SU1079063A1 - Apparatus for measuring parameters of underground mineral deposits - Google Patents

Description

The invention relates to the field of geophysics and is intended for direct measurements of the depth, thickness and concentration of underground minerals that give a magnetic resonance signal, such as water or oil, without drilling wells. In the case of measuring aquifers, the invention may find application in exploration work in the construction of railways, transmission towers and other structures, as well as in choosing a site for production water wells.

Devices are known for measuring parameters of deposits of underground minerals based on measuring a nuclear magnetic resonance signal when a measuring device is lowered into boreholes.

The disadvantages of these devices are the cumbersome equipment, the long drilling process and the need for drilling large amounts of water, which creates certain

difficulties in waterless areas. I

The closest in technical essence is a device for measuring the parameters of deposits of underground minerals, which also uses the phenomenon of magnetic resonance. Using a wire loop or coil located on the surface of the earth, they create a sequence of exciting pulses of an alternating magnetic field with a carrier frequency equal to the resonant frequency of the desired mineral. Due to nutation during the action of each pulse, the magnetic moment of the deposit due to nuclear magnetism deviates from its static position determined by the magnetic field of the earth. At the end of the excitation pulse, the magnetic moment returns to its static position, making precessional movements around the induction vector BIJ of the earth’s magnetic field, thus creating damped oscillations of the alternating magnetic field (free precession signal) over the mineral deposit. In the intervals between the excitation pulses, these oscillations are received using the same wire loop. The presence or absence of a signal at the receiver & triality at a given oscillation frequency indicates, respectively, the presence or absence of the desired mineral.

The device contains a wire loop located on the surface of the earth, connected through a matching transformer to a software-controlled switch, to the outputs of which are connected an RF generator and series-connected matching transformer of an amplifier, amplifier, two-channel device on a tape recorder for preliminary processing of a signal with resonant circuits and detectors at the output of each channel, subtractor, combining the outputs of the channels, integrator

and recorder. f

The device starts with an excitation cycle, which is ensured by connecting a loop to the generator output using a software-controlled switch. At the end of the excitation cycle, the software-controlled switch connects the loop to the amplifier input and the signal reception cycle begins. At the same time, one channel of the preprocessing device remembers the amplified free precession signal plus noise on a tape recording. The other channel only remembers the noise, in connection with which it is switched on after the first channel, i.e. when the free precession signal drops off. Then, the signals stored in the channels are simultaneously read from the tape, are separately filtered by resonant circuits, detected and fed to a subtractor, which subtracts the voltage received at the output of the second channel detector from the detected voltage of the first channel. As a result, the output of the subtractor remains only a useful signal of free precession. With repeated repetition of the excitation and reception cycle, the signal from the output of the subtractor is averaged by the integrator and recorded on a recorder. In this way, an increase in the sensitivity of the device is achieved. For the same purpose, the preprocessing device will erase the signal recorded on the tapes if a pulse disturbance has occurred in the loop during the reception cycle. For this purpose, in each channel of the preprocessing device there are auxiliary reading heads connected to their amplifiers, detectors, time delays and erasing devices. When the signal exceeds a certain predetermined level, the auxiliary detectors turn on erasing devices, the signal damaged by the signal is 11 1, and therefore does not enter the subtractor’s inputs. The disadvantage of this technical solution is that it does not offer any specific ways to obtain depth data. occurrence, thickness and concentration of the mineral. The aim of the invention is to obtain data on the depth, thickness and concentration of the mineral. The goal is achieved by the fact that a device containing a wire loop located on the surface of the earth, a program-controlled switch connected by an output to a wire loop, an RF generator connected to the input of a switch, an amplifier connected in series with a program-controlled gain controller and a synchronous detector analog-to-digital converter (ADC) connected to the output of the switch, and the reference input of the synchronous detector is connected to the output of the radio-frequency generator, additionally equipped with software-controlled amplitude and dpness regulators of radio frequency pulses and an electronic computing mask (computer), with the outputs of the amplitude and pulse duration regulators connected to the generator input, the information input of the computer connected to the output of the ADC, the control outputs of the computer, connectors of the computer, connectors of the computer, connect the output of the computer to the output of the ADC, the control outputs of the computer, connectors to the generator, connect the output of the computer, connect the output of the computer to the output of the ADC, control outputs of the computer connectors to connect the generator, and connect the output of the computer to the output of the ADC; the inputs of the switch, the gain controllers, the amplitudes, and the duration of the excitation pulses of the radio frequency generator and the ADC.

Figure 1 shows a device diagram; Fig. 2 shows measurement and calculation results.

The device contains a wire loop 1 located on the surface of the earth. The loop is connected to a software-controlled switch 2. An RF generator 3, equipped with a power output, is connected to one of the switch outputs.

