SU1277036A1 - Seismic vibrator - Google Patents

Abstract

The invention relates to seismic techniques, namely to sources of seismic signals of vibratory electro-hydraulic action. The purpose of the invention is to increase the efficiency of the vibrator by controlling the spectrum of the output signal. Two memory blocks, two code-analog converters, a reversible counter, controlled, attenuators, a frequency divider, a timer, a register, a trigger and three circuits are entered into the device. A uniform signal can be generated by adjusting the rise and fall times. amplitudes of the signal at the beginning and end of the sweep, as well as control of the amplitude of the control CMIJ depending on the frequency. 8 il.

Description

The invention relates to a seismic survey technique, namely, to a vibration technique, namely to a vibration seismic survey, and can be used in sources of seismic signals of vibrational, mainly electro-hydraulic, action during seismic surveys on oil and gas.

The purpose of the invention is to increase the efficiency of the vibrator by controlling the spectrum of the output signal.

Figure 1 shows the structural diagram of a seismic vibrator; Fig. 2 shows a variant of the software control device; FIG. 3 shows a variant of the control device; Fig. 4 is a variant of the controlled frequency dividers circuit; Fig. 5 diagrams of strain G1. clarifying the principle of operation of a seismic vibrator; figure 6 is a variant of the timer circuit; Fig. 7 shows possible options for switching on switches, a reversible counter, a block of an XI mt unit and a code converter, an analogue; Fig. 8 is a variant of a controlled attenuator circuit, a memory unit and an XJ code-to-analog converter.

The seismic vibrator (figl) contains a vibration exciter 1, consisting of a base plate 2, rigidly connected with a rod 3. hydraulically connected to a reactive mass 4, equipped with an electro-hydraulic transducer 6 position sensor 5 with a spool sensor 7. On the base plate 2 is fixed sensor 8 acceleration.

The seismic vibrator also contains a serially connected start device 9, a software control device 10, a phase synchronization unit 11, a counter 12, first and second converters 13 and 14, an analog, a controlled attenuator 15, an analog converter 16, a follower system block 17, power amplifier 13. The outputs of the sensors 5 and 7 are connected to the respective passes of the block 17 of the following system. The output of the sensor 8 is accelerated through the filtering unit 19 connected to the second input of the phase synchronization unit 11. The last detector detects the phase detector 20 and the phase equalizer 21.:. Kg sequentially, and the control unit 22.

In addition, the seismic vibrator contains a timer 22 and a controlled frequency divider 24, register 25. Schemes 1 / 126-28 trigger 29. The outputs of circuits 27 and 28 are connected to the inputs of the Addition and Subtraction of the reversible counter 30, the outputs of the Ci-BHoro counter 30, as well as its pyho, tpOpolpeni at. The summations are connected respectively with the address bypasses and the control input of the first memory block 31. The outputs of the trigger 29 connect - {s with the first inputs of the circuits And 27 and 28, the second inputs of which are connected to the output of the controlled frequency divider 24. The first input of the trigger 29 is connected to the output of the AND 26 circuit, and the overflow output when summing the reversible counter 30 is connected to the third input of the AND 28 circuit. 10 controls

 The code-to-analog converter 13 includes a memory block 33 and a voltage divider 34 to be controlled.

The control device 10 is provided with an output 35, which is connected to the counting inputs of the timer 23 and a controlled frequency divider 24, an output 36 connected to the second input of the trigger 29, an output 37. connected to the second input of the circuit 14 26. The control software 10 has an input 38 for connecting the start device 9 and the outputs 39 and 40 for connecting the phase synchronization unit 1.1. At the input 41 of the software control device, the sweep parameters codes are received from the control device 22. The output 42 is the output of the current frequency code and is connected to the memory block 32, the control input of which is connected to the control by-pass of the controlled attenuator 15 and to the second output of the control device 22.

The software control device 10 depicted in FIG. 2 comprises AND 44 and 45 clock generator 43, a frequency converter 46, a pulse sequence converter 47 and a harmonic signal, a counter 48, a timer 49, a controlled frequency divider 50, a frequency divider 51, shaper 52

pulses, triggers 53 and 54, as well as frequency converter 55 and driver of 56 pulses.

