A system for generating variable frequency tube waves includes a high pressure multiplex pump having a number of plungers, with each plunger operatively coupled to a suction valve on a suction side and a discharge valve on a discharge side. The suction valve or the discharge valve of a first one of the plungers includes an opening, such that the modified plunger on a discharge stroke pushes fluid through the opening in the suction or discharge valve. The system includes a tubular fluidly coupling the high pressure multiplex pump to a wellbore, and a pressure sensor that receives tube waves generated by the high pressure multiplex pump and reflected from the wellbore.

A method and system for reducing transducer ringing. The method may comprise identifying a first set of waveforms and a second set of waveforms from recorded waveforms taken by a transducer, estimating an invariant component for each waveform in the first set of waveforms, and subtracting the invariant component from the second set of waveforms. The system may comprise a downhole tool. The downhole tool may comprise at least one transducer and wherein the at least one transducer is configured to emit an excitation and record a plurality of waveforms. The system may further comprise an information handling system configured to identify a first set of waveforms and a second set of waveforms from the plurality of waveforms from the at least one transducer, estimate an invariant component for each waveform in the first set of waveforms, and subtract the invariant component from the second set of waveforms.

A method may comprise recording a first reflected waveform with a first transducer to form a first data set from a first excitation, recording a second reflected waveform with a second transducer to form a second data set from a second excitation, estimating a first sensitivity correction factor for the first data set, applying the first sensitivity correction factor to at least a portion of the first data set to form a first sensitivity corrected data set. The method may further comprise estimating a second sensitivity correction factor for the second data set, applying the second sensitivity correction factor to at least a portion of the second data set to form a second sensitivity corrected data set, stacking the first sensitivity corrected data set amplitudes and forming a first image, stacking the second sensitivity corrected data set amplitudes and forming a second image, and comparing the images.

A method for scanning artificial structure, wherein a scanning artificial structure apparatus comprises four magnetic-field sensors, the four magnetic-field sensors are non-coplanar configured, the method comprises following steps of: moving the scanning artificial structure apparatus along a scanning path within a to-be-tested area, in the meantime, measuring magnetic field by the four magnetic-field sensors, and recording a position sequence when measuring magnetic field, wherein four magnetic-field measurement sequences are measured by the four magnetic-field sensors; and calculating a magnetic-field variation distribution from the four magnetic-field measurement sequences and the position sequence, wherein the magnetic-field variation distribution is corresponding to at least one artificial structure distribution.

An azimuthal acoustic LWD apparatus is sequentially provided with a centralizer, a transmitting circuit, transmitting transducers, an acoustic insulator, a receiving transducer array, ultrasonic transducers and a receiving circuit on a drill collar. The azimuthal acoustic LWD apparatus is capable of operating in a dipole mode or a unipole mode, to cover all the sectors around a wellbore by adopting a fixed time interval measurement mode or an alternating time interval measurement mode according to a relationship of an interval between measurement times and a rotation speed of the apparatus, thereby achieving azimuthal acoustic LWD. This apparatus overcomes problems that the fixed time interval measurement mode may not cover all the sectors and further may not achieve azimuthal acoustic imaging in a case where the rotation speed and the interval between measurement times are under certain conditions.

An azimuthal acoustic LWD apparatus is sequentially provided with a centralizer, a transmitting circuit, transmitting transducers, an acoustic insulator, a receiving transducer array, ultrasonic transducers and a receiving circuit on a drill collar. The azimuthal acoustic LWD apparatus is capable of operating in a dipole mode or a unipole mode, to cover all the sectors around a wellbore by adopting a fixed time interval measurement mode or an alternating time interval measurement mode according to a relationship of an interval between measurement times and a rotation speed of the apparatus, thereby achieving azimuthal acoustic LWD. This apparatus overcomes problems that the fixed time interval measurement mode may not cover all the sectors and further may not achieve azimuthal acoustic imaging in a case where the rotation speed and the interval between measurement times are under certain conditions.

A central member defines a sample chamber and includes an elastic material configured to enclose at least a portion of a sample, acoustic sensors configured to detect sound waves in the sample chamber, and acoustic emitters configured to emit sounds waves in the central member. A pressure-retaining case is configured to contain a pressurized fluid between an annulus formed between the pressure-retaining case and the central member. A switch is configured to connect or disconnect a pulser and receiver circuit to a specified emitter of the acoustic emitters. A data acquisition unit is configured to receive a signal from each of the acoustic sensors. A pulser and receiver circuit is configured to send an electric pulse to an acoustic emitter and a control signal to the data acquisition unit.

A system for generating variable frequency tube waves includes a high pressure multiplex pump having a number of plungers, with each plunger operatively coupled to a suction valve on a suction side and a discharge valve on a discharge side. The suction valve or the discharge valve of a first one of the plungers includes an opening, such that the modified plunger on a discharge stroke pushes fluid through the opening in the suction or discharge valve. The system includes a tubular fluidly coupling the high pressure multiplex pump to a wellbore, and a pressure sensor that receives tube waves generated by the high pressure multiplex pump and reflected from the wellbore.

A system for generating variable frequency tube waves includes a high pressure multiplex pump having a number of plungers, with each plunger operatively coupled to a suction valve on a suction side and a discharge valve on a discharge side. The suction valve or the discharge valve of a first one of the plungers includes an opening, such that the modified plunger on a discharge stroke pushes fluid through the opening in the suction or discharge valve. The system includes a tubular fluidly coupling the high pressure multiplex pump to a wellbore, and a pressure sensor that receives tube waves generated by the high pressure multiplex pump and reflected from the wellbore.

A method for borehole measurements may comprise receiving one or more signals from a linear receiver array, computing an arctan of a Hilbert Transform, isolating a first arriving energy, selecting a reference instantaneous phase on a reference receiver, finding the reference instantaneous phase for the linear receiver array, computing a relative travel time shift, combining a reference pick time with a relative time, and determining a travel time. A system for borehole measurements comprise a conveyance, a bottom hole assembly attached to the conveyance, a linear receiver array, wherein the linear receiver array is disposed on the bottom hole assembly, and a computer system connected to the linear receiver array.