Distributed Acoustic Sensing with Multimode Fiber

• US 20140208855A1
• Filed: 01/26/2013
• Published: 07/31/2014
• Est. Priority Date: 01/26/2013
• Status: Active Grant

• Current Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Original Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Inventors: Skinner, Neal Gregory
• Granted Patent: US 9,581,489 B2
• Time in Patent Office: Days
• US Class Current: 73/655
• CPC Class Codes: G01H 9/004 using fibre optic sensors light guides per se G02B6/00, acousto-optical devices specially adapted for gating or modulating in optical wave guides G02F1/125
• CPC Class Codes: G01V 1/40 specially adapted for well-logging
• CPC Class Codes: G01V 8/24 using optical fibres

Abstract

A method and system for distributed acoustic sensing using multimode optical fibers.

Claims

1. A method for distributed acoustic sensing using multimode optical fibers comprising the steps of:

a. injecting light energy into a multimode optical sensor fiber deployed into a region of interest from a light source;

b. collecting backscattered Rayleigh light from the multimode optical sensor fiber and directing it via a return multimode optical fiber into a detector enclosure;

c. terminating the return multimode optical fiber inside the detector enclosure and allowing the light leaving the terminal end of the return multimode optical fiber to spread before it strikes at least one light detector in the detector enclosure;

d. acquiring and amplifying the signals from the at least one light detector; and

e. performing distributed acoustic analysis on the acquired and amplified signals.

2. The method for distributed acoustic sensing using multimode optical fibers of claim 1 further comprising a lens inserted between the terminal end of the return multimode optical fiber and the at least one light detector.

3. The method for distributed acoustic sensing using multimode optical fibers of claim 1 further comprising varying the distance between the terminal end of the return multimode optical fiber and the at least one light detector to minimize the number of modes received by the at least one light detector.

4. The method for distributed acoustic sensing using multimode optical fibers of claim 1 further comprising terminating the return multimode optical fiber inside the detector enclosure by cleaving and polishing the terminal end of the return multimode optical fiber.

5. A system for distributed acoustic sensing using multimode optical fibers comprising:

a. a distributed multimode optical fiber deployed into a region of interest;

b. a light source for providing a backscattered Rayleigh light from the distributed multimode optical fiber;

c. a beam splitter or coupler for redirecting the backscattered light to a multimode return fiber terminating inside a detector enclosure;

d. at least one detector in the detector enclosure situated at a predetermined distance from the terminal end of the multimode return fiber.

6. The system for distributed acoustic sensing using multimode optical fibers of claim 5 further comprising a lens deployed between the terminal end of the multimode return fiber and the at least one detector.

7. The system for distributed acoustic sensing using multimode optical fibers of claim 5 further comprising a module performing data acquisition and amplification of the signals from the at least one detector.

8. The system for distributed acoustic sensing using multimode optical fibers of claim 5 further comprising a module performing DAS signal processing.

9. The system for distributed acoustic sensing using multimode optical fibers of claim 5 wherein the detector enclosure is light tight.