WELL CEMENTING METHOD UNDER CONDITIONS OF ABNORMALLY LOW RESERVOIR PRESSURES Russian patent published in 2022 - IPC E21B33/14 C09K8/42 

FIELD: oil and gas industry.

SUBSTANCE: invention relates to the oil and gas industry and can be used for cementing casing strings in wells for various purposes. The method for cementing a well under conditions of abnormally low formation pressures includes lowering a casing string with a shoe and a sleeve into the well, which is installed above the roof of the absorbing formation. The method also includes forcing the cement slurry with a displacement fluid. When the cement slurry is forced through, a low-density cement slurry is pumped into the annular space through the bottom of the well by cementing the lower part of the production casing string with overlapping the absorption zone - up to the sleeve and subsequent injection of weighted cement slurry to cover the lower part of the casing string. Next, the upper part of the production string is pumped into the annular space above the sleeve to the wellhead. Cementing of the casing string is carried out with cement slurries of different densities. The wellhead is equipped with at least two breathing tubes - tubes installed on the side of the conductor, for communication with the annulus of the well casing string. As a coupling, a coupling with annular self-sealing packer, flowing from the bottom up, is used - a basket. As a cement slurry of reduced density, a cement slurry with a specific gravity of =1.55-1.80 g/cm³ is used. As a weighted cement slurry - grouting slurry with a specific gravity = 1.81-1.92 g/cm³. For cementing the upper part of the production casing - cement slurry with a specific gravity = 1.3-1.55 g/cm³. For cementing the upper part, the cement slurry is injected through breathing tubes, from top to bottom with a pressure not exceeding the allowable pressure on the formations. Cement slurry is pumped from bottom to top and from top to bottom after preliminary lifting of the casing string from the bottomhole by 0.2-1.0 m with rotation of the casing string, controlling the weight of the casing string and torque to prevent the casing string from surfacing and violating the integrity of its threaded connections, respectively.

EFFECT: increasing the reliability and efficiency of filling the annulus of the casing string with cement mortar.

2 cl