A systematic study of the effect of nano-additives on the functional characteristics of hydraulic fracturing gels

Currently, the main technique for the development of low-permeability reservoirs is hydraulic fracturing technology. To further enhance its efficiency and reduce costs, it is necessary to improve the formulations and properties of liquids used for hydraulic fracturing. The use of nanoparticles for these purposes may become one of the promising directions. In this paper, for the first time, the effect of concentration, size, material and form of nano-additives on colloidal stability, viscosity, wetting characteristics and filtration losses of cross-linked gels for hydraulic fracturing were studied systematically. In the preparation of cross-linked gels, a guar gum biopolymer was used as a typical gel-forming agent and sodium tetraborate in glycerin was applied as a cross-linker. Spherical nanoparticles of silicon oxide and aluminum oxide, single-walled carbon nanotubes, and aluminum oxide nanofibers were employed as nano-additives. The average size of the nanoparticles varied from 11 to 216 nm. The concentration of nano-additives in the gels ranged from 0.01 to 0.8 wt%. The temperature was changed from 25 to 70 °C. The research has shown that the dependences of the functional characteristics of nano-modified gels on the concentration and size of nano-additives are non-monotonic in nature. The optimal concentration of nanoparticles to control the properties of the gel is in the range of 0.05–0.2 wt%, and the optimal average size is 70–80 nm. With these parameters, nanomaterial additives can radically change the properties of hydraulic fracturing gels (increase the effective viscosity several times, reduce filtration losses tenfold and significantly change the hydrophobicity). [Display omitted]