GEAR FOR SLOT PERFORATION OF CASING STRING Russian patent published in 2002 - IPC

FIELD: oil industry, secondary opening of productive pools, perforation of casing string in oil or gas well. SUBSTANCE: gear includes cutting unit in the form of retractable threading roll, hydromonitor duct and hydraulic conduit placed under unit. Flushing conduit to clean shaft of well from slurry is arranged in lower part of gear along its axis. It is hydraulically coupled to hydraulic conduit in transportation position of gear. Sliding support in the form of ski is placed along entire cutting unit on side opposite to threading roll. It is made fast to body of gear. Gear also has differential non-return valve with shut-off member to drop this member from surface and activation of nonreturn valve with shutting off of hydraulic conduit. EFFECT: increased operational reliability of gear during perforation of several intervals by prevention of possibility of getting slurry into gear in process of movement of tubing string, provision for flushing of clogged section of shaft of well while gear is sunk to specified interval of perforation. 2 dwg