DEVICE FOR CUTTING SLOT-LIKE OPENINGS IN WELL BY SAND JET METHOD Russian patent published in 2006 - IPC E21B43/114 

FIELD: mining, particularly to cut slot-like openings in well bore zone of productive bed.

SUBSTANCE: device comprises tubular body fixedly connected to flow string end. Inner pipe is coaxially installed in the body so that the inner pipe is spaced from the body. Inner pipe is spring-loaded from pipe bottom with windup spring to provide sliding movement of the inner pipe. Ball valve is installed at lower end of inner pipe. Perforator is arranged over the ball valve. Device comprises upper ball valve installed at upper end of inner pipe, ball catching sleeve installed over the valve and hydraulic brake. Hydraulic brake is defined by two vertical sealed chambers filled with liquid and upper and lower plugs to restrict the chambers. The chambers are divided with piston having channel for viscous liquid flowing between the chambers. Upper plug is fixedly connected to the body and slidably connected with inner pipe. Piston is fixedly connected with inner pipe and slidably connected with the body. Lower plug may move relatively both pipes. Channel between the chambers is of self-control type and made as upper and lower dies resiliently pressed one to another so that the dies may be shifted one with respect another. Upper and lower dies have corresponding depressions and extensions formed so that extension dimensions are less than that of depressions. Upper and lower dies are made of material having different coefficients of volumetric expansion to provide constant viscous liquid flow via the channel.

EFFECT: increased reliability and productivity.

9 cl, 5 dwg