One advantage of this low density proppant is that fewer pounds of this proppant are required

One advantage of this low density proppant is that fewer pounds of this proppant are required, as compared to high density ceramic, to fill a given void in the formation. Since proppants are generally sold by the pound, the user buys fewer pounds of proppant for a particular application. Another advantage of this low density proppant is the ability to use a lower viscosity fracturing fluid during pumping operations, resulting in more economical pumping at lower pumping rates than those required with the use of heavier or denser proppants. Still another advantage is the relatively low silica content.
These advantages can be achieved by forming solid spherical pellets or particles from kaolin clay having an alumina content of between 40 and 60%. Normally, this material would have an apparent specific gravity of about 3.0 g/cc, as disclosed in Lunghofer. However, the density can be significantly reduced by carefully controlling the time and temperature of the firing process. In order to achieve an apparent specific gravity of from about 1.60 to about 2.10 g/cc and a bulk density of from about 0.95 to about 1.30 g/cc, the pellets are fired at a temperature of from about 1200 to about 1350° C.