METHOD FOR DYNAMIC MATRIX ACID TREATMENT OF CARBONATE FORMATION Russian patent published in 2021 - IPC E21B43/27 E21B43/22 

FIELD: petroleum industry.

SUBSTANCE: method for dynamic matrix acid treatment of a carbonate formation includes cyclic consequent injection of portions of an acid composition in form of a water solution of hydrochloric acid thereto. Before injecting the acid composition, the target planned petroleum production rate is set, the total volume of the injected acid composition and solvent is determined depending on the target planned petroleum production rate of the borehole. Prior to injecting the acid composition, the surface of the near-borehole area of the formation is cleaned with a hydrocarbon solvent at a volume of at least 1.0 m³. The acid composition is injected and the perforation interval is closed, and, in the absence of injectivity, the acid composition is sustained opposite the productive interval for 1 to 2 hours. Cyclic injection of the acid composition starts at a volume of at least 1 m³ and increases with each subsequent cycle, alternating with injecting the hydrocarbon solvent. At the value of the target planned production rate from 2.6 to 3.5 t/day, 2 injection cycles are executed, at the value of the target planned production rate of 3.51 to 4.5 t/day, 2 to 3 injection cycles are executed, at the value of the target planned production rate from 4.51 to 5.0 t/day, 3 to 4 injection cycles are executed. A displacement fluid is then pumped at the volume of the pumping and production tubing plus 3 to 8 m³.

EFFECT: intensified petroleum production from boreholes operating carbonate formations with petroleum viscosity in formation conditions from 10 to 300 mPa*s, formation temperature up to 40°C and formation pressure not exceeding 6 MPa, distance to the oil-water contact no less than 4 m, improved filtration capacity properties and increased depth and area of dissolution channels, increased production rate.

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