SU949587A2 - Multi-channel system for marine seismic investigations - Google Patents

Description

The invention relates to seismic survey equipment intended for the study of subterranean formations, in particular, to multichannel. Digital telemetry systems for marine seismic surveys, and is used primarily in marine geophysical work on the shelf and in the waters.

According to the main auth. 558236 a well-known multichannel system for marine seismic surveys, containing in the towed part an acoustic source, a code transmission line, a synchronization line, and fe each channel a seismic coding device, consisting of a seismic receiver in series and an analog-digital converter, and a sync generator in the side section , the receiving shift register and the recording device, between which the code correction device is switched on, as well as a temporary program device connected via a form a pulse with an acoustic source, an autosynchronization follower, a torus connected between the signal and control inputs of the receiving shift register, a. in towed

parts of the system, each device for encoding seismic signals is supplemented with a cyclic code converter, both lines are divided by the number of channels into segments, between which collecting circuits are included in the data lines, and the synchronization lines are chains from a delay device and a pulse former,

10 wherein the output of each chain is connected to the clock input of the analog-digital converter, the input is -. kidneys - to the triggering input cycli-. A transducer of codes whose output is connected to the input of the collecting circuit.

At the same time, the correction device is made in the form of an amendment adder with an amendment block connected to its second input in the form of a shift register closed in a ring. Reverse communication through the first pulse input of a two-stroke valve, the second pulse input of which is connected to the output of the transmission line. codes, and gate gates to the outputs of the temporary program device. The following autosynchronizer is made in the form of a serial connection of the selection of the marker pulse of the channel and the pulse generator of shock excitation with the control inputs of the shift registers tl. A disadvantage of the known system is the restriction of its throughput. It arises, if necessary, either to increase the number of channels by several times with detailed seismic exploration for oil and gas, or. without changing the number of channels, it will several times expand the frequency band of the excited and received seismic signals for carrying out seismo-acoustic studies for engineering geological surveys or the search for minerals. This limitation is associated with a corresponding increase in the information flow, which the recording device cannot cope with, usually performed on the basis of a digital tape recorder with fixed recording heads. The capacity of a well-known system for implementing multi-channel seismic surveys or high-frequency seismic imaging can be achieved several times at once by inserting rotating recording heads into a digital recording device, and the relative speed of the magnetic tape increases significantly due to the vector of rotational speeds of the head and the movement of the magnetic tape. . Such a recorder can be a video recorder, a typical application of which is with the registration of television video signals. For the purpose of digital recording of seismic data received by a well-known system, inserting a VCR into a recorder requires complete transformation of the multiplexed data stream coming from the code transmission line, in combination with tight synchronization of the sweep of the VCR from the system clock generator. The purpose of the invention is to increase its throughput. The goal is achieved by the fact that in a well-known multichannel system for marine seismic research, the recording device contains a video recorder having sync and video signal inputs, a dispenser, a recording sweep pulse generator, a shift register, a forward shift pulse generator, a buffer memory divided into parts by number VCR recording heads, address counters, delay elements, switch, recording head number counter, with a sync pulse input and connected via a disjunctor to the personnel and waste outputs of the write sweep pulse generator, the input of which is connected to the output of the system clock generator, the video signal input of the video recorder is connected to the output of the shift register, the first input of which is connected to the output of the waiting generator of shift pulses, the triggering input of the latter is connected to the line output of the formatter sweep pulses, and the second, the installation input of the shift register is connected to the output of the system correction device via a buffer memory its device, each part of the buffer memory device is connected to the output of the address counter, whose input is connected to the output of the delay element on each channel, and to the control inputs for writing and reading each part of the buffer memory and the input of the delay element corresponding switches connected, the signal inputs connected to the output of the allocation circuit of the marker pulse of the system channel and with the horizontal output of the pulse generator of the write sweep, whose frame output is connected to cutting the number of the recording head to the control input of the switch; the shaper of the write sweep pulses is made of serially connected frequency multipliers of the system clock, first and second frequency dividers, the outputs of which are connected to the inputs of the first and second single vibrators, respectively, the outputs of the first and second single vibrators serve as line and personnel exits of the maker; the input of the frequency multiplier of the system clock generator is the input of the write sweep pulse generator, and the standby shift pulse generator is designed as a pulse generator whose output is connected to the first input of the valve, the second input of which is connected to the output of the pulse counter via the decoder - J til, which serves as the output of the waiting generator of shift pulses, the triggering input of which is the input of setting the zero pulse counter. Figure 1 shows a block diagram of a system for marine seismic research; FIG. 2 is a block diagram of a pulse sweep pulse former; FIG. 3 is a block diagram of a waiting pulse shift generator g. In the towed part, the known system comprises an acoustic source 1, a code transmission line 2 and a synchronization line 3, and in each channel there is a device 4 for encoding seismic signals consisting of a series connection of a seismic receiver 5 s.

