MULTI-AXIAL ANTENNA AND METHOD FOR USE IN DOWNHOLE TOOLS

• US 20090302847A1
• Filed: 09/15/2006
• Published: 12/10/2009
• Est. Priority Date: 09/15/2006
• Status: Active Grant

• Current Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Original Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Inventors: Knizhnik, Sergey
• Granted Patent: US 8,471,562 B2
• Time in Patent Office: Days
• US Class Current: 324/332
• CPC Class Codes: G01V 3/104 using several coupled or uncoupled coils G01V3/101 takes precedence
• CPC Class Codes: G01V 3/18 specially adapted for well-logging
• CPC Class Codes: H01F 2005/027 wound on formers for receiving several coils with perpendicular winding axes, e.g. for antennae or inductive power transfer
• CPC Class Codes: H01Q 1/04 Adaptation for subterranean or subaqueous use
• CPC Class Codes: H01Q 25/00 Antennas or antenna systems providing at least two radiating patterns arrangements for changing or varying the orientation or the shape of the directional pattern H01Q3/00
• CPC Class Codes: H01Q 3/26 varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture H01Q3/12, H01Q3/22, H01Q3/24 take precedence
• CPC Class Codes: H01Q 7/00 Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop

Abstract

Embodiments of a multi-axial antenna system and system for measuring subsurface formations are generally described herein. Other embodiments may be described and claimed. In some embodiments, the multi-axial antenna system comprising at least two co-located coils wound around a torroidal-shaped bobbin. Each coil generates a magnetic field in a mutually orthogonal direction. Signals provided to the coils may be adjusted to simulate a tilted-coil antenna system.

Claims

1. A multi-axial antenna system with co-located coils comprising:

a first coil positioned around a portion of a torroidal-shaped bobbin through a central recess of the bobbin to generate a magnetic field in substantially a first direction when current flows through the first coil;

a second coil positioned around a second portion of the bobbin through the central recess to generate a magnetic field in substantially a second direction when current flows through the second coil, the second direction being orthogonal to the first direction; and

a third coil positioned longitudinally around the bobbin to generate a magnetic field in substantially a third direction when current flows through the third coil, the third direction being orthogonal to the first and second directions.

2. The antenna system of claim 1 wherein the central recess is provided to receive a tool body of a downhole tool,

wherein the first and second directions are orthogonal to a tool axis, the tool axis being in the third direction, and

wherein the first and second directions are in radial directions with respect to the totroidal-shaped bobbin.

3. The antenna system of claim 1 wherein the first coil is positioned on the bobbin at approximately ninety-degrees with respect to the second coil,

wherein the first and second coils are spaced apart on the bobbin, and

wherein the third coil is wound longitudinally around the bobbin overlapping the first and second portions of the bobbin to provide three co-located antennas.

4. The antenna system of claim 1 wherein the first coil comprises first and second sections provided on opposing sides of the bobbin to generate the magnetic field in the first direction when current flows through the first coil, and

wherein the second coil comprises third and fourth sections provided on second opposing sides of the bobbin to generate the magnetic field in the second direction when current flows through the second coil.

5. The antenna system of claim 4 wherein the first, second and third coils comprise wire wound around the bobbin.

6. The antenna system of claim 4 wherein at least one of the first, second and third coils comprises metal traces deposited on the bobbin.

7. The antenna system of claim 4 further comprising:

first thru-wires to electrically couple the first and second sections of the first coil; and

second thru-wires to electrically couple the third and fourth sections of the second coil,

wherein the first thru-wires form a twisted pair and couple the first and second sections in series, and

wherein the second thru-wires form a twisted pair and couple the third and fourth sections in series.

8. The antenna system of claim 4 further comprising:

first thru-wires to electrically couple the first and second sections of the first coil; and

second thru-wires to electrically couple the third and fourth sections of the second coil,

wherein the first thru-wires form a twisted pair and couple the first and second sections in parallel, and

wherein the second thru-wires form a twisted pair and couple the third and fourth sections in parallel.

9. The antenna system of claim 1 wherein the first and second coils are substantially identical in size and shape and are co-located in substantially the same longitudal position, and

wherein the bobbin includes a plurality of grooves to accept windings of the coils.

10. The antenna system of claim 1 wherein the bobbin comprises an electrically non-conductive material.

11. The antenna system of claim 1 wherein the bobbin has a high-permeability (μ

_T) core.

12. The antenna system of claim 1 wherein signals are varied to the first, second and third coils to generate a magnetic field vector that is angled with respect to the first, second and third directions to simulate a tilted coil.

13. A subsurface measuring system for measuring subsurface formations comprising:

an antenna system comprising at least two co-located coils positioned around a torroidal-shaped bobbin; and

signal generating circuitry to provide signals to the coils to generate magnetic fields in mutually orthogonal directions.

14. The system of claim 13 wherein the signal-generating circuitry varies the signals to the coils to generate a magnetic field vector that is angled to simulate a tilted coil.

