Monitoring water floods using potentials between casing-mounted electrodes

Patent metadata

Field	Value
Publication number	US-9938822-B2
Application number	US-201515507705-A
Country	US
Kind code	B2
Filing date	Nov 18, 2015
Priority date	Nov 18, 2015
Publication date	Apr 10, 2018
Grant date	Apr 10, 2018

Abstract

A system for locating water floods, in some embodiments, comprises: multiple non-reference electrodes with insulative pads for coupling to a borehole casing; a reference electrode with an insulative pad for coupling to the borehole casing; and multiple transducers coupled to the reference and non-reference electrodes, each of said electrodes coupled to one or more of the multiple transducers, wherein each transducer coupled to a non-reference electrode determines a differential non-reference potential between that non-reference electrode and the reference electrode, and wherein a transducer that couples to the borehole casing determines an absolute reference potential between the borehole casing and the reference electrode; wherein the differential non-reference potentials are mathematically combined with the absolute reference potential to produce absolute non-reference potentials; wherein scaling weights are applied to said absolute non-reference potentials to produce scaled absolute potentials that are used to determine a water flood location.

First claim

The following is claimed:

1. A system for locating water floods, comprising:
multiple non-reference electrodes with insulative pads for coupling to a borehole casing;
a reference electrode with an insulative pad for coupling to the borehole casing; and
multiple transducers coupled to the reference and non-reference electrodes, each of said electrodes coupled to one or more of the multiple transducers,
wherein each transducer coupled to a non-reference electrode sends a signal to a computer system configured to determine a differential non-reference potential between that non-reference electrode and the reference electrode, and wherein a transducer that couples to the borehole casing sends a signal to a computer system configured to determine an absolute reference potential between the borehole casing and the reference electrode;
wherein the computer system is further configured to mathematically combine differential non-reference potentials with the absolute reference potential to produce absolute non-reference potentials;
wherein the computer system is further configured to apply scaling weights to said absolute non-reference potentials to produce scaled absolute potentials that are used to determine a water flood location.

2. The system of claim 1 , wherein the computer system is further configured to determine each of said scaling weights using a set of baseline absolute non-reference potentials obtained in a no-flood environment.

3. The system of claim 2 , wherein the computer system is further configured to determine each of said scaling weights by dividing an average of said baseline absolute non-reference potentials by a baseline absolute non-reference potential to which said weight corresponds.

4. The system of claim 1 , wherein the computer system generates an interpolated polar plot using the scaled absolute potentials.

5. The system of claim 4 , wherein the computer system uses the polar plot to determine a water flood direction.

6. The system of claim 5 , wherein the computer system uses the water flood direction to determine a geometric factor, wherein said geometric factor characterizes a deformation of the polar plot.

7. The system of claim 1 , wherein the computer system obtains a geometric factor using said scaled absolute potentials, and wherein the computer system inverts the geometric factor to determine said water flood location.

8. The system of claim 1 , wherein a pair of said multiple non-reference electrodes couples to one of said multiple transducers using a twisted wire pair.

9. A system to locate water floods, comprising:
a borehole casing disposed within a formation;
multiple non-reference electrodes circumferentially positioned on insulative padding adjacent to said casing;
a reference electrode positioned on insulative padding adjacent to said casing; and
a control unit that selectively couples one or more of said multiple non-reference electrodes to a transducer and that applies scaling weights to signals received from at least some of the multiple non-reference electrodes to produce scaled signals,
wherein the transducer sends the scaled signals from one of the non-reference electrodes and from the reference electrode to a computer system configured to produce a scaled differential non-reference potential, and further sends signals from the casing and the scaled signals from the reference electrode to the computer system configured to produce a scaled absolute reference potential;
wherein the computer system is further configured to combine the scaled differential non-reference potential with the scaled absolute reference potential to produce a scaled absolute potential that it uses to determine a water flood location.

10. The system of claim 9 , wherein the computer system determines each of said scaling weights using a set of baseline differential non-reference potentials obtained in a no-flood environment.

11. The system of claim 10 , wherein the computer system determines each of said scaling weights by dividing an average of said baseline differential non-reference potentials by a baseline differential non-reference potential to which said weight corresponds.

12. The system of claim 9 , wherein the computer system generates an interpolated polar plot using the scaled absolute potential, and further wherein the computer system uses the interpolated polar plot to determine a geometric factor.

13. The system of claim 12 , wherein the computer system uses the polar plot to determine a water flood direction.

14. The system of claim 13 , wherein the computer system uses the water flood direction to determine said geometric factor, wherein said geometric factor characterizes a deformation of the polar plot.

15. A method for locating water floods in a formation, comprising:
providing multiple electrodes circumferentially arranged about a borehole casing, said multiple electrodes including a reference electrode and a non-reference electrode;
determining a baseline absolute reference potential between the reference electrode and the borehole casing;
determining a baseline differential non-reference potential between the non-reference electrode and the reference electrode;
determining a baseline absolute potential using the baseline absolute reference potential and the baseline differential non-reference potential;
computing a weight using the baseline absolute potential; and
applying said weight to signals received from the non-reference electrode and the reference electrode.

16. The method of claim 15 , further comprising:
using signals received from the casing and weighted signals received from the non-reference electrode and the reference electrode to produce a scaled absolute potential corresponding to the non-reference electrode, and
using the scaled absolute potential to determine a water flood location.

17. The method of claim 16 , further comprising using a downhole control unit to selectively couple said multiple electrodes to one or more transducers.

18. The method of claim 17 , further comprising using no more than two transducers in association with the downhole control unit.

19. The method of claim 15 , wherein said electrodes couple to the borehole casing using insulative padding.

20. The method of claim 19 , wherein said signals received from the non-reference electrode and the reference electrode are induced at least in part by a current injected into the formation through said multiple electrodes or through said borehole casing.

Assignees

• Halliburton Energy Services Inc

Inventors

• Fouda Ahmed Elsayed
• Donderici Burkay

Classifications

• G01V3/18

  specially adapted for well-logging · CPC title

• E21B43/20

  Displacing by water · CPC title

• E21B47/102 Primary

  Fixed Constructions · mapped topic

• E21B47/113 Primary

  using electrical indications; using light radiations · CPC title

• Y02A90/30

  Assessment of water resources · CPC title