Abstract: An acoustic array includes an acoustic transmitter and acoustic receivers radially or longitudinally offset from the acoustic transmitter. The acoustic array is disposed in a wellbore penetrating a subsurface formation. An acoustic signal is broadcast using the transmitter and a portion of the emitted signal is reflected by a reflector and received by the receivers. The presence or absence of fractures in the subsurface formation is inferred based on the received acoustic signal. Inferences are based on travel times and/or coherency of the received signals. Images can be made and fracture orientations determined. Frequencies in the sonic or ultrasonic range may be used. Measurements may be made while-drilling or while performing post-drilling operations. Processing may be done in real-time or post-processing may be performed on recorded data.

Abstract: In some example embodiments, a system includes a drill string having a drill bit. The drill string extends through at least part of a well bore. The system also includes a first vibrational sensor, positioned on the drill bit to measure, at a first location on the drill string, an amplitude of one or more of an axial vibration and a lateral vibration. The system also includes a second vibrational sensor, positioned above the drill bit and on the drill string. The second vibration sensor is to measure, at a second location on the drill string, one or more of an axial vibration and a lateral vibration. The system includes a processor unit to determine a type of vibration based on a comparison of the amplitude at the first location to the amplitude at the second location, wherein the type of vibration is at least one of bit whirl of the drill bit and a while of a bottom hole assembly that is part of the drill string.

Abstract: In some example embodiments, a system includes a drill string having a drill bit. The drill string extends through at least part of a well bore. The system also includes a first vibrational sensor, positioned on the drill bit to measure, at a first location on the drill string, an amplitude of one or more of an axial vibration and a lateral vibration. The system also includes a second vibrational sensor, positioned above the drill bit and on the drill string. The second vibration sensor is to measure, at a second location on the drill string, one or more of an axial vibration and a lateral vibration. The system includes a processor unit to determine a type of vibration based on a comparison of the amplitude at the first location to the amplitude at the second location, wherein the type of vibration is at least one of bit whirl of the drill bit and a while of a bottom hole assembly that is part of the drill string.

Abstract: An acoustic array includes an acoustic transmitter and acoustic receivers radially or longitudinally offset from the acoustic transmitter. The acoustic array is disposed in a wellbore penetrating a subsurface formation. An acoustic signal is broadcast using the transmitter and a portion of the emitted signal is reflected by a reflector and received by the receivers. The presence or absence of fractures in the subsurface formation is inferred based on the received acoustic signal. Inferences are based on travel times and/or coherency of the received signals. Images can be made and fracture orientations determined. Frequencies in the sonic or ultrasonic range may be used. Measurements may be made while-drilling or while performing post-drilling operations. Processing may be done in real-time or post-processing may be performed on recorded data.

Abstract: Transmitting acoustic signals from a wellbore. At least some of the illustrative embodiments are methods including transmitting an acoustic signal comprising downhole data, receiving the acoustic signal (the receiving by a receiver disposed within the internal diameter of a casing in the wellbore) converting the acoustic signal to a corresponding first electromagnetic signal, and inducing a second electromagnetic signal in a tubing responsive to the first electromagnetic signal.

Abstract: In some example embodiments, a system includes a drill string having a drill bit. The drill string extends through at least part of a well bore. The system also includes a first vibrational sensor, positioned on the drill bit to measure, at a first location on the drill string, an amplitude of one or more of an axial vibration and a lateral vibration. The system also includes a second vibrational sensor, positioned above the drill bit and on the drill string. The second vibration sensor is to measure, at a second location on the drill string, one or more of an axial vibration and a lateral vibration. The system includes a processor unit to determine a type of vibration based on a comparison of the amplitude at the first location to the amplitude at the second location, wherein the type of vibration is at least one of bit whirl of the drill bit and a while of a bottom hole assembly that is part of the drill string.

Abstract: In some example embodiments, a system includes a drill string having a drill bit. The drill string extends through at least part of a well bore. The system also includes a first vibrational sensor, positioned on the drill bit to measure, at a first location on the drill string, an amplitude of one or more of an axial vibration and a lateral vibration. The system also includes a second vibrational sensor, positioned above the drill bit and on the drill string. The second vibration sensor is to measure, at a second location on the drill string, one or more of an axial vibration and a lateral vibration. The system includes a processor unit to determine a type of vibration based on a comparison of the amplitude at the first location to the amplitude at the second location, wherein the type of vibration is at least one of bit whirl of the drill bit and a while of a bottom hole assembly that is part of the drill string.

Abstract: In some example embodiments, a system includes a drill string having a drill bit. The drill string extends through at least part of a well bore. The system also includes a first vibrational sensor, positioned on the drill bit to measure, at a first location on the drill string, an amplitude of one or more of an axial vibration and a lateral vibration. The system also includes a second vibrational sensor, positioned above the drill bit and on the drill string. The second vibration sensor is to measure, at a second location on the drill string, one or more of an axial vibration and a lateral vibration. The system includes a processor unit to determine a type of vibration based on a comparison of the amplitude at the first location to the amplitude at the second location, wherein the type of vibration is at least one of bit whirl of the drill bit and a while of a bottom hole assembly that is part of the drill string.

