ACID WELL BOTTOM ZONE TREATMENT METHOD Russian patent published in 2006 - IPC E21B43/27 

FIELD: oil industry, particularly to isolate thief zones in injection wells or water inflow zones in production wells drilled in carbonate reservoirs.

SUBSTANCE: method involves cyclically injecting hydrochloric acid solution, sulfur-containing aqueous mixture in well bottom zone and removing reaction products from well bottom zone. Desulfurization by-product obtained during sour oil preparation is used as above mixture. The by-product is 3-6% sulfur suspension in water. Above suspension is preliminarily injected through well to provide 0.8-1.0 MPa pressure increase in comparison with initial injection pressure. During cyclic hydrochloric acid solution injection 13-15% hydrochloric acid solution is forced with oil, wherein the solution has pressure of 1-2 MPa and taken in amount of 0.4-0.5 m³ per 1 meter of productive reservoir depth. Then 1.5-2.5 hour technological time delay is executed and oil in well is substituted for 13-15% hydrochloric acid solution. 13-15% hydrochloric acid solution under 1-2 MPa pressure and taken in amount of 0.9-1.1 m³ per 1 m of productive reservoir depth is injected and 3.5-4.5 hour technological time delay is executed. Then 13-15% hydrochloric acid solution is injected in hydro-impulse regime in 5-7 cycles. Each cycle includes injection operation lasting for 0.8-1.2 min, 4-6 min time-delay and solution holding under 1-2 MPa pressure. Then well is flushed with oil and reaction products are removed from the well by swabbing operation.

EFFECT: increased efficiency of highly-permeable zone isolation in carbonate reservoir.

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