Focused shock spark discharge drill using multiple electrodes

• US 4,741,405 A
• Filed: 01/06/1987
• Issued: 05/03/1988
• Est. Priority Date: 01/06/1987
• Status: Expired due to Term

• Current Assignee: SDG, LLC
• Original Assignee: Tetra Corporation
• Inventors: Small, James G., Moeny, William M.
• Primary Examiner(s): Novosad, Stephen J.
• Assistant Examiner(s): Kisliuk, Bruce M.
• Application Number:
  US07/000,768
• Time in Patent Office: 483 Days
• Field of Search: 175/2, 175/15-17
• US Class Current: 175/16
• CPC Class Codes: E21B 7/007 Drilling by use of explosives underwater drilling using explosives E21B7/1245
• CPC Class Codes: E21B 7/15 of electrically generated heat

Abstract

A spark discharge focused drill provided with one pulse forming line or a number of pulse forming lines. The pulse forming line is connected to an array of electrodes which would form a spark array. One of the electrodes of each of the array is connected to the high voltage side of the pulse forming line and the other electrodes are at ground potential. When discharged in a liquid, these electrodes produce intense focused shock waves that can pulverize or fracture rock. By delaying the firing of each group of electrodes, the drill can be steered within the earth. Power can be fed to the pulse forming line either downhole or from the surface area. A high voltage source, such as a Marx generator, is suitable for pulse charging the lines.

Claims

1. A spark discharge focused shock drill comprising:

a drill casing;

a source of potential;

a pulse forming line connected to said source of potential;

one set of electrodes provided within said drill casing and extending therein to form a drill face, said set of electrodes including a first electrode positively connected to said pulse forming line, a second electrode positively connected to ground potential and a plurality of third electrodes, said third electrodes including a first adjacent third electrode and a second adjacent third electrode, said plurality of third electrodes disposed near said first and second electrodes;

a working fluid provided in the drill surrounding the drill face; and

a first switch provided between said source of potential and said pulse forming line for causing a series spark array to be formed, when said first switch is closed, wherein a voltage gradient is created between said first electrode and a first adjacent third electrode such that a spark jumps the gap between said first electrode and said first adjacent third electrode, thereby subsequently establishing a voltage gradient between said first adjacent third electrode and a second adjacent third electrode, therefore creating a second spark jump and whereby additional spark jumps are created between said third electrode until a spark jump is created between the last of said third electrodes and said second electrode, all of said sparks produced within said working fluid to create a pressure wave directed against the material to be drilled.

2. The drill in accordance with claim 1 further including;

additional pulse forming lines each connected to said source of potential; and

additional sets of electrodes, one of said additional sets of electrodes for each of said additional pulse forming lines, each of said sets of electrodes provided within said drill casing and extending therein to form a drill face, and each of said sets of electrodes including (a) a first electrode positively connected to its respective pulse forming line, (b) a second electrode positively connected to ground potential and (c) a plurality of third electrodes disposed near said first and second electrodes; and

wherein said first switch serially connects said source of potential to said plurality of pulse forming lines.

3. The drill in accordance with claim 2 further including:

a plurality of sources of potential, a separate source of potential connected to each of said pulse forming lines; and

additional first switches connected between each of said sources of potential and each of said pulse forming lines.

4. The drill in accordance with claim 3 further including a plurality of second switches, each of said second switches provided between one of said pulse forming lines and said first electrode of one of said set of electrodes.

5. The drill in accordance with claim 3 further including:

sensing means provided on the surface for sensing the occurrence of the pressure wave produced by the drill;

computer means connected to said sensing means for determining the exact position of said drill face; and

control means connected between said computer means and said first switches for determining the proper time for closing each of said first switches to enable said pressure wave and drill face to be properly steered.

6. The drill in accordance with claim 4 further including:

sensing means provided on the surface for sensing the occurrence of the pressure wave produced by the drill;

computer means connected to said sensing means for determining the exact position of said drill face; and

control means connected between said computer means and said second switches for determining the proper time for closing each of said second switches to enable said pressure wave and drill face to be properly steered.

7. The drill in accordance with claim 5 wherein said control means delays the switching of at least one of said first switches relative to the remainder of said first switches thereby delaying the firing of the first electrode connected to the delayed first switch.

8. The drill in accordance with claim 6 wherein said control means delays the switching of at least one of said second switches relative to the remainder of said second switches thereby delaying the firing of the first electrode connected to the delayed second switch.

