of a worm-like micelle. Also, hyperconjugation becomes stronger when the hydroxyl group is introduced on the spacer of the gemini molecule.
To further enhance oil recovery of high temperature and high salinity reservoir at Tahe Oilfield, field test results from profile control and oil displacement of gel were carried out in this article. Static and dynamic evaluations were performed through gel strength code method, environment scanning electron microscope, and physical simulation experiment devices. The field test results show that, under the conditions of high temperature (100.8 8C) and salinity (19.8 3 10 4 mg/L), the stable gel system was formed with gelling time range from 26 to 45 h, gel strength ranging from E to H, and dehydrating amount lower than 3.0% after ageing 60 days. Meanwhile, the microstructure is very stable. When the permeability and gel strength ranges from 0.212 to 0.970 lm 2 and E to H, respectively, the plugging ratio is larger than 85%, and the plugging performance becomes better with the increase of permeability or gel strength. Due to the profile improvement rate of 99.8% and the oil recovery up to 28.5%, profile control and oil displacement technology of gel can effectively promote fluid diverting. The water cut reduced from 95.2% to 89.0% during field test carried out in Tahe Oilfield, which means that profile control and oil displacement technology of gel could stabilize oil production by water control effectively. Also, this technology has a wide application prospective that provides with strong technical support for further enhanced oil recovery in high temperature and high salinity reservoirs.
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