Sintered spherical pellets containing clay as a major component useful for gas and oil well proppants

Claim 1

A method of fracturing a subterranean formation located at a depth in excess of 7,000 but less than 14,000 feet, which comprises injecting a hydraulic fluid into said formation at a rate and pressure sufficient to open a fracture therein, injecting into said fracture a fluid containing composite, sintered, spherical pellets having a permeability to brine at about 200° F. (93.3° C.) which decreases not more than about three-fourths when the applied pressure on said pellets is increased from 2,000 to 10,000 psi., (140 to 700 Kg/cm 2 ) said pellets being comprised of clay and a member of the group of bauxite, alumina or mixtures thereof, said pellets being prepared from a mixture containing at least 40 percent on a dry weight basis of clay, said pellets having an alumina to silica dry weight basis ratio from about 9:1 to about 1:1, said pellets having an apparent specific gravity of less than 3.40.

Claim 2

A method of fracturing a subterranean formation located at a depth in excess of 7,000 but less than 14,000 feet, which comprises injecting a hydraulic fluid into said formation at a rate and pressure sufficient to open a fracture therein, injecting into said fracture a fluid containing composite, sintered, spherical pellets having a permeability to brine at about 200° F. (93.3° C.) which decreases not more than about three-fourths when the applied pressure on said pellets is increased from 2,000 to 10,000 psi., (140 to 700 Kg/cm 2 ) said pellets being comprised of clay and a member of the group of bauxite, alumina or mixtures thereof, said pellets being prepared from a mixture containing at least 40 percent on a dry weight basis of clay, said pellets having an alumina to silica dry weight basis ratio from about 9:1 to about 1:1, said pellets having an apparent specific gravity of less than 3.40.

Claim 5

A method for increasing permeability in a subterranean formation penetrated by a well wherein a fluid is pumped into the well to create a fracture in said subterranean formation, the improvement which comprises introducing into a fluid composite, spherical, sintered pellets comprised of clay and a member of the group of bauxite, alumina, or mixtures thereof, said pellets containing on a dry weight basis a major portion of clay, said pellets having an apparent specific gravity of less than 3.40; introducing said pellet-containing fluid into a fracture, the compaction pressure of which is between about 280 and about 700 Kg/cm 2 (4,000 and about 10,000 psi), to deposit a propping distribution of said pellets, said pellets having an average particle size between 0.1 and 2.5 millimeters.

Claim 6

A method for increasing permeability in a subterranean formation penetrated by a well wherein a fluid is pumped into the well to create a fracture in said subterranean formation, the improvement which comprises introducing into a fluid composite, spherical, sintered pellets comprised of clay and a member of the group of bauxite, alumina, or mixtures thereof, said pellets containing on a dry weight basis a major portion of clay, said pellets having an apparent specific gravity of less than 3.40; introducing said pellet-containing fluid into a fracture, the compaction pressure of which is between about 280 and about 700 Kg/cm 2 (4,000 and about 10,000 psi), to deposit a propping distribution of said pellets, said pellets having an average particle size between 0.1 and 2.5 millimeters.