An increase in effective propped lengths is evidenced in hydraulic fracturing treatments by the use of ultra lightweight (ULW) proppants. The ULW proppants have a density less than or equal to 2.45 g/cc and may be used as a mixture in a first proppant stage wherein at least one of the proppants is a ULW proppant. Alternatively, sequential proppant stages may be introduced into the formation wherein at least one of the proppant stages contain a ULW proppant and where at least one of the following conditions prevails: (i.) the density differential between the first proppant stage and the second proppant stage is greater than or equal to 0.2 g/cc; (ii.) both the first proppant stage and the second proppant stage contain a ULW proppant; (iii.) the rate of injection of the second proppant stage into the fracture is different from the rate of injection of the first proppant stage; or (iv.) the particle size of the second proppant stage is different from the particle size of the first proppant stage.
This application is a continuation of U.S. patent application Ser. No. 10/803,258, filed on Mar. 18, 2004, now U.S. Pat. No. 7,210,528, which claims the benefit of U.S. application Ser. Nos. 60/455,717, filed on Mar. 18, 2003 and 60/508,822 filed Oct. 3, 2003.