15. The system of claim 13 wherein the signal-generating circuitry provides currents with shifted phases to the coils to generate a rotational magnetic field.

16. The system of claim 13 wherein the signal-generating circuitry provides signals to the first, second and third coils in a time-shifted manner.

17. The system of claim 13 wherein the antenna system is a transmitting antenna system to generate magnetic fields for incident on subsurface formations, and

wherein the system further comprises a receiving antenna system to receive return magnetic fields from the subsurface formations.

18. The system of claim 17 wherein the transmitting antenna system comprises first and second transmitting antenna coils, at least some turns of the first transmitting antenna coil being connected in parallel and at least some turns of the second transmitting antenna coil being connected in parallel, and

wherein the receiving antenna system comprises first and second receiving antenna coils, turns of the first receiving antenna coil being connected in series and turns of the second receiving antenna coil being connected in series.

19. The system of claim 13 wherein the antenna system comprises:

a first coil positioned around a portion of the torroidal-shaped bobbin through a central recess of the bobbin to generate a magnetic field in substantially a first direction when current flows through the first coil;

a second coil positioned around a second portion of the bobbin through the central recess to generate a magnetic field in substantially a second direction when current flows through the second coil, the second direction being orthogonal to the first direction; and

a third coil positioned longitudinally around the bobbin to generate a magnetic field in substantially a third direction when current flows through the third coil, the third direction being orthogonal to the first and second directions.

20. The system of claim 19 wherein the central recess receives a tool body of a downhole tool,

wherein the first and second directions are orthogonal to a tool axis, the tool axis being in the third direction, and

wherein the first and second directions are in orthogonal radial directions with respect to the torroidal-shaped bobbin.

21. The system of claim 19 wherein the first coil is positioned on the bobbin at approximately ninety-degrees with respect to the second coil,

wherein the first and second coils are spaced apart on the bobbin, and

wherein the third coil is wound longitudinally around the bobbin overlapping the first and second portions of the bobbin to provide three co-located antennas having substantially co-located magnetic moment origins.

22. The system of claim 19 wherein the first coil comprises first and second sections provided on opposing sides of the bobbin to generate the magnetic field in the first direction when current flows through the first coil, and

wherein the second coil comprises third and fourth sections provided on second opposing sides of the bobbin to generate the magnetic field in the second direction when current flows through the second coil.

23. A multi-axial antenna system comprising at least two co-located coils positioned around a torroidal-shaped bobbin, each coil to generate a magnetic field in a mutually orthogonal direction.

24. The antenna system of claim 23 wherein the bobbin has a central recess, and

wherein the plurality of co-located coils comprise at least two of:

a first coil having first and second portions provided on opposing sides of the bobbin and through the central recess to generate a magnetic field in substantially a first direction when current flows through the first coil;

a second coil having third and fourth portions provided on second opposing sides of the bobbin and through the central recess to generate a magnetic field in substantially a second direction when current flows through the second coil, the second direction being orthogonal to the first direction; and

a third coil positioned longitudinally around the bobbin to generate a magnetic field in substantially a third direction when current flows through the third coil, the third direction being orthogonal to the first and second directions.

25. The antenna system of claim 24 wherein the central recess is to receive a tool body of a downhole tool,

wherein the first and second directions are orthogonal to a tool axis of the tool body, the tool axis being in the third direction, and

wherein the first and second directions are in orthogonal radial directions with respect to the torroidal-shaped bobbin.

26. The antenna system of claim 24 wherein the first coil is positioned on the bobbin at approximately ninety-degrees with respect to the second coil,

wherein the first and second coils are spaced apart on the bobbin, and

wherein the third coil is wound longitudinally around the bobbin overlapping the first and second portions of the bobbin to provide three co-located antennas.

27. The antenna system of claim 23 wherein signals provided to the first, second and third coils are selected generate a magnetic field vector that is angled with respect to the first, second and third directions to simulate a tilted coil.

28. A method for measuring subsurface formations comprising:

providing signals to first, second and third coils to generate magnetic fields in mutually orthogonal directions,

wherein at least two of the coils are co-located coils positioned around a torroidal-shaped bobbin.

29. The method of claim 28 further comprising selecting the signals provided to the first, second and third coils to generate a magnetic field vector that is, angled with respect to the first, second and third directions to simulate a tilted coil.

30. The method of claim 28 further comprising providing the signals to the first, second and third coils in a time-shifted manner.

31. The method of claim 28 further comprising providing currents with shifted phases to the first, second and third coils to generate a rotational magnetic field.

32. The method of claim 29 wherein the first coil is wound around a portion of the torroidal-shaped bobbin through a central recess of the bobbin to generate a magnetic field in substantially a first direction when current flows through the first coil,

wherein the second coil is wound around a second portion of the bobbin through the central recess to generate a magnetic field in substantially a second direction when current flows through the second coil, the second direction being orthogonal to the first direction, and

wherein the third coil wound longitudinally around the bobbin to generate a magnetic field in substantially a third direction when current flows through the third coil, the third direction being orthogonal to the first and second directions.