Fiberoptic systems and methods detecting EM signals via resistive heating
First Claim
1. A formation conductivity sensor that comprises:
- a transmitter that radiates electromagnetic energy into a subsurface formation;
a receiver having;
one or more loops of an optical fiber thermally coupled to a surrounding conductive element to yield an optically-detectable thermal response to electromagnetic energy from the formation, said electromagnetic energy inducing an electrical current in the conductive element along the one or more loops and through an electrical short across the ends of the one or more loops, and said thermal response resulting from the electrical current; and
an optical source and optical detector that measure said thermal response; and
a processing unit that derives a measure of formation conductivity from said thermal response.
1 Assignment
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Accused Products
Abstract
Fiberoptics can be employed to detect downhole electromagnetic signals via resistive heating. A disclosed electromagnetic energy detector embodiment includes an optically-interrogated temperature sensor; and a conductive element thermally coupled to the sensor, the conductive element having a temperature response to incident electromagnetic energy. The optically-interrogated temperature sensor may be a length or coil of optical fiber to which a distributed acoustic sensing (DAS) or distributed temperature sensing (DTS) system is attached. The conductive element may be a metal coating on the fiber that experiences resistive heating in response to electromagnetic energy and creates an optically-measurable thermal response in the sensor.
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Citations
25 Claims
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1. A formation conductivity sensor that comprises:
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a transmitter that radiates electromagnetic energy into a subsurface formation; a receiver having; one or more loops of an optical fiber thermally coupled to a surrounding conductive element to yield an optically-detectable thermal response to electromagnetic energy from the formation, said electromagnetic energy inducing an electrical current in the conductive element along the one or more loops and through an electrical short across the ends of the one or more loops, and said thermal response resulting from the electrical current; and an optical source and optical detector that measure said thermal response; and a processing unit that derives a measure of formation conductivity from said thermal response. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method comprising:
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transmitting electromagnetic energy into a formation, thereby inducing an electrical current into a shorted looped segment of a conductively-clad optical fiber in a borehole of the formation in response to the electromagnetic energy; detecting a thermal response of the conductively-clad optical fiber produced by the electrical current; and deriving information from the thermal response. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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18. An electromagnetic energy detector that comprises:
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a looped optically-interrogated temperature sensor; and a conductive element thermally coupled to and surrounding the sensor, the conductive element being electrically shorted at opposites ends of a sensor loop and having a temperature response to incident electromagnetic energy, wherein said temperature response is produced by an electrical current that flows through the conductive element along the sensor loop and through the shorted ends; and wherein said electrical current is induced by the incident electromagnetic energy. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25)
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Specification