Abstract: Enhanced symbol synchronization methods suitable for use in narrowband orthogonal frequency division multiplexed (OFDM) telemetry systems. In at least some embodiments, a logging while drilling (LWD) tool assembly communicates with the surface using low frequency electromagnetic (EM) signals. The telemetry transmitter employs OFDM modulation to fully exploit the narrow range of available bandwidth, resulting in signals that have relatively long frames. At the surface a receiver digitizes the receive signal and applies an enhanced symbol synchronization technique to identify frame boundaries before demodulation is attempted. The enhanced symbol synchronization technique employs a pulse train filter to clean up a cyclic prefix correlation signal that otherwise behaves badly in the narrowband regime. The improved timing information from the enhanced symbol synchronization significantly reduces the error rate in the demodulated signal.

Abstract: An embodiment includes a method comprising transmitting and receiving an acoustic signal that is modulated along a jointed tubing. The acoustic signal may be transmitted in multiple passbands of the jointed tubing and may be modulated differently in different passbands. A swept frequency signal may be used to determine transmission characteristics of the jointed tubing and to select the multiple passbands. Additional embodiments are disclosed.

Abstract: In some example embodiments, a system includes a drill string having a drill bit. The drill string extends through at least part of a well bore. The system also includes a first vibrational sensor, positioned on the drill bit to measure, at a first location on the drill string, an amplitude of one or more of an axial vibration and a lateral vibration. The system also includes a second vibrational sensor, positioned above the drill bit and on the drill string. The second vibration sensor is to measure, at a second location on the drill string, one or more of an axial vibration and a lateral vibration. The system includes a processor unit to determine a type of vibration based on a comparison of the amplitude at the first location to the amplitude at the second location, wherein the type of vibration is at least one of bit whirl of the drill bit and a while of a bottom hole assembly that is part of the drill string.

Abstract: Acoustic telemetry devices and methods that provide directional detection. In one embodiment, a disclosed acoustic telemetry device comprises at least two acoustic sensors and an electronics module. The electronics module combines the detection signals from the acoustic sensors to obtain a combined signal that substantially excludes signals propagating in a direction opposite to the communication signal. The disclosed systems and methods can be trained in the field and will readily accommodate an irregular and unknown signal transmission medium between the two acoustic sensors.

Abstract: Transmitting acoustic signals from a wellbore. At least some of the illustrative embodiments are methods including transmitting an acoustic signal comprising downhole data, receiving the acoustic signal (the receiving by a receiver disposed within the internal diameter of a casing in the wellbore) converting the acoustic signal to a corresponding first electromagnetic signal, and inducing a second electromagnetic signal in a tubing responsive to the first electromagnetic signal.

Abstract: Various electromagnetic LWD telemetry systems are disclosed having a wireless repeater positioned on or near the seabed. The wireless repeater receives and demodulates electromagnetic uplink signals and retransmits the uplink signals from the seabed as electromagnetic or acoustic signals. A receiver on the drilling platform or suspended from the water's surface receives the uplink signal and forwards it to a facility for processing and storage. In some embodiments, the wireless repeater takes the form of a sub threaded inline with the drill string with an electromagnetic signal sensor positioned inside the drill string. In other embodiments, the wireless repeater takes the form of a unit that rests on the seabed with electromagnetic signal sensors inserted into the sea bottom.

Abstract: Enhanced symbol synchronization methods suitable for use in narrowband orthogonal frequency division multiplexed (OFDM) telemetry systems. In at least some embodiments, a logging while drilling (LWD) tool assembly communicates with the surface using low frequency electromagnetic (EM) signals. The telemetry transmitter employs OFDM modulation to fully exploit the narrow range of available bandwidth, resulting in signals that have relatively long frames. At the surface a receiver digitizes the receive signal and applies an enhanced symbol synchronization technique to identify frame boundaries before demodulation is attempted. The enhanced symbol synchronization technique employs a pulse train filter to clean up a cyclic prefix correlation signal that otherwise behaves badly in the narrowband regime. The improved timing information from the enhanced symbol synchronization significantly reduces the error rate in the demodulated signal.

Abstract: An embodiment includes a method comprising receiving an acoustic signal that is modulated along a jointed tubing. The method also includes performing equalization over a passband of the acoustic signal to generate an equalized signal.

Abstract: Acoustic telemetry devices and methods that provide directional detection. In one embodiment, a disclosed acoustic telemetry device comprises at least two acoustic sensors and an electronics module.

Abstract: A seismic acquisition system comprising a remote-controlled buoy for conducting seismic acquisition operations. The buoy comprises an operating system for operating a seismic wave production device on the buoy, a placement system, a communications system, and dynamic position locating system. The seismic acquisition system also comprises a remote control system for controlling the buoy systems. The seismic acquisition system also comprises receivers for receiving the seismic wave and generating a data signal indicative of the received seismic wave. The seismic acquisition system operates by controlling the placement system with the remote control system to position the buoy and then controlling the operating system with the remote control system to produce a seismic wave from the seismic wave production device. The receivers then receive the seismic wave and generate a data signal indicative of the seismic wave.

Abstract: A downhole crystal-based clock that is substantially insensitive to the factors that may cause frequency deviation as a result of downhole temperature. The clock may include a plurality of crystals, where a first crystal may be more stable, with respect to temperature, than a second crystal. The crystals may be thermally coupled together so that they may have substantially the same temperature. An error detector may monitor the differences between the frequencies associated with each crystal and provide this information to a storage device. This information may be determined prior to deploying the clock downhole. When deployed downhole, the signal from the error detector may be interpreted in light of the information in the storage device to provide a temperature measurement of the two crystals. The downhole temperature measurement then may be used to reduce frequency deviations in the downhole clock that may result from downhole temperatures.

Abstract: An embodiment includes a method comprising receiving an acoustic signal that is modulated along a jointed tubing. The method also includes performing equalization over a passband of the acoustic signal to generate an equalized signal.