The control unit 22 (FIG. 3) contains registers 57 - 60 of the initial end

0 frequency, sweep duration and the initial level of the control signal.

FIG. 4 is a controlled frequency splitter circuit 24 consisting of consecutive binary ones.

5 counters 61 - 63 and a reversible counter 64. as well as the circuit OR 64, as well as the circuit OR 64. the inverter 65 and the circuit OR 66 and the inverter 67,

Figure 5 shows the diagrams for example of the Research Institute of the device nodes at Tmn (375 ms), Tp 2s. . ,

Fig. 6 shows a timer 23, consisting of after-switched on binary counters 68-70, a reversing counter 71. inverters 72 and 73,

Fig, 7 presents a diagram of the switches 27 and 28, the reversible counter 30 performed on two binary reversing counters 74 and 75 and the inverter 76. block

0 31 memory, representing a persistent storage device 77, as well as a code-analogue converter 14, performed on a controlled divider 78 of voltage i of amplifier 79.

5 FIG. B shows a circuit for sequentially switching on a controlled attenuator 15 made on resistors 80 - 84, a block of 32pam ti, made on an inverter 85 and permanent memory devices 86 - 89, and also a code-analog converter 16, including control voltage divider 90 and amplifier 91.

Seismic vibrator works as follows.

 , Before starting the sweep, the sweep parameters Fn are entered into the initial frequency 57 registers of the frequency range 58. the sweep duration 59 and the initial level of the control signal 60 of the seismic vibrator operator control device 22. A F, Tr and A.

In addition, in the same way, a code is entered into the register 25 corresponding to the required duration of the signal amplitude increase at the beginning of the sweep and the decay — at the end of the sweep.

When the power is turned on, the trigger 53 is set to the zero state (not shown in the diagram).

The start command of the seismic vibrator can be transmitted over the air from a seismic station or other recording equipment.

The trigger signal is received by the trigger unit 9, which generates a pulse arriving at the control software device 10. The signal arriving at the input 38 of the software control device 10 is fed to one of the inputs of the trigger 53, which is set to 1.

The signal from the output of the trigger 53 is fed to the input of the driver 56 pulses, which at its output generates a signal to the installation inputs of the scaling circuits of the entire device (not shown). This signal is used to set in O the counter 51, the reversible counter 30, the trigger 26, as well as the recording of the T code in the controlled frequency dividers 49 and 50, the TPC code in the timer 23 and the controlled frequency divider 24 and the Fn code in the counter 48. Setting the initial state of scaling schemes is necessary in case of a change in parameters after a previous start.

The signals from the registers of the initial frequency 57, the frequency range 58 and the sweep duration 59 are fed to the input 41 of the software control device 10. After that, through the circuit And 44 begin to pass pulses from the generator 43 clock pulses to the input of the divider 51 frequency.

The frequency divider 51 divides the frequency from the clock pulse generator 43 to a value of 1 Hz. Pulse generator 52 pulses the first positive edge of 1 Hz frequency pulses.

This front appears 0.5 s after the arrival of the trigger pulse at the input of the trigger 53.,.

The pulse from the output 36 of the driver 52 of the pulse of the trigger 54 is set to 1, and the pulse sequence from the output of the generator 43 clock pulses through the circuit 45 is fed to the input of the frequency converters 46 and 55.

From this point on, the seismic vibrator begins.

At the output of the frequency converter 55, a frequency is generated that is proportional to a predetermined frequency range of the AF sweep.

The output signal from frequency converter 55 is divided by a controlled frequency divider 50 into a number whose value is proportional to a given sweep duration Tp. Thus, the output of the controlled frequency divider 50 produces a signal whose frequency is proportional to the sweep speed Vp;

Vp -uu (1)

In counter 48, before starting the sweep, a code is entered that corresponds to the value of the initial FM frequency. In this case, the frequency converter at its output generates a frequency that is proportional to this initial frequency Rn. Under the influence of the signal on the counting input of the counter 48, the latter changes its state, and the rate of change of this state is determined in accordance with expression (1).

