Fiberoptic systems and methods detecting EM signals via resistive heating

摘要

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.

主权项

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; andan 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.