Western Geophysical Company of America

Paul M Morgan

Lee E Siems

Carl H Savit

The seismic system includes a seismic sensor cable assembly having 50 cable sections and much of the seismic data processing electronics decentralized into the cable structure itself. The cable assembly is coupled to a central station mounted in a recording vehicle. The central station includes recording circuitry and apparatus to receive, process and record digital data words from a data link in the cable assembly and circuitry for transmitting control signals into an interrogation link in the cable assembly. The electrical output of each sensor unit constitutes a separate input channel. The cable sections are spaced apart and interconnected by small-diameter, cylindrical connector modules which contain a transceiver unit for processing the signals from ten sensor units in an associated cable section. Contained within each transceiver unit is a multiplexer having a plurality of filtered input channels coupled respectively to the elemental sensor units, and an output. In response to a first interrogation pulse transmitted through the interrogation link from the central station unit, the multiplexer advances to a selected input channel to acquire a first analog data sample. A second interrogation pulse sequences the respective multiplexers in all 50 modules to select a second channel for sampling and digitizing to provide digital data-words for the respective second channels. The self clocking phase-encoded data words transmitted from the respective transceiver associated with each cable section are ordered in accordance with the propagation delay time of the interrogation link between the central station and the respective transceiver units. Self clocking data words from corresponding channels within the respective transceiver units are ordered in accordance with the channel-select sequence during a scan cycle.

Decentralized seismic data processing system

It is a purpose of this invention to dispose a large number, such as 500, of elemental seismic sensor units over the earth's surface in a desired pattern. The sensors are arranged preferably in a linear pattern, at increasing distances, remotely with respect to a central station. Each elemental seismic sensor unit comprises a short subarray consisting of three seismic detectors, electrically interconnected. Each elemental sensor unit is a separate source of seismic signals. At regular intervals the analog seismic signals from the elemental sensor units are sampled in sequence and are digitized as a 20-bit binary number. The binary numbers are representative of the analog signal levels. The binary numbers are encoded in a self-clocking, return-to-zero pulse code as digital data words. The data words from the respective elemental sensor units are time-delay multiplexed into a wide band transmission channel for transmission to the central station in a constant current mode. Spaced along the transmission link are a series of transceiver units to each of which several separate sensor units are connected. The transceiver units are connected in series and include a repeater network which receives and retransmits data words from down-link transceivers, as well as data words derived from each of the locally-connected sensor units. Each repeater network also includes a word detection circuit, a local clock, and synchronizing circuitry. In the central station, the respective data words are stored as a matrix, in a core memory in sequential order. A formatter extracts from the core memory, data words that originated from selected groups of the elemental subarrays. The data words are combined to form new composite data words representative of seismic signals originating from desired longer arrays. The composite data words are transferred to a recording medium, such as a magnetic tape, for storage or future use.

Multichannel seismic telemeter system and array former

A plurality of data acquisition and transceiver units are connected in series to a central signal processor through a common telemeter link. The telemeter link includes a data channel, an interrogation channel and a control channel. The signal propagation velocity through the control channel may, for example, be greater than the signal propagation velocity through the interrogation channel. The central signal processor sends an interrogation signal through the interrogation channel to the data acquisition units. After a selected delay, a control pulse is transmitted. The delay between transmissions of the two signals is proportional to the differential travel time of the signals in the two channels. Accordingly the signal through the control channel will overtake and intercept the signal propagating through the interrogation channel, at a selected data acquisition unit. When any selected data acquisition unit receives a control signal through the control channel at the same time that it receives an interrogation signal through the interrogation channel, that unit is activated and a desired function is performed. The control signal is a square wave pulse having a width which is adjustable by integral multiples of the differential travel time. By adjusting the width and transmission-time delay of the control pulse, any selected subset of one or more consecutive units may be activated. Each data acquisition unit may have two or more input channels, which are connected in turn through common electronics to the data transmission channel by means of a channel selector or multiplexer. The interrogation signal may exist in one of two or more states. In the first state, in combination with a control pulse, the interrogation signal resets the multiplexer. In the second state, the interrogation signal advances the multiplexer to the next input channel in sequence.

Seismic data telemetering system

A plurality of data acquisition units are connected to a central signal processor through a common telemeter link. The telemeter link includes a data channel, an interrogation channel and a control channel. The central signal processor sends an interrogation signal through the interrogation channel to the data acquisition units. As each data acquisition unit recognizes the interrogation signal, it transmits its acquired data back to the central signal processor through the data channel. Any selected data acquisition unit, when it receives a control signal through the control channel at the same time that it receives an interrogation signal through the interrogation channel, can be caused to perform a function different from all other units. The signal propagation velocity through the control channel is different from the signal propagation velocity through the interrogation channel. One of the two signals may be transmitted through the faster channel at a selected time later than the other of the two signals is transmitted through the slower channel. The selected time difference between the transmission of the two signals is proportional to the ratio of signal propagation delay difference between channels. Accordingly the signal through the faster channel will overtake and intercept the signal propagating through the slower channel, at the selected data acquisition unit. Each data acquisition unit may have two or more input channels. Each input channel is connected in turn to the data channel through a stepping switch or multiplexer. The interrogation signal may exist in one of two or more states. In the first state, the interrogation signal resets the multiplexer. In the second state, the interrogation signal advances the multiplexer to the next input channel in sequence.

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Houston, TX, United States of America

Paul M Morgan