Wear resistant electrodes for downhole imaging

Patent metadata

Field	Value
Publication number	US-9989665-B2
Application number	US-201514699009-A
Country	US
Kind code	B2
Filing date	Apr 29, 2015
Priority date	Apr 29, 2015
Publication date	Jun 5, 2018
Grant date	Jun 5, 2018

Abstract

Devices and methods for well logging using a wear-resistant electrode are provided. A downhole device may include a drill collar and a first electrode mounted on the drill collar. Further, the first electrode may include a wear-resistant face. The first electrode may be movably coupled within the drill collar, and the first electrode may be configured to extend and retract into a wellbore to maintain contact with a wall of the wellbore. Furthermore, the first electrode may be configured to measure impedance of a geological formation.

First claim

The invention claimed is:

1. A downhole device, comprising:
a drill collar configured to move along a first axis of a wellbore;
a first electrode mounted on the drill collar, wherein the first electrode comprises a wear-resistant face, wherein the wear-resistant face is electrically conductive;
wherein the first electrode is movably coupled within the drill collar, the first electrode is configured to extend and retract along a second axis that is transverse to the first axis into the wellbore to maintain contact with a wall of the wellbore, and the first electrode is configured to measure impedance of a geological formation based at least in part on an electrical current flowing through the wear-resistant face and the geological formation.

2. The downhole device of claim 1 , wherein the wear- resistant face comprises a polycrystalline diamond face formed with diamond grains and an electrically conductive solvent-catalyst.

3. The downhole device of claim 2 , wherein the electrode comprises a carbide base, and the polycrystalline diamond face comprises an unleached polycrystalline diamond material formed with a metal solvent-catalyst.

4. The downhole device of claim 3 , wherein the metal solvent-catalyst comprises cobalt or iron.

5. The downhole device of claim 1 , wherein the wear-resistant face comprises tungsten carbide or stellite.

6. The downhole device of claim 1 , wherein the first electrode comprises an upper mobile guidance surface comprising a leached polycrystalline diamond material.

7. The downhole device of claim 6 , wherein the leached polycrystalline diamond material is formed with a metal solvent-catalyst, and the metal solvent catalyst is removed from a surface of the leached polycrystalline diamond material up to 200 microns deep.

8. The downhole device of claim 7 , wherein the leached polycrystalline diamond material comprises an insulating material applied to the upper mobile guidance surface that fills void spaces after leaching.

9. The downhole device of claim 1 , wherein a transmitting toroidal transformer is mounted around the drill collar, and the transmitting toroidal transformer generates a voltage drop across the first electrode, and wherein the voltage drop stimulates a current flow into the geological formation.

10. The downhole device of claim 1 , wherein the first electrode is movably coupled within the drill collar with a hinge.

11. A downhole device, comprising:
a drill collar;
a stabilizer mounted on the drill collar;
a first electrode and a second electrode movably mounted within the stabilizer and comprising a wear resistant face, wherein the first electrode or the second electrode comprises a wear-resistant face comprising a leached polycrystalline diamond material for which a conductive metal-solvent has been removed;
a transmitting toroidal transformer mounted within the stabilizer and around a circumference of the first electrode; and
a measure toroidal transformer mounted within the stabilizer and around a circumference of the second electrode;
wherein the first electrode and the second electrode maintain contact with a wall of a wellbore during a drilling operation, the first electrode injects current into a geological formation during the drilling operation, and the second electrode receives current from the geological formation during the drilling operation.

12. The downhole device of claim 11 , wherein the wear resistant face comprises a polycrystalline diamond material formed with diamond grains and an electrically conductive solvent catalyst.

13. The downhole device of claim 11 , wherein the downhole device is configured to operate in an oil based mud (OBM) environment, a synthetic based mud (SBM) environment, and a water based mud (WBM) environment within the wellbore.

14. The downhole device of claim 13 , wherein the current injected into the geological formation is within a frequency range of 100 kHz to 100 MHz in the OBM environment within the wellbore, and the current is within a frequency range of 1kHz to 100 MHz in the WBM environment within the wellbore.

15. The downhole device of claim 11 , wherein a force supplied to the first electrode and the second electrode to maintain contact with the wall of the wellbore is provided by a drilling fluid pressure differential between drilling fluid flowing within the drill collar and the drilling fluid on an outside of the drilling collar.

16. The downhole device of claim 15 , wherein the force supplied to the first electrode and the second electrode is sufficient to maintain contact with the wall of the wellbore, but not sufficient to cut into the geological formation.

17. The downhole device of claim 16 , wherein the force supplied to the first electrode and the second electrode is between 20 psi and 130 psi.

18. The downhole device of claim 11 , wherein the wear resistant face comprises conductive tungsten carbide or stellite.

19. A downhole device, comprising:
a drill collar;
an upset mounted on the drill collar;
a first electrode movably mounted within the upset and comprising a wear-resistant face, wherein the wear-resistant face is electrically conductive;
and a hinged pad mounted on the upset, wherein the first electrode is configured to extend and retract through a hole disposed on the hinged pad, the hinged pad is movably mounted to the upset, the first electrode and the hinged pad maintain contact with a wall of a wellbore during a drilling operation, and the first electrode is configured to measure impedance of a geological formation based at least in part on an electrical current flowing through the wear-resistant face and the geological formation.

20. The downhole device of claim 18 , wherein the wear-resistant face comprises conductive polycrystalline diamond (PCD) material.

21. The downhole device of claim 18 , wherein the first electrode comprises a transmitting toroidal transformer and a measure toroidal transformer configured to measure impedance of a geological formation, and wherein the transmitting toroidal transformer operates as a current source, and the measure toroidal transformer operates as a current receiver.

22. The downhole device of claim 18 , wherein the first electrode comprises a single toroidal transformer configured to measure impedance or dielectric properties of a geological formation.

23. The downhole device of claim 18 , wherein a force exerted on the first electrode and the hinged pad to maintain contact with the wall of the wellbore is provided by a spring.

24. The downhole device of claim 18 , wherein an upper static guidance surface of the upset mounted on the drill collar comprises a polycrystalline diamond (PCD) material.

25. The downhole device of claim 18 , wherein the hinged pad comprises a measure toroidal transformer.

Assignees

• Schlumberger Technology Corp

Inventors

• Clark Brian O
• Orban Jacques
• Marshall Jonathan D
• Woolston Scott R
• Hendricks Daniel
• Cannon Neil

Classifications

• G01V3/26

  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 title

• G01V3/20 Primary

  operating with propagation of electric current · CPC title

• G01V3/18

  specially adapted for well-logging · CPC title

• E21B49/00

  Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells · CPC title

• E21B47/017 Primary

  Protecting measuring instruments · CPC title