DOWNHOLE INSTRUMENT Russian patent published in 2006 - IPC E21B43/112 

FIELD: oil production industry, particularly devices used for secondary productive formation penetration.

SUBSTANCE: downhole instrument comprises cutting tool installed in body so that the cutting tool may be extended from the body to well wall with the use of cutting tool advancing unit and rotated with the use of rotation unit and rotation transmission unit, which transmits rotation to cutting tool. The instrument also has fixing mechanism, which fixes instrument body in well. The fixing mechanism includes upper and lower supports. The instrument is additionally provided with hydraulic accumulation and displacement control unit, electrohydraulic unit and thermohydraulic pressure compensator arranged in the body and operatively connected one to another. Hydraulic accumulation and displacement control unit has hydraulic cylinders to forcedly return cutting tool and fixing mechanism in initial state. The electrohydraulic unit is provided with electromagnetic valves to recharge hydraulic cylinders of hydraulic accumulation unit. Thermohydraulic pressure compensator is adapted to relieve hydrostatic pressure on the body inside the well. Cutting tool advancing unit is provided with hydraulic cylinders and manifolds. The cutting tool may be extended after electromagnetic valve triggering when working liquid enters hydraulic cylinders of fixing mechanism and cutting tool advancing unit. The cutting tool is moved in its initial position as pressure is relieved from cutting tool advancing unit. Upper and lower supports may press the instrument to well wall from cutting tool extension side.

EFFECT: increased operational reliability and efficiency.

2 cl, 1 dwg