RU2533334C1 - Device for studies of dynamic state of rocks in well - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: device comprises the following elements: sensors (1-3) geoacoustic signals, first switch (4), first amplifier (5), filter unit (6), rectifier unit (7), second switch (8), analogue-digital converter (9), (10) digital signal transmission unit, (11) susceptometer, magnetometer measuring circuit (12) , analogue storage devices (13, 14), subtracting amplifier (15), rectangular voltage generator (16), ferrite antenna (17), third switch (18), three capacitors (19), second amplifier (20), mixer (21), low frequency filter (22), switchable generator (23), rectifier (24), control unit (25), power supply unit (26).

EFFECT: improvement of informativity of studies.

1 dwg

Description

The invention relates to geophysics and is used to study the dynamic state of rocks in a well.

The process of crack formation in rocks is accompanied by seismic-acoustic emission, and when electrical discharges occur at the crack rupture boundary, by electromagnetic radiation. However, the presence of seismoacoustic radiation is not always accompanied by intense electromagnetic radiation, since under different conditions the relaxation of electric charges occurs taking into account the properties that characterize the electrical conductivity of the medium. On the other hand, electromagnetic radiation is more sensitive to deformation of rocks, since before a brittle break occurs, the electric charges of the diverging walls of the cracks are separated. Dynamically active zones are, as a rule, zones of contact of rocks with various physical properties, mineralization zones. Measurement of the magnetic susceptibility and geomagnetic field strength along the borehole allows for geological separation of rocks according to magnetic properties and to identify potentially active zones for further research.

Simultaneous measurement of the three components of the vector of natural geoacoustic radiation, electromagnetic emission at different frequencies, the axial component of the vector of the geomagnetic field and the magnitude of the magnetic susceptibility of rocks in the well significantly increase the amount of information about the geodynamic state of rocks in their natural occurrence obtained during one tripping operation. This significantly reduces the cost of geophysical research and expands the scope of the proposed device.

A device [1] is known that contains three mutually orthogonal sensors for geoacoustic signals, a switch, a control unit, an antenna for receiving electromagnetic signals, and a high-frequency tunable amplifier.

The disadvantages of this device include the fact that it has a low sensitivity of the electromagnetic channel, does not contain a channel for measuring magnetic susceptibility and geomagnetic field. It requires a three-wire cable and does not convert the measured signals to digital form.

A device [2] is known containing three mutually orthogonal sensors for geoacoustic signals.

However, the use of a pulse-frequency modulator operating at frequencies very close to the frequency of the recorded electromagnetic signals leads to a large error in their measurement.

The closest technical solution to the proposed invention is a device [3], which contains three mutually orthogonal sensors for geoacoustic signals, switches, a signal amplifier, a filter unit, an analog-to-digital converter, a control unit, and a transmission unit in a downhole tool.

The disadvantage of this device is the lack of channels for measuring electromagnetic signals, magnetic susceptibility and geomagnetic field, which significantly reduces the ability to determine the dynamics of the environment.

The proposed device for conducting studies of the dynamic state of rocks in a well, containing three mutually orthogonal sensors for geoacoustic signals, a first switch, an amplifier, a filter unit, a rectifier unit, a second switch, an analog-to-digital converter, a transmission unit, and a ferrite antenna, characterized in that additionally introduced a third switch, capacitors, a second amplifier, a mixer, a switchable generator, a low-pass filter, a rectifier, a magnetic susceptibility sensor, a meter a magnetometer circuit, a low-frequency square-wave generator, two analog storage devices, a subtracting amplifier, and the ferrite antenna through the third switch is connected alternately to the capacitors and then, through the second amplifier and mixer, to the low-pass filter and then to the rectifier, which, in turn, is connected to the input of the second switch, and the low-frequency square-wave generator is connected to the magnetizing coil of the magnetic susceptibility sensor, and the sensor’s flux gate is measured The circuit of the magnetometer is connected to the inputs of analog storage devices, which, in turn, are connected to the input of the second switch via a subtracting amplifier.

The drawing shows a functional diagram of the device.

1, 2, 3 - sensors of geoacoustic signals

4 - first sensor switch

5 - amplifier

6 - filter block

7 - rectifier unit

8 - second switch

9 - analog-to-digital Converter

10 - transmission unit

11 - magnetic susceptibility sensor

12 - measuring circuit of the magnetometer

13, 14 - analog storage devices

15 - subtractive amplifier

16 - square voltage generator

17 - ferrite antenna

18 - third switch

19 - three capacitors

20 - amplifier

21 - mixer

22 - low pass filter

23 - switchable generator

24 - rectifier

25 - control unit

26 - power supply.

The device operates as follows. The cycle of the device consists of 15 cycles. The control unit 25 controls the operation of the device. In the first cycle, the transmission unit 10 is turned off, which allows you to synchronize the sequence of cycles following a pause in the transmission of information. In the second, third and fourth clock, the switch 4 connects the sensor of geoacoustic signals 1 to the amplifier 5. The output signal of block 5 is fed to the filter block 6, which divides the signal into three bands and feeds these frequencies to the inputs of the rectifier block 7 and, then, through the switch 8 to the input of the analog-to-digital converter 9. The output of the ADC 9 is connected to the transmission unit 10 connected to the logging cable 27. On the same cable, in addition to the digital signal, the supply voltage of the downhole tool is supplied to the power supply 26.

