| 摘要 |
<p>Downhole explosives, e.g. in a perforating gun, are detonated with a time delay between the actuation of the firing head assembly and the detonation of a downhole explosive device. A delayed detonation firing head has a housing (32), an actuation mechanism (11), e.g. a piston (50) carrying a firing pin (56), and a delay mechanism comprising a plurality of combustible columns (84,92,100,108,116) which are generally coextensive. Actuation of the firing head initiates a combustive reaction which travels sequentially from end to end of each column in turn, before being communicated to the explosive device (18). <IMAGE></p> |
