Electrical Energy Supply For Well Tools

Abstract

A device for providing an electrical current to a downhole well tools without the requirement of a conductor from the earth's surface. Energy that will subsequently be converted to electrical energy is stored in the well tool. When the electrical current is required, the stored energy is released to drive a permanent magnet through a coil and generate an electric current.

Description

BACKGROUND OF THE INVENTION

The present invention relates to an energy source and more particularly to a system for supplying an electrical current at a remote point such as deep within a well bore.

Certain well operations require an electrical current for actuating mechanisms or for performing other functions. The well tool may be at a remote point in a well bore and the well operations are often conducted under conditions that make it impractical to supply an electrical current through a conductor from the surface. Difficulties have been encountered with electrical sources of the prior art. Environmental conditions often render chemical sources of energy undesirable and other limitations make the use of the remaining prior art electrical energy sources impractical.

DESCRIPTION OF THE PRIOR ART

One prior art system for providing a source of electrical energy in the downhole well tool is a simple electrical dry cell or battery. This system is unsatisfactory because of the adverse effect of environmental conditions. High temperatures are often encountered within a well bore and the high temperatures reduce the energy available from the dry cell or battery.

Another system of producing energy at a remote point in a well bore involves the use of a capacitor for storing electrical energy. This system is dangerous and requires physical dimensions too large for many well bores.

Another of the prior art remote electrical energy supplies is shown in U.S. Pat. No. 2,944,603 to R. C. Baker et al patented July 12, 1960. This patent discloses a subsurface electrical current generating apparatus adapted to be lowered into a well bore on a running-in string, wherein institution of electrical current is responsive to manipulation of the running-in string. This system uses an element with a helical groove to supply rotary motion to a rotary generator. A spring forces the helical grooved element into motion thereby causing the rotary generator to produce a current. This system has many parts and is inefficient in use of mechanical energy to generate electrical energy.

SUMMARY OF THE INVENTION

The present invention provides a system for producing an electrical current at a remote point in a well bore without an electrical connection to the surface and regardless of the environmental conditions. Energy is carried downhole in the form of a stressed spring or other form of stored energy. This energy is then converted to electrical energy by causing relative motion between a permanent magnet and a coil. Release of the stored energy may be achieved through the use of a non-electrical wireline, a change in pressure, a physical change in the dimensions of the borehole or by a change in other physical parameters. In one embodiment of the invention, the compressed spring is latched by a releasable latch assembly. Upon command, the latch is released and the energy from the compressed spring moves the permanent magnet relative to the coil. A safety switch may be incorporated in series with the output of the energy source to prevent premature actuation of the well tool.

The well tool incorporating the electrical energy source of the present invention is lowered into position in the well bore. This may be accomplished by lowering the tool on a non-electrical wireline, dropping the tool down the well bore, pumping the well tool into position or by other systems of positioning a well tool. When the operation is to be performed, a change in conditions actuates the energy source of the present invention.

It is therefore an object of the present invention to provide a novel system for providing a surge of electrical current at a remote point in a well bore.

It is a further object of the present invention to provide a source of electrical energy at a remote point that may be actuated by change of physical characteristics.

It is a still further object of the present invention to provide a remote electrical energy source for a well tool that may be actuated from the earth's surface by means other than the use of an electrical wireline.

It is a still further object of the present invention to provide a system that will produce a surge of electrical current for detonating a perforator.

The above and other objects and advantages of the present invention will become apparent from the following detailed description of the invention when taken in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows an embodiment of the present invention in position in a well bore.

FIG. 2 shows a latch of another embodiment of the present invention.

FIG. 3 illustrates an embodiment of the present invention that can be actuated by a change in pressure.

FIG. 4 shows another embodiment of the present invention in position in a well bore.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1, a well tool 10 constructed in accordance with the present invention is shown emerging from a section of tubing 12 positioned in well bore 11. The well bore 11 is shown cased by well casing 9. When well tool 10 exits from tubing 12, it will be located in the enlarged diameter area of casing 9 and the significance of this enlarged diameter area will be demonstrated subsequently.

