System and method for sensing using diamond based microelectrodes

• US 20080257730A1
• Filed: 06/27/2008
• Published: 10/23/2008
• Est. Priority Date: 08/04/2003
• Status: Active Grant

• Current Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Original Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Inventors: Jiang, Li, Jones, Timothy Gareth John, Hall, Clive Edward
• Granted Patent: US 8,241,474 B2
• Time in Patent Office: Days
• US Class Current: 204/412
• CPC Class Codes: E21B 49/082 Wire-line fluid samplers E21B49/083 takes precedence
• CPC Class Codes: G01N 27/403 Cells and electrode assemblies

Abstract

A method and system is disclosed for monitoring one or more characteristics associated with a fluid. An insulating layer comprising non-conducting diamond is positioned within a housing and has a surface exposed directly or indirectly to the fluid. A plurality of microelectrodes made of electrically conducting diamond each have a surface exposed directly or indirectly to the fluid. An electrical circuit in electrical communication with each of the microelectrodes is adapted to convert electrical signals from the microelectrodes into at least one signal associated with a characteristic being monitored. The sensing system is well suited to hydrocarbon wellbore related applications, but can also be used in other applications.

Claims

1. A sensor for monitoring characteristics associated with a fluid, the sensor comprising:

a housing;

an insulating layer comprising non-conducting diamond positioned within said housing and having a surface exposed directly or indirectly to the fluid;

a plurality of microelectrodes each comprising electrically conducting diamond and having a surface exposed directly or indirectly to the fluid; and

an electrical circuit in electrical communication with each of the microelectrodes adapted to convert electrical signals from the microelectrodes into at least one signal associated with a characteristic being monitored, wherein the characteristic being monitored is one of the presence of hydrogen sulphide within the fluid and the pH of the fluid.

2. A sensor according to claim 1 wherein the size of the exposed surface of each microelectrode is less than 8000 sq. microns.

3. A sensor according to claim 2 wherein the size of the exposed surface of each microelectrode is less than 2000 sq. microns.

4. A sensor according to claim 3 wherein the size of the exposed surface of each microelectrode is less than 500 sq. microns.

5. A sensor according to claim 4 comprising at least seven microelectrodes.

6. A sensor according to claim 5 comprising at least 19 microelectrodes.

7. A sensor according to claim 6 comprising at least 50 microelectrodes.

8. A sensor according to claim 4 wherein the microelectrodes are arranged within the insulating layer such that the exposed surfaces of the microelectrodes form a regular pattern.

9. A sensor according to claim 8 wherein said pattern is a hexagonal pattern.

10. A sensor according to claim 9 wherein said pattern is a square pattern.

11. A sensor according to claim 5 wherein the microelectrodes are arranged within the insulating layer such that the exposed surfaces of the microelectrodes form an irregular pattern.

12. A sensor according to claim 5 wherein distance between two adjacent microelectrodes is at least five times the diameter of a circle having an area equal to the area the exposed surface of each microelectrode.

13. A sensor according to claim 12 wherein distance between two adjacent microelectrodes is at least ten times the diameter of a circle having an area equal to the area the exposed surface of each microelectrode.

14. A sensor according to claim 1 where the microelectrodes are position within the insulating layer and the exposed surface each of the microelectrodes is co-planar with the exposed surface of the insulating layer.

15. A sensor according to claim 1 further comprising a counter electrode mounted within the housing and having a surface exposed directly or indirectly to the fluid, and wherein the microelectrodes form a working electrode.

16. A sensor according to claim 15 further comprising a reference electrode mounted within the housing and having a surface exposed directly or indirectly to the fluid.

17. A sensor according to claim 15 further comprising a gas permeable membrane mounted between a main flow of fluid and the exposed surfaces of the insulating layer and the microelectrodes, wherein the sensor is adapted to sense characteristics associated with a gas that is allowed to pass though the membrane.

18. A sensor according to claim 1 wherein the housing is made from polyetheretherketone or similar material.

19. A sensor according to claim 1 wherein the exposed surface of each microelectrode is modified so as to be sensitive to pH.

20. A sensor according to claim 1 wherein the exposes surface of at least one of the microelectrodes is modified using N,N′

-dimethyl-phenylenediamine, or a structural analogue.

21. A system for monitoring fluids produced from one or more wellbores comprising a sensor according to claim 1.

22. A system according to claim 21 further comprising a wellbore fluids sampling tool, wherein the sensor is mounted within the sampling tool.

23. A system according to claim 22 wherein the sampling tool is adapted to sample wellbore fluids in open hole sections of a wellbore.

24. A system according to claim 22 wherein the sampling tool is adapted to sample wellbore fluids in cased hole sections of a wellbore.

25. A system according to claim 21 further comprising a production logging tool, wherein the sensor is mounted on a portion of the production logging tool.

26. A system according to claim 29 further comprising a subassembly for sensing characteristics within a wellbore during the drilling process, wherein the sensor is mounted with the subassembly which is adapted to be part of bottom hole assembly.

27. A system according to claim 21 wherein the sensor is mounted on a conduit through which the produced fluids flow.

28. A system according to claim 21 wherein the one or more wellbores are drilled in a water reservoir.

29. A system according to claim 21 wherein the one or more wellbores are used for CO2 sequestration.

30. A system monitoring fluids flowing in a conduit wherein a sensor according to claim 1 is mounted on the conduit.