Synthesis of self-suspending silica proppants using photoactive hydrogels

Micro and mesoscale particles in fluids are widely used from hydrocarbon extraction to drug delivery applications. Of interest are silica particles that are used as proppants for the extraction of natural gas from underground reserves. These particles have the tendency to settle out or aggregate in slurries, resulting in hindered transport. This in turn, necessitates requires high pressure pumping or additives, resulting in various environmental concerns and increased costs. As an alternative to using lighter proppant particles, here we report on a facile procedure to create self-suspending particles formed by a water swellable hydrogel shell. We graft photoactive polyethylene glycol hydrogels to large, non-spherical silica particles using a UV polymerization procedure. The proppant particles formed are stable with a high degree of hydration and reduced apparent density. A significant drop in density in comparison to unmodified particles is shown that can reduce the settling velocity and thereby, reduce hindered transport. The experimentally obtained settling velocities are in good agreement with theoretical models. The ability to tune particle density has implications in industrial applications to improve environmental impact, efficiency and productivity.