Type PR and CR Liner Packers
The type PR and CR liner packers are weight set packers applied by the C-2 setting tool packer setting dogs. The PR packer differs from the CR in that it has hold down slips which prevent upward movement due to pressure from below. The type pr packer may be set before all cement is displaced so the remaining cement may be squeezed into the liner-open hole annulus.
Types PRL and CRL are identical to PR and CR except that the sealing element is rubber with a lead retaining ring at each end. Type PRL and CRL are recommended for maximum depths and temperatures.
Any of the packers will provide a pack-off between the top of the liner and the casing.
The packer isolates the open hole and prevents reverse circulating pressure from acting on formation, thus preventing formation breakdown and loss of cement slurry.
Stuckey highly recommends the use of a liner packer on offshore wells where safety is a primary consideration.