MULTI-COMPONENT MARINE ELECTROMAGNETIC SIGNAL ACQUISITION CABLE AND SYSTEM

• US 20080265895A1
• Filed: 04/30/2007
• Published: 10/30/2008
• Est. Priority Date: 04/30/2007
• Status: Active Grant

• Current Assignee: KJT Enterprises, Inc.
• Original Assignee: KJT Enterprises, Inc.
• Inventors: Helwig, Stefan L., Strack, Kurt M.
• Granted Patent: US 7,872,477 B2
• Time in Patent Office: Days
• US Class Current: 324/347
• CPC Class Codes: G01V 3/083 Controlled source electromagnetic [CSEM] surveying
• CPC Class Codes: G01V 3/12 operating with electromagnetic waves operating with millimetre waves G01V8/005

Abstract

A marine electromagnetic sensor cable includes a plurality of sensor modules disposed at spaced apart locations along a cable. Each module includes at least one pair of electrodes associated with the module. The electrodes are arranged to measure electric field in a direction along the direction of the cable. The cable is arranged to form a closed pattern. Another marine electromagnetic sensor cable includes a plurality of sensor modules disposed at spaced apart locations along a cable. Each module includes at least one pair of electrodes associated therewith. The electrodes are arranged to measure electric field in a direction along the direction of the cable. A plurality of spaced apart magnetic field sensors is associated with each module and arranged to enable determining an electric field amplitude in a direction transverse to the direction of the cable from magnetic field gradient.

Claims

1. A marine electromagnetic sensor cable, comprising:

a plurality of sensor modules disposed at spaced apart locations along a cable, each module including at least one pair of electrodes associated therewith, the electrodes arranged to measure electric field in a direction along the direction of the cable; and

wherein the cable is arranged to form a closed pattern.

2. The cable of claim 1 wherein each module further comprises at least one triaxial magnetic field sensor and a high frequency magnetic field sensor.

3. The cable of claim 1 wherein each module further comprises at least one laterally extending sensor arm affixed to the module, the at least one sensor arm including at least one electrode thereon.

4. The cable of claim 3 wherein the at least one sensor arm comprises at least one magnetic field sensor.

5. The cable of claim 4 wherein the at least one sensor arm comprises a plurality of spaced apart magnetic field sensors.

6. The cable of claim 1 wherein each module further comprises a vertically extending sensor arm affixed to the module, the at least one sensor arm including at least one electrode thereon.

7. The cable of claim 6 wherein the vertically extending sensor arm comprises at least one magnetic field sensor.

8. The cable of claim 7 wherein the vertically extending sensor arm comprises a plurality of spaced apart magnetic field sensors.

9. The cable of claim 1 wherein each module comprises at least one seismic sensor.

10. The cable of claim 1 wherein the seismic sensor comprises a triaxial geophone.

11. The cable of claim 1 wherein each module comprises electrical circuitry for digitizing and communicating signals detected by the at least one pair of electrodes and the at least one magnetic field sensor.

12. The cable of claim 1 wherein each module comprises at least one magnetic field sensor.

13. The cable of claim 1 wherein each module comprises a gravity sensor.

14. A marine electromagnetic surveying system, comprising:

a vessel towing at least one electromagnetic antenna in a body of water;

a controllable source of electric current disposed on the vessel;

a plurality of sensor modules disposed at spaced apart locations along a cable, each module including at least one pair of electrodes associated therewith, the electrodes arranged to measure electric field in a direction along the direction of the cable, wherein the cable is arranged to form a closed pattern; and

means for recording signals generated by the electrodes and magnetic field sensors in response to electromagnetic energy imparted into the Earth'"'"'s subsurface by passing electric current through the at least one antenna.

15. The system of claim 14 wherein each module further comprises at least one triaxial magnetic field sensor and a high frequency magnetic field sensor.

16. The system of claim 14 wherein each module further comprises at least one laterally extending sensor arm affixed to the module, the at least one sensor arm including at least one electrode thereon.

17. The system of claim 16 wherein the at least one sensor arm comprises at least one magnetic field sensor.

18. The system of claim 17 wherein the at least one sensor arm comprises a plurality of spaced apart magnetic field sensors.

19. The system of claim 14 wherein each module further comprises a vertically extending sensor arm affixed to the module, the at least one sensor arm including at least one electrode thereon.

20. The system of claim 19 wherein the vertically extending sensor arm comprises at least one magnetic field sensor.

21. The system of claim 20 wherein the vertically extending sensor arm comprises a plurality of spaced apart magnetic field sensors.

