BASE FOR CALCIUM-FREE WELL-KILLING FLUID Russian patent published in 2012 - IPC C09K8/42 

FIELD: chemistry.

SUBSTANCE: invention relates to oil-and-gas industry, particularly killing of gas-condensate and oil wells with high formation pressure before conducting major overhaul at low climatic temperatures. The base for calcium-free well-killing fluid, containing a mixture of mineral salts, including a sodium salt, the sodium salt is sodium nitrate and the mixture contains a second salt in form of ammonium nitrate in ratio to sodium nitrate ranging from 1:1 to 1:2. The mixture can additionally contain sodium thiosulphate in amount of 5-33.3 wt % of the mixture of all components or urotropin or monoethanolamine, or sodium thiosulphate in amount of 0.5-0.7 wt % of the mixture of all components, as well as sodium chloride in amount of 5.5-6.4 wt % of the mixture of all components.

EFFECT: preparation of process solutions with density of not less than 1,35 g/cm from abundant materials for wells with high formation pressure and with different geologic and technical characteristics, wherein the freezing point of the fluid reaches minus 35°C, which enables its preparation and use in Northern conditions.

4 cl, 1 tbl, 16 ex