HYDRAULIC FRACTURING METHOD FOR LOW-PERMEABLE FORMATION WITH IMPERMEABLE LAYER AND WATER-BEARING INTERLAYER Russian patent published in 2015 - IPC E21B43/267 E21B34/14 

FIELD: oil and gas industry.

SUBSTANCE: method involves landing of tubing string with packer to a well, packer seating, hydraulic fracture liquid injection by the tubing string with packer to a low-permeable formation, hydraulic fracturing of the low-permeability formation with further fracture fixation by injection of liquid carrier with propping agent via the tubing string, pressure relief in the well. Before tubing string landing to the well, water-bearing interlayer interval of the low-permeable formation is perforated to form perforation holes. Then at the wellhead the tubing string is filled upwards from the bottom with a plug, lower hole rows, packer, upper hole rows and additional packer. Inside the tubing string, a mobile bushing with radial channels is inserted to seal lower hole rows of the tubing string tightly in initial position and connecting the tubing string via upper hole rows and perforation holes to the ware-bearing interlayer. A seat is installed inside the mobile bushing, the mobile bushing and the seat are fixated in initial position against the tubing string by a differential shear element. The tubing string is landed to the well, packer and additional packer are seated in the well so as to shot water-bearing interlayer off tightly at two sides, upper water0bearing interlayer is isolated by injection and flushing of water isolation composition via the tubing string through upper hole rows to the water-bearing interlayer through perforation holes under pressure twice lower than hydraulic fracture pressure of the formation, process break is made for solidification of the water isolation composition, then a ball is dropped to the tubing string from wellhead, and overpressure is formed in the tubing string. First the shear element is destroyed, and under impact of overpressure above the ball, mobile bushing is shifted down along the tubing string to a stop against the tubing string plug, overpressure increase in the tubing string is continued, and the shear element is destroyed again. The seat is brought down to a stop against the plug under impact of overpressure above the ball. Upper hole rows of the tubing string are shut off tightly by the mobile bushing, and lower hole rows are connected to the tubing string by radial channels of the mobile bushing.

EFFECT: improved efficiency of hydraulic fracturing.

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