The well tool 10 consists of a housing 13 having a diameter slightly smaller than the diameter of tubing 12. A coil spring 14 is positioned in the upper portion of well tool 10. A spring setting rod 15 extends through an opening in the upper portion of housing 13 and through the center of coil spring 14. Setting rod 15 is connected to an enlarged latch receiving element 16. A latch element 17 having an enlarged head is positioned through a hole in the housing 13 and extends into a hole in the enlarged latch receiving element 16. A pair of spring elements 18 and 19 are connected to the outside of housing 10 to extend over recess 20 formed in the side of housing 13. The spring elements 18 and 19 urge latch element 17 outward; however, latch element 17 is held in place by the side of the tubing 12. It can be appreciated that when well tool 10 passes beyond the end of tubing 12 the enlarged diameter of the well bore will allow latch element 17 to move outward due to the force of spring elements 18 and 19 and latch receiving element 16 will be released.

An elongated permanent magnet 21 is connected to the enlarged latch receiving element 16. When the latch element 17 is released, the permanent magnet is forced downward by energy stored in coil spring 14. The travel of permanent magnet 21 is guided by a bushing 22 into the central opening of an electrical coil 23. The movement of permanent magnet 21 through coil 23 produces a surge of electrical current in coil 23. The electrical leads, L1 and L2, from coil 23 are connected to an electric blasting cap used to detonate a series of shaped charges 24. It can be appreciated that the perforator charges 24 are but one type of oil well tool that may be connected to electrical leads L1 and L2. For example, the electrical leads could be connected to a gun type perforator, a well logging tool, a sampling tool, a casing cutter or other type of well tool that requires only a surge of electrical energy for operation.

The structure of the first embodiment of the present invention having been described, the operation of the system will be considered. The lower portion of housing 13 is positioned in the top of tubing 12 at the earth's surface. Spring setting rod 15 is pulled upward thereby compressing coil spring 14. Latch element 17 is forced into the enlarged latch receiving element 16 thereby locking element 16 in place. Spring elements 18 and 19 are deformed and apply an outward force on latch element 17. The housing 13 is moved further into tubing 12 until latch element 17 bears against the side of tubing 12. This locks latch element 17 in place. The well tool 10 is moved down the well bore until it reaches the lower end of tubing 12. When latch element 17 passes beyond the end of tubing 12, the spring elements 18 and 19 will force latch element 17 outward, thereby releasing the latch receiving element 16 and allowing permanent magnet 21 to be forced through electrical coil 23 by spring 14. A surge of electrical current is generated which actuates the shaped perforator charges 24.

Referring now to FIG. 2, another embodiment of the present invention is illustrated. A spring setting rod 25 extends longitudinally inside of a well tool 26. The lower portion of well tool 26 may be constructed in accordance with the previous description and includes a permanent magnet adapted to travel through a coil for generating a surge of electrical current. The coil is electrically connected to the operating portion of a well tool such as well logging device, a sampling device, or perforator.

A power spring 27 is positioned in well tool 26 and compressed when spring setting rod 25 is in the position shown in FIG. 2. The upper end of spring setting rod 25 forms a spear point 28 that cooperates with a pair of latch elements 29 and 30 to releasably lock the spring setting rod 25 in position. The latch elements 29 and 30 are pivotally connected to well tool 26 by pins 31 and 32. A spring 33 connects the upper ends of latch elements 29 and 30 and acts to urge the upper ends together and thereby release spear point 28. The lower ends of latch elements 29 and 30 contact the side of tubing 34 and are thereby restricted from moving outward. As long as the lower ends of latch elements 29 and 30 are inside of tubing 34, the spear point 28 is latched in position. However, when the well tool 26 exits from the lower end of tubing 34, the lower ends of latch elements 29 and 30 move outward and the spear point 28 will be released creating a surge of electrical energy to actuate the well tool.

A well tool 35 that may be actuated by a change in pressure in the borehole is shown in FIG. 3. The upper end of spring setting rod 36 forms a hook 37. Hook 37 is engaged by a pivotal hook 38. Pivotal hook 38 is connected to well tool 35 by a pin 39. A piston 40 is mounted in the upper end of well tool 35 and a rod 41 extends from piston 40 to the upper portion of pivotal hook 38. Movement of piston 40 in a downward direction will pivot hook 38 and release spring setting rod 36. Piston 40 forms a fluid seal with the side of well tool 35. A fluid seal may be insured by a pair of "O" rings 42 and 43. The lower portion of well tool 35 is constructed in accordance with the description of the well tool shown in FIG. 1 and includes a permanent magnet adapted to travel through a coil for generating a surge of electrical current. The coil is electrically connected to the operating portion of a well tool such as a well logging device, a sampling device, or perforator.

