US Patent 7686082 Full bore cementable gun system

A completion method delivers cement to an open hole below a cemented casing. A gun or guns are run below a liner and a hanger and advanced into the cement before it sets up. With the gun and the liner surrounded in cement up to close to the hanger that supports the liner to the already cemented casing, the cement is allowed to set around the gun with no tubular surrounding the gun. The gun carries extra shot to enhance the perforation and can be fluid filled with clean fluid. Prior well cleaning such as with brine circulation is now limited to the region of the hanger and above. Production flow is through the perforations into the gun body allowing any residue of the explosive charge used to perforate to flow to surface.