US Patent 7600476 Geometric/mechanical apparatus to improve well perforator performance

Shaped charges that generate fan-like jets can produce slotted holes in rock formations. A shaped charge includes a case having on open front end, an external surface and a longitudinal axis, all transverse cross-sections of the case being bi-symmetric; an explosive material disposed in the case, the case including at least one opening extending from the external surface to the explosive material for initiation of the explosive material; and a liner disposed over the explosive material; wherein a pair of substantially identical longitudinal slots are formed on the external surface, the longitudinal slots being about 180 degrees apart.