Apparatus and method for determining earth's near-surface properties with on-time measurements from airborne time-domain electromagnetic data

Patent metadata

Field	Value
Publication number	US-10520635-B2
Application number	US-201615738685-A
Country	US
Kind code	B2
Filing date	Aug 31, 2016
Priority date	Sep 2, 2015
Publication date	Dec 31, 2019
Grant date	Dec 31, 2019

Abstract

A device and method for calculating electrical properties of a surveyed underground formation. The method includes selecting a waveform having multiple current transition rates; placing a time-domain electromagnetic (TEM) system above the underground formation while generating with a transmitter a transient primary magnetic field during an on-time period and no magnetic field during a following off-time period, due to the waveform; and recording with a receiver magnetic related data generated by the earth as a result of the transient primary magnetic field. The receiver records the magnetic related data during the on-time period using plural on-time gates sampling.

First claim

What is claimed is:

1. A method for calculating electrical properties of a surveyed underground formation, the method comprising:
selecting a waveform having multiple current transition rates;
placing a time-domain electromagnetic (TEM) system above the underground formation while generating with a transmitter a transient primary magnetic field during an on-time period and no magnetic field during a following off-time period, due to the waveform; and
recording with a receiver magnetic related data generated by the earth as a result of the transient primary magnetic field,
wherein the receiver records the magnetic related data during the on-time period using plural on-time gates sampling.

2. The method of claim 1 , wherein the waveform has continuously varying current transition rates.

3. The method of claim 1 , wherein the waveform has multiple different current transition rates.

4. The method of claim 1 , wherein the gates are placed in time to more densely sample the magnetic related data near changes in a slope of the multiple different current transitions.

5. The method of claim 1 , wherein the waveform is part of a sine function.

6. The method of claim 1 , wherein the waveform has a continuously varying slope.

7. The method of claim 1 , wherein the on-time gates have a width that varies in time.

8. The method of claim 7 , wherein the width of the on-time gates increases in time.

9. The method of claim 1 , further comprising:
recording with the receiver the magnetic related data during the off-time period.

10. The method of claim 1 , wherein the off-time period is followed by another on-time period.

11. The method of claim 1 , further comprising:
generating an image of the surveyed underground formation based on the recorded magnetic related data.

12. A time-domain electromagnetic (TEM) system for calculating electrical properties of a surveyed underground formation, the TEM system comprising:
a controller for receiving a waveform having multiple current transition rates;
a transmitter for generating a transient primary magnetic field during an on-time period and no magnetic field during a following off-time period, when the waveform is applied to the transmitter; and
a receiver for recording magnetic related data generated by the earth as a result of the transient primary magnetic field,
wherein the receiver records the magnetic related data during the on-time period using plural on-time gates sampling.

13. The TEM system of claim 12 , wherein the waveform has continuously varying current transition rates.

14. The TEM system of claim 12 , wherein the waveform has multiple different current transition rates.

15. The TEM system of claim 12 , wherein the waveform is part of a sine function.

16. The TEM system of claim 12 , wherein the waveform has a continuously varying slope.

17. The TEM system of claim 12 , wherein the on-time gates have a width that varies in time.

18. The TEM system of claim 12 , wherein the receiver also records the magnetic related data during the off-time period.

19. The TEM system of claim 12 , wherein the controller is further configured to generate an image of the surveyed underground formation based on the recorded magnetic related data.

20. A non-transitory computer readable medium including computer executable instructions, wherein the instructions, when executed by a processor, implement instructions for calculating electrical properties of a surveyed underground formation, the instructions comprising:
selecting a waveform having multiple current transition rates;
instructing a time-domain electromagnetic (TEM) system to generate, with a transmitter, a transient primary magnetic field during an on-time period and no magnetic field during a following off-time period, due to the waveform; and
recording with a receiver magnetic related data generated by the earth as a result of the transient primary magnetic field,
wherein the receiver records the magnetic related data during the on-time period using plural on-time gates sampling.

Assignees

• Cgg Services Sas

Inventors

• Smiarowski Adam
• Hodges Greg

Classifications

• G01V3/16

  specially adapted for use from aircraft (G01V3/165 - G01V3/175 take precedence) · CPC title

• G01V3/36 Primary

  Recording data (G01V3/34 takes precedence) · CPC title

• G01V3/17

  operating with electromagnetic waves {(operating with millimetre waves G01V8/005)} · CPC title

• G01V3/165

  operating with magnetic or electric fields produced or modified by the object or by the detecting device (with electromagnetic waves G01V3/17) · CPC title

• G01V3/06 Primary

  using AC · CPC title