METHOD OF BOTTOMHOLE ACIDISING Russian patent published in 2010 - IPC E21B43/27 

FIELD: oil and gas production.

SUBSTANCE: method involves injection of acid system - acetic acid ester and aqueous hydrochloric acid - into formation, process well holding to produce acetic acid in the well and reaction of mixed acids and deposit rock, putting into the operation; and the well and bottomhole basin are cleaned up of asphalt-resin-paraffin deposits by flushing-out in a mutual solvent either alone, or mixed with acetic acid ester; injection of the acid system is followed with driving with the acid system additionally containing the mutual solvent in the ratio of acetic acid ester to the mutual solvent to inhibited hydrochloric acid equal to 1:0.5:3.5, the mutual solvent is presented with butyl alcohol or a butyl alcohol by-product recovered at the rectification stages with boiling temperature within 40-110°C, said acetic acid ester is ethyl acetate or butyl acetate, 3-15% aqueous inhibited hydrochloric acid, the entire scheduled amount of the latter in injected in two portions every hour.

EFFECT: greater radius of a processed formation interval, cleaning-up of the basins from ASPD, higher penetrability of the acid composition in the low-permeable layers, more complete removal of the spent solution and reaction products from the acidised zone, restoration and increasing natural permeability of the carbonate basins.

6 tbl, 1 dwg