SU1469490A1 - Electromagnetic logging device - Google Patents

Abstract

The invention is used to measure the electrical characteristics of rocks when conducting a GIS. The purpose of the invention is to improve the accuracy of measurement of the electrical characteristics of rocks and productivity of work. The equipment contains a master oscillator, power amplifiers, two three-element probes, consisting of two generator, and two pairs of measuring coils, a measuring part that includes two identical mixer-multiplexer, oscillator-local oscillator, intermediate-frequency limit amplifiers, RF blocks: control , telemetry, measurement of phase shift, carrier frequency period, ground recording device. The generator coils are connected via power amplifiers to the master frequency generator. The measuring coils are connected to the inputs of transducer amplifiers, to the second inputs of which the outputs of the oscillator-local oscillator are connected, and the outputs are connected via amplifiers-limiters to the inputs of the digital phase of the measuring unit. The lengths and bases of three-probe probes are chosen in such a way as to provide the same radial depth of investigation. Reducing the effect of frequency deviation improves the accuracy of determining the electrical resistivity and relative dielectric constant of rocks. Simultaneous measurement of two probes for one tripping operation of a downhole tool during well logging increases the productivity of geophysical work. 1 il. G S HY OE CO 4; i co O

Description

one

The invention relates to field geophysics and can be used in the study of wells using electromagnetic logging methods.

The purpose of the invention is to improve the accuracy of measurement of the electrical characteristics of rocks and productivity of work.

The drawing shows the structural scheme of the proposed electromagnetic logging unit.

The device contains a generator unit 1, a probe 2, a receiving-transforming part 3, a measuring-teh-hemmetric part 4 and a ground-based part 5,

The generator unit 1 includes a dual frequency driving oscillator 6 and two power amplifiers 7 and 8. The two three element probes consist of generator coils 9 and 10 and two receiving coils 11 and 12 (13 and 14). The receiver / converter portion contains a local oscillator 15, p. The detectors are m-ultiplexers 16 and 17, limiters 18 and 19. The measuring and telemetry part includes the control unit 20, the phase difference and period difference generator 21, the phase difference meter 22, the intermediate frequency period meter 23, the multiplexer 24, the transmitter 25 and line 26 communication. The ground part contains the receiver 27, the register-index 28 of the measured values, the register 29 of the phase shift, the register 30 of the measurement period, the divider 31, the converter 32 of the phase shift, digital-analog converters 33 and 34.

The device works as follows.

The master oscillator 6 of two frequencies, controlled by the control unit 20, cyclically triggers power amplifiers 7 and 8, which supply the generating coils 9 and 10 with currents of two different high frequencies. High-frequency electromagnetic fields created in the surrounding space induce in the receiver: coils. 11-14 signals arriving at the inputs of the mixers-multiplexers 16 and 17, the other inputs of which receive signals from the control unit 20 and the controlled oscillator-local oscillator 15. The converted intermediate frequency signals are amplified and limited The amplitude of the limiters 18 and 19 is transferred to the shaper of the phase difference and period, where time intervals are formed, which are proportional to the phase difference and the intermediate frequency period. The shaper 21 phase difference and period outputs are connected to phase difference meter 22 and 23. frequencies in which the amounts of high-frequency filling pulses are calculated in the generated time intervals of the phase difference and the period of the intermediate frequency. Digital data from these blocks is converted by multiplexer 24 and by transmitter 25 to serial and transmitted to a ground receiver.

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the recording unit via the communication line .26. The converted serial code from the receiver is fed to the register-pointer 28 of the measured, values, in particular, for example, f or, the phase shift register 29, the measurement period register 30, C divider 31, dividing the signals from the phase shift register 29 and the register 30 period, the signals are sent to the phase shift converter 32 into measured values of p and, which is a matrix of tents. The digital data from the phase shift converter 32 is converted to analog form by digital-to-analog converters 33 and 34. Divider 31 operates on the contents of registers 29 and 30.

,, .i80, iTi,

where l M is the true phase shift)

 - the sum of the phase shifts for the periods of the intermediate frequency, T- is the total measurement time

for n periods of intermediate frequency.

The operation of all blocks is synchronized by control block 20.

For measuring p and the control unit, negative pulses of duration T are produced, and positive pulses of duration T constituting a full measurement cycle, and during time T, the generator is measured and the generator 3 MHz is performed, and during TI measurement E is performed 43 mHz generator operation. During each measurement period T, or T2, the control unit gates the multiplexer-multiplexers twice, prohibiting the measurement, in order to eliminate errors resulting from transients in analog circuits after switching.

Control of the mixer by multiplexers by the control unit allows switching input signals from the measuring coils to the mixer by the multiplexers and making direct measurement and reversal measurement in order to reduce the systematic error due to the nonidentity of the phase characteristics of the receiving-converting part. At the same time, a corresponding reversal of the phase difference meter occurs.

The control unit also clocks and starts the transmitter 25 after the measurement of the phase difference has ended.

The introduction of a period measurement of the intermediate frequency removes the limitation on the accuracy of maintaining the intermediate frequency, which, in turn, simplifies the requirements for the stability of the local oscillator and, moreover, after the division procedure in the divider 31, the phase shift information has an increased accuracy of measurement, which ultimately increases the accuracy of determining p and

Claims (1)

Invention Formula An electromagnetic logging device containing a master oscillator, a power amplifier, three-element probes consisting of a pair of oscillator and a common pair of measuring coils, a receiving-transforming part comprising two identical mixers, intermediate frequency amplifiers, limiters, oscillator-heterodyne, measuring-telemetry part consisting of phase measurement unit, telemetry, and ground recording part, while the inputs of power amplifiers are connected to the outputs of the master frequency generator, and the outputs are connected to the generator rolls of three-element probes, the measuring coils of the probes are connected to the inputs of the mixers, the second inputs of which are connected to the output of the oscillator-heterodyne , and the outputs through the limiters are connected to the phase-measuring unit, the output of which is connected via the telemetry unit, the communication line with the ground-based recording unit, o. t that, in order to improve the accuracy of measurement of the electrical characteristics of rocks and productivity of work, five 0 five additionally introduced a second pair of measuring coils, mixers, multiplexers in the receiving-converting part, a digital measuring circuit containing a phase difference and period generator, an intermediate frequency period meter, telemetry, a control unit, in the ground-based recording unit a receiver, a register-indicator measuring values, phase shift register, divisor, measurement period register, phase shift converter of measured values, digital-to-analog converters, with the second pair of measurement kits The carcasses are connected to a pair of mixers-multiplexers, the inputs of the phase difference and intermediate frequency period generator are connected to the outputs of the limiters and the control unit, and the outputs are connected to the phase difference and intermediate frequency period meter, the outputs of which are connected to the input and the multiplexer, the transmitter inputs are connected to the multiplexer output. and a control unit, and the output is connected to the communication line and further to the receiver input of the ground Q part, the output of which is connected to the inputs of the register-indicators of measured values, phase Vig, measurement period, outputs of phase shift registers and measurement period are connected to the inputs of the divider, the output of which is connected to the phase shift converter, to its other input is connected to the output of the register-pointer, the output of the phase shift converter is connected to digital-analogue converters, control outputs the control unit is connected to a two-frequency master oscillator, mixers by multiplexers, a local oscillator, a multiplexer, phase difference and period meters, and the length and base of the probes in They are selected in such a way as to ensure the same depth of exploration with two probes. 0 five 0 five