Thus, the frequency of the signal at the output of frequency converter 46 will also change with this speed.

The signal from the output 39 of the frequency converter 46 is supplied to the phase synchronization unit 11, as well as to the converter 47,

The signal at output 40 of converter 47 is typically a periodic, sinusoidal voltage.

This sinusoidal signal is a reference signal for the operation of the phase synchronization unit 11 in a seismic vibrator.

At the input of the timer 49 which is a time counter in the seismic vibrator, pulses with a frequency of 1 Hz are received.

The pulse from the output 36 of the driver 52 pulses also sets D 1 trigger 29,

At the same time, from the output 35 of the software control device 10 to the counting inputs of the timer 23 and the controlled divider 24. the frequencies begin to receive pulses of the clock frequency fe. The pulse sequence from the output 39 of the frequency converter 46 of the software control device 10 is fed to the input of the phase corrector 21 of the phase synchronization unit 11. Further, these pulses arrive at the input of the counter 12. The code generates a code at its outputs, which is the address code for the memory block 33 of the converter 13, the code is analog. The memory cells of the block 33 store binary codes corresponding to the values of the sinusoidal function.

The binary code of the output of the memory block 33 is fed to the input of the controlled divider 34 of the voltage converter 13 code analog, the reference voltage of which is a constant voltage. Thus, at the output of the converter 13, the analog code forms an analog sinusoidal signal with a constant amplitude.

This signal enters the reference circuit at the input of the converter 14 of the code analog, which controls the amplitude of the sinusoidal 1st signal at the beginning and end of the sweep,

 the increase in the amplitude of the signal at the beginning of the decompression is as follows.

As mentioned, after the shaper 52 produces the pulses of the signal, the trigger 29 is set to 1, and the clock pulses start to flow to the counting inputs of the timer 23 and the controlled frequency divider 24.

The controlled frequency divider 24, ω1, permits the division of these pulses from a code that is proportional to the desired duration of the gradual rise and fall of the amplitude according to the beginning and π sweep.

The value of the frequency rnn of the signal at the output of the controlled frequency divider 24 is equal to

(2)

inn -k Tnn where k is a constant division factor.

Since the reversible counter 30 before the start of work was in a reset state, the summing overflow at its output was a logical y b b 1. Therefore, the frequency pulses fnn arrive at its summing flow, and the reversible counter 30 starts counting the pulses.

Let the number of binary bits of the reversible counter be 30 differently. Then the number of states of the reversing counter 30 before overflow during summation is 2.

Duration of a smooth rise. And amplitudes at the beginning of the sweep t.nn rapna

t o .t

tnn f- -f- Inn

ABOUT

where Tnn is the code recorded in register 25.

The value of the coefficient k is chosen so that when the value of the code C register 25, equal to 1, the value of tnn corresponds to the required minimum d gis-ing. If, for example, the minimum rise time is equal to v3iia, equal to 62.5 ms, with n 5 and fo, then the value of k should be equal to 2.

Fig. 4 shows the controllable frequency divider 24, consisting of a divider with a constant conversion factor k on the counters 61 - 63 and a divider with a variable conversion factor on the reversian counter G4. The variable conversion factor is given by a Tnn register of register 25. An overflow pulse with

summation (output of the reversible binary counter 64) records the code Tnn in the reversing counter 64.

 in a time equal to tnn and

proportional to the code TPP, reversible counter 30, operation in the summation mode, will pass all its states. The outputs of the bits of the reversible counter 30 (reversible counters 74 and 75) are connected to an appropriate input terminal

memory device 77.

In the cells of the Permanent Memory 77, binary codes are written that determine the law of the amplitude rise of the signal supplied as a reference voltage to the input of the control divider 70 of the voltage. This may be, for example, either a linear law of variation, or a cosine, etc.

0 Thus, the law of change of the signal amplitude at the output of the converter 14 code — the analog is determined by the code that is fed from the outputs of the memory block 31 to the control inputs of the converter 14

5 code analog.

