GB617817A - Improvements in or relating to gun perforators particularly for perforating well casings - Google Patents

Abstract

617,817. Perforating well casings. BYRON JACKSON CO. Oct. 9, 1946, No. 30132. Convention date, Oct. 13, 1944. [Classes 9 (i) and 92 (ii)] [Also in Group XXII] A gun particularly for perforating well casings comprises a gun-bore, a projectile in the bore being driven rearwardly to detonate a propelling charge behind the projectile, when an explosive charge in the muzzle end of the bore is ignited. The body 10 of the gun perforator is lowered into the well by a cable through which an electrical conductor 12 passes to an adapter 11 where it is connected to a second conductor 14 leading to an electrical fuze 15 arranged to ignite an explosive fuze element 16 placed in a longitudinal groove 17 in the body 10. The groove 17 extends across the muzzles of a number of laterally directed coplanar gunbores 19 containing a powder charge 20 behind a fluid-tight seal 22 in front of which is a bullet 21. The fuze element 16 extends in a loop 23 into the muzzle of each gun-bore where it is held by a flat wedge 25. When ignited by the electrical fuze 15, the fuze element 16 explodes almost instantaneously forcing the bullets 21 back against the powder charges 20 to detonate the charges. The fuze element 16 may be carried straight across each muzzle instead of being looped as described. Penta erithritol tetranitrate may be used as the core of the fuze element 16. Alternative fillings are " Primacord," " Mericalcord " and " Cordeau." The cross-section of the gun body 10 may be circular or rectangular. Modifications of the arrangement of the gun bores 19 in the body 10 are described. Additional detonating elements may be placed in the muzzle of each gun bore. To increase the force of the detonating explosive each muzzle may be sealed with a quick-drying cement. One modification has detachable gun barrels held by snap rings in sockets in the body of the apparatus. In the modification shown in Fig. 9 an explosive charge 40 is placed in the bore 19f in front of the bullet 21 and sealed by a disc 41. A longitudinal hole 42 intersects the bores 19f and is filled with a powder ignited by an electrical fuse 15f. Screw plugs 44 having transverse passages 45 are screwed into the hole 42 immediately above and below each bore 19f to prevent dissipation of the energy of the explosive 40 when it is exploded.