RU2054700C1 - Geophone - Google Patents

Abstract

FIELD: geophysical instrumentation engineering. SUBSTANCE: device has electrodynamic acceleration geophone, transformer in which capacitor and resistor are additionally mounted and are connected in series with geophone and primary winding of transformer. Parameters of geophone, capacitor, resistor and transformer are related at definite relationship. EFFECT: enhanced reliability. 3 dwg

Description

 The invention relates to geophysical instrumentation.

 Known electrodynamic eddy current vibration converter, which, together with the input transformer of the seismic exploration station, constitutes a seismic receiver providing a rise proportional to the square of the frequency of the high-frequency part of the spectrum of seismic signals having a bell-shaped rise at medium frequencies and a fall at low and high frequencies.

 The disadvantage of the seismic receiver is that its amplitude-frequency characteristic (AFC) to the eigenfrequency of the converter equal to 12 Hz is proportional to the fourth power of the frequency, and therefore the low-frequency components of seismic signals with a small level, falling below the level of microseisms or hardware noise, are lost to the output of the seismic receiver and cannot be restored by subsequent processing, thereby reducing the resolution of the seismic survey.

 The prototype of the seismic acquisition device is an electrodynamic transducer block of the acceleration seismic receiver, which, together with the input transformer of the seismic exploration station, constitutes a seismic reception device that ensures the raising of the high-frequency part of the spectrum of seismic signals in proportion to the square of the frequency.

 The disadvantage of the prototype seismic receiver is the same as that of the analogue, but for lower frequencies because the frequency response of the seismic receiver is linear in the entire seismic frequency range.

 The technical task of the proposed technical solution is to increase the resolution of seismic exploration by creating a seismic acquisition device that provides the rise of low-frequency components of the spectrum of seismic signals in comparison with the prototype.

L₁=

C

где R_Σ R_сп + R_тр + R_p + R_л сумма сопротивлений обмотки катушки сейсмоприемника, первичной обмотки трансформатора, резистора и линии связи;
U_ш среднеквадратичное значение шума усилителя сейсморегистрирующей системы, приведенного к выходу трансформатора сейсмоприемного устройства, подключаемого к входу усилителя;
Δf полоса частот сейсмического сигнала;
W₂/W₁ коэффициент передачи трансформатора, равный отношению числа W₂ витков вторичной обмотки к числу W₁ витков первичной обмотки;
L₁ индуктивность первичной обмотки трансформатора;
π 3,1415;
f_н нижняя частота полосы частот сейсмического сигнала;
β затухание электрического колебательного звена на частоте f_н;
С емкость конденсатора.The task is achieved by the fact that in a seismic receiver consisting of an electrodynamic acceleration seismic receiver and a transformer containing a primary and secondary windings, a capacitor and a resistor are installed, connected in series with the seismic receiver and the transformer primary winding, and the parameters of the seismic receiver, capacitor, resistor and transformer are connected by the relations
R _Σ ≅

L ₁ =

C

where R _Σ R _sp + R _Tr + R _p + R _{l the} sum of the resistances of the coil winding of the geophones, the primary winding of the transformer, resistor and communication line;
U _{W the} rms value of the noise of the amplifier of the seismic recording system, reduced to the output of the transformer of the seismic receiver connected to the input of the amplifier;
Δf seismic signal frequency band;
W ₂ / W ₁ the gear ratio of the transformer, equal to the ratio of the number W ₂ turns of the secondary winding to the number W _{1 of} turns of the primary winding;
L ₁ inductance of the primary winding of the transformer;
π 3.1415;
f _{n the} lower frequency band of the seismic signal;
β attenuation of the electrical vibrational link at a frequency f _n ;
With capacitor capacitance.

 In FIG. 1 shows an electrical diagram of a seismic receiver; in FIG. 2 shows a spectrum of seismic signals, frequency response of seismic receivers and spectra of seismic signals at the outputs of seismic receivers; in FIG. 3 shows a signal graph of a seismic receiver.

