drop-off gun

1. n. [Perforating]
A perforating gun assembly designed to be detached from the tubing or running string after firing. The detached assembly can then drop, or be pushed, to the bottom of the well depending on deviation and production requirements. Drop-off gun assemblies often are used in underbalanced perforating applications, eliminating the need to kill the well to recover the spent gun assembly. In such cases, the wellbore will be designed to accommodate the spent gun assembly without compromising productivity, while recovery of the gun assembly may be planned during subsequent workover operations. The drop-off mechanism may be automatic and actuated at time of firing, or be actuated after firing.