Logging Tool With Electric Dipole Source and Magnetic Sensor For Forward and Lateral Imaging

• US 20180292560A1
• Filed: 04/10/2017
• Published: 10/11/2018
• Est. Priority Date: 04/10/2017
• Status: Active Grant

• Current Assignee: Saudi Arabian Oil Company (Government of Saudi Arabia)
• Original Assignee: Aramco Services Company (Government of Saudi Arabia)
• Inventors: Hagiwara, Teruhiko
• Granted Patent: US 10,557,961 B2
• Time in Patent Office: Days
• CPC Class Codes: G01V 3/26 operating with magnetic or electric fields produced or modified either by the surrounding earth formation or by the detecting device with electromagnetic waves G01V3/30
• CPC Class Codes: G01V 3/28 using induction coils

Abstract

A logging method and system for imaging forward and lateral sections of a subterranean formation. An electric dipole source generates electromagnetic field in the formation that is sensed with magnetic flux sensor that is spaced a distance away from the electric dipole source. The resulting electric dipoles can be axial or transverse, and magnetic flux sensors can sense magnetic fields oriented axially or orthogonally. The axial and transverse electric dipoles can be collocated, and magnetic flux sensors that sense axial or orthogonal magnetic fields can be collocated. Analyzing changes in the magnitude of signals sensed by magnetic flux sensors can indicate the presence and distance of bed boundaries that are ahead and lateral to the electric dipole source.

Claims

1. A method of operations in a borehole comprising:

generating an electric dipole in the borehole with an electric dipole source that comprises oppositely charged electrodes, the electric dipole forming an electromagnetic field in a formation that surrounds the borehole;

using a coil in the borehole at a location spaced axially away from the electrodes to sense magnetic flux that is generated by the electromagnetic field; and

based on the step of sensing magnetic flux, identifying a distance and a direction from the electric dipole source to a bed boundary that is in the formation.

2. The method of claim 1, wherein the bed boundary is spaced away from the electric dipole in an axial direction of the borehole.

3. The method of claim 1, wherein the bed boundary is spaced away from the electric dipole in a radial direction of the borehole.

4. The method of claim 1, wherein the electric dipole is oriented along a path that is substantially transverse to an axis of the borehole and wherein a direction of the measured magnetic flux extends along a path that is oriented substantially parallel to an axis of the borehole.

5. The method of claim 1, wherein the electric dipole is oriented along a path that is substantially parallel to an axis of the borehole and wherein a direction of the measured magnetic flux extends along a path that is oriented substantially orthogonal to an axis of the borehole.

6. The method of claim 1, wherein the electric dipole is oriented along a path that is substantially transverse to an axis of the borehole and wherein a direction of the measured magnetic flux extends along a path that is oriented substantially orthogonal to an axis of the borehole and to an orientation of the electric dipole source.

7. The method of claim 4, further comprising measuring magnetic flux in a direction that extends along a path that is oriented substantially orthogonal to an axis of the borehole.

8. The method of claim 4, further comprising generating an electric dipole that is oriented along a path that is substantially parallel to an axis of the borehole.

9. The method of claim 4, wherein the measured magnetic flux provides an indication of a bed boundary that is spaced away from the electric dipole along a path that is substantially parallel with an axis of the borehole.

10. The method of claim 5, wherein the measured magnetic flux provides an indication of a bed boundary that is spaced away from the electric dipole along a path that is substantially transverse to an axis of the borehole.

11. The method of claim 6, wherein the measured magnetic flux provides an indication of a bed boundary that is spaced away from the electric dipole along a path that is substantially transverse to an axis of the borehole.

12. A method of operations in a borehole comprising:

generating a magnetic field in a formation that surrounds the borehole by generating an electric dipole in the borehole;

measuring magnetic flux in the borehole at a location that is spaced axially away from the electric dipole; and

identifying a bed boundary in the formation based on the step of measuring magnetic flux.

13. The method of claim 12, wherein the electric dipole extends along a path generally transverse to an axis of the borehole, and wherein lines of magnetic flux being measured extend along a path that is selected from the group consisting of generally parallel with an axis of the borehole and generally orthogonal to the axis of the borehole and to the transverse electric dipole.

14. The method of claim 12, wherein the electric dipole extends along a path generally parallel with an axis of the borehole, and wherein lines of magnetic flux being measured extend along a path that is orthogonal with the axis of the borehole, and wherein the electric dipole is formed within a drill string having a drill bit, the method further comprising steering the drill bit away from the bed boundary.

15. A tool for use in a borehole comprising:

a means for forming an electric dipole that generates a magnetic field in a formation surrounding the borehole, the means being coupled to the housing;

a means for sensing magnetic flux generated by the electric dipole;

a housing disposable in the borehole that is coupled to the means for forming an electric dipole and coupled to the means for sensing magnetic flux; and

a means for identifying the presence of a bed boundary in the formation in a direction spaced axially and radially from the housing.

16. The tool of claim 15, wherein the means for forming an electric dipole comprises transversely disposed electrodes that generate an dipole that projects transverse to an axis of the housing, and wherein the means for sensing magnetic flux generated by the electric dipole comprises windings that are generally coaxial with a path that extends orthogonal with the axis of the housing.

17. The tool of claim 15, wherein the means for forming an electric dipole comprises transversely disposed electrodes that generate an dipole that projects transverse to an axis of the housing, and wherein the means for sensing magnetic flux generated by the electric dipole comprises a winding that is generally coaxial with an axis of the housing.

18. The tool of claim 15, wherein the means for forming an electric dipole comprises axially spaced apart ring electrodes that generate an dipole that projects generally parallel with an axis of the housing, and wherein the means for sensing magnetic flux generated by the electric dipole comprises windings that are generally coaxial with a path that extends orthogonal with the axis of the housing.

19. The tool of claim 15, wherein the means for forming an electric dipole comprises transversely disposed electrodes that generate an dipole that projects transverse to an axis of the housing, and wherein the means for sensing magnetic flux generated by the electric dipole comprises windings that are generally coaxial with a path that extends orthogonal with the axis of the housing and a winding that is generally coaxial with an axis of the housing.

20. The tool of claim 15, wherein the means for forming an electric dipole comprises transversely disposed electrodes that generate an dipole that projects transverse to an axis of the housing and axially spaced apart ring electrodes that generate an dipole that projects generally parallel with the axis of the housing, and wherein the means for sensing magnetic flux generated by the electric dipole comprises windings that are generally coaxial with a path that extends orthogonal with the axis of the housing.