SU1000981A1 - Device for electromagnetic well-logging - Google Patents

Description

The invention relates to geophysical studies in the well, in particular, to technical means used for studying the electrical properties of rocks by electromagnetic logging methods. A device for dielectric logging is known, which includes a three-element probe with two receiving and one generator coils, a high-frequency generator that excites an electromagnetic field through a radiating coil in the medium surrounding the probe, receiving coils connected to series-connected high-frequency and low-frequency amplifiers, heterodyne, frequency converters, blocks for receiving signals proportional to the phase difference on the receiving coils, as well as the recorder of measured parameters С 1 1 However info matsi of the permittivity of the test race, characterized by phase difference. It can not always be isolated without using data from other logging methods, which reduces the accuracy and efficiency of determining the desired parameter. A device for electromagnetic logging, a generator with a radiating coil, two receiving coils, respectively connected to two amplifiers loaded on a signal ratio meter, and a recorder 2, is known. The measured ratio of signals is complex in connection with the dielectric constant and specific resistance of the medium at high frequencies. These parameters for information about the relationship of the signals can not be accurately determined without additional information about the electromagnetic field in the environment. The disadvantages of this device include low productivity and the need to take into account the effect of medium conductivity according to other logging methods when determining the dielectric constant of rocks.

The closest to the present invention is an electromagnetic logging device, comprising a high frequency generator connected to a generator coil, first and second receiving coils, high and low frequency amplifiers, two frequency converters, an amplitude ratio forming unit, an amplifier with an amplifier, a phase meter the unit and the recorder, each receiving one, the coil is connected respectively to one of the high-frequency amplifiers, the outputs of which are connected by G to the first inputs of the converters h simplicity, to the second inputs of inverters is connected through an oscillator amplifier, frequency converters exits through low frequency amplifiers are connected to inputs of the block forming the ratio of amplitudes of the received signals and having two inputs fazometricheskogo block.

The generator part of the device, through the generator coil, excites in the studied space the following: an electromagnetic frequency field, which is received and converted into high frequency signals by the receiving elements of the probe. The received signals are amplified at a high frequency, transferred to a low frequency, and then amplified at a low frequency in two identical receiving channels. From the outputs of the low frequency amplifiers, signals are fed to the inputs of measuring units for the amplitude ratio of the field at the receiving points and phase differences, and from the outputs of these units, the measured characteristics of the field are fed to the recorder.

The known device allows to measure two characteristics of the field: the phase shift of the signals between the receiving coils and the ratio of the amplitudes at the receiving points, i.e. in coils 3.

The disadvantages of the known device are that the measured

Signals proportional to the phase difference and the ratio of the amplitudes of the received field have a significantly non-linear resolution sensitivity to the dielectric susceptibility of the studied rocks when

their various resistivity; which falls with a decrease in the latter.

At high frequencies, the measured signal characteristics of the field are interdependent so that the measurement errors of each of them affect simultaneously the dielectric constant and resistivity estimates, and the logging results are subject to significant errors, especially in low-cut sections.

The disadvantages also include the low efficiency of E measurements due to the inability to read the values directly from the logging chart and the need to use materials obtained by other logging methods.

In addition, the practice of well logging shows that productive rock complexes with lower specific resistivity (for example, polymictic sandstones of Western Siberia and others) are widespread, which reduces the efficiency of using the known dielectric constant apparatus.

The aim of the invention is to increase labor productivity and efficiency of measurements of dielectric constant and electrical resistivity of rocks.

