METHOD FOR WELL REPAIR Russian patent published in 2009 - IPC E21B29/10 E21B33/13 

FIELD: oil and gas industry.

SUBSTANCE: invention is related to oil industry and may find application in well repair. According to method, pipe string is lowered in well. Pipe string bottom is lowered to the depth that is 20-30 m below interval of detected violation of casing pipe. Minimum circulation of liquid is created through pipe string and well tube space. Liquid outlet from tube space is sent to ditch system. Back pressure of 3-4 MPa is established at wellhead by closure of valve at the outlet from tube space. Cement mortar is pumped through casing string with its discharge from casing string bottom to interval of violation. Casing string is lifted, and its bottom is installed by 20-40 m higher than interval of violation, gate valve is closed at the outlet from well annular space, and cement grout is pushed into interval of violation in design volume. Pipes shoe is lifted to the height where it is planned to install head of cement bridge, and excess cement mortar is removed by return circulation of liquid in annular space and pipe string. Pipe string is lifted or completely withdrawn. Technological exposure is performed for cement hardening. Depth of cement sleeve location is identified. Casing string is pressurised. Cement sleeve is drilled down to interval by 5-10 m below interval of violation. Repeated pressurisation of casing string is carried out. In case of string tightness, cement sleeve is completely drilled. In case of insufficient tightness of casing string, which as a rule occurs after quite considerable violations, repeated sealing of violation is carried out.

EFFECT: increased reliability of well casing pipe repair.

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