201633478-Perforating-Gun-Types.pptx - Explosives used in...

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Explosives are categorized according:
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To the ease with which they are detonated
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The speed with which they react
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The combustion pressure that they generate
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Low explosives
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low combustion pressures
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react at velocities in the 500- to 1500-m/s range
Explosives used in Perforating

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Gunpowder is the most common example
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reaction rate depends on the grain size, temperature,
degree of confinement, and packing density
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High explosives
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3000 to 9000 m/s and generate high pressures
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subdivided into primary high explosives (or initiator
explosives) and secondary high explosives
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Primary high explosives
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generally high-density compounds of metals and nitrogen
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detonate when subjected to a heat source
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purpose of primary explosives is to initiate the more
powerful and less sensitive secondary high explosives

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Secondary high Explosives
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highest reaction rate (7000 to 9000 m/s) and generate
the highest pressures
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most secondary explosives are so insensitive to
detonation that they can be melted, cast, and machined
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These explosives are generally organic compounds of
nitrogen and oxygen - when a detonator initiates the
breaking of the molecules' atomic bonds, the atoms of
nitrogen lock together with much stronger bonds,
releasing tremendous amounts of energy

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Typical secondary explosives include:
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RDX
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HMX
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PS (picryl sulfone)
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HNS (hexanitrostilbene)
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Composition B (60% RDX, 40% trinitrotoluene)
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Amoniumnitrate (fertilizer, also used in seismic
operations)

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When a perforating gun is fired:
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an electrical current sets off the primary explosive in the
blasting cap, which in turn sets off an RDX base or booster
charge within the cap.
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This in turn detonates the Primacord (5 g of RDX per foot)
used to carry the detonation to the individual charges.
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As the pressure wave reaches the shaped charge, it
detonates fine-grained RDX primer in the tunnel at the base
of the charge casing.
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Detonation of this primer in turn detonates the main body of
RDX (generally with 1% wax binder) and the wave achieves
full speed and pressure as it bears on the metallic liner.
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This pressure collapses the liner, forming the "jet" of high-
speed material that strikes the target at high pressure and
does the penetrating.