SU296884A1 - DEVICE FOR ACOUSTIC WELLSING OF WELLS - Google Patents

Description

The invention relates to well logging by acoustic methods.

A device for acoustic well logging is known, which contains a downhole tool and a surface part with blocks of synchronization and forming different polarity starting pulses and blocks for recording parameters of elastic waves.

When developing equipment for acoustic logging, especially with high heat resistance, the problem arises of creating confident synchronization of the operation of the downhole tool and surface equipment. Currently, two types of hardware synchronization are most widely used: sync "bottom and sync" on top. In the first embodiment, the master oscillator, which determines the frequency of the elastic pulses, is located in the downhole tool. The pulses of this generator trigger the emitter excitation circuits — when using the I1I2P probe or the switching circuit of the receivers and exciting the emitters when using the probe and njlg. The ground equipment is synchronized by probe pulses that are formed in the excitation circuit of the ultrasonic emitters. These pulses correspond in time to the moments of sending elastic waves to the rock surrounding the well.

The pulses are transmitted from the downhole tool to the surface through a channel, as a rule, independent of the transmission channel of signals recorded by the receiver, and allocated by special circuits. With this option, in circuits operating in the temperature range O-250 ° C, it is impossible to provide the required frequency stability of the master oscillator. In the second synchronization method, the master oscillator is installed in the surface unit and is used to synchronize both the surface and well equipment. The low temperatures at which the ground blocks operate allow, if necessary, by simple means to synchronize the master oscillator with the frequency of the mains supply. In this variant, the starting point of the time intervals is the moment of sending sync pulses to the downhole tool, and

not the moment of excitation of elastic pulses. This leads to the appearance of various unrecognizable delays in the measurement channels ti and / 2 due to the flooding of the threshold response of the triggers of both channels

and to the measurement error of the time interval D / (the running time on the base between the elements of the acoustic probe of the same name).

ambient temperature over a wide range. It is achieved by the fact that the downhole tool is equipped with a switching unit control unit, providing per-channel separation of starting pulses and a delay in the moment of excitation of 1 emitters relative to starting pulses, and a circuit for forming and transmitting pulses to the surface part corresponding to the moments of excitation of emitters. The control unit contains a circuit for separating start-up pulses and key elements controlling the operation of the switching elements.

FIG. 1 shows a block diagram of the proposed device; in fig. 2 - signal plots at the output of individual circuit blocks.

The device consists of a downhole tool / and surface equipment //, connected by a logging cable ///.

The downhole device contains emitters / and 2, receiver 3 acoustic pulses, amplifier 4 of these pulses, output transformer 5, separation circuit 6 of starting pulses transmitted to the downhole tool, key elements 7 and 8, controlling the operation of switching devices 9 and 10, a cumulative element eleven.

The ground-based recording equipment contains an input filter 12, a clock and clock generator 13, a trigger pulse generator M, a probe pulse extraction circuit 15, recording blocks 16-18, respectively, of time, amplitude and other parameters, the recorder 19, which is a part of the logging station, and power supply unit 20. The generator 13 generates two series of pulses (Fig. 2, a and b) used to synchronize the auxiliary units of ground equipment and the generator 14 of starting pulses, which generates Independent user Hetero-polar pulses of sufficient power for transmission over the logging cable to the downhole tool. In the downhole tool, these pulses are filtered from the mains voltage by an LC filter consisting of a capacitor Ci and a primary winding (winding A) of a transformer Tr. The pulse shape on the primary winding is similar to that shown in FIG. 2, d. Emissions of the opposite polarity reach 50-80% of the amplitude of the main pulses (shaded in Fig. 2, d). Two independent secondary windings of the transformer (windings B and C} start-up pulses in antiphase (Fig. 2, e and e) are fed to detector passing lamps L1 and L2. The starting impulse of the first channel (detected in Fig. 2, b) opens the lamp. / Zi and charges the Ca capacitance in such a way that the capacitor plate, connected to the control grids of the JIz and Lz lamps, is charged with a negative potential (Fig. 2, das), the value of which must be sufficient for locking both lamps. Starting impulse of the first channel not pass

