WELL STAGE CEMENTING METHOD Russian patent published in 2017 - IPC E21B33/14 

FIELD: oil and gas industry.

SUBSTANCE: according to method, two cement stage collars provided with sleeves in the form of dampers are mounted oncasing string at a distance of at least one tube, before cementing of the first stage. These dampers are made suitable for opening and closing radial holes depending on pressure variation inside the casing string. Flexible elastic protection in the form of a sleeve connecting the inner cavity of the casing string to behind-the-casing annular cavity is fixed at the lower collar. Packer device is positioned behind the cement stage lower collar. Portion ofviscoelastic separator is pumped into the process fluid volume to squeeze the grout mix during cementing of the first stage, with a view to its subsequent disposition in the interval from above the upper cement stage collar to below the lower cement stage collar. Packing of annular space is carried out after plug seating into a shoe. Radial holes of cement stage upper collar are opened. Batched volume of process liquid with viscoelastic separator and shutoff balls positioned inside the volume are used during cementing of the second stage. After the radial holes of the lower collar are opened by increasing pressure and mixing zone is displaced into annular cavity of behind-the-casing space, the radial holes of the cement stage lower collar are closed by shutoff balls. Subsequent increase in pressure causes the operation of the cement stage lower collar to radial hole closure.

EFFECT: free passage inside the casing string after the completion of well cementation is ensured.

2 cl, 1 ex, dwg 10