Abstract: A system includes an optical fiber integrated into a conveyance subsystem that is positionable downhole in a wellbore. The system also includes a backscattering sensor system positionable to monitor temperature and optical fiber strain along the optical fiber using backscattered light signals received from the optical fiber. Further, the system includes a fiber optic rotary joint positionable to optically couple the optical fiber with the backscattering sensor system to provide an optical path for the backscattered light signals to reach the backscattering sensor system.

Abstract: A distributed acoustic system (DAS) with an interrogator, an umbilical line attached at one end to the interrogator, and a downhole fiber attached to the umbilical line at the end opposite the interrogator. A method for optimizing a sampling frequency may begin with identifying a length of a fiber optic cable connected to an interrogator, identifying one or more regions on the fiber optic cable in which a backscatter is received, and optimizing a sampling frequency of a distributed acoustic system (DAS) by identifying a minimum time interval that is between an emission of a light pulse such that at no point in time the backscatter arrives back at the interrogator that corresponds to more than one spatial location along a sensing portion of the fiber optic cable.

Abstract: In some embodiments, a method and apparatus, as well as an article, may operate to determine downhole properties based on detected optical signals. An optical detection system can include a fiber optic cable having a sensing location to generate a backscattered Rayleigh signal representative of measurement parameters. The optical detection system can further include a light source to transmit a measurement signal to cause the sensing location to provide the backscattered Rayleigh signal. The optical detection system can further include an optical detector comprising a single-photon detector (SPD) for detecting the backscattered Rayleigh signal received over the fiber optic cable. The optical detection system can further include circuitry to produce an acoustic signal representative of a downhole property based on the phase of the backscattered Rayleigh signal. Additional apparatuses, systems, and methods are disclosed.

Abstract: Systems and methods are provided for determining a presence, type, or amount of an analyte in fluid. An analyte sensor can include a substrate that includes a chiral molecule for sensing the presence of the analyte in the fluid. A property of the chiral molecule may change in response to sensing the presence of the analyte. The change in the property of the chiral molecule can cause a change in polarization of a beam of light traveling through the substrate. The presence, type, or amount of the analyte can be determined based on the change in polarization of the beam of light. The analyte sensor, along with optical fibers, can be used to determine the presence, type, or amount of an analyte in a fluid sample from a wellbore.

Abstract: Included are cement compositions and methods and systems for locating the cement compositions in a wellbore. An example method comprises deploying a sensing system in the wellbore and introducing the cement composition into the wellbore. The cement composition comprises a cement and hollow beads having a crush pressure and configured to emit an acoustic signal when imploded. The method further comprises pumping the cement composition through the wellbore to a depth with a wellbore pressure exceeding the crush pressure of the hollow beads to induce implosion of the hollow beads and the emission of the acoustic signal. The method further comprises sensing the emitted acoustic signal and determining the location of the cement composition in the wellbore from the sensed emitted acoustic signal.

Abstract: Methods and systems for the use of partially reflective materials and coatings for optical communications in a wellbore environment are provided. In one embodiment, methods for remote communication in a wellbore comprise: positioning an optical fiber in the wellbore, wherein at least a portion of the optical fiber comprises a partially reflective coating; transmitting an output optical signal from an optical source through the optical fiber; and receiving a reflected optical signal from the optical fiber at an optical detector, wherein at least one optical property of the reflected optical signal is indicative of a downhole condition.

Abstract: An optical detection system for analyzing a fluid sample including a light source configured to emit a light beam to interact with the sample to form a spectrum, an optical fiber to transmit the spectrum, an array of single-photon detectors (SPDs), and wherein each SPD is configured to receive and is tunable to analyze spectral characteristics of the spectrum across a spectral range.

Abstract: Pipeline segments can contain cables, such as communication cables (e.g., fiber optic cables) within insulation material surrounding the pipeline segments. Cables can be embedded within the insulation material, run through conduits embedded within the insulation material, placed in channels formed in the insulation material, or otherwise. Channels containing one or more cables can be filled with supplemental insulation material, thus securing the cables within the channels. Pipelines created as disclosed herein can enable data transfer between distant points without the need to lay fiber optic cable in addition to the pipeline. Further, fiber optic cable embedded thusly can be used to sense conditions in the pipeline, such as leaks, seismic activity, strain, and temperature information.

Abstract: In some embodiments, a method and apparatus, as well as an article, may operate to determine downhole properties based on detected optical signals. An optical detection system can include a fiber optic cable having a sensing location to generate a reflected measurement signal representative of measurement parameters. The optical detection system can further include a light source to transmit a measurement signal to cause the sensing location to provide the reflected measurement signal. The optical detection system can further include an optical detector comprising a single-photon detector (SPD) for detecting the reflected measurement signal received over the fiber optic cable. The optical detection system can further include a housing for enclosing the optical detector and to optically shield the optical detector, the housing including an aperture for passage of the fiber optic cable. Additional apparatuses, systems, and methods are disclosed.

Abstract: A borehole fluid imaging system includes a plurality of radiation sources located circumferentially around the borehole. A plurality of radiation detectors are located circumferentially around the borehole. The plurality of radiation detectors detect the radiation transmitted by each of the respective ones of the plurality of radiation sources. A controller is coupled to the plurality of radiation detectors to determine an attenuation of the radiation at the plurality of detectors and generate an image of the fluid in response to the attenuation of the radiation.

