NON-AQUEOUS, ACID-SOLUBLE, HIGH-DENSITY FLUIDS FOR WELL COMPLETION AND METHOD Russian patent published in 2015 - IPC E21B21/14 E21B43/22 C09K8/36 C09K8/82 

FIELD: oil and gas industry.

SUBSTANCE: method involves displacement of the first fluid on a hydrocarbon basis, which is present at a non-cased interval of a well shaft, with the second fluid, contact of the second fluid to acid natural formation fluid so that the third fluid is formed, where the second fluid contains aqueous liquid dispersed as a disperse phase in oily liquid, and surface active substance (SAS) based on amine and chosen so that the above contact performs protonation of at least some part of SAS with formation of the third fluid included in an emulsion containing oily liquid reversely dispersed as a disperse phase in aqueous liquid, where at least 40 vol % of any solid substances that do not refer to a proppant and are present in the fluid are water-soluble at pH that is lower than or equal to 6.5, and SAS has the above said structure. An underground well treatment system. The fluid containing a reversible invert emulsion containing an aqueous liquid dispersed as a disperse phase in oily phase and the above SAS.

EFFECT: improving destruction efficiency of a filter cake.

20 cl, 6 dwg, 3 tbl, 2 ex