US Patent 7849923 Proppant entrainment prevention method

Elimination of sand entrainment and a significant increase in hydrodynamic permeability of the sand pack in an area near the wellbore are achieved through the use of a sand and/or proppant, and proppant material mixture at the final stage of the fracture filling process, where individual particles of the proppant material have at least one shape of plates, lattices, hollow bars, inside-hollow tubes with a closed impermeable cavity or cavities, toroidal particles, elongated particles in the form of ovals, pellets or plates, cylinders with a closed impermeable cavity or cavities, or blocks with a comb multi-channel structure with throughout channels of the ellipse or polygon cross-section.