Claims (3)

The goal is achieved by the fact that in the electromagnetic logging device, comprising a high frequency generator, connected to the generator coil, the first and second. receiving coils, high and low frequency amplifiers, two frequency converters, a ratio formation unit of the amplitudes of the received signals, a local oscillator with an amplifier, a metering unit and a recorder, each receiving coil being connected to one of the high frequency amplifiers, whose outputs are connected to the first inputs of the frequency converter, a local oscillator is connected to the second inputs of the frequency converters via an amplifier, the outputs of the frequency converters are connected to the block inputs via low-frequency amplifiers Amplification of the ratio of the amplitudes of the received signals to the two inputs of the phase metering unit, additionally, a nonlinear conversion unit, a phase shifter unit, a second phaseometric unit, and two signal multiplication units were added, the output of the received signal ratio shaping unit being connected to the input of the nonlinear conversion unit, the output of which connected to the first inputs of the signal multiplying units; the first input of the first phase metering block is connected to the first input of the second phase metering block; the second input of the first phase The electric unit is connected to the input of the phase-shifting unit, the output of which is connected to the second input of the second phase-measuring unit, the outputs of the phase-measuring units are connected respectively to the second inputs of the multiplication units, the outputs of which are connected to the recorder inputs. FIG. 1 shows a functional diagram of the proposed device; in fig. 2 is the calculated dependence of the parameters V and W recorded by the device and dependent on the dielectric constant and electrical resistivity of the medium under study. The device contains a generator 1 connected to a radiating element (generating coil) 2, receiving elements (coils 3 and) connected to high-frequency amplifiers 5 and 6, frequency converters 7 and 8, local oscillator 9 with amplifier 10, amplifying 11 and 12 low frequency, connected respectively to frequency converters 7 and 8, unit 13 forming the amplitude ratio of signals connected to the outputs of amplifiers 11 and 12, first phaseometric unit Neither phase shifting unit 15 connected also to outputs of amplifiers 11 and 12, second phaseometric block 16, connected to the output of the phase-shifting unit 15, nonlinear conversion unit 17, connected to the output of block 13, multiplication blocks 18 and 19, the inputs of which are connected to the outputs of blocks 17, 1 and 16, and the outputs connected to the recorder 20. The device works as follows . Generator 1 feeds a high-frequency current with a radiating element 2 which excites an electromagnetic field in the surrounding environment. A propagating field in a rock induces electrical signals in receiving elements 3 and 4, characterized by absolute amplitudes ./, phase shifts relative to generator signals (and (f, and simultaneously these signals are fed through inputs 5 and 6 to high frequencies). frequency converters 7 and 8, to the other inputs of which signals are supplied from the local oscillator 9 through the amplifier 10. The signals converted in frequency are further amplified by low frequency amplifiers 11 and 12 and fed to the inputs of the block 13 formed the amplitudes of the received signals, the output of which generates a signal proportional to the parameter / H2 /// H, /, as well as the inputs of the phaseometric unit 14, the output of which produces a signal proportional to the sine half of the phase difference of the received signals А У) (( ff, i.e., G ac. "; - 1 SiH-:. The phase shifting unit shifts the phase of the signal by 180, as a result of which an output proportional to the output of the phaseometric unit produces a signal proportional to cos. The signal conversion characteristic of the non-linear conversion unit 17 has a power dependence with a power of 0.5, i.e. the output of this block produces a signal proportional to | h2 ® // i, the input signal / bc, /// I, / DG "of this block 17 input is connected to the output of the amplitude ratio measurement block 13, the inputs of which are connected to the outputs of amplifiers 11 and 12. A signal) proportional to the values of / b // / arriving at the inputs of blocks 8 and 19 of multiplication, np i, form the parameters V and W proportional to the products of the relative characteristics of the field, i.e. (Ihaif lsr. B (f -W /) which possess the required metrological properties, in contrast to the known measured signals of the field characteristics. From the outputs of multiplication blocks 18 and 19, signals proportional to V and W, respectively, arrive at the outputs of the recorder and are fixed in The additional phase metering unit 16 may be identical in operating parameters, as the phase metering unit used in phase metering unit 16 may be identical in operation parameters, and the phase metering unit used will be OK I. A nonlinear signal conversion unit 17 can be performed on an operational amplifier