After the counter 30 has passed all its states, and this will happen at the end of the time tnn, from its output overflow during summation, i.e. At output 76 of the inerter, a signal O is generated and an AND 28 circuit will prohibit the passage of a pulse to the summing input of counter 30. This signal will also be fed to the selection input of crista LL of the permanent storage device

5 77, with the result that the output impedances of the information buses of the memory unit 31 take on very large values. In this mode, the maximum code will go to the input of the controlled voltage divider 78 and

0 the amplitude of the signal at the output of the operational amplifier 79 will be maximum.

This completes the shaping of the amplitude of the signal at the beginning of the sweep.

5 The signal from the output of the converter 14 code - the tax is fed to the input of the controlled attenuator 15, where it is attenuated in accordance with the desired value. This value is set by control unit 22.

A sinusoidal signal from the output of the attenuator 15 is fed to the input of the reference signal of the converter 16 code - analog. The code-ana5 log converter 16 is controlled by a memory block 32. The input of block 17 of the tracking system receives a signal from the output of converter 16, the code being analog. In the servo system unit, this signal is amplified by voltage and is supplied to the input of amplifier 18 with a powerful gig, where the signal is amplified to the power required to control the electro-hydraulic converter 6 of the vibration exciter 1.

The electrohydraulic converter 6 converts the electrical signal into a mechanical movement of the spool, which is controlled by the flow of the working fluid. Under the action of the flow of the working fluid entering the cylinder, the inertial mass 4 oscillates.

The predetermined mode of oscillations is provided by feedback with the mass sensor 5 and 7 and the spool, respectively, in block 17 of the tracking system.

In block 17 of the servo system, the signals from the outputs of the sensors 7 and 6 of the spool and the masses are respectively algebraically summed with a signal from the output of the converter 16 and the code is analog. This summation occurs so as to ensure the operating mode of the seismic vibrator.

The oscillations of the inertial mass 4 through the rod 3 are transmitted to the base plate 2, which, acting on the ground, emits a seismic signal.

The acceleration sensor 8 detects oscillations of the base plate and generates a signal that is fed to the input of the filtering unit 19. The signal from the output of the acceleration sensor 8 has a large number of harmonic components. This is explained by the nonlinearity inherent in both the electro-hydraulic part of the vibrator and its mechanical part, for example, the support plate-soil system.

The filtering unit 19 filters and separates the first harmonic from the acceleration signal of the base plate.

The signal from the output of the filtering unit 19 is supplied to one of the inputs of the phase detector 20 of the phase locking unit 11. The second input of the phase detector 20 receives a reference signal from the software control device 10.

The phase detector 20 generates at its output a signal proportional to the phase shift between the signals from the outputs of the filtering unit 19 and the converter 47 of the software control unit 10.

Under the action of the signal from the output of the phase detector 20, the phase corrector 21 divides the pulse sequence from the output of the frequency converter 46 of the software control unit 10. Thus, the frequency of the signal at the output of the phase synchronization unit 21

changes, which ultimately leads to acceleration or deceleration (depending on the sign of the phase shift) of the motion of the reactive mass 4. As a result, the phase shift between the signals from the filtering unit 19 and the converter 47 becomes 0.

Let us consider in more detail the operation of the memory block 32 and the controlled attenuator 15. The study and analysis of the amplitude-frequency characteristics of vibrating electro-hydraulic sources shows that the mechanical characteristics of the electro-hydraulic system and the design of the vibrator have a primary effect on the amplitude of the output signal. And since these characteristics do not change during operation, the influence on the amplitude-frequency characteristic can be taken into account in advance using a memory block 32, the inputs of which are connected to the code outputs of the current frequency of the control software 10, and the outputs the inputs of the converter 16 code-analogue.