During the measurement, the curve of the dependence of the amplitude E of the initial part of the signal emitted by the mineral on the product of the amplitude I, the pulse of the excitation current in the loop by the duration S of this pulse is recorded. Then, the dependence g (2) of the distribution of the mineral concentration on the distance to the surface of the earth Z from the integral of the program-controlled amplitude controls 4 and the duration of 5 excitation pulses is found. The output of the switch 6 is connected in series with the amplifier 6 with the software-controlled gain control 7 and the synchronous detector 8. To the output of the detector, an information input is connected to the software-controlled analog-to-digital converter (ADC) 9, the output of which is connected to the information input of the computer 10 The control outputs of the computer are connected to the corresponding inputs of the software-controlled switches 2, the amplitude controller 4, the controller duration 5, the gain controller 7 and the ADC 9. The generator 3 has an additional The reference voltage output is connected to the reference input of the synchronous detector 8. The device starts with an excitation cycle. In order to eliminate the overload of the amplifier 6 by parasitic voltage seeping through the switch 2 during the excitation, and by reducing the very Dead time of the receiving path of the computer 10 sets the gain control to the minimum gain position. At the same time, the computer 10 sets the controllers 4 and 5 to the initial state, and switches 2 to connect the loop 1 to the generator. 3. At the end of these settings, a pulse of excitation current arises in loop 1. At the end of the pulse, the computer 10 switches the loop to amplifier 6 with switch 2, and sets the gain controller 7 to the position corresponding to the reception of a free precession signal. The amplified signal is fed to the detector 8. At the command of the computer, U triggers the ADC 9 and the detected and digitized signal is sent to the memory of the computer 10.

, (I.) FiBof 7 (Z) - j dx. Dy / i.Cr) sin | -i-jp. () L, oj where) r is the hydromagnetic ratio of the dll of the magnetic core contained in the mineral B - induction vector of the earth's magnetic field; M is the static magnetic moment per unit volume of pure mineral, due to nuclear magnetism, in the field of the earth; fl, F) is perpendicular to the vector BQ of the magnetic induction component of the ground loop with a current IA in it at the deposit point with coordinates t (x, y, Z). Dependence 7 (Z) gives full information about the deposit located under the loop, i.e. depth, layer thickness and change in the concentration of the mineral in the layer thickness. Due to the inevitable dead time of the receiving path, the initial part of the free precession signal E is usually lost. At the same time, the accuracy of determining the concentration of a mineral depends on the accuracy of measuring the value of E. Therefore, the computer 10 from the received signal by extrapolation calculates the value of EQ, and stores this first point of the curve), and erases unnecessary information in the memory. After this, the computer 10 sets the controllers 4 and 5 to a new position and cycle of the excitation, reception and processing of the signal. As a result, the computer stores the second point of the curve Eod, -). So the process is repeated until the limit position of the controllers 4 and 5 is reached and all the initial part of the curve Ер (1, -) is in the memory of the computer 10. The point of break of this curve is determined by the maximum achievable or specific device with an area of 1 , the exciting impulse. To improve the accuracy of measurements, the curve Eg (I.f) should be accumulated in the memory of the computer 10 by its repeated passage and averaging. After the accumulation of the computer 10 produces by the formula the calculation of the function H f which is recorded on its output device. Verification of the proposed technical solution was carried out on aquifers with the following parameters: A - depth “5.5 m; thickness of the layer“ 25.5 m; K - depth z.5.5 m, thickness of the layer 14.5 m; B — depth of s24 m; thickness of the layer —4.0 m. There were no data on the distribution of water concentration over the layers. It is only known that, on average, -0.2, the measurements were made by a loop with a diameter of 50 m, consisting of two turns of wire. The results of measurements and calculations are shown in FIG. 2. The solid lines show the curves Eg (,) calculated by the formula for the above aquifers A, B and B. The experimental values obtained for the same layers are also plotted. The water concentrations measured by the device turned out to be for the formations: A - 2 0.12; B - 2 0.18; B - H 0.175, which will give a satisfactory agreement of the experimental points with the calculated curves.

Claims (1)

DEVICE FOR MEASURING PARAMETERS OF DEPOSITS OF UNDERGROUND MINERALS, giving a magnetic resonance signal, comprising a wire loop located on the surface of the earth, a program-controlled switch connected by an output to a wire loop, a radio-frequency generator connected to a switch input, an amplifier connected in series with a program-controlled regulator amplification, a synchronous detector and an analog-to-digital converter (ADC) connected to the output of the switch, and the reference input of the synchronous detector connected to the output of the radio frequency generator, characterized in that, in order to obtain data on the depth, power and concentration of the mineral, it is equipped with programmable amplitude and duration regulators of the exciting pulses of the radio frequency and an electronic computer, and the outputs of the amplitude and duration regulators connected to the input of the generator, the information input of the computer is connected to the output of the ADC, the control outputs of the computer are connected to the control inputs of the switch, gain controls, the amplitude and duration of the exciting pulses of the radio frequency generator and ADC. 9ig 1 ..S and. ..1079063