Providing high power optical pulses over long distances

Patent metadata

Field	Value
Publication number	US-10072498-B2
Application number	US-201615527673-A
Country	US
Kind code	B2
Filing date	May 11, 2016
Priority date	May 11, 2016
Publication date	Sep 11, 2018
Grant date	Sep 11, 2018

Abstract

The disclosed embodiments include a method and fiber optic cable to provide optical pulses for sensing, and an optical telemetry system. In one embodiment, the method includes sequentially transmitting a plurality of optical pulses through a first end of a first optical fiber disposed in a first section of a wellbore. The plurality of optical pulses is combined into a combined optical pulse at a distance from the first end of the first optical fiber. The method further includes transmitting the combined optical pulse through a second optical fiber disposed in a second section of the wellbore, and the second optical fiber includes a second dispersion value, where an absolute value of the first dispersion value is greater than an absolute value of the second dispersion value.

First claim

We claim:

1. A method to provide optical pulses along a fiber optic cable, the method comprising:
sequentially transmitting a plurality of optical pulses through a first end of a first optical fiber disposed in a first section of a wellbore and having a first dispersion value, wherein the plurality of optical pulses combine into a combined optical pulse at a distance from the first end of the first optical fiber; and
transmitting the combined optical pulse through a second optical fiber disposed in a second section of the wellbore, the second optical fiber having a second dispersion value,
wherein an absolute value of the first dispersion value is greater than an absolute value of the second dispersion value.

2. The method of claim 1 , wherein sequentially transmitting the plurality of optical pulses comprises transmitting each optical pulse of the plurality of optical pulses at approximately a first signal intensity.

3. The method of claim 2 , wherein the combined optical pulse has a signal intensity that is approximately m times the first signal intensity, and wherein m is equal to a total number of the plurality of optical pulses transmitted through the first optical fiber that are combined into the combined optical pulse.

4. The method of claim 1 , further comprising modulating each of the plurality of optical pulses, wherein each optical pulse of the plurality of optical pulses is phase shifted from a previous optical pulse by a value ϕ n .

5. The method of claim 4 , wherein ϕ n is approximately equal to πn 2 (m−1)/m, wherein n is a pulse number of an optical pulse of the plurality of optical pulses that is transmitted, and wherein m is a total number of the plurality optical pulse transmitted through the first optical fiber.

6. The method of claim 1 , further comprising: determining the distance from the first end of the optical fiber to a location where the plurality of optical pulses are combined.

7. The method of claim 6 , wherein the distance is approximately equal to mT 2 /(2π|β 2 |), wherein T is equal to a repetition period of the plurality of optical pulses, wherein β 2 is equal to a dispersion value of the first optical fiber, and wherein m is a total number of optical pulses transmitted through the first optical fiber to be combined into form the combined optical pulse.

8. The method of claim 1 , further comprising:
receiving the combined optical pulse at a downhole location; and
modulating the received combined optical pulse to modify the combined optical pulse to alter transmission of the combined optical pulse to a receiver,
wherein the combined optical pulse is modified to indicate a digital bit of 0, and
wherein the combined optical pulse is transmitted unmodified to the receiver to indicate a digital bit of 1.

9. The method of claim 8 , further comprising transmitting the combined optical pulse through the second optical fiber and a third optical fiber disposed in the first section of the wellbore to the receiver.

10. The method of claim 1 , further comprising:
receiving the combined optical pulse at a downhole location;
performing a pulse-amplitude modulation of a signal intensity modifying the received combined optical pulse to form a modulated optical pulse; and
transmitting the modulated optical pulse to a receiver.

11. The method of claim 1 , further comprising:
performing at least one of a distributed acoustic sensing, a distributed temperature sensing, and a distributed strain and temperature sensing of a wellbore property along a length of a portion of the second optical fiber,
wherein the combined optical pulse is used to perform at least one of the distributed acoustic sensing, the distributed temperature sensing, and the distributed strain and temperature sensing of the wellbore property.

12. The method of claim 11 , further comprising utilizing at least one of Rayleigh back scattering, Raman back scattering, and Brillouin back scattering techniques to perform at least one of the distributed acoustic sensing, the distributed temperature sensing, and the distributed strain and temperature sensing of the wellbore property.

13. The method of claim 1 , Further comprising:
providing the combined optical pulse to a sensor deployed proximate the second optical fiber,
wherein the combined optical pulse is utilized by the sensor to measure at least one property of the wellbore.

14. An optical telemetry system comprising:
a laser source operable to sequentially emit a plurality of repeating optical pulses;
a modulator disposed proximate to a surface and operable to modulate a phase shift of each of the plurality of optical pulses relative to a phase of a previously emitted optical pulse of the plurality of optical pulses;
a first optical fiber having a first dispersion value and disposed in a first section of a wellbore, the first optical fiber operable to receive the plurality of optical pulses through a first end of the first optical fiber, wherein the plurality of optical pulses is combined to form a combined pulse at a first distance from the first end of the first optical fiber; and
a second optical fiber having a second dispersion value and disposed in a second section of the wellbore, the second optical fiber operable to receive the combined optical pulse; and
a modulator operable to modulate the combined optical pulse for transmission of an uplink data,
wherein an absolute value of the first dispersion value is greater than an absolute value of the second dispersion value.

15. The system of claim 14 , wherein the combined optical pulse traverses from the second optical fiber without being modulated by the modulator, and wherein the combined optical pulse is indicative of a digital bit of 1 of a digital bit of the uplink data.

16. The system of claim 14 , wherein the modulator is further operable to modulate the combined optical pulse to alter transmission of the combined optical pulse up-hole, wherein the modulated combined optical pulse is indicative of a digital bit of 0 of a digital bit of the uplink data.

17. The system of claim 14 , wherein sequentially transmitting the plurality of optical pulses comprises transmitting each optical pulse of the plurality of optical pulses at approximately a first signal intensity.

18. The system of claim 14 , wherein a portion of the second optical fiber is used for distributed acoustic sensing.

19. A fiber optic cable for providing optical pulses, the fiber optic cable comprising:
a first section having a first optical fiber, the first optical fiber having a first dispersion value and disposed in a first section of a well; and
a second section having a second optical fiber, the second optical fiber having a second dispersion value and disposed in a second section of the well,
wherein an absolute value of the first dispersion value is greater than an absolute value of the second dispersion value,
wherein the first optical fiber is operable to combine a plurality of optical pulses having a phase relationship and having approximately identical amplitudes into a combined optical pulse, and
wherein the second optical fiber is operable to transmit the combined optical pulse to a region where the combined optical pulse is utilized to perform a measurement of the region.

20. The fiber optic cable of claim 19 , wherein the first section comprises a plurality of optical fibers, wherein the first optical fiber is operable to transmit the combined optical pulse from a surface location to the second optical fiber, and wherein the

Assignees

• Halliburton Energy Services Inc

Inventors

• Bhongale Satyan Gopal
• Stark Daniel Joshua

Classifications

• H04B10/541

  Digital intensity or amplitude modulation · CPC title

• H04B10/25 Primary

  Arrangements specific to fibre transmission · CPC title

• G01L1/246

  using integrated gratings, e.g. Bragg gratings · CPC title

• G01D5/35361

  using elastic backscattering to detect the measured quantity, e.g. using Rayleigh backscattering · CPC title

• E21B47/135 Primary

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