may, since it is applied to lamp A2 from the opposite polarity (Fig. 2, e). At the time of the appearance of a parasitic emission of positive polarity, the lamp Lg is closed by the negative potential of the capacitor Cz. After some time, determined by the constant discharge of Rt and Cz, which is shorter than the period of the starting pulses, the capacitor Cz is discharged to zero potential (Fig. 2, g), returning the pulse selection circuit to its original state. The starting impulse of the second channel (shaded in Fig. 2, e) passes through the detector lamp L and charges the capacitance Cz (Fig. 3, i) connected to the lamps. //I and L /. This impulse cannot pass through lamp L for reasons similar to those described above. Consequently, upon receipt of opposite-pole starting pulses, it is provided through channel separation: the positive starting pulse charges the capacitance Cz, and the negative capacitance Cz.

The control electrodes of the switching devices are connected via resistors R, Re and H, 4 to the sources of positive + g and negative - EI voltages. In the initial state (in the absence of starting pulses), the Lz and L key lamps are open, and the switching devices 9 and 10 are locked by

control electrodes, as well as R6 Ri + Rijj, where Rijj and internal resistances of the key lamps with respect to direct current. Starting impulse first

as described above, the capacitance Cz is charged and the key lamp Lz is closed. This leads to an increase in the potential at its anode and the control electrode of the switching device Lb (arkatron).

After some time, which is necessary for transferring the arc from the auxiliary anode to the main one, the arkatron is ignited and discharges the storage capacitance Cv to the winding of the first radiator /. Starting impulse second

the channel charges the capacitance C3 and closes the key lamp L / ,,, which triggers the second switching element L. At the same time, the storage capacitor St discharges to the winding of the second radiator 2.

At the moment of passage of the discharge current of the accumulative capacitance S to the resistor Rj, connected in series with it, a probe pulse is generated, which is transmitted through the amplifier 4 and the cable to the surface and after

additional gain is used to start the measuring multivibrator (Fig. 2, m) of the block 16 for recording time intervals. The multivibrator returns to the initial state with the first inputs of the signals recorded by the receiver 3 (Fig. 2, L) from the near / far 2 emitters. For this, the signals are amplified in the downhole tool to amplitudes of 30-50 volts. As a result, the measurement multivibrator is then outputted to the conversion circuits to obtain a voltage proportional to the difference of these times. Voltages proportional to the amplitude or other parameters of elastic waves recorded during acoustic logging are generated in blocks 17 and 18, which can be constructed on the principle of SPAK-2 or any other equipment. In order for transmitting pulses to the surface (Fig. 2, / s) to interfere with starting pulses of much greater amplitude (Fig. 2, d), it is necessary to delay them with respect to the moment of starting impulses. For delay 15, you can use special delay generators made on the basis of widely known schemes. However, this complicates the design of the instrument. Therefore, the following 20 phenomena are used in this device to obtain a delay. If the arkatron control electrode pa gives a positive pulse of such an amplitude that the total voltage on it becomes 10-50 V, then the arkatron will not be set on fire immediately. The magnitude of the delay 25 is determined by the time required to transfer the arc between the auxiliary anode VA and the cathode K. arkatron to the main anode OA. To increase this time and select equal delays on both channels 30, the integrating capacitances Ci and Sat are included in the anodes of the key lamps. The subject matter of the invention is an acoustic well logging device comprising a downhole tool with a three- or four-element acoustic probe, a ground part comprising a block for synchronizing and forming different polarity starting pulses, blocks for recording elastic will parameters, characterized in that, in order to improve accuracy measurement of parameters, reliability and stability of the downhole tool when the ambient temperature1: the environment changes; the downhole tool is equipped with a switching element control unit, ensuring ivayuschim channelized triggering pulses and the time delay of the excitation emitters otpositelpo triggering pulses, and circuitry generating and transmitting pulses to surface blocks corresponding to the time of excitation emitters. 2. A device according to claim 1, characterized in that, in order to ensure reliable channel separation, the control unit contains a circuit for separating the starting pulses and key elements controlling the operation of the switching elements.

Ijh

.jY

-4 / - L / - / w4- / -4-lA- -V

tft, tc t.t, t, ti,

-L / V -A / W

rL P

Fig