COMPOSITION AND METHOD FOR PREPARING AND USING HYDROPHOBIC EMULSION IN INTEGRATED WELL KILLING AND COMPLETION TECHNOLOGY Russian patent published in 2007 - IPC C09K8/42 C09K8/72 E21B43/12 E21B43/27 

FIELD: oil and gas production.

SUBSTANCE: blocking hydrophobic emulsion composition contains, wt %: heavy aromatic hydrocarbon solvent with density at least 1000 kg/m³ (thermal gas oil) or anthracene fraction, 20-25; oil-soluble emulsifier (Neftenol NZ or Sankor 9701), 2-5; 45.3% aqueous sodium nitrite solution, 23-25; 52.2% aqueous urea solution, 40-45; and aqueous calcium chloride solution with density not lower than 1400 kg/m³ - the rest. In a method of preparing this composition via mechanical mixing of components in a blade-type mixer, the latter is first loaded with above-indicated solvent, emulsifier, and sodium nitrite and urea solutions, after which the mixture is stirred for 15-20 min and then aqueous calcium chloride solution is added by small portions at stirring until emulsion with density at least 1200 kg/m³ is obtained. Unblocking hydrophobic emulsion composition contains, wt %: kerosene-gas oil fraction of petroleum hydrocarbons, 25-30; emulsifier, 5-7; aqueous hydrochloric acid with density at least 1170 kg/m³, 25-30; and aqueous calcium chloride solution with density at least 1400 kg/m³ - the rest. In a method of preparing this composition via mechanical mixing of components in a blade-type mixer, the latter is first loaded with kerosene-gas oil fraction of petroleum hydrocarbons and emulsifier, after which the acid is added by small portions at constant stirring and then aqueous calcium chloride solution is added in the same manner until emulsion with density at least 1200 kg/m³ is obtained. In integrated well killing and completion technology, blocking hydrophobic emulsion is first injected into annular space of well, well is closed and kept closed for 24 h, after which pressuring fluid is injected, volumes of emulsion and pressuring fluid being calculated according to presented formulae. In a well completing method following the well killing and involving creation of depression in formation by displacing pressuring fluid with a gas phase, completion of well is accomplished by injecting unblocking emulsion into well in a volume by two times superior to the volume of blocking emulsion, the two emulsions being destroyed in well bottom to release free-form nitrogen and carbon dioxide in volumes large enough to reduce level of pressuring fluid in well in order to provide required depression in formation. Destruction of emulsions proceeds at excess (at least 5 wt %) hydrochloric acid in reaction products, while temperature briefly rises to 300°C or higher to form microemulsions of solvents with emulsifiers in aqueous solutions of acid and sodium and calcium chlorides, which provide acid and heat actions of formation to clean and it and create hydrophobicity therein.

EFFECT: extended hydrophobic emulsion application area.

7 cl, 5 tbl