REPAIR METHOD OF CASING STRING IN WELL WITH DEFECTIVE AREA Russian patent published in 2014 - IPC E21B29/10 

FIELD: oil and gas industry.

SUBSTANCE: tool is assembled on the well head in the following sequence in an upward direction: UVU general-purpose cutting device, a string of heavy-weight drill pipes, a string of drill pipes, and the tool is lowered to the well. The upper end of the drill pipe string is attached to two pump units; rotation of the tool at the speed of 70 rpm is performed from the well head, and at the same time, process liquid is pumped to the drill pipe string by means of one pump unit at the liquid pressure of 3.0 MPa; then, every 10 minutes, without any decrease in rotation speed of the tool, there step-by-step increased is liquid pressure by 1 MPa until it is 5.0 MPa. The second pump unit is put into operation without any decrease in rotation speed; liquid pressure is increased step-by-step by 1 MPa till the pressure of 9.0 MPa is reached; two pump units are changed over to a process liquid supply mode, and the defective area is cut out at the pressure of 9.0 MPa. Without any reduction of operating parameters of pump units and a rotor, a load on UVU is selected, which does not exceed 40 kN; the cutting-out operation is performed within the whole interval of the defective area. Flushing is performed; pump units are stopped and the tool is raised to the well head. The filling pipe string is lowered and the well is isolated with an insulating compound from the working face till the upper interval of the defective area.

EFFECT: lower loads on the tool and shorter duration of operations.

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