Sensor system for downhole galvanic measurements

Patent metadata

Field	Value
Publication number	US-9983329-B2
Application number	US-201515021980-A
Country	US
Kind code	B2
Filing date	Jun 5, 2015
Priority date	Jun 5, 2015
Publication date	May 29, 2018
Grant date	May 29, 2018

Abstract

A downhole galvanic logging system including a first transmitter electrode configured to convey an exciter current into a formation and a second transmitter electrode configured to receive a return current from the formation. A first transmission line being coupled to the first transmitter electrode and configured to carry the exciter current, and a second transmission line being coupled to the second transmitter electrode and configured to carry the return current. The transmission lines can be arranged in a twisted pattern. A receiver device is positioned between the transmitter electrodes along an axial length of the downhole galvanic logging system. The receiver device can be configured to detect an electrical signal that is proportional to a resistivity of the formation. The second transmitter electrode can be coupled to one end of the receiver device with the second transmission line coupled to the second transmitter electrode through the receiver device.

First claim

What is claimed is:

1. A downhole galvanic logging system, comprising:
a first set of transmitter electrodes configured to convey an exciter current into a formation;
a second set of transmitter electrodes configured to receive a return current based on the exciter current conveyed through the formation, the first set of transmitter electrodes and the second set of transmitter electrodes being permanently placed in a borehole;
a first transmission line conductor coupled to the first set of transmitter electrodes and configured to carry the exciter current;
a second transmission line conductor coupled to the second set of transmitter electrodes and configured to carry the return current back to a termination point of the second transmission line conductor, the first transmission line conductor arranged in a parallel pattern with the second transmission line conductor; and
a receiver device positioned between the first set of transmitter electrodes and the second set of transmitter electrodes along an axial length of the downhole galvanic logging system, the receiver device configured to detect an electrical signal induced by the exciter current flowed within the formation where the electrical signal is altered by at least one parameter of the formation, the second set of transmitter electrodes being coupled to one end of the receiver device with the second transmission line conductor coupled to the second set of transmitter electrodes through the receiver device.

2. The downhole galvanic logging system of claim 1 , further comprising an exciter coupled to the first transmission line conductor and the second transmission line conductor, the exciter configured to generate the exciter current.

3. The downhole galvanic logging system of claim 1 , wherein the first set of transmitter electrodes and the second set of transmitter electrodes have connections at opposite ends of the receiver device that are substantially centered and axially oriented with respect to the receiver device for at least a first axial distance along a wellbore.

4. The downhole galvanic logging system of claim 3 , wherein the first set of transmitter electrodes and the second set of transmitter electrodes are substantially equidistant from respective ends of the receiver device.

5. The downhole galvanic logging system of claim 3 , wherein the first set of transmitter electrodes and the second set of transmitter electrodes have connections at opposite ends of the receiver device for at least a second axial distance along the wellbore, the second axial distance being greater than the first axial distance.

6. The downhole galvanic logging system of claim 5 , wherein the first set of transmitter electrodes is located at a first distance from a first end of the receiver device and the second set of transmitter electrodes is located at a second distance from a second end of the receiver device, the second distance being greater than the first distance.

7. The downhole galvanic logging system of claim 1 , wherein the receiver device comprises a magnetic based electromagnetic sensor configured to obtain one or more magnetic measurements.

8. The downhole galvanic logging system of claim 1 , wherein the receiver device comprises an optical sensor coupled to one or more optical fibers extending along the axial length of the downhole galvanic logging system, the optical sensor configured to generate an optical signal based on one or more electromagnetic measurements and send the optical signal to the surface through the one or more optical fibers.

9. The downhole galvanic logging system of claim 8 , wherein the receiver device comprises at least two voltage electrode sensors that are configured to detect a voltage drop between the at least two voltage electrode sensors.

10. The downhole galvanic logging system of claim 9 , wherein the receiver device comprises a housing made of a conductive material with the optical sensor located within the housing.

11. The downhole galvanic logging system of claim 10 , wherein the housing has a cylindrical shape with substantially symmetrical dimensions, wherein the housing has a metallic lining and an insulator layer over the metallic lining, and wherein the second transmission line conductor has connections at opposite ends of the housing that are electrically connected to each other through the metallic lining.

12. The downhole galvanic logging system of claim 10 , wherein each of the at least two voltage electrode sensors is located within a respective groove on a surface of the housing, and wherein the at least two voltage electrodes have connections to the optical sensor through the housing.

13. The downhole galvanic logging system of claim 1 , wherein an in-phase component of the electrical signal is substantially proportional to a resistivity of the formation, or an out-of phase component of the electrical signal is substantially proportional to a dielectric constant of the formation.

14. The downhole galvanic logging system of claim 1 , further comprising a second receiver device at a first distance from the surface and coupled to the first and second transmission line conductors, the receiver device being a second distance from the surface, the first distance being greater than the second distance, the second receiver device configured to detect a second electrical signal based on a second exciter current flowed within the formation, the second exciter current being smaller than the exciter current.

15. The downhole galvanic logging system of claim 1 , wherein the at least one parameter of the formation comprises one or more of a resistivity, a dielectric constant, a magnetic permeability or a layer boundary position.

16. A method for downhole galvanic measurements, comprising:
conveying a downhole logging cable into a wellbore, the downhole logging cable having a surface end and a distal end, and comprising a plurality of optical fibers and a logging tool with an exciter arranged at the surface end, the plurality of optical fibers extending along an axial length of the downhole logging cable, the conveyed downhole logging cable having the logging tool located between a pair of transmitter electrodes permanently placed along a first axial distance of the wellbore, at least one transmitter electrode of the pair of transmitter electrodes having a connection to the exciter through opposite ends of the logging tool;
injecting an exciter current between the pair of transmitter electrodes from the exciter to force the exciter current through a formation, the pair of transmitter electrodes having a parallel pattern that enables substantially no resulting magnetic fields to form beyond the pair of transmitter electrodes;
receiving electromagnetic measurements from the plurality of optical fibers with a signal processor arranged at the surface end, the electromagnetic measurements being obtained by the logging tool based on an electrical signal that is proportional to a resistivity of the formation; and
determining an image of the formation based on the resistivity of the formation included in the electromagnetic measurements.

17. The method of claim 16 , further comprising detecting the electrical signal as a voltage drop using at least two voltage electrodes arranged in the logging tool.

18. The method of claim 16 , further comprising at least one of:
providing the electrical signal to the plurality of optical fibers with an optical sensor arranged within the logging tool, or
providing the electromagnetic measurements as an optical signal from the optical sensor to the

Assignees

• Halliburton Energy Services Inc

Inventors

• Donderici Burkay
• Goodman George David
• Samson Etienne

Classifications

• G01V3/26 Primary

  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

• E21B47/135

  using light waves, e.g. infrared or ultraviolet waves · CPC title

• G01V3/28 Primary

  using induction coils · CPC title

• E21B47/123

  Fixed Constructions · mapped topic