Perforating gun drop sub

摘要

A perforating gun assembly comprises a drop sub linking the firing head to the gun tube or tubes. The drop sub includes a 360° perimeter shaped charge explosive for severing pipe having an axial bore to accommodate a pass-through of the perforation charge detonation chord. Consequently, the severing tool is detonated by the traverse of a detonation wave along the chord length to disconnect the perforating gun prior to detonation of the perforation charges.

主权项

1. A method of detonating perforation charges in a well perforation gun comprising the steps of:
combining a serially aligned assembly including a detonation cord, a firing head, a shaped charge pipe cutting sub having a tube cutting explosive enclosed within a housing and a perforating gun; connecting said cutting sub housing to said firing head and to said perforating gun to unitize said assembly; providing an aperture through said tube cutting explosive along an axis thereof; providing a plurality of shaped charge perforating explosives along a length of said perforating gun; threading said detonation cord from said firing head through said tube cutting explosive aperture; continuing said detonation cord from said tube cutting explosive aperture along the length of said perforating gun in sequential detonation proximity with said perforating explosives; positioning said assembly at a predetermined location within a well bore; activating said firing head to initiate a detonation wave along said detonation cord; detonating said tube cutting explosive by said detonation wave to sever said assembly by cutting said housing; and, detonating perforating charges within said perforation gun by said detonation wave after severance of said assembly.