The mechanical characteristics of the electrohydraulic system and the design of the vibrator are taken into account in the proposed device by introducing changes in the amplitude into the control signal, and the magnitude of this amplitude at each frequency is such that the amplitude of the output signal of the vibrator remains constant. It is obvious that the amplitude-frequency characteristic of the vibrator is determined largely by such parameters as the magnitude of the reactive mass of the vibration exciter 1, the rigidity of the elements transmitting the oscillations from the vibrator to the ground, as well as the initial level of the control signal. For a particular type of vibrator, the values of the reactive mass and the rigidity of the elements transmitting vibrations to the ground are practically constant, therefore the amplitude-frequency characteristic, determined by these parameters, can be calculated or obtained experimentally.

The deviation of the amplitude, for example, from some average value, can be compensated by changing the amplitude of the control signal received at the output of the converter 16, the code is analogous to it.

The memory unit 32 generates a code defining the amplitude of the signal and corresponding to the code of the frequency of the program control device 10.

The operation of the memory block 32 is that for each code G (F-i, Fz .-. Fn) of the current frequency of the program device

10, the control supplied from the input of the memory block 32, is also created at the output; digital amplitude code A (Ai, A2 .., Al), incoming fia input of converter 16 code - analogue.

The dependence A p (F) is of such a form that the spectrum of the output signal of the vibrator is uniform in a given frequency band.

The controlled attenuator 15 (Fig. 8) represents resistors 30 to 84 on the Cigarette. The resistors are switched to a common point by the register 60 of the control unit 22. Register code 60 determines the initial level of the control signal.

The output of the control attenuator 15 (connection point of resistors 80- 84) is fed to the input of the controllable QO lelitella) Ap. The control code for controlling the divider 1p 1 and is formed by a group of permanent storage devices 86 - 89. In this case, the control of the controlled divider 90 gpr is performed by the permanent if the first storage devices 86 and 87 or 88 and 89. This depends on what initial control level signal is set. Since the seismic vibrator is co (5th in the general case, the system, it is natural that its output amplitude-frequency characteristic depends on the level of the control signal. For example, resonance phenomena in the mechanical elements of the vibration exciter 1 depend on the control level of its signal. Therefore One bit of register 60, in addition to switching resistor 84, also controls the connection of various permanent storage devices to the controlled voltage divider 90. This bit, indicated in the diagrams as a selection . Crystal and applied to the input of inverter 85 takes the potential permitting either permanent storage devices 86 and 87 or 88 and 89. In these permanent memories recorded with two depending A T) for the two levels uprayl w tssgo signal -.

Thus, tia output, opamp 91, the amplitude of the signal varies with frequency. This happens as follows; if the amplitude of the seismic signal from the seismic transmitter (for example, the acceleration of the base plate) decreases, the signal at the input of the power amplifier 18 increases, and vice versa. Consequently, the memory block 32, depending on the frequency of the emitted signal and the level of vibration given by the control unit 22, forms such a dependence of the code on the frequency that the seismic vibrator radiates a signal with a uniform amplitude-frequency characteristic.

The operation of the seismic vibrator before the end of the sweep

figure 5, as well as the scheme of the timer 23 in figure 6.

Timer 23 contains a frequency divider with a constant counting factor on binary counters 68 - 70, a reversible counter 21, in which the beginning of a sweep

0 was recorded code TPP.

A frequency divider with a constant counting factor divides the frequency fo to a frequency, the period of which determines the discreteness of setting the duration of the drop in the amplitude of the signal at the end of the sweep.

6, for example, the frequency at the input of the binary counter 70 is 16 Hz, i.e. the discreteness of the set duration of the decline and

0 rise 62.5 ms.

The plots in FIG. 4 are also constructed for this value of the frequency at the input of the reversible binary estimator, 71, as well as for the value of Tr — 3c, and TPP 6, i.e. 37.5 ms

5The pulses at the output of the inverter 72, regardless of the code, have the same frequency value of 1 Hz.

When the code changes, the phase changes, i.e. the position of the first pulse relative to the start of the vibrator.

Thus, pulses with a frequency of 1 Hz are input to the AND 26 circuits. Until the last second of the sweep, these pulses pass through the AND 26 circuit, since there is a forbidding potential at the second input.

