US Patent 7228906 Propellant ignition assembly and process

Method and apparatus for stimulating a subterranean formation that is penetrated by a well bore in fluid communication with the formation. At least one length of propellant is assembled with at least one shaped explosive charge that is aimed axially along the well bore toward the propellant. Detonation of the explosive charge ignites the propellant and any successive explosive charge positioned in the well bore. Detonation of the successive explosive charge ignites the next successive length of propellant and next successive explosive charge.