SU220904A1 - DEVICE FOR ACOUSTIC RESEARCH OF WOLVES - Google Patents

Description

The proposed device is used in field and exploration geophysics and is intended for acoustic investigation of wells filled with fluid, based on recording changes in the prevailing frequency of the acoustic pulse in the non-displaced instrument and in the well. The device consists of a downhole tool and a ground part, containing, their emitter and receiver of acoustic vibrations, an electrical pulse generator, an amplifier-limiter, a time window forming cascade, a coincidence cascade, an integrating cascade and a recorder. It is known that when sending impulses of ultrasonic vibrations with a constant spectrum that have a certain prevailing frequency to different rocks, the frequency of received vibrations varies depending on the type of rocks and their condition. At the same time, each type of rock or its state corresponds to one or another frequency of received vibrations prevailing in the spectrum, which differs from the frequency emitted into the rock, usually in a smaller direction, due to attenuation of the high-frequency components of the spectrum. Thus, if during continuous movement of the device, including an ultrasonic emitter, sending normal pulses with a constant frequency spectrum, and a receiver of these pulses, a functional change in the frequency of the received oscillations depending on the depth of the device will be recorded, then it will be possible to judge the type of rocks intersected by the well, as well as the degree and nature of fluid saturation.

The proposed device is capable of detecting a change in the frequency prevailing in the spectrum of an acoustic signal when a downhole tool is moved, i.e., to determine rocks in a well by their frequency-absorbing 1M properties. It has a higher noise immunity and sensitivity, due to the use of a frequency-to-amplitude signal frequency converter as a frequency meter, including a resonant circuit, as well as a selector and detector elements.

FIG. 1 is a block diagram of the device according to the invention; FIG.

characteristic of the resonant circuit, in FIG. 3 - stress diagrams at various points of the circuit.

The proposed device contains a downhole tool /, emitter 2 acoustic pulses, the receiver 5 acoustic pulse

5 ows, 4 electric impulses generator, cable core 5, amplifier-limiter 6, oscillating circuit 7, time window formation stage 8, coincidence stage 9, amplitude detector 10, integrating

The operation of the device is as follows. From the surface of the generator 4. through the cable 5, electrical impulses are applied, under the influence of which the emitter sends acoustic pulses through the fluid surrounding the device to the rock. Acoustic impulses, having passed through the rock, reach the receiver 3, from which acoustic oscillations, converted into electric, are transmitted to the surface and arrive at the input of the amplifier of the limiter 6, which converts it into square impulses. The signal then goes to the resonant circuit 7, where the frequency variations of the received oscillations are converted into amplitude ones. The work is one of the branches of the resonant curve of contour a, since the prevailing frequency of acoustic oscillations changes due to the attenuation of the high-frequency components of the spectrum in the genus in the smaller direction from the natural frequency of the radiator. At the same time, the working point P corresponding to the natural frequency of the emitter / i is chosen so that the changes in the prevailing frequency of the signal fit in the linear portion of the resonant curve of circuit 7. To eliminate the nonlinear distortions caused by the curvature of the resonant curve at its apex, circuit 7 must eigenfrequency of the radiator, and for an hour: tu / cut, different from it by the value of b /, due to the value of permissible distortions and usually chosen by experimental means. The output of the circuit will be a signal modulated in amplitude. The selector cascade 9 is unlocked within the limits of the temporary

The window allows you to select the desired section from the entire train of received oscillations and pass them to the amplitude detector 10. Next, the signal is averaged at the integrating stage // and is fed to the recorder 12. The sensitivity of the converter constructed

to and

on the resonant circuit, there will be l,

T

where A / is the change of the Predominant frequency on the circuit,

Af / - corresponding amplitude changes,

K. - the tangent of the angle of inclination of the contour branches.

With the appropriate configuration of the circuit can be obtained K ..

Subject invention

Acoustic Examination Device

wells, consisting of wells of the first device and the ground part, containing the emitter and receiver of acoustic oscillations, the generator of electric pulses, the amplifier-limiter, the cascade of forming a temporary

"Windows, a cascade of coincidences, an integrating cascade and a recorder, characterized in that, in order to determine the rocks in the well according to their frequency-absorbing properties, simplify the design and improve the measurement accuracy, the converter of frequency changes of the signal to the amplitude, has from the oscillatory circuit tuned to the resonance with the natural frequency of the radiator, and the amplitude detector.

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