Abstract: An apparatus for detecting a location of an optical fiber having an acoustic sensor disposed subsurface to the earth includes an acoustic emitter configured to emit a first signal having a first frequency and a second signal having a second frequency that is higher than the first frequency, the first and second emitted acoustic signals being azimuthally rotated around the borehole and an optical interrogator configured to interrogate the optical fiber to receive an acoustic measurement that provides a corresponding first received signal and a corresponding second received signal. The apparatus also includes a processor configured to (i) frequency-multiply the first received signal to provide a third signal having a third frequency within a selected range of the second frequency, (ii) estimate a phase difference between the second received signal and the third signal, and (iii) correlate the phase difference to the location of the optical fiber.

Abstract: An apparatus for detecting a location of an optical fiber having an acoustic sensor disposed subsurface to the earth includes an acoustic emitter configured to emit a first signal having a first frequency and a second signal having a second frequency that is higher than the first frequency, the first and second emitted acoustic signals being azimuthally rotated around the borehole and an optical interrogator configured to interrogate the optical fiber to receive an acoustic measurement that provides a corresponding first received signal and a corresponding second received signal. The apparatus also includes a processor configured to (i) frequency-multiply the first received signal to provide a third signal having a third frequency within a selected range of the second frequency, (ii) estimate a phase difference between the second received signal and the third signal, and (iii) correlate the phase difference to the location of the optical fiber.

Abstract: A downhole tool orientation determination system to determine a radial orientation of a tool conveyed downhole into a pipe via a carrier and a method of determining a radial orientation of a tool conveyed downhole into a pipe via a carrier are described. The system includes an orientation tool conveyed downhole by the carrier that conveys the tool, and a distributed acoustic sensor (DAS). The DAS includes an optical fiber disposed axially along an outer surface of the pipe; and a processor to determine an orientation of the orientation tool with respect to the optical fiber based on a measurement by the optical fiber at different rotational positions of the orientation tool. The processor determines the radial orientation of the tool with respect to the optical fiber based on the orientation of the orientation tool with respect to the optical fiber.

Abstract: An apparatus for sensing vibration in a borehole penetrating the earth includes an optical fiber having a plurality of pairs of reflectors configured to reflect light between each of the pairs of reflectors in the plurality, wherein each pair of reflectors is separated by a nominal distance L and an adjacent pair of reflectors in the plurality are separated by a nominal distance D, and an optical interrogator configured to sense a distance between each pair of reflectors in the plurality over time to sense the vibration. A laser emits semi-coherent light over a swept range of wavelengths to illuminate the optical fiber, wherein the semi-coherent light provides for sensing over distance L in the optical fiber between each pair of reflectors and for no sensing in the optical fiber over distance D between different pairs of reflectors. A photodetector senses light received from the optical fiber.

Abstract: A vibration detector and method of measuring vibration are described. The vibration detector includes an optical fiber comprising a reference reflector and a delay coil, and one or more sensors comprised at respective one or more locations in the optical fiber, each of the one or more sensors including a center reflector and two side reflectors on either side of the center reflector, the delay coil eliminating detection of interference among reflections from the one or more sensors. The vibration detector also includes a light source to introduce light into the optical fiber to interrogate the optical fiber, a detector to obtain interference signals, each of the interference signals being based on interference between reflections from the reference reflector and one of the one or more sensors; and a processor to process each of the interference signals to obtain vibration measurements.

Abstract: An apparatus for monitoring vibration of a downhole component includes an optical fiber sensor including at least one optical fiber operably connected to an interrogation unit. The at least one optical fiber has a resonant segment that is fixedly attached to the component via attachment points on the component, the resonant segment between the attachment points being separate from the component and having a resonant frequency based at least on the length of the resonant segment.

Abstract: A method of monitoring fluid flow in a borehole includes measuring acoustics at a plurality of locations along a downhole assembly in a borehole and calculating a fluid flow rate at the plurality of locations along the downhole assembly based on measuring the acoustics at the plurality of locations.