When spring setting rod 36 is released, energy from power spring 44 moves the magnet through the coil. Release of spring setting rod 36 is accomplished by increasing the pressure in the borehole fluid to force piston 40 downward and pivot hook 38. The chamber 45 immediately below piston 40 contains a predetermined volume of gaseous fluid. An increase in pressure of the fluid above piston 40 will cause piston 40 to move downward decreasing the volume of chamber 45 until the pressure of the two fluids are equal. The movement of piston 40, of course, releases spring setting rod 36.

Referring now to FIG. 4, another embodiment of a well tool 46 constructed in accordance with the present invention is shown positioned in a well bore 47. The well bore 47 is cased by well casing 48. Well tool 46 includes a main housing 49 having a diameter smaller than the diameter of well casing 48. Positioned within housing 49 and slidable therein is a piston 50. A pair of "O" rings 51 and 52 insure that piston 50 forms a tight seal with housing 49. The portion of the housing 49 immediately below piston 50 forms a chamber 53 adapted to contain a compressed gas for driving piston 50 upward upon release. A permanent magnet 54 is connected to the upper portion of piston 50 and positioned axially below the central opening of a coil 55. A pair of electrical leads L3 and L4 extend from coil 55 to an explosive casing cutter 56. The explosive casing cutter 56 consists of a ring-shaped explosive charge that will sever the entire diameter of casing 48 when detonated. An elongated rod 57 is connected to the upper end of magnet 54 and extends upward through the central openings in coil 55 and explosive casing cutter 56 and through an opening in the upper end of housing 49. The upper portion of rod 57 includes a section having a reduced diameter that serves as a latch seat for latches 58 and 59. Latches 58 and 59 are pivotally connected to the upper end of housing 49 by pins 60 and 61. Latches 58 and 59 are substantially L shaped and include extended end portions 62 and 63 respectively that extend outward. It can be appreciated that downward pressure on extended end portions 62 and 63 will release latches 58 and 59 from the latch seats on rod 57. A non-electrical wireline 64 is connected to rod 57 and extends to the surface equipment for positioning well tool 46 in the well bore 47.

Prior to lowering well tool 46 into well bore 47, the chamber 53 is filled with a sufficient amount of compressed gas to drive piston 50 upward when latches 58 and 59 are released. The gas may be introduced to chamber 53 through a one-way valve 65. The well tool 46 is lowered into well bore 47 and positioned at the point the casing 48 is to be severed. An actuating device 66 is dropped down the well bore to release latches 58 and 59 by striking extended end portions 62 and 63. The actuating device 66 may be a section of pipe with a diameter somewhat smaller than the diameter of casing 48. When latches 58 and 59 are released, the force of the compressed gas in chamber 53 drives piston 50 upward moving magnet 54 into the opening in coil 55. The movement of magnet 54 through coil 55 generates a surge of electrical energy in coil 55 thereby detonating casing cutter 56.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An electrical energy source for a borehole tool, comprising:

a housing adapted to traverse a borehole;

a magnet positioned in said housing;

a coil located in said housing;

electrically actuated means for performing a selected borehole tool operation, electrically connected to said coil;

storage means located in said housing for storing energy for moving said magnet relative to said coil; and

release means located in said housing for releasing the stored energy in said storage means.

2. The electrical energy source of claim 1 wherein said storage means is a chamber containing compressed gas.

3. The electrical energy source of claim 1 wherein said storage means is a spring.

4. The electrical energy source of claim 3 wherein said electrically actuated means is a perforating gun.

5. The electrical energy source of claim 3 wherein said electrically actuated means is a cutter for tubular goods.

6. An electrical energy source for supplying a surge of electrical energy to a borehole tool, comprising:

a borehole tool housing adapted to traverse a borehole;

an elongated permanent magnet positioned in said housing;

a coil having a central opening positioned in said borehole tool housing;

electrically actuated means for performing a selected borehole tool operation, electrically connected to said coil;

storage means located in said housing for storing energy to drive said magnet through the central opening in said coil; and

controllable release means located in said housing for releasing the stored energy in said storage means upon command.

7. The electrical energy source of claim 6 wherein said storage means is a chamber containing compressed gas.

8. The electrical energy source of claim 6 wherein said storage means is a spring.

9. The electrical energy source of claim 6 wherein said electrically actuated means is a perforating gun.

10. The electrical energy source of claim 6 wherein said electrically actuated means is a cutter for tubular goods.