METHOD FOR PLUGGING OF LOST-CIRCULATION ZONES Russian patent published in 2014 - IPC E21B33/138 

FIELD: oil and gas industry.

SUBSTANCE: suggestion refers to remedial cementing of wells at oil deposits, in particular, to plugging of lost-circulation zones, methods of well casing recovery. Method of los-circulation zone plugging includes running-in of cementing string to plugging space. Two components of cementing mixture are pumped in sequence through cementing string until the first component egresses fully in annular space through an open end of cementing string and they are squeezed further by displacement liquid. At that before running-in of cementing string to plugging space packer and cutting sleeve consisting of body with end-to-end channel of circular section with side port and spreader, housing, driving washer are installed additionally. Cementing string is run-in upstream the plugging space per 30 m. Two components of cementing mixture are pumped in sequence until the first component egresses fully in annular space through an open end of cementing string. Packer seating is performed. Squeezing of the second component is continued through cementing string and pressure is increased simultaneously up to 2 MPa, at that driving washer can move and the first component egresses through spreader under pressure to flow of the second component. Components of cementing mixture are squeezed. At that squeezing of the first and second components is made by batches 3-4 times at volume ratio of the components in batches from 1:4 up to 1:1 respectively starting from 1:4 and completing with 1:1. When the last batch of cementing mixture components egresses from the cementing string squeezing is completes, and squeezing of cementing mixture components is made by displacement liquid considering that a cement plug equal to 20 m is to be left in the well. At that stock oil is used as displacement fluid.

EFFECT: improving efficiency of remedial cementing works due to increase of sweep depth, formation of homogenous and dense cementing mixture and due to equal distribution and mixing of pumped components.

1 dwg, 2 tbl, 1 ex