CASING STRING BACK CEMENTING METHOD Russian patent published in 2020 - IPC E21B33/14 

FIELD: oil and gas industry.

SUBSTANCE: invention relates to oil and gas industry, namely to a method for cementing a casing string in a well shaft with back circulation of a grouting mortar. Tool is lowered to the borehole of the casing string. Grouting mortar is pumped into space between casing string and well bore. Volume of grouting mortar is taken from preliminary calculated volume of space between well bore and casing string. At that, after lowering into well shaft of casing pipe string, technical fluid is pumped inside casing string in amount equal to volume of inner space of casing string of pipes. In addition, a ball valve is installed between the cementing head and the driving drill pipe. Rotary cementing head is used as cementing head. During pumping of grouting mortar with permanent rotation of casing string reciprocation is carried out to height of 1–1.5 m at a rate of not more than 1 m/s times until completion of cementing process. Casing string is continuously rotated clockwise at 10–12 rpm using rotor of drilling rig or top power drive. Rotation of the casing string creates vortex flow of the grouting mortar. Inverse circulation of borehole fluid is controlled through rotary valve of cementing head.

EFFECT: expansion of technological capabilities and increase the efficiency and reliability of the process due to more complete replacement of drilling fluid by grouting mortar behind the casing to obtain a continuous and hermetic cement sheath along the entire length of the casing.

1 cl, 1 dwg