METHOD OF SELECTIVE TREATMENT OF PRODUCTIVE CARBONATE FORMATION Russian patent published in 2017 - IPC E21B43/27 E21B33/138 

FIELD: oil-and-gas industry.

SUBSTANCE: invention relates to oil producing industry. The method of selective treatment of productive carbonate formation includes the determination of specific injectivity of treatment interval, cyclic sequential injection therein of viscous material portions - VM containing the water solution of cationic surfactant that increases its viscosity upon contact with formation water and disintegrated upon contact with oil, and acidic compositions based on hydrochloric acid, followed by oil flush. Before each injection of VM into each treatment interval the buffer portion of reservoir or process water in the amount of 2-4 m³ is injected. VM is added by 10-20% of its volume of 22-24% aqueous solution of hydrochloric acid to obtain a viscoelastic composition - VEC. The volume of the first part of injected VEC is determined depending on the specific injectivity based on experimental work, after that the first portion of VEC is forced into the formation by acid composition in the form of water solution of hydrochloric acid containing the substances that improve the filtration characteristics of the acid composition in the volume 0.5-1.0 m³ per meter of the treatment interval for vertical wells, or 0.05-0.1 m³ - for horizontal wells. And the acid composition is injected in two portion, the first of which is injected in the volume sufficient for full displacement of the volume of the tubing and the annulus of the treatment interval, after which the downhole is left for technical exposure sufficient to structure VEC in the treatment interval. Then the second part of acid composition is injected, and then the second portion of VEC in the volume of 40-60% from the first portion of VEC, and the amount of acid composition flush is increased 2-4 times from the originally injected composition for vertical wells and 1.1-4 times - for horizontal wells, and then the acid composition is flushed by oil in the volume of tubing plus 3-5 m³.

EFFECT: invention provides a temporary blocking of reservoir intervals with high specific injectivity, efficient acidic treatment of rock, oil production increase.

2 cl, 1 tbl