Encapsulation of particles using brittle coatings for subterranean applications

The production of a brittle and moisture-resistant coating for particles, which reduce or break the viscosity of fracturing fluids, was explored.;The viscosity-reducer was ammonium persulfate. Polyurethane and acrylate coatings were investigated. The coated particles were assessed for dissolution in water before and after being subjected to a compression test. Polyurethane-coated particles had a high leach prior to compression and were considered unsuitable. Acrylate coatings gave much better results. The addition of significant quantities of silica in the coat increased significantly its brittleness. The acrylate formed agglomerates during the coating process. These were easier to break than single particles. These agglomerates also gave a low leach rate and large release upon compression.;Agglomerates coated with acrylate and silica provide a novel solution to the opposing constraints of high water resistance and high susceptibility to brittle fracture