METHOD FOR LARGE-VOLUME SELECTIVE ACID TREATMENT OF BOTTOMHOLE FORMATION ZONE IN CARBONATE RESERVOIRS Russian patent published in 2021 - IPC E21B43/27 E21B33/138 C09K8/74 

FIELD: oil industry.

SUBSTANCE: invention relates to the oil industry, in particular to methods of influencing the bottomhole zone of a formation composed of carbonate rocks or terrigenous rocks with a carbonate content of more than 15%. In the method of large-volume selective acidizing of the bottomhole formation zone in carbonate reservoirs, including the injection into the well of a solvent, an acid composition and a diverter fluid with an optimal flow rate and an optimal ratio of the diverter volume to the acid composition volume, the core is first taken, the geological and physical characteristics of the formation and features of the void space are determined.

Filtration studies of the core are carried out by pumping the chemicals used through the core samples to determine the type and concentration of the acid composition, types of solvent, diverter and modifying additives. Next, the design of a large-volume selective acid treatment of the bottomhole formation zone is made using a computer program and acid treatment of the bottomhole formation zone is carried out by injecting in any sequence with a flow rate of 0.3-2.0 m³/min of a solvent, acid composition with a specific volume of 3-20 m³ per 1 perforated interval meter and diverter fluid. A mutual solvent or a hydrocarbon solvent is taken as a solvent, a modified inhibited hydrochloric acid of grade PAKS-1M (a,b) and grade KSMD-1 M (a,b) as an acid composition, and a mixture of the reagent TATOL/TATOL®-KVS 1-3 with the reagent TATOL/TATOL-GEL® (TG) is used as a diverter.

EFFECT: increasing efficiency of large-volume selective acid treatment (LSAT) of wells in carbonate treatment reservoirs, creating a branched network of fluid-conducting channels in the form of a wormhole throughout the perforated formation thickness, preventing the formation and destruction of sludge complexes.

3 cl, 12 dwg, 3 tbl