Abstract: Example embodiments are described for a method and system for direct current (DC) bias control in downhole optical intensity modulators. After receiving an optical signal from a downhole intensity modulator, a harmonic distortion analysis is performed on the optical signal to determine whether a power spectrum of the optical signal deviates by a preselected amount from an expected power spectrum. The expected power spectrum occurs when a bias point is positioned at a quadrature point of a sinusoid associated with the optical signal. A DC bias voltage of the intensity modulator is subsequently adjusted in response to the harmonic distortion analysis.

Abstract: A distributed acoustic system may comprise an interrogator which includes a single photon detector, an umbilical line comprising a first fiber optic cable and a second fiber optic cable 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 comprise 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 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: A system for conducting real-time chemical analysis of deposits is provided. The system includes an electromagnetic radiation source positioned on a downhole tool that emits electromagnetic radiation to a surrounding downhole environment within a field of view of interest. The system also includes a multivariate optical element positioned on the downhole tool that has optical filters configured to receive reflected radiation from the field of view of interest and generate respective filtered radiation signals. Each of the optical filters has a different transmission function that corresponds to a respective chemical species of interest. The system also includes an image sensor positioned on the downhole tool that detects each of the respective filtered radiation signals from the multivariate optical element. The image sensor provides image information of the field of view of interest that indicates a presence of at least one chemical species of interest located in the surrounding downhole environment.

Abstract: Disclosed are methods and apparatus for using an audible signal to monitor conditions at a downhole location in a well through use of a well cable containing a fiber optic, which may be either a slickline or a wireline fiber-optic cable, and providing an audible signal which varies in response to the monitored condition. The condition monitored can be strain in the fiber optic well cable, which can be sensed in one or more locations in the fiber optic well cable, in many examples through use of a sensor such as a Bragg grating associated with or formed in an optical fiber within the well cable. In some examples, a temperature measurement may be used to compensate for temperature effects impacting the strain measurement.

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 method and system for in-sit calibration of a gravimeter. A method may comprise disposing a downhole tool in a borehole, wherein the downhole tool comprises the gravimeter attached to a linear actuator, recording a first set of measurements with the gravimeter while the linear actuator is stationary, activating the linear actuator, recording a second set of measurements with the gravimeter, and calibrating the gravimeter based on the first and second set of recorded measurements. A system may comprise a downhole tool, a conveyance, and an information handling system. The downhole tool may further comprise a hanger, a sonde, connected to the hanger, a linear actuator, connected to the hanger, and a shaft, connected to the linear actuator. The downhole tool may further comprise a linkage, connected to the shaft, a package, connected to the linkage, and a gravimeter, disposed in the package.

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: The disclosed embodiments include downhole communication networks and methods to form downhole communication networks. In one embodiment, a downhole communication network includes a plurality of communication tags deployed in a wellbore. Each communication tag of the plurality of communication tags includes a sensor operable to detect wellbore and hydrocarbon resource properties proximate the respective communication tag. Each communication tag of the plurality of communication tags also includes a storage medium operable to store data indicative of the at least one of wellbore and hydrocarbon resource properties proximate the respective communication tag. Each communication tag of the plurality of communication tags further includes a transmitter operable to transmit a signal indicative of one or more of the wellbore and hydrocarbon resource properties.

Abstract: Optical fiber having a graphene coating, a method to apply a graphene coating onto an optical fiber, and a fiber optic cable having a graphene coating are disclosed. A first carbon based coating is applied to an optical fiber along a longitudinal axis of the optical fiber. A laser beam is focused at the first carbon based coating. A first surface of the first carbon based coating is photothermally converted into a first layer of graphene.

Abstract: Example embodiments are described for a method and system for direct current (DC) bias control in downhole optical intensity modulators. After receiving an optical signal from a downhole intensity modulator, a harmonic distortion analysis is performed on the optical signal to determine whether a power spectrum of the optical signal deviates by a preselected amount from an expected power spectrum. The expected power spectrum occurs when a bias point is positioned at a quadrature point of a sinusoid associated with the optical signal. A DC bias voltage of the intensity modulator is subsequently adjusted in response to the harmonic distortion analysis.