Abstract: An apparatus for sensing vibration in a borehole penetrating the earth includes an optical fiber having a plurality of pairs of reflectors configured to reflect light between each of the pairs of reflectors in the plurality, wherein each pair of reflectors is separated by a nominal distance L and an adjacent pair of reflectors in the plurality are separated by a nominal distance D, and an optical interrogator configured to sense a distance between each pair of reflectors in the plurality over time to sense the vibration. A laser emits semi-coherent light over a swept range of wavelengths to illuminate the optical fiber, wherein the semi-coherent light provides for sensing over distance L in the optical fiber between each pair of reflectors and for no sensing in the optical fiber over distance D between different pairs of reflectors. A photodetector senses light received from the optical fiber.

Abstract: An acoustic sensing system includes, an optical fiber, a plurality of pairs of reflectors distributed along the optical fiber at specific areas where acoustic energy data is sought, a source of coherent radiation in operable communication with the optical fiber, and a detector in operable communication with the optical fiber configured to detect a different wavelength of coherent radiation reflected from each of the plurality of pairs of reflectors including a portion of the coherent radiation reflected from the reflector nearer the detector after having reflected from the reflector further from the detector that define one of the pairs of reflectors.

Abstract: A downhole tool orientation determination system to determine a radial orientation of a tool conveyed downhole into a pipe via a carrier and a method of determining a radial orientation of a tool conveyed downhole into a pipe via a carrier are described. The system includes an orientation tool conveyed downhole by the carrier that conveys the tool, and a distributed acoustic sensor (DAS). The DAS includes an optical fiber disposed axially along an outer surface of the pipe; and a processor to determine an orientation of the orientation tool with respect to the optical fiber based on a measurement by the optical fiber at different rotational positions of the orientation tool. The processor determines the radial orientation of the tool with respect to the optical fiber based on the orientation of the orientation tool with respect to the optical fiber.

Abstract: A vibration detector and method of measuring vibration are described. The vibration detector includes an optical fiber comprising a reference reflector and a delay coil, and one or more sensors comprised at respective one or more locations in the optical fiber, each of the one or more sensors including a center reflector and two side reflectors on either side of the center reflector, the delay coil eliminating detection of interference among reflections from the one or more sensors. The vibration detector also includes a light source to introduce light into the optical fiber to interrogate the optical fiber, a detector to obtain interference signals, each of the interference signals being based on interference between reflections from the reference reflector and one of the one or more sensors; and a processor to process each of the interference signals to obtain vibration measurements.

Abstract: A method of monitoring fluid flow in a borehole includes measuring acoustics at a plurality of locations along a downhole assembly in a borehole and calculating a fluid flow rate at the plurality of locations along the downhole assembly based on measuring the acoustics at the plurality of locations.

Abstract: A system and method for measuring the vibration of a structure of interest are disclosed. The disclosure provides an acoustic isolation structure to substantially reduce response to acoustic energy generated by external physical stimuli. The acoustic isolation structure is formed by placing a housing, such as an outer conduit, around an inner conduit, forming a gap between the housing and the inner conduit. The gap is then configured to serve as an acoustic isolation layer by either filling the gap with an acoustic isolation material or by substantially evacuating the gap and sealing the ends thereof.

Abstract: An acoustic sensing system includes, an optical fiber, a plurality of pairs of reflectors distributed along the optical fiber at specific areas where acoustic energy data is sought, a source of coherent radiation in operable communication with the optical fiber, and a detector in operable communication with the optical fiber configured to detect a different wavelength of coherent radiation reflected from each of the plurality of pairs of reflectors including a portion of the coherent radiation reflected from the reflector nearer the detector after having reflected from the reflector further from the detector that define one of the pairs of reflectors.

Abstract: An apparatus for monitoring vibration of a downhole component includes an optical fiber sensor including at least one optical fiber operably connected to an interrogation unit. The at least one optical fiber has a resonant segment that is fixedly attached to the component via attachment points on the component, the resonant segment between the attachment points being separate from the component and having a resonant frequency based at least on the length of the resonant segment.