METHOD FOR AIR-TIGHTNESS RECOVERY IN CASING ANNULUS OF WELL DRILLED IN GAS POOL OR IN DEPOSIT CONTAINING GAS Russian patent published in 2006 - IPC E21B33/13 

FIELD: oil and gas production industry, particularly to prevent annular gas flow.

SUBSTANCE: method involves cutting window in casing pipe within productive pool cap interval; removing casing pipe area occupying 20-80% of cap thickness; removing plugging material within above casing pipe interval to be removed; expanding well bore in casing pipe window so that final well bore diameter exceeds dimension of plugging material filtering area obtained by primary casing pipe plugging and is more than dimension of residual stress zone formed by primary and secondary cap penetration. The well bore is expanded in several stages so that well bore diameter is increased by not more than 10% at each stage and so that final well bore diameter exceeds dimensions of above residual stress zones for 10-40%. After that the expanded section is covered with lining and space behind the lining is plugged with non-hardening plugging material, for instance with visco-elastic composition based on polyacrylamide, hydrolyzed polyacrylonitrile or natural or synthetic latex or with hardening plugging material in which resilient material particles are added. The particles are made of rubber or are formed as gas-filled microspheres.

EFFECT: increased air-tightness of casing annulus.

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