RU47110U1 - MAGNETIC RESONANCE GEOINTROSCOPE - Google Patents

Abstract

The proposed device relates to the field of technical means of exploration and detection of underground mineral deposits and is intended for remote search for water deposits. The technical result of the proposed utility model is to increase the maximum detection depth of aquifers and the accuracy of determining the depth of their occurrence due to a significant improvement in the ratio of the useful signal to interference. The proposed utility model helps to solve the important problem of providing water to the population of arid zones.

Description

The proposed device relates to the field of technical means of exploration and detection of underground mineral deposits and is intended for remote search for water deposits.

A similar device is known for remote detection of underground mineral deposits [1, 2], based on the reception of nuclear magnetic resonance (NMR) signals by an induction sensor from the nuclei of a substance located in a geomagnetic field and remote from the sensor at a considerable distance. The device contains a resonant circuit in the form of a loop deployed on the soil surface, tuned to the frequency of magnetic resonance of the nuclei in the geomagnetic field, a switching device, a transmitter, an amplifier, and a measuring device. The disadvantage of this device is the exposure to external electromagnetic interference, which is induced in the circuit and which can be very significant due to the large size of the loop, and the useful signal can be very small, especially for deep deposits. Another disadvantage is the inability to implement the synchronous detection mode, since the frequency of nuclear magnetic resonance in a geomagnetic field is not stable enough due to the existence of its variations. These circumstances limit the depth of detection of the mineral.

A device for nuclear magnetic logging [3], consisting of an induction sensor lowered into the well, and an additional sensor located on the surface of the earth and compensating for electromagnetic interference induced on the main sensor are known. The disadvantage of this device is the ability to receive nuclear magnetic resonance signals only from an area close to the main sensor, which does not allow using it for remote detection of water.

It is also known a device adopted as a prototype of this model, designed for remote detection of underground water deposits, based on the same principle and having the same composition [4], however, in order to improve the ratio of the useful NMR signal to the interference signal, the induction sensor of this device is made in in the form of a loop having a special shape in the form of a "figure eight". A positive effect is achieved due to the mutual compensation of electromagnetic interference signals induced in each of the parts of the "eight" in opposite phases.

A disadvantage of the known device is the limitation of the depth of detection of a water pool and the insufficient accuracy of its determination due to the additional attenuation of the NMR signal as the depth increases due to the fact that mutual compensation in the known device is subjected not only to interference signals, but to a certain extent also useful signals from cores. In this case, the degree of attenuation of the total useful signal is the greater, the deeper the water pool is, that is, in that situation in which it is especially important to have a sufficient ratio of the useful signal to interference.

The technical result of the proposed utility model is to increase the maximum detection depth of aquifers and the accuracy of determining the depth of their occurrence due to a significant improvement in the ratio of the useful signal to interference, compensation for variations in the geomagnetic field and ensuring the processing of data in synchronous detection mode.

The technical result is achieved by the fact that in the proposed device - a magnetic resonance geo-introscope - containing an induction sensor of nuclear magnetic resonance signals from underground water in the form of a loop deployed on the soil surface and an additional reference sensor of NMR signals from a standard sample, tuned to the frequency of magnetic resonance of hydrogen nuclei in geomagnetic field and connected through a switch to a pulse generator and a multi-channel amplifier, which are connected through a controller to

A computer, due to the presence of an additional reference sensor, a signal is generated that is used as a reference for synchronous detection and to compensate for interference, which ensures a good ratio of the useful signal to interference.

A block diagram of a magnetic resonance geointroscope is shown in Fig.1.

An induction sensor of nuclear magnetic resonance signals in the form of a loop (1) and a reference sensor (7) are connected through a switch (2) to a generator (3) and an amplifier (4), which are connected to the analog inputs of the controller (5); digital input and output of the controller (5) are connected to the computer interface (6).

The work of a magnetic resonance geointroscope is as follows.

The computer interface (6), upon the operator’s command, generates a command in the form of a digital code that is sent to the digital input of the controller (5) under the action of the program loaded into the computer. In the controller (5), the digital code is converted into an analog signal, which is sent to its analog output connected to the generator (3), and under the influence of which the generator generates pulses of a given duration with a filling frequency equal to the NMR frequency in the geomagnetic field. The pulses through the switch (2) are fed to the induction sensors (1) and (7) and excite the precessing nuclear magnetization in groundwater and a standard sample, respectively. The signals induced in the same sensors by precessing nuclear magnetization enter through the switch (2) and amplifier (4) into the controller (5), where they are digitized and sent to the computer. The computer implements the functions of digital filtering of useful signals, compensation of the interference signal and synchronous detection, and the NMR signal from an additional sensor is used as a reference signal that tracks the variations of the geomagnetic field. The existence of a signal after detection indicates the presence of water in a given place, and the depth of its occurrence is determined from the dependence of its intensity on the duration of the exciting pulse.

The proposed utility model is tested in the laboratory conditions of St. Petersburg State University.

The implementation of the proposed utility model will contribute to a simple and relatively inexpensive compared to world analogues solution of an important problem - providing water to the population of arid zones.

Used sources

[1] Semenov A.G., Burshtein A.I., Pusep A.Yu., Shchirov M.D. A.s. 1070063 USSR. Device for measuring the parameters of underground mineral deposits. A.s. 1070063 USSR. 1988.

[2] Semenov A.G., Schirov V.D., Legchenko A.V., Burstein A.I., Pusep A.Ju. Device for measuring the parameters of underground mineral deposit. GB Patent 2198540 B, 1989.

[3] Trushkin D.V., Shushakov O.A., Legchenko A.V. The potential of a noise-reducing antenna for surface NMR groundwater surveys in the earth's magnetic field. 1988.

[3] Chernyshev Yu.S. A.s.SSSR No. 166419 dated 03/29/1963.

Claims (1)

A magnetic resonance geo-introscope containing a transmit-receive circuit tuned to the frequency of proton magnetic resonance in a geomagnetic field and representing a loop deployed on the surface of the soil in the search zone; a switching device having a pulse input, two outputs and two signal outputs; a pulse generator having a filling frequency equal to the frequency of proton magnetic resonance in a geomagnetic field and creating a precessing nuclear magnetization in groundwater; amplifier; a controller that controls the measurement process by the program loaded into the computer and creates a digital code of the signals and transfers it to the computer; a computer that organizes the measurement process and emulates synchronous detection, as well as displays data on the water content and its depth, characterized in that the amplifier and controller have additional channels for transmitting pulses to an additional sensor and receiving signals from it and transmitting their digital code to a computer while the output of the generator is connected to the pulse input of the switching device, the corresponding conclusions of the switching device are connected to the main and additional circuits, and its signal s outputs are connected to inputs of a multichannel amplifier, the outputs of which are connected to respective inputs of the controller, and the controller output is connected to a computer port.