WELL KILLING METHOD Russian patent published in 2006 - IPC E21B43/12 

FIELD: oil and gas industry, particularly to perform processing operations in wells, namely for well killing and perforation, for downhole processing equipment replacement or to process injection wells.

SUBSTANCE: method involves filling well killing fluid, namely aqueous mineral salt solution, in well bore, wherein the aqueous mineral salt solution includes double or triple salt systems of potassium chloride with sodium and/or magnesium chloride and target additive. Method of well killing solution preparation involves solving above salts in water supplied from oil treatment plants or in Cenomanian water having temperature of not less than +40°C and precipitating the obtained solution. Above solution is prepared in two stages. At the first stage the salts are solved until solution temperature reduction to obtain temperature of not less than +30°C and solution is precipitated for 20-30 min. The solution obtained at the first stage and having density of 1.2-1.2 tn/m³ is injected in well in amount necessary and enough for hydraulic column creation in well bore above productive reservoir top. At the second stage the precipitated sediment is solved and precipitated. The solution obtained at the second stage and having density of 1.05-1.2 tn/m³ is injected in well to fill the well up to well mouth. The double and triple salt systems are selected from group containing enriched carnallite, carnallite ore, grinded sylvinite, sylvinite ore and potassium chloride flux. Cenomanian water is produced from well having temperature of not less than +40°C. The target additive is oil-and-gas bearing layer clay swelling inhibitor, namely nitrildimethylphosphonic acid taken in amount of 0.01-0.05% by solved salt weight.

EFFECT: increased well killing efficiency with aqueous mineral salt solutions along with maintaining reservoir properties and reduced power inputs.

4 cl, 8 ex, 2 tbl