and diode limiters, piecewise-linear approximation of the conversion function of the input signal Iliol / bJ into the wl lLC / lJ 1 1 n-uL input | L2 | / 1 1 "The multiplication unit 18 and 19 are also implemented on operational amplifiers. The phase shifting unit is executed, for example, as an inverter. From the calculations of the dependence of the V and W parameters recorded by the device on the measured ceoitcTB medium - dielectric constant nical resistance R Sfig.2 seen that for layers with a specific electric resistance of 10 V characteristic is virtually independent of p and directly proportional to the measured permittivity pronitsaemoeti. The characteristic of the floor W is weakly dependent on E and is proportional to p. Therefore, measuring the values of V and V / under the conditions of a low-ohm section allows you to measure the S values of the environment with a given error directly in the logging process. In this case, the scale of the recorder can be calibrated in such a way that in a low-resistance section, where the characteristic V depends practically only on f, and W depends on p, the measured characteristics of the field V and V / indicated directly and the medium p. To do this, you can select the signal level W on the chart tape, for example, above which you can read the measurement results directly in units of b and p., And below this level (W 2i1) interpret by; tent (figure 2). The form of the relationship between / and U and the electrical properties of the medium 6 and p (Fig. 2) is determined by the dimensions of the base of the probe (the distance between the receiving elements 3 and), the frequency of the field and the length of the probe. FIG. 2 an example of the calculated dependence corresponds to a probe with a length L m, with a base L1 0.3 m at an excitation frequency of half MHz. It should be noted that the sensor is. The device to the dielectric constant in low-resistance rocks is close to its sensitivity in the high-resistance part and almost twice exceeds the corresponding value of the characteristic in the noneco-ohm part. Measurement errors of the characteristics of the V and W to a lesser extent than in the known relative xapair characteristics mutually influence the evaluation of the electrical properties of rocks. Thus, the introduction of a non-linear converter electromagnet carriage, FW2, U0PYiL1GHGGHhlhchp ... moving shift and additional phasometric units, as well as signal multiplying units, allows the above-mentioned algorithm to transform known devices and perform Low impedance measurements of dielectric constant and electrical resistivity directly in the logging process. The economic efficiency of the implementation of the proposed device lies in expanding the range of application of the method of measuring the dielectric constant in low-resistance sections, as well as accelerating the research time due to the direct measurement of the quantities and the rocks in low-resistance rocks and contributes to reducing the number of cases of producing skips . An electromagnetic logging device comprising a high frequency generator connected to a generator coil, first and second receiving coils, high and low frequency amplifiers, two frequency converters, an amplitude collection unit of the received signals, an LO with an amplifier, phasometric unit and recorder, with each receiving coil being connected respectively to one of the high-frequency amplifiers, whose outputs are connected to the first inputs of frequency converters, to the second inputs The frequency converters provide a local oscillator through an amplifier, and the frequency converter outputs are connected via low-frequency amplifiers to the inputs of the amplitude ratio of the received signals and to the two inputs of the phase-measuring unit, which are designed to increase the productivity and efficiency of dielectric constant measurements and the electrical resistivity of rocks, a non-linear conversion unit, a phase-shifting unit, a second phase meter ok and two signal multiplying units, the output of the ratio signal receiving unit is connected to the input of the nonlinear conversion unit, the output of which is connected to the first inputs of the signal multiplying units, the first input of the first phaseometric unit is connected to the first bother of the second phaseometric unit, the second input of the first the phase meter block is connected to the input of the phase shift block, the output of which under1 81 is connected to the second input of the second phase meter block, the outputs of the phase meter blocks are connected respectively to the second inputs of multipliers, whose outputs are connected to inputs of the registrar. Sources of information taken into account in the examination 1. D. Dayev. High-frequency electromagnetic well research methods. M., Nedra, 197, p. 139-15 2. Zaslono I. M. Well logging, based on the measurement of the attenuation of the electromagnetic field. - In Sat. Applied Geophysics, vol. b7. I., Nedra, 1972, p. 195-203. 3.Sharov G.V. A method for measuring relative characteristics in electromagnetic logging methods. Works VNIIneftepromgeofiziki. Vol, 9. Ufa, 1979, p. 30-35 (prototype).