When a pulse appears at the output of timer 49 (FIG. 4), one of the pulse train passes through circuit 26 and sets

0 flip-flop 29 to the zero state, while before the end of the sweep there remains a time interval corresponding to the TTC code in register 25. The inverse output of the flip-flop 29 allows the frequency fnn to pass from the exit

Claims (1)

5 of the controlled frequency divider 23, which D turn is inversely proportional to the TPP code through the AND 27 circuit, on the subtraction of the reversible counter 30. Reversible counter 30 will begin counting in the reverse sequence from the maximum value (all units) to the minimum (all zeros). When the atom, the permitting potential will arrive at the control input of the memory 31, which will lead to the connection of the outputs of the last 5 to the control inputs of the converter 14, the code is analog. Since the reversing counter 30 performs counting in the reverse order, the code to the converter 14 in the reverse sequence is supplied as a counterpart code. At the same time, the amplitude of the signal at its output decreases, which ensures a smooth decrease in the amplitude at the end of the sweep. As soon as the code in the reversible counter 30 becomes zero, timer 49 will issue a command to reset all the vibrator recalculating circuits (not shown in the diagrams). This completes the formation of a smooth decline in the amplitude of the signal at the end of the sweep and the whole sweep. The next time the seismic vibrator is started, the operation of the device is repeated. Claims of the invention A seismic vibrator comprising a vibration exciter comprising a support plate rigidly connected to the rod, with an acceleration sensor mounted on it, a reactive mass connected to the rod, a mass sensor and an electro-hydraulic converter with a sensor of the valve, a control system including in series connected start device, software control device, phase synchronization unit, counter and first code converter - analogue, as well as serially connected tracking unit A power amplifier and power amplifier, the output of which is connected to the input of the electro-hydraulic converter, the first and second inputs of the tracking system unit are connected respectively to the outputs of the mass sensors and the spool, and the acceleration sensor is connected to the second input of the phase synchronization unit through the second input which is connected to the second exit of the profile control device, the second input of which is connected to the output of the control device, of which there is one. that, in order to increase the efficiency of the vibrator by controlling the spectrum of the output signal, a series-connected reversible counter, the first memory block, the second converter code - analog, controlled attenuator and the third converter code - analog, input of the second converter code - analog An analog code is connected to the output of the first converter, and the code of the third converter, the analog, is connected to the third input of the block of the tracking system, the successively connected timer, first AND circuit, trigger and second Hema I, as well as a controlled frequency divider, a third AND circuit, a register, a second memory block whose inputs are connected to the code outputs of the current frequency of the software control device, and the output to the control input of the third code-analog converter, the third output of the software device control connected to the counting inputs of the controlled frequency divider and timer, the control inputs of which are connected to the outputs of the register, the first input of the third circuit I is connected to the second output of the trigger, the second input of which is connected to the fourth output The software control device, the output of the controlled frequency divider is connected to the second inputs of the second and third AND circuits, the outputs of which are connected respectively to the inputs of the reverse and forward counting of the recursion counter, the output of the sweep termination signal of the software control unit is connected the control input of the attenuator and the descent of the control of the second memory block are connected to the second output of the control device, the control input of the first memory block and the third input of the third I circuit with are united with the second output of the reverse counter. Fig FIG. ri eleven 61 f {J55HBS Initial 1 / С / ш / адка H1551 7 / Hl P at mL. and with 62 ;; / f / s. . / 2 f. .W . - 9J Start one of 05 U51 U52 t) U % I t I | w I  sh Bpefifli I Time t Phage..5  CSJ OM  f -CJ P ca c " rO CSI Pvl "Nj f- Co / ccj one; СЧ1 Cir с: Ь / Ь A D A tf k , -, NJ N--. NJI Cij fv l "41 A bi l Th , Cvj N- -d I c c Ci "O IfTTi-oL A Th I h i l. c. Ui c tvi ij o  sj rr S: v Vouvffbti / i} cvefffw / ( PeSepcijSffi / if d8biich / 1 / cvf / fv thirty 31 f S / A V / 77 Vb 78 eleven YU n L l-I // 4 "C Figure 1 Of} epai4uo / f6 / i / yfuj7 {// 7 eM ./