Multiplexed Microvolt Sensor Systems

• US 20170146685A1
• Filed: 06/17/2015
• Published: 05/25/2017
• Est. Priority Date: 06/17/2015
• Status: Active Grant

• Current Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Original Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Inventors: Mandviwala, Tasneem A., Barfoot, David Andrew, Choi, Han-Sun
• Granted Patent: US 9,864,095 B2
• Time in Patent Office: Days
• CPC Class Codes: E21B 47/092 by detecting magnetic anomalies
• CPC Class Codes: E21B 47/113 using electrical indications; using light radiations
• CPC Class Codes: E21B 47/135 using light waves, e.g. infrared or ultraviolet waves
• CPC Class Codes: G01D 5/3539 using time division multiplexing
• CPC Class Codes: G01L 1/247 using distributed sensing elements, e.g. microcapsules along a single optical fibre G01L1/242
• CPC Class Codes: G01V 8/02 Prospecting
• CPC Class Codes: G01V 8/16 using optical fibres

Abstract

Multiplexed microvolt sensor systems and methods are described. An example system may include a pulsed light source, a first optical waveguide segment operatively coupled to the pulsed light source, an optical circulator including a first port, a second port, and a third port, the first port being operatively coupled to the first optical waveguide segment, a second optical waveguide segment operatively coupled to the second port of the optical circulator, and an array of sensor elements. Each of the sensor elements may include a detector and an electro-optical modulator, the electro-optical modulator being operatively coupled to the second optical waveguide segment. The example system may further include a third optical waveguide segment operatively coupled to the third port of the optical circulator, a compensating interferometer operatively coupled to the third optical waveguide segment, and a time division multiplexed demodulator operatively coupled to the compensating interferometer and the pulsed light source.

Claims

1. A system comprising:

a pulsed light source;

a first optical waveguide segment operatively coupled to the pulsed light source;

an optical circulator comprising a first port, a second port, and a third port, the first port being operatively coupled to the first optical waveguide segment;

a second optical waveguide segment operatively coupled to the second port of the optical circulator;

an array of sensor elements, each of the sensor elements comprising a detector and an electro-optical modulator, the electro-optical modulator operatively coupled to the second optical waveguide segment;

a third optical waveguide segment operatively coupled to the third port of the optical circulator;

a compensating interferometer operatively coupled to the third optical waveguide segment; and

a time division multiplexed demodulator operatively coupled to the compensating interferometer and the pulsed light source.

2. The system of claim 1, wherein pulsed light source is a high-power, low-coherent pulsed light source.

3. The system of claim 1, wherein the pulsed light source comprises a polarization element.

4. The system of claim 1, wherein the second optical waveguide segment is a single optical path.

5. The system of claim 1, wherein the detector is a coil of electrically conductive material.

6. The system of claim 1, wherein each of the electro-optical modulator except for a last electro-optical modulator in the array of sensor elements is operatively coupled to the second optical waveguide segment via a directional coupler.

7. The system of claim 1, wherein a last electro-optical modulator in the array of sensor elements is operatively coupled to the second optical waveguide segment via a direct connection to an end of the second optical waveguide segment.

8. The system of claim 1, wherein the electro-optical modulator comprises a sensing interferometer.

9. The system of claim 8, wherein the sensing interferometer is a Lithium Niobate Michelson-type interferometer.

10. The system of claim 8, wherein the sensing interferometer comprises a first waveguide channel arm and a second waveguide channel arm longer than the first waveguide channel arm.

11. The system of claim 10, wherein a distance by which the second waveguide channel arm is longer than the first waveguide channel arm is between 0.1 mm and 5.0 mm.

12. The system of claim 10, wherein:

the first waveguide channel arm has a proximal end with respect to the pulsed light source and a distal end at which a first reflective element is disposed; and

the second waveguide channel arm has a proximal end with respect to the pulsed light source and a distal end at which a second reflective element is disposed.

13. The system of claim 12, wherein the sensing interferometer comprises an ingress/egress waveguide channel comprising a proximal end with respect to the pulsed light source and a distal end that connects to the proximal end of the first waveguide channel arm and the proximal end of the second waveguide channel arm.

14. The system of claim 10, wherein the sensing interferometer comprises a first electrode, a second electrode, and a third electrode, wherein the first waveguide channel arm is disposed between the first electrode and the second electrode, and wherein the second waveguide channel arm is disposed between the second electrode and the third electrode.

15. The system of claim 14, wherein the first electrode and the third electrode are electrically coupled to a first end of the detector, and wherein the second electrode is electrically coupled to a second end of the detector.

16. The system of claim 10, wherein the compensating interferometer is configured to provide a compensating path difference approximately equal to a path difference in the sensing interferometer corresponding to the first waveguide channel arm and the second waveguide channel arm.

17. The system of claim 1, further comprising:

an emitter configured to emit an electromagnetic field for detection by the array of sensor elements.

18. The system of claim 1, further comprising:

an additional compensating interferometer operatively coupled to the third optical waveguide segment and the time division multiplexed demodulator, and

wherein the array of sensor elements comprises a first set of sensor elements and a second set of sensor elements,

wherein each electro-optical modulator in the first set of sensor elements comprises a first-set sensing interferometer comprising a first waveguide channel arm having a proximal end with respect to the pulsed light source and a distal end at which a first reflective element is disposed, and a second waveguide channel arm longer than the first waveguide channel arm by a first-set distance, the second waveguide channel arm having a proximal end with respect to the pulsed light source and a distal end at which a second reflective element is disposed, and

wherein each electro-optical modulator in the second set of sensor elements comprises a second-set sensing interferometer comprising a first waveguide channel arm having a proximal end with respect to the pulsed light source and a distal end at which a first reflective element is disposed, and a second waveguide channel arm longer than the first waveguide channel arm of the second set of sensor elements by a second-set distance greater than the first-set distance, the second waveguide channel arm having a proximal end with respect to the pulsed light source and a distal end at which a second reflective element is disposed.

19. A method comprising:

emitting an electromagnetic field into a subterranean formation for detection by a sensor element, the sensor element being coupled to an optical waveguide;

transmitting a light pulse by a high-power, low-coherent pulsed light source having a coherence length shorter than a path difference of a sensing interferometer of a sensor element, and longer than a path difference matching error of a compensating interferometer and the path difference of the sensing interferometer, the light pulse being transmitted via the optical waveguide; and

receiving two return light pulses via the optical waveguide from the sensor element, the two return light pulses being modulated based on detection of the electromagnetic field by the sensor element.

20. The method of claim 19, further comprising:

directing the two return light pulses to the compensating interferometer, the compensating interferometer having two optical waveguide paths and two mirror assemblies for reflecting the two return light pulses;

receiving four compensated return light pulses from the compensating interferometer; and

determining a signal of the sensor element based on the four compensated return light pulses.

21. A well system comprising:

an interrogator system configured to generate a light pulse and receive a plurality of return light pulses;

an optical waveguide operatively coupled to the interrogator system; and

an array of sensor elements operatively coupled to an optical waveguide, the array of sensor elements being disposed proximal to an exterior of at least one of a casing or liner of a wellbore, each of the sensor elements comprising a detector and an electro-optical modulator, the electro-optical modulator being operatively coupled to the optical waveguide,

wherein each of the electro-optical modulator comprises a first waveguide channel arm and a second waveguide channel arm longer than the first waveguide channel arm.

22. The well system of claim 21, wherein the array of sensor elements operatively coupled to the optical waveguide extends a distance greater than 1,500 meters.

23. The well system of claim 21, wherein a distance between each sensor element in the array of sensor elements is between 10 meters and 50 meters.