The seismic acquisition device consists of an acceleration electrodynamic seismic receiver 1 having an internal resistance (coil winding resistance) R _sp , from a communication line 2 with a resistance R _l , from a capacitor 3 with a capacitance C, from a resistor 4 with a resistance R _p and a transformer 5, the primary winding of which has an inductance L ₁ and resistance R _Tr . The output signal of the seismic receiver is removed from the secondary winding of the transformer.

The seismic receiver can be made in one housing, then the communication line 2 is absent, and the resistance R _l is zero. The inductance of the acceleration seismic receiver winding is small compared to the transformer inductance L ₁ and is not taken into account.

 In figure 2, 6 the spectrum of the seismic signal, 7 frequency response of the seismic receiver (1, 2), 8 frequency response of the seismic receiver (2, 3), 9 frequency response of the proposed device, 10, 11 and 12 resulting spectra.

 Seismic device works as follows.

The seismic signal that has passed the studied geological environment has a spectrum depicted in graph 6 in figure 2. The seismic signal causes oscillations of the earth's surface, converted by the seismic receiver 1 into electrical signals (voltages), proportional to the acceleration of movement of its body. The electrical voltage generated by the generator E _{1 of the} geophone 1 causes alternating current in the series circuit: the voltage generator E ₁ and the resistance of the coil winding R _{sp of the} geophone 1 resistance R _l / 2 of the communication line 2 capacitance C of the capacitor 3 resistance R _{p of the} resistor 4 resistance R _tr and inductance L _{1 of the} primary winding of the transformer 5 resistance R _l / 2 communication line 2. The current flowing through the primary winding of the transformer is converted by the secondary winding of the transformer into a voltage U _o , increased in proportion to the ratio of the number W ₂ turns of the secondary winding to the number W _{1 of} turns of the primary winding.

. АЧХ сейсмоприемного устройства изображена графиком 7 на фиг.2. АЧХ прототипа изображена графиком 8, а АЧХ сейсмоприемного устройства (1, 2) графиком 9. Спектр на выходе сейсмоприемного устройства (1, 2) изображен графиком 10, спектр на выходе прототипа графиком 11, а спектр на выходе предлагаемого сейсмоприемного устройства графиком 12.The use of a transformer in a seismic survey station implements its main property: signal amplification and an increase in the signal-to-noise ratio. To transmit lossless low-frequency signals (from 2.5 Hz and above) of the seismic frequency range, the inductance L _{1 of the} transformer primary winding must have a value of several hundred Henry. The seismic receiver uses this basic property of a transformer. In addition, the large value of the inductance of the primary winding allows you to create, together with the calculated value of the capacitance C of the capacitor, a voltage resonance that provides the rise of the low-frequency signal at the output of the seismic receiver at frequencies close to a frequency equal to the ratio of unity to 2π

. The frequency response of the seismic device is shown in graph 7 in figure 2. The frequency response of the prototype is shown in graph 8, and the frequency response of the seismic receiver (1, 2) is graph 9. The spectrum at the output of the seismic receiver (1, 2) is shown in graph 10, the spectrum at the output of the prototype is shown in graph 11, and the spectrum at the output of the proposed seismic receiver is shown in graph 12.

 The seismic acquisition device is an interconnected electromechanical system. Find the transfer function of the seismic receiver using the signal graph shown in Fig.3. Inductive (transformer) connection between the frame and the coil winding of the electrodynamic converter unit is not significant and it is absent in the signal graph.

