Abstract: A distributed control system can be used to implement failover capabilities for control units that control well equipment during a well operation. For example, a system can include first well equipment that performs a first physical task and second well equipment that performs a second physical task different from the first physical task. Additionally, the system can include a distributed control system with a first control unit coupled to the first well equipment and a second control unit coupled to the second well equipment. Both control units may include a first control module and a second control module for automatically controlling the first physical task and the second physical task, respectively. The distributed control system can detect a failure of the second control unit and initiate a failover process in which the first control unit takes over control of the second physical task by enabling the second control module.

Abstract: Fluid characteristics of a well fluid can be monitored. For example, a computing device can receive sensor signals from an acoustic sensor positioned on a well tool. The sensor signals can indicate characteristics of acoustic emissions generated by a well fluid impacting the well tool. The computing device can determine an acoustic signature for the well fluid using the characteristics of the acoustic emissions. The computing device can determine a difference between the acoustic signature a baseline acoustic-signature for the well fluid. The computing device can determine one or more fluid characteristics of the well fluid using the difference between the acoustic signature and the baseline acoustic-signature. The computing device can transmit a notification indicating the one or more fluid characteristics.

Abstract: An apparatus includes a processor and a machine-readable medium having program code to cause the apparatus to obtain a first dictionary based on a first training set of signals and determine a first subset of the first training set of signals based on a training reconstruction accuracy threshold and the first dictionary, wherein each atom in the first dictionary includes at least one of a signal pattern and a function representing the signal pattern. The program code also includes code to generate a second dictionary based on a second training set of signals, wherein the second training set of signals includes the first subset of the first training set of signals.

Abstract: An apparatus includes a subsurface sensor for use in a borehole to provide a subsurface measurement series, a subsurface processor to receive the subsurface measurement series, and a machine-readable medium. The machine-readable medium has program code to cause the apparatus to obtain the subsurface measurement series and generate an atom combination based on the subsurface measurement series using the subsurface processor, wherein the atom combination comprises a subset of atoms from a dictionary. The code also has instructions to generate a set of characterizing values and transmit the set of characterizing values to a different physical location, wherein the set of characterizing values comprises an atom identifier and at least one corresponding atom weight for at least one atom from the atom combination.

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: A well monitoring system includes a plurality of transmitter coils coupled to an exterior of a casing positioned within a wellbore, wherein one or more first transmitter coils are positioned at a first location and one or more second transmitter coils are positioned at a second location axially offset from the first location. At least one receiver coil is coupled to the exterior of the casing and positioned at the second location. A power source is communicably coupled to the one or more first and second transmitter coils. The one or more first transmitter coils generates a magnetic field detectable by the at least one receiver coil, and the one or more second transmitter coils generates a bucking signal that minimizes a direct coupling between the one or more first transmitter coils and the at least one receiver coil.

Abstract: An apparatus includes a processor and a machine-readable medium having program code to cause the apparatus to obtain a first dictionary based on a first training set of signals and determine a first subset of the first training set of signals based on a training reconstruction accuracy threshold and the first dictionary, wherein each atom in the first dictionary includes at least one of a signal pattern and a function representing the signal pattern. The program code also includes code to generate a second dictionary based on a second training set of signals, wherein the second training set of signals includes the first subset of the first training set of signals.

Abstract: In accordance with embodiments of the present disclosure, systems and methods for triggering detonation of a perforating gun via optical signals are provided. An improved laser firing head may be used with an optical cable (e.g., fiber optic cable) run through the wellbore to trigger detonation of a perforating gun in response to an optical signal. The laser firing head may be activated, and the perforating gun fired, upon the application of an optical signal output from the surface and transmitted through the optical cable. The disclosed system using the laser firing head with the optical cable may be impervious to electrical interference, since the laser firing head may only fire the perforating gun when a properly modulated laser or light source is directed down the optical cable for a specific period of time.

