Particulate ceramic useful as a proppant

Abstract

A two-phase ceramic particulate useful as a proppant in hydraulic fracturing operations is provided which comprises a vitreous matrix phase containing a crystalline alumina phase. The new ceramic particles are characterized by: (i) a concentration gradient of alumina which increases from very low in the center to relatively high near the surface of the particles; (ii) a fired density less than about 2.9 g/cc; and (iii) closed cell microporosity. Certain embodiments of the inventive ceramic particulate are also characterized by a Krumbein roundness of at least 0.8 and are chemically stable. The ceramic is made by a process comprising the steps of: a. mixing and pelletizing, with the aid of water, the dry raw materials including a mineral particulate such as nepheline syenite and a binder such as bentonite; b. drying the wet pelletizer product; c. mixing the dried pellets with a parting agent; and d. firing the mixture of pellets and parting agent at sufficient temperature and for sufficient time to cause vitrification to occur.

Dependencies are inferred from the claim text.