METHOD OF REPAIR-INSULATION WORKS IN OIL AND GAS WELL Russian patent published in 2020 - IPC E21B33/138 E21B43/22 E21B43/32 C09K8/504 C09K8/508 

FIELD: oil, gas and coke-chemical industries.

SUBSTANCE: invention relates to oil and gas industry, in particular, to repair and insulation works in oil and gas wells performed for elimination of behind-the-casing flows of fluids, limitation of water influxes, isolation of water-bearing horizons and improvement of well operation efficiency. Method is characterized in that pumping of aqueous solution of calcium chloride with concentration of 10–12 % and aqueous solution of sodium sulphate with concentration of 13–15 % is performed at casing pressure, not exceeding 70 % of allowable internal pressure on pipes of the casing string. Well is maintained at rest for 15–30 minutes until the formation of CaSO₄ precipitate as per the specified chemical formula. Then water solution of polyacrylamide with concentration of 0.5–3 % is pumped to create effect of attachment of isolated interval at the same value of pressure with further holding of well for 2–7 hours till completion of gel formation process.

EFFECT: technical result is higher tightness of annular space of oil and gas wells, isolation of formation fluids arriving to perforations from underlying or overlying beds on fractures in cement stone and gaps on contacts "column-cement-rock", and shorter time for formation of plugging substance when filling channels of overflow in well.

1 cl, 1 ex, 1 dwg