ELECTRO-CHEMICAL SENSOR

• US 20080023328A1
• Filed: 07/23/2007
• Published: 01/31/2008
• Est. Priority Date: 01/08/2004
• Status: Active Grant

• Current Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Original Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Inventors: Lawrence, Nathan, Wildgoose, Gregory, Jiang, Li, Pandurangappa, Malingappagari, Meredith, Andrew, Compton, Richard, Jones, Timothy, Mullins, Oliver, Pagels, Markus
• Granted Patent: US 8,177,958 B2
• Time in Patent Office: Days
• US Class Current: 204/407
• CPC Class Codes: G01N 27/302 pH sensitive, e.g. quinhydron, antimony or hydrogen electrodes ion selective electrodes G01N27/333, glass electrodes G01N27/36
• CPC Class Codes: G01N 27/308 at least partially made of carbon
• CPC Class Codes: G01N 27/3335 the membrane containing at least one organic component G01N27/3271 takes precedence; aspects concerning the enzyme reagent in enzyme electrodes C12Q1/001

Abstract

An electro-chemical sensor is described having one or more redox species sensitive to a certain analyte and one or more redox species that are insensitive to that analyte, for the purpose of making measurements in a downhole environment in aquifers or oilfield reservoirs.

Claims

1. An electro-chemical sensor for sensing properties of fluids in a downhole environment in aquifers or oilfield reservoirs, comprising:

a first set of redox species, wherein the first set of redox species comprises one or more redox species that are sensitive to a certain analyte; and

a second set of redox species, wherein the second set of redox species comprises one or more redox species that are insensitive to the certain analyte.

2. The electro-chemical sensor in accordance with claim 1, wherein the first set of redox species and the second set of redox species are coupled with a working electrode.

3. The electro-chemical sensor in accordance with claim 1, wherein the first set of redox species and the second set of redox species are contained in a single component.

4. The electro-chemical sensor in accordance with claim 2, wherein the single component comprises a polymer.

5. The electro-chemical sensor in accordance with claim 1, wherein the certain analyte comprises protons.

6. The electro-chemical sensor in accordance with claim 1, further comprising:

a signal processor coupled with the first set of redox species and the second set of redox species, wherein the signal processor is configured to determine a presence of the certain analyte from an electro-chemical signal difference between the first set of redox species and the second set of redox species.

7. The electro-chemical sensor in accordance with claim 1, further comprising:

a detector adapted to measure a redox potential of said first set of redox species and said second set of redox species in the presence of the certain analyte and to convert measurements into an signal indicative of the concentration of said certain analyte.

8. The electro-chemical sensor in accordance with claim 1, further comprising a first

a voltage supply and an electric current detector to perform voltammetric measurements;

and

an analyzer to detect relative shifts in said voltammetric measurements.

9. The electro-chemical sensor in accordance with claim 6, wherein the electro-chemical signal difference comprises an electro-chemical potential between a first redox couple and a second redox couple.

10. The electro-chemical sensor in accordance with claim 1, wherein:

the first set of redox species comprises one or more redox species sensitive to pH; and

the second set of redox species comprises one or more redox species insensitive to pH.

11. The electro-chemical sensor in accordance with claim 10, wherein the one or more redox species sensitive to pH contain a hydroquinone or quinone moiety.

12. The electro-chemical sensor in accordance with claim 10, wherein the one or more species insensitive to pH contain one of a ferrocene moiety, a ruthenocene moiety and a hexacyanometallate moiety.

13. The electro-chemical sensor in accordance with claim 1, wherein the first set of redox species and the second set of the redox species are immobilized onto a surface of one or more electrodes, and wherein the one or more electrodes comprise carbon.

14. The electro-chemical sensor in accordance with claim 1, wherein:

the first set of redox species is immobilized onto a first surface of a first carbon electrode; and

the second set of redox species is immobilized onto a second surface of a second carbon electrode.

15. The electro-chemical sensor in accordance with claim 13, wherein the immobilization is achieved by direct mixing of the first set of redox species and the second set of redox species with carbon and sealing of the mixture of the first set of redox species, the second set of redox species and the carbon in a binder matrix.

16. The electro-chemical sensor in accordance with claim 14, wherein:

the immobilization of the first set of redox species is achieved by direct mixing of the first set of redox species with carbon and sealing of the mixture of the first set of redox species and the carbon in a binder matrix; and

the immobilization of the second set of redox species is achieved by direct mixing of the second set of redox species with carbon and sealing of the mixture of the second set of redox species and the carbon in a binder matrix.

17. The electro-chemical sensor in accordance with claim 13, wherein the immobilization is achieved by direct mixing of the first set of redox species and the second set of redox species with carbon and pressing the mixture of the first set of redox species, the second set of redox species and the carbon into a cavity to form a compact layer.

18. The electro-chemical sensor in accordance with claim 14, wherein:

the immobilization of the first set of redox species is achieved by direct mixing of the first set of redox species with carbon and pressing the mixture of the first set of redox species and the carbon into a cavity to form a compact layer; and

the immobilization of the second set of redox species is achieved by direct mixing of the second set of redox species with carbon and pressing the mixture of the second set of redox species and the carbon into a cavity to form a compact layer.

19. The electro-chemical sensor in accordance with claim 13, wherein the one or more electrodes comprise one of glassy carbon spheres, carbon nanotubes, graphite powder and boron doped diamond powder.

