Title: Hydraulic fracturing process using reverse flow

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Abstract: Well productivity is increased by multiple hydraulic fracturing cycles. A double cycle first creates a long primary fracture by fluid injection and forms spalls by subsequently allowing the pressure in the fracture to drop below the initial fracturing pressure by discontinuing injection and shutting the well in or allowing it to flow back, resuming injection to displace said spalls longitudinally in said fracture and again discontinuing injection, whereupon the fracture is propped open by the displaced spalls. Multiple applications of this double cycle successively create transversely directed secondary long fractures. Fracture extension and fluid loss is controlled by the sandout of fine spalls at terminal ends of the fractures, supplemented when necessary by the injection of sand of selected size to filter pack the natural joint system and, in some instances, to filter pack the vertical downward extent of joints and fractures thus limiting further fractures to the upper portion of the producing formation where upward leakage is inhibited by the overburden.


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