APPARATUS AND METHOD FOR MEASURING CONCENTRATIONS OF SCALE-FORMING IONS

• US 20100255587A1
• Filed: 06/22/2010
• Published: 10/07/2010
• Est. Priority Date: 07/24/2003
• Status: Active Grant

• Current Assignee: Schlumberger Technology Corporation (SLB)
• Original Assignee: Schlumberger Technology Corporation (SLB)
• Inventors: De Silva, Amilra Prasanna, Pagels, Markus, Jiang, Li, Meredith, Andrew, Jones, Timothy Gareth John
• Granted Patent: US 9,034,651 B2
• Time in Patent Office: Days
• US Class Current: 436/28
• CPC Class Codes: G01N 17/008 Monitoring fouling
• CPC Class Codes: G01N 33/1853 Hardness of water
• CPC Class Codes: Y10T 436/21 Hydrocarbon
• CPC Class Codes: Y10T 436/25 including sample preparation
• CPC Class Codes: Y10T 436/25375 Liberation or purification of sample or separation of material from a sample [e.g., filtering, centrifuging, etc.]
• CPC Class Codes: Y10T 436/255 including use of a solid sorbent, semipermeable membrane, or liquid extraction

Abstract

This invention relates to methods and apparatus for determination of ion concentrations, particularly in downhole water from hydrocarbon wells, aquifers etc. It is useful in a wide range of applications, including predicting the formation of scale and fingerprinting waters from different sources. More particularly, the invention relates to the use of ligands whose electronic configuration is altered by the binding of the scaling ions within a water sample. These alterations are detected electrochemically by applying varying potential to electrodes and measuring current flow as potential is varied, from which is derived the concentration of scaling ions in the fluid.

Claims

1. An apparatus for determining the concentration of scale-forming ions;

the apparatus comprising;

a ligand which binds scaling ions in a fluid, said ligand having an electronic configuration which is altered on binding of a scaling ion, and

a detector comprising a plurality of electrodes and means for applying varying potential to the electrodes and measuring current flow,

the apparatus being configured to place the ligand in the vicinity of a flow of said fluid and in the vicinity of said electrodes such that alterations in the electronic configuration through binding of a scaling ion, change the flow of current in response to applied potential, the amount of said alterations being indicative of the concentration of the scaling ion in the sample.

2. An apparatus according to claim 1 wherein the scaling ion is selected from the group consisting of Ca²⁺, Ba²⁺ and Sr²⁺ ions.

3. An apparatus according to claim 1 wherein the ligand is immobilised on conducting particles attached to one or more of said electrodes.

4. An apparatus according to claim 3 wherein said conducting particles are carbon or metal particles.

5. An apparatus according to claim 4 wherein the metal particles are gold particles.

6. An apparatus according to claim 3 wherein said conducting particles with immobilised ligands thereon form a conducting porous electrode.

7. An apparatus according to claim 1 wherein the ligand comprises oxygen and/or nitrogen.

8. An apparatus according to claim 1 wherein the ligand binds two or more different scaling ions and generates a different electronic configuration and different changes to the flow of current in response to binding of different scaling ions.

9. An apparatus according to claim 1 comprising two or more different ligands, said detector being adapted to determine alterations in the electronic configuration of each of the different ligands independently.

10. An apparatus according to claim 9 wherein each of the said two or more ligands binds to a different combination of scaling ions.

11. An apparatus according to claim 1 further comprising a processor for calculating the concentration of one or more scaling ions in the fluid from measurements of current flow in response to applied potential.

12. An apparatus according to claim 1 further comprising a porous membrane which allows ions from the fluid to contact the ligand.

13. An apparatus according to claim 12 wherein the membrane is ceramic or zeolite.

14. An apparatus according to claim 1 wherein the ligand is embedded in a block of porous material for exposure to a fluid flow.

15. An apparatus according to claim 1 wherein the ligand comprises a redox-active group.

16. An apparatus according to claim 15 wherein the ligand comprises a portion binding a scaling ion and a redox-active group attached thereto.

17. An apparatus according to claim 1 wherein the fluid is a wellbore effluent.

18. An apparatus according to claim 1 wherein the fluid stems from a production flow from a wellbore.

19. An apparatus according to claim 1 adapted to be placed in a subterranean location.

20. A method of monitoring the concentrations of scaling ions comprising;

contacting a fluid flow with a ligand which selectively binds scaling ions, wherein the binding of scaling ions to the ligand alters the electronic configuration of the ligand;

applying varying potential to electrodes placed in the vicinity of the ligand such that alterations in the electronic configuration through binding of a scaling ion change the flow of current in response to applied potential,

measuring the current flowing in response to applied potential, and thereby measuring alterations in the electronic configuration of the ligand; and

,

determining the concentration of said scaling ion from the measurements of current flow.

21. A method according to claim 20 wherein the scaling ions are selected from the group consisting of Ca²⁺, Ba²⁺ and Sr²⁺ ions.

22. A method according to claim 20 wherein the ligand comprises a redox-active group.

23. A method according to claim 22 wherein the ligand comprises a portion binding a scaling ion and a redox-active group attached thereto.

24. A method according to claim 20 wherein the ligand binds two or more different scaling ions and generates a different electronic configuration and different changes to the flow of current in response to binding of different scaling ions.

25. A method according to claim 20 comprising contacting the fluid with two or more different ligands and determining alterations in the electronic configuration of each of the two or more different ligands.

26. A method according to claim 25 wherein each of the said two or more ligands binds to a different combination of scaling ions.

27. A method according to claim 20 including the step of monitoring the production of a wellbore.

28. A method according to claim 20 including the step of predicting the scaling of hydrocarbon production tubulars or equipment.

29. A method according to claim 20 including the step of monitoring the scaling of hydrocarbon production tubulars or equipment in a downhole location.