20. The electro-chemical sensor in accordance with claim 15, wherein the binder matrix comprises one of epoxy resin, the redox species sensitive to the certain analyte and mineral oil.

21. The electro-chemical sensor in accordance with claim 13, wherein the immobilization comprises direct adsorption.

22. The electro-chemical sensor in accordance with claim 13, wherein the first set of redox species and the second set of redox species are chemically attached to the one or more electrodes.

23. The electro-chemical sensor in accordance with claim 22, wherein the chemical attachment is made via a chemical reduction of a diazo moiety.

24. The electro-chemical sensor in accordance with claim 14, wherein:

the first set of redox species is covalently attached to the first surface of the first electrode; and

the second set of redox species is covalently attached to the second surface of the second electrode.

25. The electro-chemical sensor in accordance with claim 24, wherein:

the first surface comprises one of basal plane pyrolytic graphite, edge plane pyrolytic graphite, glassy carbon and highly orientated pyrolytic graphite; and

the second surface comprises one of basal plane pyrolytic graphite, edge plane pyrolytic graphite, glassy carbon and highly orientated pyrolytic graphite.

26. The electro-chemical sensor in accordance with claim 2, further comprising of up to two further electrodes, wherein the first of these electrodes forms the counter electrode, being much larger than the working electrode detailed in claim 1 and the second is a reference electrode.

27. The electro-chemical sensor in accordance with claim 26, wherein the counter electrode and the reference electrode comprise of two distinct electrodes.

28. The electro-chemical sensor in accordance with claim 26, wherein the first electrode comprises one of platinum, steel and carbon and the second electrode comprises Ag/AgCl.

29. The electro-chemical sensor in accordance with claim 14, further comprising:

a potentiostat device, wherein the first and second electrodes are crossed connected to a single input of the potentiostat device to provide that a single voltammetric sweep from the potentiostat device generates an analytical signal.

30. The electro-chemical sensor in accordance with claim 14, further comprising:

a working electrode; and

a protector configured to protect the working electrode, wherein the protector comprises one of a frit, a fiber mesh, a non-conducting wire mesh and porous polymer film.

31. The electro-chemical sensor in accordance with claim 1, further comprising:

a detector adapted to measure a redox potential of said first set of redox species and said second set of redox species in the presence of the certain analyte and to convert the measured redox potential into an signal indicative of the concentration of said certain analyte.

32. A downhole tool for measuring characteristic parameters of wellbore effluents comprising the electro-chemical sensor in accordance with claim 1.

33. The electro-chemical sensor in accordance with claim 1, wherein the electro-chemical sensor is configured for use in a reservoir sampling tool.

34. The electro-chemical sensor in accordance with claim 1, wherein the electro-chemical sensor is configured for use in a production logging tool.

35. The electro-chemical sensor in accordance with claim 1, wherein the electro-chemical sensor is configured for use in a measurement-while-drilling tool.

36. The electro-chemical sensor in accordance with claim 1, wherein the electro-chemical sensor is configured for use in a surface testing module.

37. The electro-chemical sensor in accordance with claim 1, wherein the sensor is configured for use in a surface pumping module, the surface pumping module delivering well treatment fluids

38. The electro-chemical sensor in accordance with claim 1, wherein the sensor is configured for integration into part of a sensor string installed permanently or temporarily within a monitoring, production, or injection well in aquifers.

39. The electro-chemical sensor in accordance with claim 1, wherein the sensor is configured to be permanently installed in a pipeline for transporting hydrocarbons.

40. The electro-chemical sensor in accordance with claim 1, wherein the sensor is configured to be permanently installed on a downhole pump.

41. The electro-chemical sensor in accordance with claim 1, wherein the sensor is configured for use on one of a downhole treatment monitoring tool for stimulation or formation damage removal, an end of a tubing section, a drillpipe and a coiled tubing unit.

42. The electro-chemical sensor in accordance with claim 1, wherein the sensor forms part of a permanent monitoring system within a well, the sensor being disposed in the well behind casing.

43. The electro-chemical sensor in accordance with claim 1, wherein the sensor is configured to monitor CO2 sequestration.

44. An electro-chemical sensor for making measurements in a downhole environment in aquifers or oilfield reservoirs, comprising:

a working electrode;

a reference electrode;

a counter electrode;

a first set of redox species, wherein the first set of redox species comprises one or more redox species that are sensitive to a certain analyte; and

a potentiostat device configured to generate an analytical signal.

45. The electro-chemical sensor in accordance with claim 44, further comprising:

a detector adapted to measure a redox potential of said first set of redox species in the presence of the certain analyte and to convert the measured redox potential into an signal indicative of the concentration of said certain analyte.

46. The electro-chemical sensor in accordance with claim 44, further comprising:

a protector configured to protect the working electrode, wherein the protector comprises one a frit, a fiber mesh, a non-conducting wire mesh and porous polymer film.

47. The electro-chemical sensor in accordance with claim 44, wherein the working electrode comprises a plurality of individual electrodes.

48. The electro-chemical sensor in accordance with claim 47, wherein the first set of redox species is coupled with the plurality of individual electrodes.

49. The electro-chemical sensor in accordance with claim 44, further comprising:

a second set of redox species, wherein the second set of redox species comprises one or more redox species that are insensitive to the certain analyte.