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Abstract

A method of hydraulically fracturing subterranean coal seams to improve the rate and total recovery of gas therefrom. The coal seam is fractured with acid and a proppant-laden fracing fluid in alternating injection stages. The initial injection stage of the fracturing fluid contains from about 0 to about 4 pounds of a spherical proppant having a particle size distribution substantially between 60 and 140 mesh. The subsequent fracing fluid injection stages are alternated with injection stages of a smaller volume of acid. The proppant loading in the fracing fluid is increased with each injection stage until the loading is from about 8 to about 12 pounds of proppant per gallon of fluid. The subsequent and terminal fracing fluid injection stages are with the higher proppant loading. Preferably, the volume of the fracing fluid injection stages is increased in successive stages from about 2000 to about 4000 gallons per stage initially to from about 6000 to about 8000 gallons per stage in the subsequent and terminal stages. The terminal fracing fluid injection stage is followed by a flushing of the well with a proppant-free fluid.

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First Claim