Hydraulic Packer for Collar Cementing PGMC is applied for collar cementing and to ensure separation
of filtering and cementing parts of liners and isolation of gas-, oil- and water-bearing formations.
The packer PGMC consists of two devices combined in one body: a hydraulic packer and a cementing
collar. The collar part of the device is the system of mechanically interconnected bushes fixed on
shear bolts that overlap cementing slots and the entrance to the under-hose cavity. The design of
the packing part is similar to the design of PGP packer.
The packer works as follows: before cementing, a ball is dropped into the transport string and pumped
until setting down a seat. With pressure build-up to 4,0 MPa ± 10% bolts are sheared off and the
plug is moved down until bumping the shoulder thus opening liquid access to the valve system of
the device packer part. After that the pressure is dropped down to 0 and the valve system prepares
the packer to actuation. On subsequent pressure build up to 6-8 MPa the hose inflates separating
hermetically cementing and noncementing parts of the liner in the outer annular space. The following
pressure relief to 0 switches the valve system and shuts liquid access to the packer part of the device.
PGMC2 and PGMC4 packers work in the similar way, but they do not require pressure release for
preparation of the valve system for packer setting.
The next cycle of the pressure build-up to 16 (14,5; 14) MPa opening of cementing ports is performed. After mixing and displacing of cement slurry, the hollow cementing plug (together with the
top cementing plug) is set down to the seat and after the internal overpressure build up to 5 MPa it
closes cementing ports and fixes its position.