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Disclosed is a casing conveyed perforating apparatus and method for externally perforating a wellbore casing. The perforating apparatus is attached to the outside of the casing and is conveyed along with the casing when it is inserted into the wellbore. The perforation is accomplished using two grou

Disclosed is a casing conveyed perforating apparatus and method for externally perforating a wellbore casing. The perforating apparatus is attached to the outside of the casing and is conveyed along with the casing when it is inserted into the wellbore. The perforation is accomplished using two groups of charges, which are contained in protective pressure chambers. Each pressure chamber is positioned radially around the outside of the wellbore casing. The pressure chambers form longitudinally extending ribs, which conveniently serve to center the casing within the wellbore. One group of charges is aimed inward in order to perforate the casing. A second group is aimed outward in order to perforate the formation. In an alternative embodiment, only one group of bi-directional charges is provided.

대표청구항 ▼

1. An apparatus for perforating a subterranean earth formation through a wellbore lined with casing comprising:a cylinder longitudinally secured on said casing, said cylinder having an inside surface, an outside surface, and two ends; an end cap secured at each end of said cylinder fluidly isolating

1. An apparatus for perforating a subterranean earth formation through a wellbore lined with casing comprising:a cylinder longitudinally secured on said casing, said cylinder having an inside surface, an outside surface, and two ends; an end cap secured at each end of said cylinder fluidly isolating a chamber from all wellbore fluids, said chamber defined by said inside surface of said cylinder and said end caps; a first explosive charge being disposed in said chamber, said first charge being oriented toward said casing; and a second explosive charge being disposed in said chamber, said second charge being oriented toward said formation, wherein said first and second charges are contained within a single charge capsule. 2. The apparatus of claim 1, further comprising:a carrier having at least one U-shaped channel defined thereby, said U-shaped channel adapted to receive said cylinder therein; a pair of clamps, each of said clamps having a profile adapted to receive and hold a mating profile on each of said end caps. 3. The apparatus of claim 2 wherein portions of each of said profile of said clamp and mating profile on each of said end caps have substantially flat portions which engage each other to prevent the rotation of said cylinder within said carrier.4. The apparatus of claim 2 wherein at least one of the cylinder, end caps, carrier, and clamps are at least partially constructed of composite materials.5. An apparatus for perforating a subterranean earth formation through a wellbore lined with casing using a plurality of explosive charges, comprising:a plurality of hollow cylinders, each having an inside surface, an outside surface, and two ends; an end cap secured at each end of each of said plurality of cylinders, said end caps fluidly isolating each of said cylinders to define a chamber from all wellbore fluids therein, said chamber in each defined by said inside surface of said cylinder and said end caps; at least one charge being disposed in each of said chambers; a carrier attached to said casing having first and second halves, each of said halves having at least one longitudinally running U-shaped channel defined thereon, said at least one U-shaped channel of said first half adapted to receive said at least one of said plurality of cylinders therein, said at least one U-shaped channel of said second half adapted to receive at least one other of said plurality of cylinders therein; and a clamp at each end of said carrier adapted to receive said each of said end caps, and hold said plurality of cylinders in said U-shaped channels. 6. The apparatus of claim 5 wherein each of said first and second halves of said carrier have first and second transverse edges, said first and second halves being adapted to be coaxially secured around the outside surface of said casing when a flange on said first edge on said first half is fixed to a flange on said first edge on said second half by at least one fastener and a flange on said second edge on said first half is fixed to a flange on said second edge on said second half by at least one additional fastener.7. The apparatus of claim 6 wherein at least one pair of flanges fixed together define there between a longitudinal canal which is used as a protective space in which a continuous medium may be deployed without being vulnerable to damage when said at least one charge is detonated.8. A gun assembly used for perforating a subterranean earth formation through a wellbore lined with casing wherein said casing has inside and outside surfaces, comprising:a first charge directed outward towards the formation to perforate the formation; and a second charge directed inward towards the casing to perforate the casing, wherein said first and second charges are contained within a single charge capsule. 9. The gun assembly of claim 8, wherein the first charge has sufficient explosive charge to enable it to sufficiently penetrate the formation, while the second charge has sufficient explosive charge to perforate the casing, but not so much that collateral damage is caused to untargeted portions of the casing.10. The gun assembly of claim 8, wherein the first and second charges are fluidly isolated from wellbore fluids by being included in a protective chamber, said chamber being defined by a module comprising:a hollow cylinder secured to said casing, said cylinder having an inside surface, an outside surface, and two ends; an end cap secured at each end of said cylinder; said protective chamber being defined by said inside surface of said cylinder and said end caps. 11. The gun assembly of claim 10, wherein the module maintains said first and second charges in close proximity to said outer surface of said casing.12. A method of perforating a subterranean earth formation through a wellbore lined with casing, comprising the steps of:attaching a plurality of explosive charges to an outside surface of said casing as said casing is run in the wellbore, wherein said explosive charges are comprised of opposing charges in a single charge capsule; directing at least one of said plurality of explosive charges to perforate said casing and at least one of said plurality of explosive charges to perforate said formation; positioning said plurality of explosive charges on said casing substantially adjacent a preferred zone within said formation to be perforated; and detonating said plurality of explosive charges. 13. The method of claim 12, wherein said plurality of explosive charges are detonated by a signal transmitted from a surface of said formation.14. The method of claim 13, wherein said signal is transmitted using a telemetry system.