COMPOSITION FOR REMOVING BARIUM AND CALCIUM SULPHATE SCALING AND METHOD FOR APPLICATION THEREOF Russian patent published in 2021 - IPC C09K8/528 

FIELD: petroleum industry.

SUBSTANCE: invention relates to the petroleum and gas industry, namely to a composition and method for application thereof for treatment - cleaning of the bottom and the bottom-hole formation zone (BHFZ) of a borehole from barium and calcium sulphate scaling, and can also be applied for destroying the mud cake in deposits wherein productive formations are drilled and opened on weighted drilling muds containing barium sulphate. The composition for the treatment of the bottom-hole formation zone from barium and calcium sulphates scaling comprises ethylenediaminetetraacetic acid as a complexing substance, potassium hydrate as an alkali metal hydroxide, the surface-active agent "Neftenol VUPAV" and water, at the following ratio of components, % wt.: ethylenediaminetetraacetic acid 25.0, potassium hydrate 20.0, "Neftenol VUPAV" 0.1 to 2.0, fresh water the rest. Also described is a method for treatment of the bottom-hole formation zone, including flushing the borehole, injecting an active reagent, sustaining said reagent for reaction with bridging substances, collecting the spent composition, removing the reaction products from the formation, and putting the borehole into operation, the process of injection and collection of the spent active reagent is executed incycles, until the natural permeability of the bottom-hole formation zone is restored. After collection, the spent active reagent is regenerated by adding a solution of an acid. A composition containing ethylenediaminetetraacetic acid, potassium hydrate, "Neftenol VUPAV" and fresh water in the above amount is used as an active reagent, taken diluted with water in a ratio from 1:0 (without dilution) to 1:40 by weight.

EFFECT: provided dissolution and extraction of the bridging agents from the BHFZ – barium and calcium sulphate scale, possibility of reusing the active reagent, elimination of the corrosive and aggressive effects on surface and downhole equipment, since the proposed alkaline solutions are stable in storage and do not have a corrosive effect on equipment made of carbon and stainless steels in the used concentrations, reduction in the risk of conducting works in terms of safety regulations, since strong mineral acids are not used in the proposed method, increase in the effectiveness of treatment of the BHFZ represented by carbonate rocks or those having carbonate cement, since the active reagent dissolves CaSO₄ and CaCO₃ as well as barium sulphate.

2 cl, 1 tbl, 7 ex