Cementing of casing strings is one of the most important processes of well construction for the exploration and exploitation of oil, gas and gas condensate fields. Despite more than half a century of research and development of grouting mortars, they are not able to provide high strength and good adhesion to the casing string. The article considers the possibility of using microsilica (waste of silicon production) in the oil industry, as an additive of a plugging solution to increase the strength, expansion valve, and reduce the permeability of the plugging stone.