Detection of strain in fiber optics cables induced by narrow-band signals
First Claim
1. A method, comprising:
- transmitting a narrowband signal into a formation using a transmitter located in a wellbore, wherein the narrowband signal is modified by passage through the formation and the formation reflects at least a portion of the narrowband signal back to the wellbore resulting in a modified narrowband signal;
sensing the modified narrowband signal with an optical waveguide positioned in the wellbore;
transmitting a source signal along a length of the optical waveguide, the source signal being modulated due to an interaction between the modified narrowband signal and the optical waveguide and thereby resulting in a backscattered return signal;
sampling the backscattered return signal at less than a Nyquist rate and obtaining an undersampled backscattered return signal; and
processing the undersampled backscattered return signal to obtain an amplitude of the modified narrowband signal sensed with the optical waveguide.
1 Assignment
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Accused Products
Abstract
A method may include transmitting a narrowband signal into a formation using a transmitter located in a wellbore. The narrowband signal is modified by passage of through the formation and the formation reflects at least a portion of the narrowband signal back to the wellbore resulting in a modified narrowband signal having a first frequency. The method also includes sensing the modified narrowband signal with an optical waveguide positioned in the wellbore, transmitting a source signal along a length of the optical waveguide, and obtaining a backscattered return signal from the optical waveguide. The backscattered return signal is sampled at a second frequency that is less than the Nyquist rate of the modified narrowband signal. The method further includes processing the backscattered return signal to obtain an amplitude of the modified narrowband signal.
22 Citations
19 Claims
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1. A method, comprising:
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transmitting a narrowband signal into a formation using a transmitter located in a wellbore, wherein the narrowband signal is modified by passage through the formation and the formation reflects at least a portion of the narrowband signal back to the wellbore resulting in a modified narrowband signal; sensing the modified narrowband signal with an optical waveguide positioned in the wellbore; transmitting a source signal along a length of the optical waveguide, the source signal being modulated due to an interaction between the modified narrowband signal and the optical waveguide and thereby resulting in a backscattered return signal; sampling the backscattered return signal at less than a Nyquist rate and obtaining an undersampled backscattered return signal; and processing the undersampled backscattered return signal to obtain an amplitude of the modified narrowband signal sensed with the optical waveguide. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A system, comprising:
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a transmitter located in a wellbore and generating a narrowband signal into a formation, wherein the narrowband signal is modified by passage through the formation and the formation reflects at least a portion of the narrowband signal back to the wellbore resulting in a modified narrowband signal; an optical waveguide positioned in the wellbore and interacting with the modified narrowband signal; and an interface configured to; transmit a source signal along a length of the optical waveguide, the source signal being modulated due to the interaction between the modified narrowband signal and the optical waveguide and thereby resulting in a backscattered return signal obtained from the optical waveguide, sample the backscattered return signal at less than a Nyquist rate and obtain an undersampled backscattered return signal, and process the undersampled backscattered return signal to obtain an amplitude of the modified narrowband signal. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A computer program product comprising a non-transitory computer readable medium having computer readable computer program code stored thereon that, when executed by a computer, configures the computer to:
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control a transmitter located in a wellbore to transmit a narrowband signal into a formation, wherein the narrowband signal is modified by passage through the formation and the formation reflects at least a portion of the narrowband signal back to the wellbore resulting in a modified narrowband signal, the modified narrowband signal interacting with an optical waveguide positioned in the wellbore; program an interface to transmit a source signal along a length of the optical waveguide, the source signal being modulated due to the interaction between the modified narrowband signal and the optical waveguide and thereby resulting in a backscattered return signal obtained from the optical waveguide, the backscattered return signal being sampled at less than a Nyquist rate to obtain an undersampled backscattered return signal; and program the interface to process the undersampled backscattered return signal to obtain an amplitude of the modified narrowband signal. - View Dependent Claims (15, 16, 17, 18, 19)
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Specification