HYDROCHLORIC ACID COMPOSITION FOR REMOVING FILTER CAKE FROM BOTTOMHOLE FORMATION ZONE Russian patent published in 2010 - IPC C09K8/72 C09K8/78 

FIELD: chemistry.

SUBSTANCE: invention relates to oil and gas production, specifically to compositions for acid treatment during well development and exploitation, and can be used to stimulate flow of oil or gas from the formation due to chemical effect, including dissolving carbonate rocks, breaking down and dispersing clay and polymer-clay components, barite filler, covering bottomhole formation zone (BFZ). The hydrochloric acid composition for treating and removing filter cake from a bottomhole formation zone contains the following, in wt %: hydrochloric acid 10-25; surfactant 0.05-0.5; carbamide nitrate 0.5-3.0; sodium bisulphate 1-4; chelating agent - substance selected from a group of trilons - sodium salts of ethylene ethylene diaminetetra-acetic acid 0.1-1; corrosion inhibitor 0.2-1; water - the rest.

EFFECT: providing the composition the capability of dissolving not only the carbonate matrix of the reservoir rocks, but also to efficiently break down and disperse the filter cake together with the natural clay component and the polymer-clay component, reinforced with barite particles, where the filter cake is formed at the bottom of the well and inside bottomhole formation zone.

3 cl, 3 tbl, 1 ex