Abstract: An apparatus includes a subsurface sensor for use in a borehole to provide a subsurface measurement series, a subsurface processor to receive the subsurface measurement series, and a machine-readable medium. The machine-readable medium has program code to cause the apparatus to obtain the subsurface measurement series and generate an atom combination based on the subsurface measurement series using the subsurface processor, wherein the atom combination comprises a subset of atoms from a dictionary. The code also has instructions to generate a set of characterizing values and transmit the set of characterizing values to a different physical location, wherein the set of characterizing values comprises an atom identifier and at least one corresponding atom weight for at least one atom from the atom combination.

Abstract: Electromagnetic field monitoring methods and systems for obtaining data corresponding to subsurface rock formations. An electromagnetic field monitoring system includes an electromagnetic transmitter located downhole in a well bore and configured to radiate electromagnetic radiation into a subsurface formation; a fiber optic cable coupled with a fiber optic interrogator, the at least one fiber optic cable and the interrogator located at the surface; and an array of electromagnetic sensors integrally formed in the fiber optic cable and configured to detect the electromagnetic radiation radiated through the subsurface formation. A method of detecting electromagnetic radiation at the surface of an oil well includes transmitting, from an electromagnetic transmitter, electromagnetic radiation into a subsurface formation; and sensing, from the subsurface formation, electromagnetic radiation at the surface of the oil well.

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: 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: 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: Fluid characteristics of a well fluid can be monitored. For example, a computing device can receive sensor signals from an acoustic sensor positioned on a well tool. The sensor signals can indicate characteristics of acoustic emissions generated by a well fluid impacting the well tool. The computing device can determine an acoustic signature for the well fluid using the characteristics of the acoustic emissions. The computing device can determine a difference between the acoustic signature a baseline acoustic-signature for the well fluid. The computing device can determine one or more fluid characteristics of the well fluid using the difference between the acoustic signature and the baseline acoustic-signature. The computing device can transmit a notification indicating the one or more fluid characteristics.

Abstract: A magnetic field sensor unit for a downhole environment includes an optical fiber, a magnetic field sensor, and an optical transducer. The sensor unit also includes a sealed housing that encloses the magnetic field sensor and the optical transducer. The optical transducer is configured to generate a light beam or to modulate a source light beam in the optical fiber in response to a magnetic field sensed by the magnetic field sensor. Related magnetic field measurement methods and systems deploy one or more of such magnetic field sensor units in a downhole environment to obtain magnetic field measurements due to an emitted electromagnetic field.

Abstract: Methods and systems of electromagnetic sensing in a wellbore are presented in this disclosure for monitoring annulus fluids and water floods. An array of transmitters and one or more receivers are located along a casing in the wellbore. A transmitter in the array and one of the receivers can be mounted on a same collar on the casing forming a transmitter-receiver pair. The receiver can receive a signal originating from the transmitter and at least one other signal originating from at least one other transmitter in the array, wherein the signal is indicative of a fluid in the wellbore in a vicinity of the transmitter-receiver pair and the at least one other signal is indicative of another fluid in a formation around the wellbore. The receiver can further communicate, via a waveguide, the signal and the at least one other signal to a processor for signal interpretation.

Abstract: Reelable sensors arrays are independently fabricated separate from a downhole tubular. The sensor arrays are then reeled together onto a spool. At the well site, the sensor array is unreeled from the spool and attached to the tubular as it is deployed downhole, resulting in a fast and efficient method of sensor deployment.

Abstract: Electromagnetic (EM) measurement systems and methods for a downhole environment are described herein. An example system includes an optical fiber, an EM source to emit an EM field, and a magnetic induction sensor. The magnetic induction sensor comprises a coil and an electro-optical transducer coupled to the coil and the optical fiber. The electro-optical transducer generates a light beam or modulates a source light beam in the optical fiber in accordance with a voltage induced in the coil by the EM field.

Abstract: An electric field sensing system comprises a magnetic shield, an optical magnetometer shielded from external magnetic fields by the magnetic shield, a conductive coil proximate to the optical magnetometer, and first and second electrodes coupled to opposite ends of the coil. The electrodes are disposed outside of the magnetic shield. The conductive coil generates a magnetic field within the optical magnetometer when electrical current passes through the conductive coil.

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.