Minimal resistance scallop for a well perforating device

Abstract

The present invention is an improvement in the design of a perforating gun to perforate the casing in oil and gas wells. Perforating guns have a cylindrical body member with explosive charges at specified intervals designed to shoot outwardly through the body member, the well casing, cement sheath, and into the rock formation. There are recessed areas, scallops, on the outer surface of the body member where the perforating jets, formed by the explosive charges, exit the body member. The present invention uses the strength of an arching geometric shape for the recessed area to be able to further reduce the thickness of steel for minimal resistance to the perforating jet. Minimizing the resistance to the perforating jet increases the depth of penetration into the rock formation and increases the hole size.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] Not Applicable STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT [0002] Not Applicable REFERENCE TO A MICROFICHE APPENDIX [0003] Not Applicable BACKGROUND OF THE INVENTION [0004] The invention relates generally to an improvement in the design of an oil and gas well perforating device. The improvement applies to a type of perforating device that is typically lowered into the well through the casing or tubing in the well to a position where the explosive charges are detonated at the desired depth. The improvement is a method of modifying the scallop that is cut on the exterior of the device, at the location of a perforating charge, so as to minimize the resistance to the explosive charge which in turn improves the performance of the perforating charge by increasing its depth of penetration and hole size. [0005] After an oil or gas well is drilled, steel casing is lowered into the well and cemented to the adjoining rock forma...

AI Technical Summary

Benefits of technology

[0016] The present invention is an improvement for a well perforating device and method of manufacture to make a modification to the industry standard method of cutting a scallop on the outer surface of the hollow steel carrier that contains the perforating charges. The scallops are made at the location of each charge to reduce the energy needed to exit the carrier. The present invention is the use of an arching geometric cut for the scallop. The thickness of the carrier at the location of the scallop can be reduced while maintaining sufficient structural strength to withstand the pressures exerted on the carrier, as a result of the additional strength imparted from the arched geometric cut. The deeper arching geometric shape reduces the thickness of steel that the perforating jet must penetrate to exit the carrier which increases the remaining energy for greater penetration and hole size. Increasing the depth of cut of the scallop alone to the same thickness would result in significantly reduced structural strength of the carrier and failure to withstand the external pressures exerted on the carrier. The additional smaller geometric cut utilizes the additional strength created from the rigidity of the geometric cut to counter the effects of the reduced thickness.

Problems solved by technology

Increasing the depth of cut of the scallop alone to the same thickness would result in significantly reduced structural strength of the carrier and failure to withstand the external pressures exerted on the carrier.

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