SU1638688A1 - Downhole tool generator for acoustic well logging - Google Patents

Abstract

The invention relates to the field of well logging by acoustic methods. The aim of the invention is to increase the dynamic range of the signal transmission channel to the surface. To achieve this goal, the start-up unit, made of two coincidence circuits, an inverter, a limiting amplifier, a frequency doubler and an odd-numbered dividing circuit, ignites the first bit at the beginning of the positive voltage and the second at the beginning of the negative half-wave. 2 Il. $ (L

Description

The invention relates to well logging by acoustic methods.

The aim of the invention is to increase the dynamic range of the signal transmission channel to the surface.

Figure 1 shows the block diagram of the device; figure 2 - timing diagram

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The generator consists of block 1

connection with the cable of the start-up unit 2, arresters 3, 4, capacitors 5, 6, emitters 7, 8, diodes 9, 10, autotransformer 11, limiter 12, frequency doubler 13, dividing circuit 14 into an odd number, coincidence circuits 15, 16 and inverter 17.

The device works as follows.

The supply voltage supplied from the surface through the communication unit 1 with the cable (plot 2A) is fed to the start-up unit 2, in which pulses are generated from the control of the arresters 3, 4, connecting the storage capacitors 5, 6 to the radiators 7, 8 At the same time, the trigger pulse applied to the discharge 3 corresponds to the beginning of the negative, and to discharge 4 to the positive half-wave of the supply voltage. The sum of impulses (plot-2B) is fed through block 1 of communication with a cable to the surface for the tap-off of the measuring apparatus. With such switching and polarity turn on

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After 9, 10, the recharge of the storage capacitors 5, 6 from the boost autotransformer 11 begins after a signal is emitted due to k after half a period of network voltage. Plots 2B and 2D show voltages on storage capacitors 5 and 6, respectively. The dotted lines in them show the corresponding half-wave voltage at the output of the autotransformer. Plots 2G and 2E show charging currents of capacitors 5 and 6, respectively. The total current flowing through the cable and collector of the logging elevator is shown on the plot 2G. By comparing it with the information signal transmitted via the communication lines (plot 23), it can be seen that at the time of their passage the current in the cable is small compared to its value at another time. This reduces the level of electrical noise and noise in the collector.

Unit 2 run works as follows.

Limiter 12 forms a square meander from the power supply network. The doubler 13 generates short pulses at the time of positive and negative fronts of the meander, the frequency of which at its output is therefore 2 times higher than in the network. These pulses are recalculated in an odd-numbered dividing circuit 14 and are then fed to the inputs of the matching circuits 15 and 16, the second inputs of which receive the square wave from the output of the limiting amplifier 12, and one directly, and the other through the inverter 17. As a result Drives 3 and 4 receive start-up pulses in a strictly defined manner. On discharger 3, the start pulse corresponds to the onset of a negative one, and on discharger 4, to the beginning of a positive half-wave of the mains voltage. The pulses from the output of the dividing circuit 14 are transmitted through the communication unit 1 with the cable to the surface, where with the help of the mains voltage they are disassembled and fed to the start of the measuring equipment.

Thus, at the moment the useful signal passes through the cable, only the current flows basically due to the charge of the storage capacitor of the second channel (the power supply

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The power supply of the remaining borehole / projectile units in this case can be neglected, since they are usually a small fraction of the total consumption).

The charge current of the storage capacitor decreases exponentially in proportion to the coefficient ± I A

e, where t is the current time,

And about

constant charge circuit time. In order for the capacitor to be fully charged during the time between two starts, in practice the condition 3i, Tjqn must be satisfied, where is the start-up period of one radiator.

From this data it can be seen that by the time the signal of the second probe is transmitted, the current of the first will have time to fall.

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fЈnr to. 5 times

about f

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the level of electrical interference and collector noise will decrease by the same amount of time and, consequently, the dynamic range of the signal transmission channel to the surface will increase.

Claims (1)

Invention Formula ds 0 five 0 50 55 An acoustic logging well generator, comprising a cable removal unit, a triggering unit, two radiators, two digits, two capacitors, two diodes and an autotransformer, with the communication unit having the first output cable connected to the generator output and the second connected to the low-voltage output of the autotransformer and the input of the start-up unit, in which the first and second outputs are connected to control electrodes of the first and second arresters, respectively, whose outputs are grounded, and the third output of the start-up unit is connected to the input the communication unit with the cable, at the autotransformer, the common output is grounded, and the high-voltage one is connected to the cathode of the first diode, the anode of which is connected to the input of the first bit and the first capacitor, the second output is connected to ground through the first radiator with a second capacitor, the second terminal of which is connected via the second radiator to the ground, characterized in that, in order to expand the dynamic on the surface of the signal transmission channel, the anode of the second diode is connected to the high-voltage output of the autotransformer, and the cathode to the input of the second discharge, and the start-up unit contains two coincidence circuits, an inverter and a series-connected limiting amplifier, frequency doubler and dividing circuit by an odd number the output of the amplifier-limiter is connected to the first input of the second circuit but 1638688 ° neither through the inverter - with the first coincidence circuit, and also through the frequency doubler, with the division circuit c into an odd number, the output of which connected to the second inputs of the matching circuit, the output of the first matching circuit is first, and the second matching circuit has the second output of the starting block, and the third output of the starting block is connected to the output of the dividing circuit and the second input of the matching circuit. ON Karotamny Kaam FIG. / BUT Www a. SI1 b fr AT g BUT L l d 17TGTP -N-u-i / ./l v / / Ug whitefish SI1 t eleven i / i /one t t V / toag