REPAIR METHOD OF CASING STRING IN WELL WITH DEFECTIVE SECTION Russian patent published in 2013 - IPC E21B29/10 

FIELD: mining.

SUBSTANCE: assembly of a tool is performed on a well mouth in the following upward sequence: a cutting-off device equipped with extendable cutters, a downhole screw motor-DSM, and a tubing string. The tool is lowered to the well. A space between the tubing string and the casing string is sealed on the mouth and the tubing string is fixed. Connection of the upper end of the tubing string is performed through a T-piece to two pump units. At the same time, pumping of process liquid to the tool is performed using them, and liquid pressure is increased up to 3 MPa. Liquid pressure in the tool is increased by 1 MPa every 2 minutes and till the liquid pressure of 12 MPa is achieved. By maintaining the pressure, cutting into the casing string is performed during 15 minutes. Load for the cutting-out device is chosen so that it does not exceed 40 kN, and cutting-off of the defective section at the whole string interval is performed. When the lower cutting-out interval is reached, a tool is lifted to the distance of 1.0 m with a speed of 0.1 m/s, and flushing in the well volume is performed without decreasing the pressure. A jet nozzle is lowered and rock is flushed out of the defective section along the perimetre of the formed cut-out. A string of grout pipes is lowered and a well is isolated from the face to upper interval of the defective section.

EFFECT: reduction of load on the tool and duration of work.

3 dwg