передаточная функция механического колебательного звена без затухания, возбуждаемого со стороны корпуса, где Z относительное перемещение корпуса сейсмоприемника и инерционного элемента катушки;
Х перемещение корпуса сейсмоприемника;
р оператор, равный

τ_o постоянная времени колебательного механического звена, равная единице, деленной на круговую собственную частоту;
b

pK_п1 коэффициент передачи электродинамического преобразователя, где К_п1 коэффициент преобразования электродинамического преобразовательного блока,
d

передаточная функция проводимости последовательной цепи, содержащей R_сп, R_л, R_тр, С и L₁, где I₁ ток, протекающий в этой последовательной цепи;
e

pM₁₂= pL₁

коэффициент передачи взаимного индуктивного сопротивления трансформатора, где M₁₂

взаимная индуктивность обмоток трансформатора;
j

K_п1 коэффициент преобразования электродинамического преобразователя, где F сила, действующая на катушку при протекании тока через ее обмотку;
g

передаточная функция механического колебательного звена без затухания, возбуждаемого со стороны инерционного элемента катушки;
h

pK_п2 коэффициент передачи электродинамического преобразователя каркаса катушки;
m

коэффициент передачи проводимости каркаса катушки;
r

K_п2 коэффициент преобразования каркаса катушки.The branches of the signal graph are expressed by the following transfer functions:
a

the transfer function of the mechanical oscillating link without attenuation excited from the side of the body, where Z is the relative movement of the body of the geophone and the inertial element of the coil;
X movement of the receiver body;
p operator equal to

τ _{o the} time constant of the oscillatory mechanical link, equal to unity, divided by a circular natural frequency;
b

pK _{p1 is} the transfer coefficient of the electrodynamic converter, where K _{p1 is} the conversion coefficient of the electrodynamic converter unit,
d

the transfer function of the conductivity of a serial circuit containing R _sp , R _l , R _Tr , C and L ₁ , where I _{1 the} current flowing in this serial circuit;
e

pM ₁₂ = pL ₁

gain of the mutual inductive resistance of the transformer, where M ₁₂

mutual inductance of transformer windings;
j

K _{p1 is} the conversion coefficient of the electrodynamic transducer, where F is the force acting on the coil when current flows through its winding;
g

transfer function of a mechanical vibrational link without attenuation excited from the side of the inertial element of the coil;
h

pK _{p2 is} the transmission coefficient of the electrodynamic transducer of the coil frame;
m

transmission coefficient of the conductivity of the coil frame;
r

K _{p2 is} the conversion coefficient of the coil frame.

Подставив значения ветвей сигнального графа в передаточную функцию сейсмоприемного устройства и учтя то, что обратные связи hmrg и bdjg отрицательные, после преобразования получим в знаменателе передаточной функции многочлен четвертой степени. Определив собственные частоты сейсмоприемного устройства известным способом решения, приравняв нулю сумму членов с четными степенями плюс единица многочлена знаменателя и затем определив затухание найденных многочленов второй степени, получим передаточную функцию сейсмоприемного устройства

Полученная передаточная функция сейсмоприемного устройства представляет собой произведение передаточной функции электродинамического преобразовательного блока и электрического колебательного звена R_Σ L₁C, включающего коэффициент передачи трансформатора W₂/W₁.Using known methods of solution, it is easy to find the transfer function of the seismic receiver by the signal graph:
W (p)

Substituting the values of the branches of the signal graph into the transfer function of the seismic receiver and taking into account that the feedback hmrg and bdjg are negative, after the conversion, we obtain a fourth-degree polynomial in the denominator of the transfer function. Having determined the eigenfrequencies of the seismic receiver in a known solution, equating to zero the sum of members with even degrees plus the unit of the denominator polynomial and then determining the attenuation of the found polynomials of the second degree, we obtain the transfer function of the seismic receiver

The obtained transfer function of the seismic receiver is a product of the transfer function of the electrodynamic transducer block and the electric oscillating link R _Σ L ₁ C, including the transmission coefficient of the transformer W ₂ / W ₁ .

A significant increase in the conversion coefficient of the seismic receiver by a large increase in the transmission coefficient of the transformer W ₂ / W ₁ runs into a limitation due to the fact that the thermal noise of the sum of the resistances R _{Σ of the} seismic receiver should not exceed the noise of the amplifier of the seismic acquisition system.