analog-digital converter b Each seismic receiver 5 has a piezoelectric or electret hydrophone, a preamplifier and a band-pass seismic filter, and each analog-digital converter b is equipped with a device for generating and storing a seismic signal sample. Each coding device 4 is connected with its output to code transmission line 2 via cyclical code converter 7 and collecting circuit 8 In synchronization line 3, its adjacent segments are interconnected via chains from delay device 9 and driver 10, and the output of each chain is connected to a clock input 11 analog-to-digital converter -6, and the input of the chain to the triggering input of 12 c -clic converter 7,

In the on-board part 13, the system contains a synchronous generator 14, a receiving shift register 15 and a recording device 16, between which the correction device 17 is turned on. It is made in the form of an amendment adder with the correction memory unit 19 connected to its second input 18, made in the form of a shift register, closed to the feedback ring via the first pulse input .20 of the push-pull valve 21-22, the second pulse input 23 of which is connected to the output of the code transmission line 2, and the gate inputs 24-25 to the temporary program device 26, to its outputs are 27 and 28. Its third output 29 through the pulse shaper 30 is connected to an acoustic source 1. The system has a tracking autosynchronizer containing a circuit 31 for allocating a marker pulse of a channel and a pulse generator 32 of shock excitation, connected in series and connected between the signal 33 and control The 34 inputs of the receive shift register 15. The distinguishing feature of the system (FIG. 1) is the execution of the recording device 16.

It contains a video recorder 35 having a sync pulse 36 and video signal 37 inputs, the first of which is connected via a disjunctor 38 to a frame 39 and a line 40 outputs of the imaging unit 41 of recording sweep pulses connected by its input 42 to the output of the system clock 14 (figure 1). The second video input 37 of the VCR 35 is connected to the output of the shift register 43, equipped with a waiting generator 44 of the shift pulses, the triggering input 45 of which is connected to the line output 40 of the imaging unit 41, and the installation code input 46 sdv register register 43 is connected to

the output of the device 17 correction, sistegll through the buffer storage device, divided into parts

47.1 and 47.2 according to the number of recording heads of the video recorder 35 (in the described embodiment it has 2 rotating recording heads. Each memory portion 47.1 and 47.2 is equipped with a counter 48.1 and

48.2 addresses with elements 49.1 and

49.2 delays at its entrance and has

0 control inputs 50.1. and 50.2 records and 51.1 and 51.2 readings, respectively.

All of the above inputs 50.1 and 51.2 of the storage device and the inputs of the delay elements 49.1 and 49.2 are connected to the respective outputs by a switch 52, signal inputs 53 and 54 of which are connected to the output of the channel marker pulse extraction circuit 31 and with the horizontal output 40 of the write sweep pulse generator 41 , frame output 39 of which is connected via the counter 55 of the number of the recording head to the control input 56 of the switch 52.

Shaper 41 pulses of the write sweep (Fig. 2) are made in the form of serially connected multipliers 57 of the frequency of the synchronous generator 14 of the system of the first 58 and second 59 frequency dividers, the outputs of which are connected to the first 60 and second 61 one-vibrators, the inputs of the latter serve respectively 40 and frame 39 output shaper 41, Introduction to the shaper 41 multiplier 57 frequency is necessary if the frequency of horizontal pulses is higher than the frequency of the system synchronizer 14, and the required

0, matching of the mentioned frequencies is carried out when frequency dividers 58 and 59 are executed according to known pulse-feedback circuits.

Standby generator 44. Pulses

5 shift (FIG. 3) is made in the form of a pulse generator 62, the output of which is connected to the first input 63 of the valve 64, the second input 65 of which through the decoder 66 is connected to the output of the pulse counter 67, the input of which is connected to the output of the waiting 64 generator 44. The starting input 45 of the latter is the input of the installation of a 5 l liter counter of 67 pulses.

The system (fig.1) works as follows.

 The pulses of the clock generator 14, the next in line 3 synchronization

Claims (1)

1. USSR author's certificate. / №558236, cl. 3 G 01V 1 / 24,1975 (as shown) I 2 I J