22. The system of claim 14 wherein each module comprises at least one seismic sensor.

23. The system of claim 14 wherein the seismic sensor comprises a triaxial geophone.

24. The system of claim 14 wherein each module comprises electrical circuitry for digitizing and communicating signals detected by the at least one pair of electrodes and the at least one magnetic field sensor.

25. The system of claim 14 wherein the antenna comprises at least one of a vertical electric dipole, a horizontal electric dipole, a horizontal current loop and a vertical current loop.

26. The system of claim 14 wherein the vessel tows at least one seismic energy source.

27. The system of claim 14 wherein the electric current is at least one of switched direct current and alternating current.

28. The system of claim 27 wherein the switched direct current comprises at least one of switching current on, switching current off, reversing current polarity, and combinations thereof.

29. The system of claim 14 wherein the means for recording comprises a data storage device disposed in a node at an end of the cable.

30. A marine electromagnetic sensor cable, comprising:

a plurality of sensor modules disposed at spaced apart locations along a cable, each module including at least one pair of electrodes associated therewith, the electrodes arranged to measure electric field in a direction along the direction of the cable; and

a plurality of spaced apart magnetic field sensors associated with each module and arranged to enable determining an electric field amplitude in a direction transverse to the direction of the cable from magnetic field gradient.

31. The cable of claim 30 wherein each module further comprises at least one triaxial magnetic field sensor and a high frequency magnetic field sensor.

32. The cable of claim 30 wherein each module further comprises at least one laterally extending sensor arm affixed to the module, the at least one sensor arm including at least one electrode thereon.

33. The cable of claim 32 wherein the at least one sensor arm comprises at least one magnetic field sensor.

34. The cable of claim 33 wherein the at least one sensor arm comprises a plurality of spaced apart magnetic field sensors.

35. The cable of claim 30 wherein each module further comprises a vertically extending sensor arm affixed to the module, the at least one sensor arm including at least one electrode thereon.

36. The cable of claim 35 wherein the vertically extending sensor arm comprises at least one magnetic field sensor.

37. The cable of claim 36 wherein the vertically extending sensor arm comprises a plurality of spaced apart magnetic field sensors.

38. The cable of claim 30 wherein each module comprises at least one seismic sensor.

39. The cable of claim 30 wherein the seismic sensor comprises a triaxial geophone.

40. The cable of claim 30 wherein each module comprises electrical circuitry for digitizing and communicating signals detected by the at least one pair of electrodes and the at least one magnetic field sensor.

41. The cable of claim 30 wherein each module comprises a gravity sensor.

42. The cable of claim 30 wherein each module comprises at least one magnetic field sensor.

43. The cable of claim 30 wherein each module comprises a gravity sensor.

44. A marine electromagnetic surveying system, comprising:

a vessel towing at least one electromagnetic antenna in a body of water;

a controllable source of electric current disposed on the vessel;

a plurality of sensor modules disposed at spaced apart locations along a cable, each module including at least one pair of electrodes associated therewith, the electrodes arranged to measure electric field in a direction along the direction of the cable; and

a plurality of spaced apart magnetic field sensors associated with each module and arranged to enable determining an electric field amplitude in a direction transverse to the direction of the cable from magnetic field gradient.

45. The system of claim 44 wherein each module further comprises at least one triaxial magnetic field sensor and a high frequency magnetic field sensor.

46. The system of claim 44 wherein each module further comprises at least one laterally extending sensor arm affixed to the module, the at least one sensor arm including at least one electrode thereon.

47. The system of claim 46 wherein the at least one sensor arm comprises at least one magnetic field sensor.

48. The system of claim 47 wherein the at least one sensor arm comprises a plurality of spaced apart magnetic field sensors.

49. The system of claim 44 wherein each module further comprises a vertically extending sensor arm affixed to the module, the at least one sensor arm including at least one electrode thereon.

50. The system of claim 49 wherein the vertically extending sensor arm comprises at least one magnetic field sensor.

51. The system of claim 50 wherein the vertically extending sensor arm comprises a plurality of spaced apart magnetic field sensors.

52. The system of claim 44 wherein each module comprises at least one seismic sensor.

53. The system of claim 44 wherein the seismic sensor comprises a triaxial geophone.

54. The system of claim 44 wherein each module comprises electrical circuitry for digitizing and communicating signals detected by the at least one pair of electrodes and the at least one magnetic field sensor.

55. The system of claim 44 wherein each module comprises a gravity sensor.

56. The system of claim 44 wherein each module comprises at least one magnetic field sensor.

57. The system of claim 44 wherein each module comprises a gravity sensor.