Perforating methods - PetroWiki

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Bullet gun, abrasive, water jets, and shaped charges are perforating methods used to initiate a hole from the wellbore through the casing and any cement sheath into the producing zone. Bullet speed exiting the barrel is usually approximately 900 m/s (3000 ft/sec). Penetration in higher strength casing alloy pipe and harder formations is more difficult in most cases and not feasible in others.[1] When successful, the bullet creates a very round entrance hole but may often create a hole with sharp internal burrs. Figure 1 shows a bullet-perforated casing from a surface test.