Abstract: A property of a downhole fluid, for example, a chemical species or ion concentration, may be accurately determined and logged based on measurements received from an optical detector where the optical detector is fed information or signals from an optical system coupled to one or more electrochemical probes calibrated for one or more properties of a fluid. The one or more electrochemical probes provide a potential to the optical system based, at least in part, on exposure to the downhole fluid. The optical system receives an optical signal from a light source that is transmitted via a transmission line, such as a fiber optic cable. Downhole information from the optical system is transmitted to the surface via the same or another transmission line. Thus, the signals are in the optical domain rather than the electrical domain. Multiple properties may be measured simultaneously using the same transmission line.

Abstract: A borehole fluid imaging system includes a plurality of radiation sources located circumferentially around the borehole. A plurality of radiation detectors are located circumferentially around the borehole. The plurality of radiation detectors detect the radiation transmitted by each of the respective ones of the plurality of radiation sources. A controller is coupled to the plurality of radiation detectors to determine an attenuation of the radiation at the plurality of detectors and generate an image of the fluid in response to the attenuation of the radiation.

Abstract: In some embodiments, a method and apparatus, as well as an article, may operate to determine properties based on detected optical signals. An optical detection apparatus can include an optical detector for detecting light received through a fiber optic cable; a housing for enclosing the optical detector; a light source; and a cooling mechanism having the housing mounted thereto. The cooling mechanism can maintain the temperature of a light-sensitive region of the optical detector within a temperature range below 210 degrees Kelvin. Additional apparatus, systems, and methods are disclosed.

Abstract: A method of optical communication in a well can include launching light having substantially coherent phase into an optical waveguide extending in a wellbore, modulating light having substantially coherent phase in the wellbore, and receiving the modulated light transmitted via the same optical waveguide. A well system can include at least one optical waveguide extending in a wellbore, and a downhole optical modulator which modulates light transmitted via the optical waveguide, the optical modulator comprising a potassium titanyl phosphate crystal. Another method of optical communication in a well can include launching light into an optical waveguide extending in a wellbore, the light launched into the optical waveguide having information modulated thereon using a carrier, modulating light in the wellbore, the modulating comprising modulating information using a subcarrier of the carrier, and transmitting the light modulated in the wellbore via the same optical waveguide.

Abstract: In some embodiments, a method and apparatus, as well as an article, may operate to determine downhole properties based on detected optical signals. An optical detection system can include a fiber optic cable having a sensing location to generate a backscattered Rayleigh signal representative of measurement parameters. The optical detection system can further include a light source to transmit a measurement signal to cause the sensing location to provide the backscattered Rayleigh signal. The optical detection system can further include an optical detector comprising a single-photon detector (SPD) for detecting the backscattered Rayleigh signal received over the fiber optic cable. The optical detection system can further include circuitry to produce an acoustic signal representative of a downhole property based on the phase of the backscattered Rayleigh signal. Additional apparatuses, systems, and methods are disclosed.

Abstract: A hybrid fiber optic assembly and system for use in a well, where the system includes a hybrid fiber optic cable with at least a first transmission region and at least a first sensory region as well as an interrogator system coupled to the hybrid fiber optic cable. The hybrid fiber optic cable can have a plurality of transmission regions and sensory regions, as well as transition regions in between and coupling individual pairs of transmission regions and sensory regions.

Abstract: A method of logging a well can include conveying an optical waveguide and at least one signal generator with a conveyance into the well, causing the signal generator to generate at least one signal in the well, and receiving the signal as distributed along the optical waveguide. A well logging system can include a conveyance with an optical waveguide, and at least one signal generator which is conveyed by the conveyance into a well with the optical waveguide, whereby the signal generator generates at least one signal received with the optical waveguide.

Abstract: A downhole sensing method includes modulating light to form a soliton that propagates through an optical fiber acting as a sensing element that measures a downhole parameter. The method further includes obtaining scattered light created as the soliton propagates through the optical fiber. The method further includes determining a value for a downhole parameter based on the scattered light, and displaying a representation of the value.

Abstract: An illustrative distributed acoustic sensing system includes a multi-mode optical fiber cable for distributed sensing and a distributed acoustic sensing interrogator coupled to the multi-mode optical fiber cable via a single mode optical fiber. The interrogator derives distributed acoustic measurements from Rayleigh backscattering light that is initiated with a substantially under-filled launch configuration that is designed to excite only the lowest-order modes of the multi-mode optical fiber. Mode conversion within the multi-mode optical fiber is anticipated to be negligible. For elastic scattering (i.e., Rayleigh scattering), it is further anticipated that the scattered light will be primarily returned in the incident propagation mode, thereby escaping the extraordinarily large coupling loss that would otherwise be expected from coupling a single-mode optical fiber to a multi-mode optical fiber for distributed sensing. Experiments with graded index multi-mode optical fiber have yielded positive results.

Abstract: Pipeline segments can contain cables, such as communication cables (e.g., fiber optic cables) within insulation material surrounding the pipeline segments. Cables can be embedded within the insulation material, run through conduits embedded within the insulation material, placed in channels formed in the insulation material, or otherwise. Channels containing one or more cables can be filled with supplemental insulation material, thus securing the cables within the channels. Pipelines created as disclosed herein can enable data transfer between distant points without the need to lay fiber optic cable in addition to the pipeline. Further, fiber optic cable embedded thusly can be used to sense conditions in the pipeline, such as leaks, seismic activity, strain, and temperature information.