Method and apparatus for determining the nature of submarine reservoirs

• US 7,567,084 B2
• Filed: 03/17/2004
• Issued: 07/28/2009
• Est. Priority Date: 03/17/2003
• Status: Expired due to Fees

• Current Assignee: Electromagnetic Geoservices ASA
• Original Assignee: Electromagnetic Geoservices ASA
• Inventors: Pettersen, legal representative, Pedersen, Hans Magne, Johansen, Stale, Farestveit, Anders, Ellingsrud, Svein, Eidesmo, Terje
• Primary Examiner(s): LEDYNH, BOT L
• Application Number:
  US10/549,660
• Publication Number:
  US 20060197532A1
• Time in Patent Office: 1,959 Days
• Field of Search: 324/330-332,334,337,344-345,354,357,365 367/141,178 181/101,108-113,122
• US Class Current: 324/334
• CPC Class Codes: G01V 11/00 Prospecting or detecting by methods combining techniques covered by two or more of main groups G01V1/00 - G01V9/00
• CPC Class Codes: G01V 2210/6163 Electromagnetic

Abstract

A system for investigating subterranean strata. An electromagnetic field and a seismic event are applied from the same location and the responses are detected using respective receivers both located at a second location spaced from the first. The responses are combined to identify the presence and/or nature of subterranean reservoir. The refracted wave components are used.

Claims

1. A method of producing a survey report of subterranean strata which comprises:

deploying an electromagnetic (EM) field transmitter;

deploying a seismic source at substantially the same location as the EM field transmitter;

deploying an EM field receiver at a predetermined offset distance from the transmitter;

deploying a seismic receiver at substantially the same location as the EM field receiver;

applying an EM field to the strata using the EM field transmitter;

detecting the EM wave field response using the EM field receiver;

applying a seismic event to the strata using the seismic source at substantially the same location as the EM field transmitter;

detecting the seismic response using the seismic receiver at substantially the same location as the EM field receiver;

analyzing the EM wave field response;

analyzing the seismic response;

reconciling the two responses, in order to produce a report on the presence and nature of the strata;

identifying the refracted wave component of the EM wave field response;

identifying the refracted wave component of the seismic response; and

using the two refracted wave components to produce the survey report.

2. A method as claimed in claim 1, which additionally includes extracting and using phase and/or amplitude information from the responses.

3. A method as claimed in claim 1, in which phase and/or amplitude information from the two refracted wave components is used.

10. A method as claimed in claim 1, in which the EM field transmitter comprises an electric dipole antenna.

11. A method as claimed in claim 1, in which the EM field receiver comprises an electric dipole antenna.

12. A method as claimed in claim 1, in which the EM field receiver and the seismic receiver are mounted on the same structure.

13. A method as claimed in claim 1, in which the EM field and the seismic event are applied simultaneously.

14. A method as claimed in claim 1, in which the EM field and the seismic event are applied closely sequentially.

15. A method as claimed in claim 1, in which the reflected wave component of the seismic response is identified and the reflected wave component is used to identify subterranean strata.

16. A method as claimed in claim 1, which includes:

additionally, deploying a magnetic receiver at substantially the same location as the EM field receiver;

detecting a magnetic field response; and

using the magnetic field response in combination with the EM wave field response and the seismic response.

17. A method as claimed in claim 1, which comprises repeating the procedure with the EM field transmitter and seismic source, and/or the EM field receiver and seismic receiver, in different locations for a plurality of EM transmissions and seismics events.

18. A method as claimed in claim 1, in which the procedure is repeated at different offsets.

19. A method as claimed in claim 1 which includes the deployment and use of a plurality of EM field receivers and/or a plurality of seismic receivers.

20. A method as claimed in claim 19, in which the EM field receivers and the seismic receivers are mounted on a cable.

21. A method as claimed in claim 1, in which the EM field transmitter and/or the seismic source, and/or EM receiver and/or seismic receiver, are located on or close to the seabed or the bed of some other area of water.

22. A method as claimed in claim 21, in which the seismic source is located at or near the surface of the area of water.

23. A method as claimed in claim 1, in which the frequency of the EM field is continuously varied over the transmission period.

24. A method as claimed in claim 1, in which the EM field is transmitted for a period of time for 3 seconds to 60 minutes.

25. A method as claimed in claim 24, in which the transmission time is from 10 seconds to 5 minutes.

26. A method as claimed in claim 1, in which the wavelength of the transmission is given by the formula:

0.1 s≦

λ

≦

10 s;

wherein λ

is the wavelength of the transmission through the overburden and s is the distance from the seabed to the reservoir.

27. A method as claimed in claim 1, in which the offset between the EM field transmitter and the EM field receiver is given by the formula:

0.5λ

≦

L≦

10λ

;

where λ

is the wavelength of the transmission through the overburden and L is the distance between the transmitter and the receiver.

28. A method as claimed in claims 23, in which the transmission frequency is from 0.01 Hz to 1 kHz.

29. A method as claimed in claim 28, in which the transmission frequency is from 0.1 to 20 Hz.

30. A method as claimed in claim 1, in which the seismic receiver records a full flow component seismic recording, comprising three displacement vector components and a pressure component.

31. Apparatus for use in carrying out a method as claimed in claim 1, including a receiver assembly comprising:

a support structure;

an electric dipole receiver antenna mounted on the support structure;

a three axis seismic receiver mounted on the support structure;

a geophone arrangement mounted on the support structure;

a hydrophone mounted on the support structure; and

an anchor arranged to attach the support structure to a sea bed.

33. A method as claimed in claim 14, in which the EM field is applied within approximately 5 to 25 seconds of the seismic event.

4. A method of producing a survey report of subterranean strata using an electromagnetic (EM) wave field response from an applied EM field and a seismic response from an applied seismic event, the method comprising:

deploying an EM field transmitter;

deploying a seismic source;

deploying an EM field receiver at a predetermined offset from the EM field transmitter;

deploying a seismic receiver at a predetermined offset from the seismic source;

applying an EM field to the strata using the EM field transmitter;

detecting the EM wave field response using the EM field receiver;

applying a seismic event to the strata using the seismic source;

detecting the seismic response using the seismic receiver;

identifying a first refracted wave component of the EM wave field response;

identifying a second refracted wave component of the seismic response; and

using the first and second refracted wave components to produce a report on a presence and a nature of the strata.

5. A method as claimed in claim 4, in which the EM field transmitter, the seismic source and the two receivers are all in the same plane.

6. A method as claimed in claim 4, in which the distance between the two receivers is 25 meters or less.

7. A method as claimed in claim 4, in which the distance between the EM field transmitter and the seismic source is ≦

0.01 times the value of the offset between the EM field transmitter and the EM field receiver.

8. A method as claimed in claim 4, in which the EM field transmitter and the seismic source are at substantially the same location.

9. A method as claimed in claim 4, in which the EM field receiver and the seismic receiver are at substantially the same location.

32. A method as claimed in claim 6, in which the distance between the two receivers is 5 meters or less.