SU859982A1 - Device for well inductive prospecting - Google Patents

Description

(54) DEVICE FOR BOTTOM INDUCTION

one

The invention relates to geophysical electrical prospecting devices and can be used in apparatus for measuring complex components of harmonic signals, in particular in electrical measuring equipment.

A well-known induction apparatus, comprising an alternating voltage generator with an alternating magnetic field emitter, an alternating magnetic field radiation receiver, a preamplifier and an electronic unit connected to the preamplifier output with a logging cable, with which the received signal 1 is amplified, processed and recorded.

The disadvantages of the apparatus include insufficient measurement accuracy caused by phase shifts that occur in the wireline when transmitting the signal from the preamplifier to the electronic unit.

The closest technical solution to the invention is a device for downhole induction electrical prospecting, comprising a working frequency generator, an emitter of an alternating magnetic field, connected

connected to an operating frequency generator, a series-connected alternating magnetic field receiver, a preamplifier, an initial phase shift compensator, a selective amplifier, and two phase-sensitive phase-sensitive detectors (PSDs) connected in parallel, the reference inputs of which are supplied with operating frequency voltages,

10 shifted relative to each other by E0 ° using a 90 ° phase shifter, and an indicator.

These elements of the operating frequency generator are placed in zones 15 of the device. The signal from the PDP outputs is fed through a wireline cable to a surface unit consisting of a working frequency generator and an indicator. To compensate for the initial phase shifts, phase shifters included in the alternating voltage circuit are used, in this case they are placed as a field and phase-sensitive detector 2.

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In practice, two modifications of the device are used. With dipole electromagnetic well profiling (DEMP), the compensator for initial phase shifts is located in

downhole measuring unit. At that, its transfer to the surface unit is impossible, since the measured signals are transmitted by direct current through the cable connecting the downhole tools with the ground control unit.

Compensator initial phase. The shifts used in the DEMPS and located in the downhole block include an RC phase shifter with interchangeable elements corresponding to the selected operating frequency, an electric motor with a gearbox, on the axis of which a variable resistance is fixed, and an electrical circuit controlling the phase shifter (from the ground console).

When operating in the version with ground loop emitter, the field of the initial phase shifts is also included in the AC circuit between the field receiver and the phase sensitive detector, but is placed in the ground instrument, as in this variant the measured signal is transmitted by alternating voltage through the cable and phase-sensitive detection is carried out in a ground-based instrument.

However, the placement of a compensator for initial phase shifts in a borehole device when operating in the dipole version leads to a significant increase in temperature measurement errors. The temperature in the well is usually very different from the temperature on the surface and changes; . ..- Tc on the well on average for every 100 m of its depth. After the devices are lowered into the well, they must be maintained for 2030 minutes, which significantly reduces the productivity of work, but even in this case the temperature errors remain significant due to a change in the temperature of the medium with depth.

The placement of the initial phase shift compensator in the downhole tool (in the dipole version) significantly increases the downhole tool length, complicates the equipment design and is associated with the need to change elements, which practically forces the well to open the well at each change in the operating frequency.

Compensation of the initial phase shifts in each of the modifications is carried out by different elements, which leads to the complication of the equipment and its operation.

The purpose of the invention is to improve the accuracy and speed of measurements by increasing the efficiency of compensating phase shifts.

The goal is achieved by the fact that in a device for borehole induction electrical survey, which contains a working frequency generator, a variable magnetic field emitter connected to a working frequency generator, an alternating magnetic field receiver and a preamplifier compensator of initial phase shift 90 phase converter, sequentially connected selective amplifier and two phase-sensitive operating frequency detectors in parallel, the reference input of one of which is connected en to enter the operating frequency of the generator itself, and the other -: 90-shifter, and an indicator of the initial phase shift compensator is designed as a generator ancillary | frequency with an additional phase shifter, first and second phase splitters, two modulators connected by control inputs to the output of the auxiliary frequency generator through the first phase splitter, and two phase-sensitive auxiliary frequency detectors, the reference inputs of which are connected to the output of the auxiliary frequency generator through the second phase splitter and an additional phase shifter , the measuring inputs to the outputs of each of the modulators, and the parallel-connected inputs, 1s of the modulators are the input of Com The initial phase shift sensor and connected to the parallel-connected outputs of phase-sensitive operating frequency detectors, the outputs of the phase-sensitive auxiliary frequency detectors are the output of the initial phase shift compensator and are connected to the indicator input, and the input of the selective amplifier is connected to the output of the preamplifier.

The drawing shows the functional diagram of the device.

