Abstract: A seismic logging system for VSP or cross well data capture set forth. It is comprised of M duplicate recording stations connected serially below a main structure suspended on a logging cable. Each of the recording stations preferably includes orthogonally arranged displacement transducers, and they are in turn connected with suitable amplifiers, filters and converters to form digital words, and the digital words are recorded in organized fashion in a memory. A telemetry unit is connected to that memory for transfer of data. This data transfer takes place over a short distance into the main unit, and the main unit includes a much larger memory for storing and holding data from M recording stations deployed along and there below in the well borehole, and further including telemetry means for transfer of data along the logging cable.

Abstract: A rotary ultrasonic transducer logging tool is set forth which has a transmitter connected to a transducer for transmitting pulses periodically, and a rotor with angle sensor connected thereto. One full revolution is divided into a specified number of incremental steps. The output of the receiver is supplied to an automatic gain control amplifier, then to an analog to digital converter. A gain control setting for the AGC amp is included. The AGC setting for the particular corresponding points in a first revolution of the transducer are used to provide settings for the AGC amplifier in the next revolution. A first buffer is used to store the data for the first revolution, a second buffer for the second revolution, and alternately back to the first buffer. These two buffers provide an output signal for a gain control buffer then input to the AGC amplifier. Alternate forms of gain control signal selection are used such as prior gain control settings.

Abstract: For use in an acoustic logging tool, an apparatus which digitizes simultaneously obtained acoustic signals is set forth in the preferred and illustrated embodiment. The device cooperates with N acoustic receivers in a sonde. After an acoustic pulse is transmitted, data is observed at all N acoustic receivers. This apparatus comprises a multiplexer which is connected to the several receivers. The several input signals are multiplexed, thereafter input to a digital data converter forming a procession of output digital words, and the words are stored in a selected order in a digital data buffer. They are delivered to the surface through a telemetry transmitter at a slower rate than the rate at which the data is created. In addition, a transmitter monitor is included. This provides a signal alternately digitized for a specified interval to enable coordination of the data reduction from the acoustic receivers in contrast with the timing of the transmitted acoustic pulse.

Abstract: In an acoustic well logging system having an acoustic transmitter in a sonde and spaced acoustic receivers, an acoustic transmitter control circuit enabling transmission of high frequency pulses, acoustic receivers therefor, received signal frequency filter selector means and a digital signal processing system assist in data processing. The received signal is passed through high and low frequency filters, the filters being selectively switched, the signals are converted to digital form and then available for further processing.

Abstract: For use in an acoustic logging tool, an apparatus which digitizes simultaneously obtained acoustic signals is set forth in the preferred and illustrated embodiment. The device cooperates with N acoustic receivers in a sonde. After an acoustic pulse is transmitted, data is observed at all N acoustic receivers. This apparatus comprises a multiplexer which is connected to the several receivers. The several input signals are multiplexed, thereafter input to a digital data converter forming a procession of output digital words, and the words are stored in a selected order in a digital data buffer. They are delivered to the surface through a telemetry transmitter at a slower rate than the rate at which the data is created. In addition, a transmitter monitor is included. This provides a signal alternately digitized for a specified interval to enable coordination of the data reduction from the acoustic receivers in contrast with the timing of the transmitted acoustic pulse.

Abstract: For use in a downhole acoustic logging system including an acoustic transmitter and spaced acoustic receiver, the preferred and illustrated embodiment incorporates a gain control for the receiver system. The automatic gain control (AGC) controls data capture without clipping or fadeout, and provides the digitized value of gain setting to be recorded to assist in data reduction whereby the digitized signal and gain of the system are obtained. The inbound signal is divided into a pressure wave, a shear wave and a fluid wave. The gain function is divided into three gain control regions indentified hereinafeter as the P, S and F regions, and the gain is stepped automatically to provide an output voltage within specified limits. Those limits are observed, thereby operating the gain controlled in the AGC in digital fashion, and the received signal is amplified in a controlled manner, thereby enabling recordal of the wave form without clipping or fadeout while capturing the gain to enable recovery of the data.

Abstract: A well logging method and apparatus for detecting the first arrival of an acoustic wave in a logging signal under adverse signal conditions. The received acoustic signal is amplified at a fixed gain until clipped at the largest amplitude throughout the logging procedure. This amplified signal is converted RMS to DC level signal and stored in sample and hold means for a period shortly before first arrival of the acoustic wave. The continuing DC level signal and the stored DC level signal are compared to produce a comparator output DC signal when the continuing DC signal has a certain increased magnitude. This certain increased magnitude is used to generate a pulse of given magnitude and duration that is especially suitable in digital data systems.