Wettability, interfacial tension, and capillary imbibition of nanomaterial-modified cross-linked gels for hydraulic fracturing

For the first time, systematic studies were conducted to investigate the effect of concentration, size, material, and shape of nanoadditives on the wettability, interfacial tension, and capillary imbibition rate of cross-linked gels for hydraulic fracturing. Guar gum biopolymer was used as the gelling agent and sodium tetraborate in glycerol was used as the crosslinker in the preparation of cross-linked gels. Spherical nanoparticles of silica and alumina, as well as single-walled carbon nanotubes, and alumina nanofibers were used as nanoadditives. The nanoparticles had an average size ranging from 11 to 216 nm, and their concentration in the gels ranged from 0.01 to 0.8 wt%. The study revealed a nonmonotonic dependence of the contact angle, interfacial tension coefficient, and capillary imbibition rate of nanomodified cross-linked gels on the concentration and average size of nanoparticles. The gels exhibited maximum hydrophobic properties at a nanoparticle concentration of 0.2 wt% and an average size of 70-80 nm. At the same time, the addition of single-walled carbon nanotubes has the most significant effect on the wettability properties of the gels, reducing the capillary imbibition rate by three times. Thus, it has been shown that controlling the concentration, size, material, and morphology of the nanoadditives can significantly alter the wetting characteristics of hydraulic fracturing fluids. This provides an opportunity for more flexible control of the hydraulic fracturing process depending on the reservoir characteristics.