Synthesis and characterization of in-situ self-growth mineralization-responsive dispersed gel nanoparticles

Abstract

This study employed a reverse emulsion method to prepare dispersed nanoparticle gels that respond to mineralization and exhibit excellent characteristics such as small particle size, high dispersion, and strong stability by introducing catechol-like structures and temperature/salt-resistant functional monomers. Experimental results showed that the particle size of the dry dispersed gel particles ranged from tens to 100 nm, as observed by scanning electron microscopy. Laser particle size analyzer testing demonstrated that the size of the dispersed gel particles progressively increased with the mineralization degree of the dispersed particle gel, indicating a certain level of mineralization responsiveness. Additionally, these particles could maintain stable dispersion for up to 40 days in a solution with a mineralization degree of 20,000 mg/L. The rheology testing results indicate that the dispersed particle gels exhibited the properties of the pseudo-plastic fluid. Even under extreme conditions such as high temperature and mineralization, the strength of the dispersed particle gels remained intact, measuring 95.76 kPa after 40 days of aging. Using Materials Studio molecular simulation software, the stability and self-growth mechanism of dispersed gel particles were explained from the quantum mechanics perspective. The geometry of the dispersed gel particles was optimized using the Compass II force field, and the total energy of the model was calculated to be −757.579 kcal/mol, with the dihedral torsion energy contributing the most to the total energy. The molecular bond lengths in the polymer chain were then calculated, with the O–H bond being the shortest and the O-Na bond in the carboxylate sodium group being the longest. This indicated that the –OH group was more stable and the carboxylate sodium group was prone to hydrolysis, forming a –COOH group and increasing the dispersion stability. The charge distribution and molecular orbitals in the polymer molecule were also calculated, with the LUMO value being −7.405 eV and the HOMO value being −4.487 eV. This study used a reverse emulsion method to in-situ generate mineralization-responsive, multi-haired dispersed gel nanoparticles, which fundamentally solved the injection problem of low-permeability oil reservoirs and provided new materials for long-term plugging of high-temperature and high-salinity oil reservoirs.