In the fifth, sixth, seventh cycles, the switch 4 connects the sensor of geoacoustic signals 2 to the amplifier 5. The device works similarly to 2-4 cycles.

In the eighth, ninth, and tenth cycles, a geoacoustic signal sensor 3 is connected. The process of work is repeated, as in 2-4 cycles.

In the eleventh, twelfth, thirteenth cycles, the third switch 18, controlled by the control unit 25, connects three different capacitors 19 in turn to the ferrite antenna 17, changing the resonant frequency of the input circuit formed from the ferrite antenna 17 and the capacitors 19. At the same time, the frequency of the generator 23 which in each cycle corresponds to the frequency of the input circuit. Amplified by the unit 20, the input signal and the signal from the switched generator 23 are fed to the inputs of the mixer 21. At the output of the mixer 21, a signal is generated in the frequency band:

(f _in ± f _low ) -f _g ,

where f _I - the frequency of the received signal;

f _low - _high pass filter low-pass filter 22;

f _g - the frequency of the generator 23 and the input circuit 17, 19.

In this case, the signal at a frequency f _g will be zero.

The output signal of the mixer 21 through the low-pass filter 22 and the rectifier 24 is fed to the input of the switch 8, the ADC 9 and the received digital signal through the transmission unit 10 to the wireline cable 27.

In the fourteenth and fifteenth clocks, the inputs of the switch 8 and, further, to the ADC 9 receive magnetic susceptibility signals from block 15 and the axial component of the geomagnetic field from block 12.

The magnetic susceptibility sensor 11 consists of a magnetizing coil NK, compensating coil KK and a flux probe. The flux gate is connected to the input of the measuring circuit of the magnetometer 12. At the twelfth and thirteenth clocks, the generator 16 delivers two rectangular current pulses of different polarity to the serially connected NK and KK coils. The compensating coil compensates for the direct field of the magnetizing coil NK. After converting the fluxgate signal by block 12 into pulsed DC signals characterizing the magnetic susceptibility χ and the axial component of the geomagnetic field Z _oc , they are fed to the inputs of the analog storage devices 13, 14, which are turned on one in the positive cycle of the generator 16, and the other in the negative cycle of the generator 16.

The voltage at the outputs of blocks 13, 14 will be equal to:

U ₊ = Z _OS + K · H · χ

U _- = Z _OS -K · H · χ

The voltage at the output of the subtracting amplifier 15 will be equal to:

U = U ₊ + U _- = 2KH _χ ,

where Z _OS - axial component of the geomagnetic field;

K is the coefficient of conversion of the magnetic field recorded by the flux gate into a direct current signal;

H is the field strength created by the magnetizing coil HK;

χ is the magnitude of the magnetic susceptibility.

Thus, for 15 cycles of operation of the device, data are recorded and transmitted from three sensors of geoacoustic signals in three frequency ranges, electromagnetic signals at three frequencies, magnetic susceptibility of rocks and the axial component of the geomagnetic field. Simultaneous measurement of the complex of signals of three geophysical fields in the well allows you to obtain new information about the geodynamic state of rock masses in their natural occurrence.

Information sources

1. Fadeev V.A. Equipment for recording natural seismic-acoustic and electromagnetic radiation of rocks in wells. Sat scientific tr Geological and geophysical methods for the study of mineral deposits. - Karaganda, 1991, p. 45-48.

2. Astrakhantsev Yu.G., Troyanov A.K. A device for conducting geoacoustic logging. RF patent No. 2445653, G01V 1/40.

3. Astrakhantsev Yu.G., Troyanov A.K. Device for measuring geoacoustic noise in a well. RF patent №2123711, G01V 1/40.

Claims (1)

    A device for conducting studies of the dynamic state of rocks in a well, containing three mutually orthogonal sensors for geoacoustic signals, a first switch, an amplifier, a filter unit, a rectifier unit, a second switch, an analog-to-digital converter, a transmission unit, a ferrite antenna, characterized in that it additionally introduced a third switch, capacitors, a second amplifier, a mixer, a switched generator, a low-pass filter, a rectifier, a magnetic susceptibility sensor, a measuring circuit m a gnitometer, a low-frequency generator of rectangular pulses, two analog storage devices, a subtracting amplifier, while the ferrite antenna through the third switch is connected alternately to the capacitors and then through the second amplifier and mixer to the low-pass filter and then to the rectifier, which in turn is connected to the input of the second switch, and the low-frequency square-wave generator is connected to the magnetizing coil of the magnetic susceptibility sensor, and the sensor’s flux gate through the measuring circuit Magnetometer - to the inputs of the analog memory devices which, in turn, through the subtracting amplifier is connected to the input of the second switch.