Abstract: The disclosed embodiments include an optical fiber having a graphene coating, a method to apply a graphene coating onto an optical fiber, and a fiber optic cable having a graphene coating. In one embodiment, the optical fiber includes an optical core that extends along a longitudinal axis. The optical fiber also includes a carbon based coating that covers the optical core along the longitudinal axis. The optical fiber also includes a layer of graphene formed on a first surface of the carbon based coating. The layer of graphene is formed from a laser induction process that includes focusing a laser beam at the carbon based coating to photothermally convert the first surface of the carbon based coating into graphene.

Abstract: Systems and methods generally useful in medicine, cellular biology, nanotechnology, and cell culturing are discussed. In particular, at least in some embodiments, systems and methods for magnetic guidance and patterning of cells and materials are discussed. Some specific applications of these systems and methods may include levitated culturing of cells away from a surface, making and manipulating patterns of levitated cells, and patterning culturing of cells on a surface. Specifically, a method of culturing cells is presented. The method may comprise providing a plurality of cells, providing a magnetic field, and levitating at least some of the plurality of cells in the magnetic field, wherein the plurality of cells comprise magnetic nanoparticles. The method may also comprise maintaining the levitation for a time sufficient to permit cell growth to form an assembly.

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: The disclosed embodiments include an optical fiber having a graphene coating, a method to apply a graphene coating onto an optical fiber, and a fiber optic cable having a graphene coating. In one embodiment, the optical fiber includes an optical core that extends along a longitudinal axis. The optical fiber also includes a carbon based coating that covers the optical core along the longitudinal axis. The optical fiber also includes a layer of graphene formed on a first surface of the carbon based coating. The layer of graphene is formed from a laser induction process that includes focusing a laser beam at the carbon based coating to photothermally convert the first surface of the carbon based coating into graphene.

Abstract: A system, in some embodiments, comprises: a light source; a fiber optic cable coupled to surface equipment and to downhole equipment and illuminated with fixed-wavelength light by said light source; and a modulator to modulate said fixed-wavelength light in the fiber optic cable to communicate data between the surface equipment and the downhole equipment, wherein the modulator uses a modified half-duplex telemetry scheme.

Abstract: A telemetry system is operable to transmit data by bridging the low signal bandwidth available to high temperature electronics with the high spectral bandwidth available in optical fiber. A transmitter, such as a frequency comb, generates light to a fiber and the light is demultiplexed to separate the light into separate wavelengths. Modulators encode downhole data onto each wavelength and a multiplexer recombines the wavelengths onto a single fiber that passes the light back to the surface where a second demultiplexer separates the light to be transmitted to distinct receivers that detect the encoded data. A dual fiber system may also be utilized. One or more commands may also be transmitted to the downhole tools by transmitted the encoded command to a coupler that is coupled to a multiplexer where a downhole receiver determines the downhole tool that should receive the associated command.

Abstract: The present disclosure relates to systems and methods for analyzing fluids. The method for analyzing a chemical sample within a wellbore, contained within an interrogation device, may comprise broadcasting a coherent light from a frequency comb module, directing the coherent light through a fiber optic line to the interrogation device, irradiating the chemical sample with the coherent light, capturing light resulting from the irradiation of the chemical sample, and producing a spectrum resulting from the captured light from the chemical sample. A frequency comb system for analyzing a chemical sample may comprise a frequency comb module configured to broadcast a coherent light and a fiber optic line that extends into a wellbore to an interrogation device. The interrogation device may further be configured to contain the chemical sample for irradiation by the coherent light. The frequency comb system may further comprise a receiver and an information handling system.

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: A downhole tool is positioned in a borehole of a geological formation at a given depth. A formation property is determined at the given depth. The positioning and determining is repeated to form data points of a data set indicative of formation properties at various depths in the borehole. One or more outlier data points is removed from the data set based on first gradients to form an updated data set. One or more properties associated with a reservoir compartment are determined based on second respective gradients associated with the updated data set.

Abstract: Disclosed herein are methods and systems that use magnetic complexes in wellbore monitoring. A well monitoring system may comprise magnetic complexes disposed in a subterranean formation, wherein the magnetic complexes each comprise a first magnetic portion, a second magnetic portion, and a spacer portion; and an electromagnetic interrogator, wherein the electromagnetic interrogator comprises an electromagnetic source and an electromagnetic detector.