A polished bore receptacle (PBR) is another class of wells packers category that can be utilized in place of a permanent packer. The PBR accepts an inner seal assembly that provides a seal off between the tubing and the PBR Figure (1) and (2). The Polished Bore Receptacle is generally employed in a casing liner completion, where it’s installed as an essential part of the liner hanger system. While running the completion tubing string, the seal assembly, like to that employed on a permanent packer, is run on the end of the tubing string. There are 2 options for the seal assembly
- Firstly, to be latched onto the PBR,
- Secondly, left floating to permit tubing movement.
For the bore of the seal assembly, it shall be equal to the ID of the casing liner below. This requirement is to give a free passage of electric wireline or slickline. Typically, the Polished Bore Receptacle radius is larger than the radius of the liner below it. Most workover instruments and operations can be run through the PBR with ease. In completion, the sealing characteristics and capabilities between the tubing and PBR are the same as between the tubing and packer body of a permanent packer completion.
Disadvantages of Polished Bore Receptacle
The Polished Bore Receptacle has a drawback that the permanent packer does not. The position of the PBR is fixed in the hole, typically in the liner hanger, which may be several hundred meters above the zone of interest. As mentioned previously, one of the applications of the packer system is to secure the casing string from the corrosiveness of wellbore fluids by providing a seal off the tubing annulus. Since the PBR is set at the uppermost of the liner string, the total length of the liner string will be exposed to potentially corrosive fluids when the well is produced. For example, in a well with a 150-meter liner and a producing zone 15 m in length, the entire length of the liner will be exposed to the effect of the product fluids, as opposed to a normal installation in which the packer would be positioned exactly above the pay.
Running Of PBR
The polished bore receptacle (PBR). Figure 3 shows a typical conﬁguration. The seals are multiple (often chevron seals) and connected to the male, top section. The seals can therefore be recovered during top-hole workover operations. We are able to run the PBR in two trips or run pinned together with shear pins or more normally a shear ring. When the top section is run separate from the polished bore, the seals will need protection. This is easiest to achieve with TBG centralization just above the seals – this also will help engage into the PBR. Some PBRs contain a shearable cover to protect the seals as they are run. With a PBR, debris in the annulus may settle on the seals. A well-designed PBR geometry and debris barriers above the seals can lower this risk.