SU881304A1 - Self-sustained down-hole device for logging while drilling - Google Patents

Description

one

The image relates to field geophysics and can be used in logging equipment during drilling.

A stand-alone downhole tool is known, consisting of a probe unit, a probe current generator, a sinusoidal, xypensation recorder measurement unit, and a power source.

Single output stage transistors in the amplification mode of sinusoidal current and in the presence of high ambient temperature are out of order.

Also known is an autonomous downhole tool comprising a probe installation, a rectangular probing current generator, a forco, a compensation measuring unit, a power source, and a recorder. The use of transistors in the output stage of the generator in the Kyuch mode in this autonomous device allows measurements to be carried out at higher ambient temperatures 2.

The disadvantages of the described device is that the measurement process does not take into account the phase shift between the measuring and compensating

voltage, as well as the need to stabilize the probing current, which is difficult in the borehole conditions. All this leads to errors in measurements.

The purpose of the invention is to increase the reliability and accuracy of measurements under conditions of elevated temperature in the well.

ten

To achieve the goal, the device is equipped with a master oscillator with a pulse frequency eight or more times the frequency of the probing current, a frequency divider, a decoder and a null 15 organ, with this frequency oscillator connected with the probing current generator, which train delivered to generator output

20 probing current, with the outputs of the master oscillator and the frequency divider connected to a decoder, which is connected to a null organ associated with the compensation meter block.

FIG. 1 shows the device structure, the turn scheme; in FIG. 2 a time diagram of the operation of the blocks. -;

A stand-alone device contains a master frequency generator 1, a divider

frequencies 2-4, output stage 5, probe current generator, rectangular shape, compensation decoder 6, measuring unit 7, amplifier 8, null organ 9 and recorder 10

The numbers indicate the diagrams of the voltages at the output of the blocks corresponding to the number given in FIG. one.

Autonomous device works as follows.

The probe current generator, which includes the master oscillator 1, the frequency divider 2-4, and the output stage 5, creates an electric field in the rock, due to which a potential difference is created at the measurement electrodes. The device uses a compensation measuring method, in accordance with which the voltage on the measuring electrodes is compared with the compensating voltage (block 7), and their difference is fed through the amplifier 8 to the null organ 9.

The counting input of the frequency divider 2-4 is applied to the pulses of the master oscillator 1 with a frequency eight times the frequency of the probing current. The pulses of the last trigger 4 of the splitter frequency, are fed to the output stage 5 of the probe current generator and then, after passing through the rock, are induced on the measuring electrodes of the probe unit EMF proportional to the measured parameter. Due to the presence of nonlinear elements in the measuring path, a phase shift of the measured voltage relative to the reference voltage occurs.

The amplitude-sum signal of the measured and compensating voltages is fed to the input of the amplifier 8 of the compensation measuring unit, and this is consistently in antiphase. With the help of the decoder 6 and the frequency divider, a narrow pulse is formed, the duration of which depends on the frequency division factor. The generated narrow pulse is applied to one of the inputs of the nullorgan 9. To the other input of the nullorgan, a total signal is amplified by the amplifier 8. With U,, at the input of the zero-organ 9, the phase of the total voltage (plot 8a) does not coincide with a narrow pulse. Prii, although there are voltage spikes at the input of the null organ, associated with the presence of a phase shift UHJM and UK, however, they do not coincide in phase with a narrow pulse. And only at Uv (3N4, does the phase coincide the total voltage with a narrow pulse generated by the decoder 6, which triggers the null oragan 9. At the same time, the measured pulse is recorded on the recorder 10 with the same impulse 9 the generator of the probe current in the switching mode allows to reduce the power dissipated by the transistors of the electronic circuit of the device,

Q, which makes it possible to make measurements with an autonomous device up to an ambient temperature of 200 ° C, and the use of a master oscillator and a frequency divider with the subsequent release of a narrow pulse by the decoder eliminates the influence of the phase

the shift of the measured voltage to the measurement accuracy. The utility of the proposal consists in expanding the temperature range and increasing the reliability and accuracy of the instrument, which makes it possible to increase the duration of the instrument.

Claims (2)

1. USSR Author's Certificate No. 215158, cl. E 21 B 44/00, 1969. 2. Molchanov A.A., Siraev A.Kh. Stand-alone autonomous measuring systems with magnetic registration. M., Nedra., 1979, p. 116 (prototype).