•

Решая уравнение относительно

, получим

≅

Решив то же уравнение относительно R_Σ получим
R_Σ ≅

•

Зная сопротивление R_Σ легко найти формулу для расчета индуктивности L₁ первичной обмотки, предварительно получив из передаточной функции электрического колебательного звена формулу его АЧХ:
W(ω)

На частоте резонанса ω_н член (1 ω $\genfrac{}{}{0ex}{}{\text{2}}{\text{н}}$ L₁C)² равен нулю, а значение АЧХ равно добротности, выраженной отношением 1/2β

Решив уравнение относительно L₁, получим
L₁=

На частоте резонанса
1 ω $\genfrac{}{}{0ex}{}{\text{2}}{\text{н}}$ L₁C 0;
Из уравнения получим
C

Предлагаемое сейсмоприемное устройство позволяет поднять низкочастотную часть АЧХ (график 9) по отношению к прототипу, имеющему линейную АЧХ по ускорению перемещения во всем сейсмическом диапазоне частот (график 8), и тем самым дает возможность сохранить низкочастотные составляющие сейсмических сигналов, подняв их над уровнем аппаратурных шумов и микросейсм и сохранив их для последующей обработки, а в результате позволяет повысить разрешающую способность сейсморазведки.Having optimality criterion noise ratio of seismic noise amplifier devices and systems seysmoregistriruyuschey given to its input, the equality of Nyquist for the temperature 27 ^{° C} we obtain an equation
U _W = 1.29 • 10 ^-10 •

•

Solving the equation for

we get

≅

Solving the same equation for R _Σ we get
R _Σ ≅

•

Knowing the resistance R _Σ, it is easy to find a formula for calculating the inductance L _{1 of the} primary winding, having previously obtained from the transfer function of the electric oscillating link the formula for its frequency response:
W (ω)

At the resonance frequency ω _n term (1 ω $\genfrac{}{}{0ex}{}{\text{2}}{\text{n}}$ L ₁ C) ² is equal to zero, and the frequency response is equal to the quality factor expressed by the ratio 1 / 2β

Solving the equation for L ₁ , we obtain
L ₁ =

At resonance frequency
1 ω $\genfrac{}{}{0ex}{}{\text{2}}{\text{n}}$ L ₁ C 0;
From the equation we get
C

The proposed seismic device allows you to raise the low-frequency part of the frequency response (graph 9) with respect to the prototype, which has a linear frequency response to accelerate movement in the entire seismic frequency range (graph 8), and thereby makes it possible to maintain the low-frequency components of the seismic signals, raising them above the level of instrument noise and microseism and saving them for further processing, and as a result allows to increase the resolution of seismic exploration.

 In the case of the use of an electrodynamic seismic receiver of the speed of movement in the proposed device, it will allow you to expand the frequency response of the speed of movement towards low frequencies.

Claims (1)

A SEISMIC RECEIVER, comprising an electrodynamic seismic receiver, made in the form of a coil with a winding, a communication line and a transformer including a primary winding and a secondary winding connected to an amplifier of the seismic recording system, characterized in that it has a capacitor and a resistor connected in series with the seismic receiver and the primary winding transformer, while the parameters of the geophone, capacitor, resistor and transformer are related by

where R _Σ = R _sp + R _Tr + R _p + R _l - the sum of the resistances of the winding of the coil of the geophone, the primary winding of the transformer, resistor and communication line;
U _W - the rms value of the noise of the amplifier of the seismic recording system, reduced to the output of the transformer of the seismic receiver;
Δf is the frequency band of the seismic signal;
W ₂ / W ₁ - gear ratio of the transformer, equal to the ratio of the number w ₂ turns of the secondary winding to the number of turns W _{1 of the} primary winding;
L _i - the inductance of the primary winding of the transformer;
f _n is the lower frequency band of the seismic signal;
β is the attenuation of the electrical vibrational link R _Σ L _I C at a frequency f _n ;
C is the capacitance of the capacitor.

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