Detection of seismic signals using fiber optic distributed sensors
First Claim
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1. A seismic event detection system in a well, comprising:
- a first fiber optic cable disposed in a borehole extending from an earth surface into a formation, the first fiber optic cable configured to react along its length to incident seismic signals originating;
inside the borehole and propagating through the formation and the borehole or outside the borehole and propagating through the formation;
an optical source to launch optical pulses into the first fiber optic cable while the seismic signals are incident on the first fiber optic cable; and
a data acquisition system coupled to the first fiber optic cable to detect coherent Rayleigh noise (CRN) generated in response to the optical pulses to determine characteristics of the well based on the detected CRN.
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Abstract
A fiber optic distributed vibration system for detecting seismic signals in an earth formation is provided. The system includes a fiber optic cable deployed in a borehole that extends into the earth formation and which is configured to react along its length to a seismic wave incident on the fiber optic cable from outside the borehole. An optical source launches an optical signal into the fiber optic cable while the seismic wave is incident thereon. A receiver detects coherent Rayleigh noise (CRN) produced in response to the optical signal. A processing circuit processes the detected CRN signal to determine characteristics of the earth formation.
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Citations
19 Claims
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1. A seismic event detection system in a well, comprising:
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a first fiber optic cable disposed in a borehole extending from an earth surface into a formation, the first fiber optic cable configured to react along its length to incident seismic signals originating;
inside the borehole and propagating through the formation and the borehole or outside the borehole and propagating through the formation;an optical source to launch optical pulses into the first fiber optic cable while the seismic signals are incident on the first fiber optic cable; and a data acquisition system coupled to the first fiber optic cable to detect coherent Rayleigh noise (CRN) generated in response to the optical pulses to determine characteristics of the well based on the detected CRN. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for conducting a seismic survey of a well, comprising:
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launching a first optical signal into a first fiber optic cable disposed in a borehole extending from an earth surface into an earth formation; generating a seismic wave that propagates through the well from inside or outside of the borehole; and analyzing coherent Rayleigh noise (CRN) produced in response to the first optical signal while the seismic wave is incident along a length of the first fiber optic cable to determine characteristics of the well. - View Dependent Claims (11, 12, 13)
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14. A system in a well comprising:
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a first optical fiber disposed in a borehole that extends from an earth surface into an earth formation, the first optical fiber configured to react to a seismic wave incident on the first optical fiber at any of a plurality of locations along its length; a seismic source to generate a seismic wave that originates outside or inside of the borehole; an optical source to launch an optical signal into the first optical fiber to produce a backscattered optical signal while the seismic wave is incident on the first optical fiber; a receiver to detect coherent Rayleigh noise (CRN) in the backscattered signal; and a processing circuit to process the CRN to determine characteristics of the well. - View Dependent Claims (15, 16, 17, 18, 19)
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Specification