DOWNHOLE ACTIVATED SYSTEM FOR PERFORATING A WELLBORE

摘要

2117085 9306336 PCTABS00021 This invention relates to a method and apparatus for perforating the formation (F) in a wellbore (W) wherein the wellbore is established for the production of hydrocarbons. The formation is perforated by explosive material carried in pistons (50) which are carried within either the pipe casing (60) or the collars or both and remain generally within the maximum outward profile of the pipe string so as not to interfere with the movement and placement of the pipe string in the wellbore. The pipe string may be rotated, reciprocated and circulated which enhances the ability of the installer to place the pipe string in a deviated or long reach wellbore. Once the pipe string is in place, the pistons may be deployed by one of several methods such that pistons mounted in openings in the peripheral wall of the pipe string move outwardly with sufficient force to move the pipe string way from the walls of the wellbore sufficient to form a complete annulus for cementing. Once the wellbore is cemented the explosive charges (671) in the pistons may be detonated to perforate the formation adjacent the piston. The charge may be particularly designed to focus the explosion so that an extensive perforation extends away from the pistons so that the formation is opened up for production of hydrocarbons.