PROCEDURE FOR RECOVERY OF TIGHTNESS IN FLOW STRING AND ELIMINATION OF BEHIND-CASING FLOWS Russian patent published in 2014 - IPC E21B33/138 

FIELD: oil and gas industry.

SUBSTANCE: in procedure of recovery of tightness in flow string and elimination of behind-casing flows involving determination of injectivity of failure, preparation of polymer-cement mortar containing mixing of cement and liquid consisting of acetone-formaldehyde resin, sodium hydrate and water, its pumping in by the flow string until alignment of liquid columns in the flow string and annulus space, raising the flow string to the safe height and displacement in the interval of leakiness of the flow string or the destructed cement ring with the casing valve closed with further holding till hardening; at that, with low and medium values of injectivity polymer-cement mortar is prepared with the fluid-cement ratio 0.73-0.87 and filtrate separation of at least 40% of mixing fluid, it is injected by the flow string and displacement of polymer-cement mortar is carried out cyclically by successive increase of pressure up to the acceptable limit pressure for the flow string and its decrease to stable value; at that, cyclic displacement is performed before reaching the acceptable limit pressure for the flow string and its stabilisation at this value, pressure is reduced by 2 MPa below the acceptable pressure for the flowing string and the well is closed for hardening of polymer-cement mortar.

EFFECT: increased efficiency of remedial cementing works for recovery of sealing of flow string and elimination of behind-casing flows at low and medium values of injectivity failure due to use of polymer-cement mortar with advanced filtrate separation, high mobility and low viscosity.

2 tbl