Shock Load Mitigation in a Downhole Perforation Tool Assembly

• US 20120318508A1
• Filed: 08/25/2012
• Published: 12/20/2012
• Est. Priority Date: 04/29/2011
• Status: Active Grant

• Current Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Original Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Inventors: Glenn, Timothy S., Rodgers, John P., Nelson, Jeff A., Burleson, John D., Serra, Marco, Hales, John H.
• Granted Patent: US 8,714,251 B2
• Time in Patent Office: Days
• US Class Current: 166/297
• CPC Class Codes: E21B 17/07 Telescoping joints for varying drill string lengths; Shock absorbers
• CPC Class Codes: E21B 43/11 Perforators; Permeators
• CPC Class Codes: E21B 43/117 Shaped-charge perforators E21B43/118 takes precedence
• CPC Class Codes: G06F 30/17 Mechanical parametric or variational design

Abstract

A perforation tool assembly is provided. The perforation tool assembly comprises an energy train, a first perforation gun, and a second perforation gun. The energy train comprises a moderator to reduce the speed of propagation of a detonation in a direction parallel to the axis of the perforation tool assembly. The first perforation gun comprises a plurality of explosive charges coupled to a first portion of the energy train. The second perforation gun comprises a plurality of explosive charges coupled to a second portion of the energy train, wherein the second portion of the energy train is coupled to the first portion of the energy train.

Claims

1. A perforation tool assembly, comprising:

an energy train comprising a moderator to reduce the speed of propagation of a detonation in a direction parallel to the axis of the perforation tool assembly, wherein the moderator reduces the speed of propagation of the detonation in the direction parallel to the axis of the perforation tool assembly by an amount in a range from 1% to 50%;

a first perforation gun comprising a plurality of explosive charges coupled to a first portion of the energy train; and

a second perforation gun comprising a plurality of explosive charges coupled to a second portion of the energy train, wherein the second portion of the energy train is coupled to the first portion of the energy train.

3. The perforation tool assembly of claim 1, wherein the moderator reduces the speed of propagation of the detonation in the direction parallel to the axis of the perforation tool assembly by an amount in a range from 15% to 30%.

4. The perforation tool assembly of claim 1, wherein the moderator is implemented by extending the length of the energy train.

5. The perforation tool assembly of claim 1, wherein the moderator comprises a modified detonation cord that has incorporated dilutants.

6. The perforation tool assembly of claim 1, wherein the moderator comprises delay elements incorporated in the energy train.

2. (canceled)

7. A method of perforating a wellbore, comprising:

analyzing a speed of propagation of a shock wave through a tool body of a perforation tool assembly, wherein the perforation tool assembly comprises a plurality of explosive charges;

analyzing a speed of detonation propagation in an energy train in a direction parallel to an axis of the tool body of the perforation tool assembly;

designing the perforation tool assembly, based on analyzing the speed of propagation of the shock wave and analyzing the speed of detonation propagation, to mitigate a shock load associated with an interaction between detonation of the explosive charges;

building the perforation tool assembly based on the perforation tool assembly design; and

perforating a wellbore by firing the perforation tool assembly.

8. The method of claim 7, wherein the perforation tool assembly comprises structures that alter the propagation of the shock wave through the tool body of the perforation tool assembly.

9. The method of claim 8, wherein the structures that alter the propagation of the shock wave are selected from the group consisting of a mass energy absorber, a deformable energy absorber, a hydraulic shock absorber, a spacer providing an acoustic impedance mismatch, and a decoupler.

10. The method of claim 8, wherein the structures that alter the propagation of the shock wave comprises a spacer having a tool body composed of a composite material.

11. The method of claim 7, wherein designing the perforation tool assembly to mitigate the shock load associated with the interaction between the explosive charges comprises designing the perforation tool assembly to offset the speed of shock wave propagation through the tool body of the perforation tool assembly and the speed of detonation propagation in the direction parallel to the axis of the tool body of the perforation tool assembly.

12. The method of claim 11, wherein analyzing the speed of shock wave propagation is based on analyzing properties of a tool body of the perforation tool assembly in the context of a downhole environment.

13. The method of claim 11, wherein the perforation tool assembly is designed to offset the speed of shock wave propagation relative to the speed of detonation propagation by at least 5%.

14. The method of claim 7, wherein the perforation tool assembly comprises structures that alter the speed of detonation propagation in the energy train in the direction parallel to the axis of the tool body of the perforation tool assembly relative to a speed of detonation propagation in an energy train in a direction parallel to an axis of a tool body of a conventional perforation tool assembly.

15. The method of claim 14, wherein the structures are selected from the group consisting of a spacer incorporating an indirect path into an energy train segment of the spacer, a spacer incorporating a reduced speed detonation cord into an energy train segment of the spacer, a spacer incorporating a bullet firing gun as a portion of an energy train segment of the spacer, and a perforation gun incorporating a reduced speed detonation cord into an energy train segment of the perforation gun.

16. The method of claim 14, wherein at least one of the structures delays the propagation of the energy train through an energy train segment of the structure.

17. The method of claim 7, wherein designing the perforating tool to mitigate the shock load is based on a number of charges that are detonated.

18. The method of claim 7, wherein designing the perforating tool to mitigate the shock load is based on at least one of the elasticity of the tool body, an extent to which energy in the shock wave is dissipated in the tool body, or an extent to which the energy in the shock wave decays in the tool body.

19. The method of claim 7, wherein the perforating tools of the perforating tool assembly are fired in a top to bottom sequence.

20. The method of claim 7, wherein designing the perforating tool to mitigate the shock load comprises increasing the speed of the detonation propagation by using an electrical signal as the energy train.

21. The method of claim 7, wherein the perforating tools of the perforating tool assembly are fired substantially concurrently.