Detonation of shaped charges carried by a perforating gun creates a complex physical and chemical process that occurs within a very short time. During the process the shaped charge case usually disintegrates and is partially oxidized. The oxidization emits heat in addition to that of the explosive detonation and hence could eventually affect the post-detonation condition of the perforating gun.

Zinc and steel are common materials used in the manufacture of shaped charge cases, but their physical and chemical properties result in quite different impacts on the performance of the perforating gun and on its survivability. About 1,000 ms after detonation, a charge with a zinc case generates a pressure approximately 50% higher than one with a steel case. The zinc case creates an impulse about 30% higher and a temperature about 220°F higher. It results in more than 45% oxidation; for the steel case oxidation is less than 5%. Conversely, the zinc and steel case contributions to the detonation process are quantifiable in terms of energy. Such a quantified study is first reported in respect to perforating. Details can be incorporated into a recently developed gun survivability model for risk management in both new perforating product development and job execution. In field operations it can be used in post-perforating evaluation of formation damage.

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