Study on a Novel Cross-Linked Polymer Gel Strengthened with Silica Nanoparticles

Abstract

This paper studied the strengthening effects of silica nanoparticles on the polyacrylamide (PAM)/hydroquinone (HQ)–hexamethylenetetramine (HMTA) composite gel. Pure PAM/HQ–HMTA gel and PAM/HQ–HMTA gels containing silica nanoparticles up to 0.3 wt % were prepared at 110 °C. Influences of silica nanoparticles on gelation performances were systematically evaluated. By the addition of silica nanoparticles, the gelation time became shorter and the gel strength was improved observably. Rheological measurements showed that silica nanoparticles enhanced both elasticity and viscosity of the gel significantly. Thermal stability of the gel was studied by differential scanning calorimetry (DSC) measurements. The maximum tolerated temperature of the gel was improved from 137.8 to 155.5 °C by the addition of silica nanoparticles with a concentration of 0.3 wt %. Furthermore, to study the strengthening mechanisms of silica nanoparticles to the gel, the microstructure and existing state of water within the gel were investigated by environmental scanning electron microscopy (ESEM) and DSC measurements. Micrographs of the gel showed that massive aggregations and arrangements of silica nanoparticles existed in uniformly distributed three-dimensional network structures of the gel, which greatly improved the structural strength of the gel. Moreover, the mass fraction of bound water within the gel increased from 22.5 to 39.9% by the addition of silica nanoparticles with a concentration of 0.3 wt %. The hydrogen bonds and electrostatic attractions between silica nanoparticles and water molecules/hydronium ions make a higher bound water ratio, which contributes to better water holding capacity and thermal stability of the gel.

Environmental and strength‐enhanced nanosilica‐based composite gel for well temporary plugging in high‐temperature reservoirs

“…Hence, the higher bond water ratio could contribute to improving the system's thermal stability. This result is consisted with the polyacrylamide/hydroquinone‐hexamethylenetetramine composite gel with adding nanosilica …”

“…The general gel without nanosilica can withstand the temperature of only 105.0°C, whereas for the composite gel systems respectively with 2, 4, 6, and 8 nanosilica, the peak temperature under which the composite gel can be stable respectively increased to 106.4, 108.3, 112.7, and 115.5°C, indicating the addition of the nanosilica does have a positive effect on improving the gel's thermal stability. According to Liuet et al the mechanism of thermal stability improvement by nanosilica contains two aspects. On one side, the hydroxyl groups on the surface of nanosilica particles can react with the water molecule, and then the hydrogen bond will be generated; thus, the water becomes bond water.…”

“…This result is consisted with the polyacrylamide/hydroquinone-hexamethylenetetramine composite gel with adding nanosilica. 38…”

In situ organically cross‐linked polymer gel for high‐temperature reservoir conformance control: A review

“…There is also a study on the influence of silica nanoparticles on the gelation behavior of HMTA‐HQ cross‐linked polymer gel by Liu et al The result indicates that silica nanoparticles enhance both elasticity and viscosity of the gel significantly. Its presence makes rheological properties of the gel more solid‐like.…”

“…Hence, CFA also has a potential to be a retarder for PAM/PEI gel system. There is also a study on the influence of silica nanoparticles on the gelation behavior of HMTA-HQ cross-linked polymer gel by Liu et al 90 The A study on the effect of the presence of montmorillonite clay (MMT) in PAM nanocomposite also has been conducted by Pu et al 78 The result shows that the final strength of PAM/MMT nanocomposite/PEI gel was significantly stronger than pristine PAM/PEI gel at the same conditions. It is believed that the presence of high MMT clay content reinforces the gel strength.…”