Completion perforating enables large, long strings of guns to be installed with the completion and fired with the right completion fluid in place for immediate cleanup and production. After firing, the guns are normally dropped into the rathole or left connected to the completion, in which case production is through perforated tailpipe. Additional hardware such as automatic drop subs, shock absorbers, valves, and debris subs can be included in the string.
Perforating guns can be run before the completion to position guns that are larger than the ID of the tubing. In vertical or deviated wells, guns can be hung off in the liner using a MAXR anchor. When the guns are fired, the anchor automatically releases to drop the guns into the rathole. In a monobore completion, the guns and anchor can also be recovered to the surface. In horizontal wells, guns can be placed in the horizontal section before the upper completion is run by using disconnect devices run below coiled tubing or drillpipe.
The CWOK process uses underbalance, dynamic underbalance (PURE), or extreme underbalance perforating for clean perforations, then removes the guns without killing the well.