METHOD OF PREPARATION FOR CEMENTING OF WELLS DRILLED USING INVERT-EMULSION DRILLING MUD Russian patent published in 2012 - IPC E21B33/13 C09K8/40 C09K8/467 

FIELD: mining.

SUBSTANCE: method of preparation for cementing of wells drilled using invert-emulsion drilling mud is characterised by the fact that casing column is lowered into the well and washed with invert-emulsion drilling mud; four flush fluids are pumped subsequently into the well: parting-displacement fluid, solvent fluid, washing fluid and displacement fluid, and their further forcing to behind-the-casing space with well cement mortar and flushing fluid with their complete displacement from the well and installation of well cement mortar in behind-the-casing space at the required interval; at that, mixture of invert-emulsion drilling mud with formation water and with organic solvent in volume ratio of (4-6):(2.5-5.5.):(0.5-1.5) respectively is used as parting-displacement flush fluid; mixture of organic solvent, tall oil and 40% of water solution of sodium hydroxide in volume ratio of (9.0-9.6):(0.2-0.5):(0.2-0.5) respectively is used as solvent flush fluid; water solution of detergent also acting as demulsifying agent with 0.5-4% mass concentration is used as washing flush fluid; light-weight cement slurry with density of 1.35-1.45 g/cm³ is used as displacement flush fluid. At that, rheological characteristics: plastic viscosity and dynamic shear stress of solvent flush fluid are higher than rheological characteristics of the previous one - parting-displacement fluid, and further washing flush fluid, and density and rheological characteristics of displacement flush fluid are higher than those of the previous one - washing flush fluid.

EFFECT: increasing the volume of dense contact of cement stone with enclosing surfaces.

4 cl, 1 ex, 3 tbl