Multi-sensor system for airborne geophysical prospecting and method

Patent metadata

Field	Value
Publication number	US-11531134-B2
Application number	US-202117182399-A
Country	US
Kind code	B2
Filing date	Feb 23, 2021
Priority date	Dec 17, 2014
Publication date	Dec 20, 2022
Grant date	Dec 20, 2022

Abstract

A multi-sensor electromagnetic (EM) system and method for measuring gradients of EM signals. The multi-sensor EM system includes a frame; a transmitter device attached to the frame and configured to generate a primary EM field; a receiver device attached to the frame and configured to record a secondary EM field generated by the earth after being excited by the primary EM field; and a gradient sensor device attached to the frame and configured to record a gradient of the secondary EM field.

First claim

What is claimed is:

1. A multi-sensor electromagnetic (EM) system for measuring earth EM response to an EM excitation while the multi-sensor EM system is flown over a surveyed area, the multi-sensor EM system comprising:
a transmitter device configured to generate the EM excitation;
a receiver device configured to detect and record an EM field generated by the earth in response to the EM excitation;
a gradient sensor device configured to record a gradient of the EM field,
wherein a transmitter coil of the transmitter device and at least one receiver coil of the receiver device are arranged substantially in a plane, and the gradient sensor device includes two coils placed out of the plane.

2. The system of claim 1 , wherein the two coils of the gradient sensor device are placed substantially parallel with and on either side of the plane.

3. The system of claim 2 , wherein the two coils of the gradient sensor device are placed substantially at same distance from the plane.

4. The system of claim 1 , wherein the two coils of the gradient sensor are electrically connected and configured to have current flowing in opposite directions.

5. The system of claim 1 , wherein the receiver device has two receiver coils coplanar with the transmitter coil, one of the two receiver coils surrounding the transmitter coil and another of the two receiver coils being surrounded by the transmitter coil.

6. The system of claim 5 , wherein the two receiver coils are electrically connected and configured to have current flowing in opposite directions.

7. The system of claim 1 , further comprising a peripheral sensor configured to determine a location and/or an orientation of at least one of the transmitter device, the receiver device and the gradient sensor.

8. The system of claim 7 , wherein the peripheral sensor includes a global positioning system.

9. The system of claim 7 , wherein the peripheral sensor includes at least one of a radar, laser altimeter, gyroscope, or inclinometer.

10. The system of claim 1 , further comprising:
a controller electrically connected to the transmitter device, the controller controlling each of three transmitter coils of the transmitter device to generate a magnetic field with a given pulse repetition frequency.

11. The system of claim 1 , wherein the transmitter device includes three transmitter coils perpendicular to each other, the receiver device includes three receiver coils perpendicular to each other, and the gradient sensor device includes three pairs of gradient coils perpendicular to each other, the transmitter coil and the at least one receiver coil of the receiver device arranged substantially in the plane, being one of the three transmitter coils and of the three receiver coils, respectively, and having one of the three pairs of gradient coils being the two coils placed out of the plane.

12. The system of claim 11 , wherein each of the three pairs of gradient coils have coils arranged parallel to one another, on either side of a respective one of the three receiver coils.

13. The system of claim 12 , wherein coils of any of the three pairs of gradient coils are electrically connected so that a current flowing in one of the coils has opposite direction to a current flowing in another one of the coils.

14. The system of claim 1 , further comprising a support structure configured to maintain relative positions of coils of the transmitter device, of the receiver device and of the gradient sensor while the multi-sensor EM system is flown over a surveyed area.

15. A multi-sensor electromagnetic (EM) system for measuring earth EM response to an EM excitation while the multi-sensor EM system is flown over a surveyed area, the multi-sensor EM system comprising:
a transmitter device configured to generate the EM excitation;
a receiver device configured to detect and record an EM field generated by the earth in response to the EM excitation;
a gradient sensor device configured to record a gradient of the EM field,
wherein the transmitter device, the receiver device and the gradient sensor device are configured to generate the EM excitation, detect the EM field and the gradient of the EM field on three non-coplanar directions,
wherein, for at least one of the three directions, coils of the transmitter device and of the receiver device are coplanar and two coils of the gradient sensor device are placed symmetrically on either side and parallel with a plane of the coils of the transmitter device and of the receiver device.

16. The multi-sensor electromagnetic (EM) system of claim 15 , wherein the three non-coplanar directions are perpendicular to one another.

17. The multi-sensor electromagnetic (EM) system of claim 15 , wherein the two coils of the gradient sensor device are electrically connected and configured to have current flowing in opposite directions.

18. The multi-sensor electromagnetic (EM) system of claim 15 , further comprising:
a support structure configured to maintain an arrangement of the transmitter device, the receiver device and the gradient sensor while the multi-sensor EM system is flown over the surveyed area; and
a peripheral sensor configured to determine location and/or orientation of at least one of the transmitter device, the receiver device and the gradient sensor while the multi-sensor EM system is flown over the surveyed area.

19. A method of geophysical exploration using a multi-sensor electromagnetic (EM) system for measuring earth EM response to an EM excitation, the method comprising:
flying a multi-sensor EM system over a surveyed area;
controlling a transmitter device of the multi-sensor EM system to generate an EM excitation;
recording an EM field generated by the earth in response to the EM excitation, using with a receiver device of the multi-sensor EM system; and
recording a gradient of the EM field with a gradient sensor device of the multi-sensor EM system,
wherein the transmitter device, the receiver device and the gradient sensor device are configured to generate the EM excitation, to detect the EM field and the gradient of the EM field, respectively, on three directions perpendicular to one another,
wherein, for at least one of the three directions, coils of the transmitter device and of the receiver device are coplanar and two coils of the gradient sensor device are placed symmetrically on either side and parallel with a plane of the coils of the transmitter device and of the receiver device.

Assignees

• Cgg Services Sas

Inventors

• Miles Philip

Classifications

• G01V3/16

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

• G01V3/165 Primary

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