9. The drill in accordance with claim 1 wherein said pulse forming line is a Blumlein pulse forming line.

10. The drill in accordance with claim 1 wherein said pulse forming line is a slow wave pulse forming line.

11. The drill in accordance with claim 1 wherein said pulse forming line is a concentric cylinder.

12. The drill in accordance with claim 1 wherein said pulse forming line is a discrete component pulse forming line.

13. The drill in accordance with claim 1 further including solid insulative material between each of the electrodes of said one set of electrodes, said one set of electrodes and said insulative material forming a continuous drill face and said one set of electrodes and said insulative material constructed from material which will erode approximately at the same rate when sparks repeatedly cross said insulative material between adjacent electrodes.

14. The drill in accordance with claim 2 further including solid insulative material between each of the electrodes of each of said additional set of electrodes, said each of said electrodes and said insulative material forming a continuous drill face and said additional set of electrodes and said insulative material constructed from material which will erode at approximately the same rate when sparks repeatedly cross said insulative material between adjacent electrodes of one set of electrodes.

15. The drill in accordance with claim 1 wherein said source of potential and said pulse forming line are provided outside said drill casing.

16. The drill in accordance with claim 3 wherein each of said sources of potential and each of said pulse forming lines are provided outside said drill casing.

17. The drill in accordance with claim 1 wherein said source of potential is a high voltage Marx generator.

18. The drill in accordance with claim 3 wherein each of said sources of potential is a high voltage Marx generator.

19. The drill in accordance with claim 1 wherein said source of potential and said pulse forming line are provided within said drill casing.

20. The drill in accordance with claim 3 wherein each of said sources of potential and said pulse forming lines are provided within said drill casing.

21. The drill in accordance with claim 15 further including a transmission line between said pulse forming line and said one set of electrodes.

22. The drill in accordance with claim 16 further including a set of transmission lines each of which is connected between one of said pulse forming lines and one set of electrodes.

23. The drill in accordance with claim 15 further including a transmission line between said transmission line and said one set of electrodes and an impedance transformer provided between said pulse forming line and said set of electrodes for matching the impedance of said transmission line to that of said spark array.

24. The drill in accordance with claim 16 further including a set of transmission lines each of which is connected between one of said pulse forming lines and one set of electrodes for matching the impedance of each of said transmission lines to that of said spark array.

25. The drill in accordance with claim 2 wherein said source of potential is a Marx generator.

26. The drill in accordance with claim 2 wherein said source of potential and said pulse forming lines are provided with said drill casing.

27. A spark discharge focused shock drill comprising:

a drill casing;

a source of potential;

a pulse forming line connected to said source of potential;

one set of electrodes provided within said drill casing and extending therein to form a drill face, said set of electrodes including a first electrode positively connected to said pulse forming line, a second electrode positively connected to ground potential and a plurality of third electrodes, said third electrodes including a first adjacent third electrode and a second adjacent third electrode, said plurality of third electrodes disposed near said first and second electrodes, said first, second and third electrodes arranged in such a manner to produce a focused pressure wave;

a working fluid provided in the drill surrounding the drill face; and

a first switch provided between said source of potential and said pulse forming line for causing a series spark array to be formed, when said first switch is closed, wherein a voltage gradient is created between said first electrode and a first adjacent third electrode such that a spark jumps the gap between said first electrode and said first adjacent third electrode, thereby subsequently establishing a voltage gradient between said first adjacent third electrode and a second adjacent third electrode, therefore creating a second spark jump and whereby additional spark jumps are created between said third electrode until a spark jump is created between the last of said third electrodes and said second electrode, all of said sparks produced within said working fluid to create a focused pressure wave directed against the material to be drilled.

28. The drill in accordance with claim 27 further including:

additional pulse forming lines each connected to said source of potential; and

additional sets of electrodes, one of said additional sets of electrodes for each of said additional pulse forming lines, each of said sets of electrodes provided within said drill casing and extending therein to form a drill face, and each of said sets of electrodes including (a) a first electrode positively connected to its respective pulse forming line, (b) a second electrode positively connected to ground potential and (c) a plurality of third electrodes disposed near said first and second electrodes; and

wherein said first switch serially connects said source of potential to said plurality of pulse forming lines.

29. The drill in accordance with claim 27 further including:

a plurality of sources of potential, a separate source of potential connected to each of said pulse forming lines; and

additional first switches connected between each of said sources of potential and each of said pulse forming lines.