Liner is a part of the casing string located at a length from the well face to the previous casing string section. Liners descent into the well on the drill string and connect to it with the help of the devices - liner hangers (disconnectors). A lot depends on the reliability of this assembly, because the elimination of an accident may take a plenty of time.
Since 2012, CJSC Scientific and Production Enterprise "RNGI" has successfully mastered the production and introduced liner hangers with a diameter of 127 to 340 mm. PH-R1 hangers were used in construction of exploratory wells of OJSC "Grozneftegaz" in the territory of the Chechen Republic. The development took into account the features of the local formation. Hangers was mainly used for intermediate liners of the main well bore, i.e. the entire casing string gradually descended on these devices. Lowering of hangers was carried out in one step, i.e. the entire drilled casing string was covered from the face to the previous casing string with its overlap not less than by 100 meters.
The process of cementing of the liners of all diameters is the same. In the lower part of the liner the pad device and CKOD are installed. During the casing string lowering, preparatory works are carried out, including: preparation of the grouting fluid for the upper and lower portions of the cement slurry, preparation of buffer structured liquid based on MBP-SM, preparation of Floatoreagent-oxal based washing liquid, weighted drilling fluid (WDF), placement of plugging equipment, injection and blowing lines. The density of liquids is selected individually, so that there is no differential pressure at the face at the moment of setting the cementing slurry.
After the liner is lowered, the cementing head produced by CJSC Scientific and Production Enterprise "RNGI" is fixed to the drill pipes. The head is fitted with a ball and an upper discharge plug with start devices.
The injection lines are crimped, after which sequential pumping down of the washing liquid, structured buffer liquid, first and second portion of the cement slurry into WDF well is started. Then the upper plug, which was in the head, is moved down and it is squeezed with the liquid in the following sequence: Hydrocarbon base solution (HBS), WDF, HBS. The liquid and the solution below the plug, as it is being squeezed, pass through the drill pipes, then through the hanger and the lower hollow plug come into the tube side of the liner. A seat bushing (from above) and the lower displacement plug are fixed on calibrated breaking pins in the liner hanger. Upon reaching the hanger by the top discharge plug, it passes through the seat bushing and joins the lower displacement plug; the pressure in the system is increased by 40-50 kg/cm2 and the pins of the lower displacement plug are cut. After that, the upper and lower plugs are pushed down superseding the cement slurry into the annular space. After the cut is done, squeezing is made with an estimated amount of HBS, then the ball is lowered and squeezed until it lands on the seat bushing in the hanger. After the touchdown, the pressure increases by 80-100 kg/cm2 and the pins of the seat bushing are cut off, the seat bushing is lowered in the hunger up to the stop, opening the washing windows. The overwinded cement slurry is washed-out according to the work schedule. After setting the slurry with right rotation, detach the hanger from the liner, with the external hanger parts remaining in the well as its component part.
In case of a leakage in the maternal column, there is a possibility of liner elevation using a male hub supplied along with each hanger. Therewith, it is allowed to unload the extensible part of the casing string to the mounting seat, as it is located below the washing windows in the hanger, i.e. is in cement stone. Also, the advantages of PH-R1 hangers include simplicity, compactness, the possibility of reusing the disconnector extracted part.