RU2266550C1 - Method of checking of digital seismic chains - Google Patents

Abstract

FIELD: geophysics.

SUBSTANCE: method can be used for seismic prospecting. Method of checking of digital seismic chains is based upon applying calibration signal to input of chain. Two measurements are performed subsequently. Levels of calibration signal at output of analog-to-digital converter are formed. Efficiency of operation of seismic chain is judged from difference in output digital signals. Variable trend of output digital signals is estimated additionally due to smoothing of trend by infinite-pulse-characteristic second order absence of offset filter.

EFFECT: improved truth of results of measurements.

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Description

The invention relates to the field of geophysics, and more particularly to measurements during seismic exploration at sea.

A known method of marine seismic exploration, in which to control the reliability of the measurement of signals by seismic acquisition channels during marine seismic exploration with registration of elastic vibrations by a multi-channel receiving device located on the vessel, the measured signals are obtained from several series of profiles at distances between profiles selected from the conditions of implementation spatial aperture [1].

This method is burdened by both objective and subjective errors due to the uneven movement of the vessel, especially during waves and wind, the need in the process of moving the vessel to continuously put additional equipment into the water at a speed equal to the speed of the vessel.

There is also known a method for monitoring digital seismic acquisition channels, including transmitting an analog calibration signal to the channel input, in which the seismic sensor channel output is used as a calibration channel, and two consecutive measurements are made with the formation of the calibration signal levels at the input of the analog-to-digital converter differing N times. In this case, the conversion signal of the calibration signal is controlled and the magnitude of the difference in the output digital signals is judged on the operation of the seismic recording channel [2].

Compared with the method [1], this method, due to two consecutive measurements of the output signals of the seismic sensor with the subsequent formation of levels at the input of the analog-to-digital converter, differing N times, with the control of the conversion time of the calibration signal, provides more reliable control of the seismic recording channel by the difference digital output signals.

However, the formation of the level of the calibration signal at the input of an analog-to-digital converter with its subsequent comparison with the value of the difference of the output signals with the conversion time control is not a way of objective monitoring of the operation of the seismic recording channel, since the seismic process is essentially irregular in nature and represents a superposition of several irregular waves in view of the fact that secondary waves with lower amplitudes and a period due to as distortions of the natural background due to heterogeneity of external geophysical phenomena, and the influence of industrial interference, which leads to the fact that the signals at the input and output of the analog-to-digital converter will be distorted by the non-stationary trend, which is variable in nature.

The objective of the proposed technical solution is to increase the reliability of measurements through seismic acquisition channels.

The problem is solved due to the fact that in the method of monitoring digital seismic recording channels, which includes supplying a calibration signal to the channel input, in which the channel output of the seismic sensor is used as a calibration signal, two consecutive measurements are made with the formation of the calibration signal levels at the analog input the digital converter and the magnitude of the difference in the output digital signals judge the operation of the seismic acquisition channel, which additionally evaluate the AC nnogo trend output digital signals by means of a smoothing filter trend astatism second order infinite impulse response.

Evaluation of the variable trend of the output digital signals by smoothing the trend using a second-order filter of astatism with an infinite impulse response allows you to select the low-frequency spectrum of digital signals with the suppression of a higher frequency, which ensures the formation of the calibration signal levels from the digital output signals, cleared of high-frequency noise. In addition, there is no need to control the conversion time of the calibration signal, since the monitoring time is determined by a constant value.

A new feature, which consists in assessing the variable trend of the output digital signals of the seismic sensor by means of a second-order filter of astatism with an infinite impulse response to form calibration signal levels for solving the problem of monitoring digital seismic acquisition channels using the output of the seismic sensor channel from the prior art, is not revealed, which allows us to conclude compliance of the claimed technical solution to the condition of patentability "inventive step".

The method is illustrated in the drawing, which shows a block diagram of a second-order filter of astatism with an infinite impulse response. The filter includes the accumulating adders 1, 2, the multipliers 3, 4, the summing unit 5. The accumulating adder 1 has an inverse input 6. The natural frequency of the filter is ω = 2π / 6. Smoothing coefficient α = 10 ³ .

The method is as follows. From the channel output of the seismic sensor, the signal is fed to the input of the filter. The signal at the input of the filter has the form

Z _bk (t) = αcos (ωt + ψ) + Nt.

At the filter output, the signal has the form Zout (t) = αcos (ωt + φ) + n (t), where n (t) = L _cf [N (t)] is the filtered input noise N (t);

. Амплитуда выходного сигнала и его фаза φ зависят от расстройки фильтра Δω=ω-ω₀ и параметра затухания α, который определяется с учетом того, что частота вынужденных колебаний фильтра в точности равна частоте ω входных колебаний.L _sf is a linear differential operator corresponding to the differential equation of a tracking filter of the second order of astatism

. The amplitude of the output signal and its phase φ depend on the filter detuning Δω = ω-ω ₀ and the damping parameter α, which is determined taking into account the fact that the frequency of the forced oscillations of the filter is exactly equal to the frequency ω of the input vibrations.

, подается на вход аналогово-цифрового преобразователя для формирования уровней калибровочного сигнала. По величине разности выходных цифровых сигналов, очищенных от высокочастотного входного шума, судят о работе сейсморегистрирующего канала.The output signal of the filter

is fed to the input of an analog-to-digital converter to form calibration signal levels. The magnitude of the difference in the output digital signals, cleared of high-frequency input noise, judges the operation of the seismic acquisition channel.

The implementation of the proposed proposal of technical complexity does not present, which allows us to conclude that it meets the condition of patentability "industrial applicability".

Information sources.

1. RF patent No. 1829665.

2. RF patent No. 2040019.

Claims (1)

A method for monitoring seismic acquisition channels, including applying a calibration signal to the input, in which the output signal of the seismic sensor is used as a calibration signal, and two consecutive measurements are made with the formation of the calibration signal levels at the input of the analog-to-digital converter, and the value of the difference between the output digital signals operation of the seismic recording channel, additionally smooth out the trend of digital output signals by means of a second-order filter of astatism f course impulse response, characterized in that the frequency of forced oscillation of the filter equals the frequency of the input vibrations at the natural frequency filter, equal to 2π / 6.