METHOD OF THERMOFOAM-ACID TREATMENT OF NEAR-WELL ZONE OF CARBONATE RESERVOIR Russian patent published in 2017 - IPC E21B43/24 E21B43/27 C09K8/592 

FIELD: oil and gas industry.

SUBSTANCE: method of thermofoam-acid treatment of the near-well zone of the carbonate reservoir involves simultaneous pumping of acid and gas-generating compositions through two channels separated from each other with their subsequent pumping in the formation. An aqueous solution of urea with sodium nitrite is used as a gas generating composition containing, wt %: urea 28.4-38.4; sodium nitrite 18.2-27.6; water is the rest. As an acid composition, the aqueous solution of inorganic acid with additives is used. In this case, in the acid composition the aqueous solution of hydrochloric acid of 19-26% concentration is used as inorganic acid, 2-alkylimidazoline is used as additive in concentration of 5-15 wt % and phosphorous acid in concentration of 0.5-2.5 wt %. The volume of acid composition is1-3 m³ per linear meter of processing interval for vertical wells and0.1-0.2 m³ - for horizontal wells. The compositions are pumped by killing fluid or commercial oil in volume of cavity of pumped channels plus 3-5 m³ followed with well closure for 4-12 h for reaction of acid composition.

EFFECT: extended application field of the technology due to reagents resistant to high temperatures while reducing the processing costs by reducing the amount of used equipment.

4 cl, 2 ex