Fracture Analysis of Ceramic Proppants

Small particles (traditionally sand) are mixed with fluid in hydraulic fracturing treatments of petroleum wells to stimulate production. The solid particles, called proppants, are used to prop open the fracture as hydraulic pressure is reduced. Deep wells can demand higher strength than provided by sand, while low specific gravity is desired to improve proppant transport. This paper considers the stress and strength analysis of proppants, and considers the use of high-strength ceramics as possible proppants. The stresses produced by interparticle contact are analyzed, which along with a failure criterion based on a critically stressed volume lead to a fracture prediction. The results show that ceramics can give adequate strength, even when used in low-density forms such as with high porosity or as hollow spheres. Laboratory tests of the effect of closure pressure on fluid permeability are seen to be in good agreement with the fracture predictions.