Claims (1)

The device contains a working frequency generator 1 connected via a logging cable to an emitter 2 of an alternating magnetic field, made in the form of, for example, a generator frame, a receiver 3 of an alternating magnetic field (receiving frame), a pre-amplifier 4. An emitter, a receiver of an alternating magnetic field and a pre-amplifier can make the receiving and amplifying unit of the probe. The output of preamplifier 4 is connected via a connecting line with a downhole measuring unit, in which the selective amplifier 5 and phase-sensing detector b and 7 of the operating frequency voltage are connected in series. Reference voltage with a phase shift of 90 ° is supplied from the output of the operating frequency generator and through 90 phase shifter 8 to the reference inputs of phase sensitive detectors of operating frequency 6 and 7, the outputs of which are connected by a three-core logging cable to the phase shift compensator located in the ground control and consisting of an auxiliary frequency generator 9, modulators 10 and 11, an additional phase shifter 12, a first and second phase splitters 13 and 14, and detectors 15 and 16 auxiliary frequencies. The device also contains an indicator 17 connected to the outputs of the phase-sensitive auxiliary frequency detectors 15 and 16. Auxiliary frequency generator 9 is connected via phase splitter 13 to moduli 10 and 11 and connected via an additional phase shifter 12 and phase splitter 14 with phase sensitive phase detectors 15 and 16 of auxiliary frequency. The arrangement of the additional phase shifter 12 is not fundamental. It can also be located between an auxiliary frequency generator and modulators. Works proposed equipment as follows. The emitter 2 of an alternating magnetic field (borehole frame) is powered by the operating frequency current from the operating frequency generator, the EMF induced in the receiver 3 of the alternating magnetic field is amplified by the preamplifier 4 Next, the measured voltage enters the downhole measurement unit, where it is amplified by selective the amplifier 5 and the detection of phase-sensitive detectors (PSD) b and 7 of the operating frequency. Phase compensation is carried out in the direct-current circuit using a compensator x phase shifts included in the ground measuring unit. Constant voltages taken from the outputs of phase-sensitive detectors B and 7 of the operating frequency and proportional to the real and imaginary components of the measured signal are transmitted to the ground-based measuring unit, where they modulate the alternating voltages of the auxiliary frequency. The auxiliary frequency voltage is supplied to the modulators 10 and 11 from the auxiliary frequency generator 9 through the phase splitter 13. The variable voltages at the outputs of the modulators 10 and 11 are in quadrature and are proportional to the amplitude of the non-substantial and imaginary components of the measured EMF. The vector sum of these voltages, formed by means of an adder (not shown), goes to the phase-sensitive detectors 15 and 16 of the auxiliary frequency (the summation function can also be provided by using the PSF 15 and 16 with a corresponding change in their circuit). The reference voltages to the phase-sensing detectors 15 and 16 of the auxiliary frequency are supplied from the auxiliary frequency generator 9 through an additional phase shifter 12, which provides phase shift from O to 360 °, and through the phase splitter 14, providing a 90 ° shift between the reference voltages by the voltage supplied to the phase-sensitive detectors 15 and 16 of the auxiliary frequency. The phase difference between the corresponding reference and modulated voltages is equal to the phase shift introduced by the additional phase shifter 12. From the output of the phase-sensitive detectors 15 and 16 of the auxiliary frequency, the variable voltages are fed to the indicator 17 of the imaginary and real components. The initial phase shift compensator, whose operation is described above, is used both when operating the equipment in the DEMPS version and in other modifications (PS, interwell borehole dipole electromagnetic profiling, induction measurements during galvanic excitation of the primary field). The proposed device also makes it possible to reduce the temperature errors of phase measurements by 4050% by placing the phase shift compensator in the surface unit, reducing the downhole gauge length by 20% by eliminating the phase shift compensator elements and actuating means for their remote adjustment. An apparatus for downhole induction electrical survey, comprising an operating frequency generator, an alternating magnetic field emitter connected to an operating frequency generator, an alternating magnetic field receiver connected in series and a preamplifier, an initial phase shift compensator, an EO phase shifter, a series-connected selective amplifier and two in parallel included phase-sensitive operating frequency detector, the reference input of one of which is connected to the output The operating frequency is directly, and the other is through a 90 ° phase shifter, and an indicator, characterized in that, in order to increase the accuracy and speed of measurements by increasing the efficiency of compensating phase shifts, the initial phase shift condenser is made as an auxiliary frequency generator with an additional torque converter, and a second phase cutter, two moduliuv, connected by control inputs to the output of the auxiliary generator