Abstract

Profile control treatment is an effective technology to improve reservoir heterogeneity and decrease the watercut. Polymer gel has become the most widely used profile control agent. The most commonly used polymer in polymer gels is HPAM, which has poor adaptability in high temperature and high salinity reservoirs resulting in poor gel performance. Amphiphilic polymers have good viscosifying action in high temperature and high salinity reservoirs due to the polymer chain entanglement and hydrophobic chain association. In this paper, one amphiphilic polymer (PADC) was developed by introducing a betaine type functional monomer. In order to further improve the anti-temperature performance of PADC, the idea of using inorganic nanoparticles for enhancement was proposed. Based on this, a composite gel with good temperature and salt resistance was developed by adding crosslinking agent. The effects of nanosilica particle concentration, polymer concentration and crosslinking agent concentration on the gel performance of the composite gel were investigated systematically. The results showed that salt viscosifying action ability was related to the ionic strength. The higher the ionic strength, the larger the polymer molecular hydraulics radius. At the same time, the strength of hydrophobic association was improved and formed a denser spatial network structure. The synergistic effects made PADC have the characteristic of salt viscosifying action. It was also found that the viscoelasticity of the polymer solution changed from a viscous system to an elastic system by adding nano-silica, and apparent viscosity increased significantly. We have demonstrated that nano-silica surface will adsorb free polymer moleculesin solution, and form molecular brushes due to charge attraction and hydrogen bonding. The molecular brushes will adsorb and combine with the spatial network structure formed by the amphiphilic polymer. A significant improvement in the gel strength of composite polymer gel compared with organic polymer gel. Our work indicates that the composite gel based on amphiphilic polymer has significantly potential applications in high temperature and high salinity reservoirs, it has certain reference significance for stabilizing oil output and controlling water content for the similar reservoirs.

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