PROTECTION OF PRODUCTION STRING BOTTOM SIDE WHILE CUTTING OUTPUT FROM PRODUCTION STRING Russian patent published in 2016 - IPC E21B7/08 E21B29/06 

FIELD: oil and gas industry.

SUBSTANCE: well system subassembly comprises casing tube connected to the casing string and forming the bottom side, at that the casing tube is made of the first material, which is softer than material of the casing string; whipstock subassembly placed in the casing tube and having deflective surface made so that it can direct the drilling subassembly to side wall of the casing tube in order to cut an output from the casing string; and wear-prone bushing coupled to the whipstock subassembly and passing axially away from it. The wear-prone bushing forms a neck passing along axial length of the wear-prone bushing grading into deflective surface, at that axial length of the wear-prone bushing overlaps the point of contact, whereat the drilling subassembly otherwise would interact with the bottom side of the casing string, at that the wear-prone bushing protects the bottom side of the casing string from wear evoked by the drilling subassembly.

EFFECT: protection of the production string lower side against wear at cutting output from the casing string in order to make the offshoot.

23 cl, 7 dwg