Air-ground well hole core multi-dimensional nuclear magnetic resonance underground disaster water detection method

Abstract

The present application is suitable for the field of geophysical prospecting technology, and provides a kind of air-ground borehole core multidimensional nuclear magnetic resonance underground disaster water detection method, comprising the following steps: using nuclear magnetic resonance detection method, laying transmitting loop on the ground, using receiving coil scanning detection in the air to circumscribe underground disaster water range;In the circumscribed underground disaster water range, using nuclear magnetic resonance detection method, laying ground transmitting and receiving loop to demarcate specific position of underground disaster water;Using nuclear magnetic resonance detection method, using vertical detection loop in underground engineering tunnel to detect disaster water of working face;Using nuclear magnetic resonance detection method, using logging probe to detect the trend of fissure water around the well in the area of underground engineering with existing borehole;Carrying out core sampling, using nuclear magnetic resonance detection method to measure and calibrate, to qualitatively and quantitatively detect disaster water enrichment degree.The present application can detect underground disaster water in all directions and multidimensionally.

Description

Technical Field

[0001] This invention belongs to the field of geophysical exploration technology, and in particular relates to a method for detecting underground hazardous water using multi-dimensional nuclear magnetic resonance in borehole cores. Background Technology

[0002] During the construction of tunnels, mountain roads and other projects, water-related disasters such as sudden water inrush, water surges and landslides have always been huge hidden dangers threatening the lives of construction workers and social and economic property. How to prevent and control water-related disasters has become a key task to ensure project safety and promote infrastructure construction and development.

[0003] In the prevention and control of water-related disasters, the detection of hazardous water is of paramount importance. Geophysical exploration technology has the advantage of being non-invasive compared to drilling technology, avoiding the risks associated with damaging the strata. The geophysical field involves a variety of technologies, such as nuclear magnetic resonance (NMR), ground-to-air electromagnetic (GTE), airborne electromagnetic (AE) detection, and seismic detection. However, electromagnetic and seismic detection technologies analyze differences between underground media through parameters such as resistivity and echo time, which are indirect detection methods. NMR, on the other hand, utilizes the basic principles of nuclear magnetic resonance, ensuring that the detected signal is only related to hydrogen protons, directly reflecting the location and content of hazardous water, offering the advantage of in-situ, direct measurement. Furthermore, current NMR detection methods often focus on one aspect, such as using surface NMR for groundwater detection or using NMR logging for wellbore exploration. Therefore, there is currently a lack of a multi-dimensional detection method applicable to the entire lifecycle and process of hazardous water detection in underground engineering projects such as tunnels and mines, comprehensively covering everything from environmental surveys to decision-making during construction, to ensure project safety and construction efficiency, and protect the lives of construction personnel and socio-economic property. Summary of the Invention

[0004] The purpose of this invention is to provide a method for detecting underground hazardous water using multi-dimensional nuclear magnetic resonance in well core samples, aiming to solve the problems mentioned in the background art.

[0005] The present invention is implemented as follows: a method for detecting underground hazardous water using multi-dimensional nuclear magnetic resonance (NMR) of borehole core samples from open-ground wells, comprising the following steps:

[0006] In the aerospace dimension, nuclear magnetic resonance detection method is used to lay transmission loops on the ground and use receiving coils in the air to scan and detect to delineate the range of underground hazardous water;

[0007] On the ground level, within the delineated area of ​​underground hazardous water, nuclear magnetic resonance detection is used to lay ground-based transmission and reception loops to pinpoint the specific location of underground hazardous water.

[0008] In the shaft dimension, nuclear magnetic resonance detection method is used to detect hazardous water at the working face in underground engineering tunnels using vertical detection loops;

[0009] In terms of borehole dimension, nuclear magnetic resonance detection method is used to detect the direction of fracture water around the well in underground engineering areas with boreholes using well logging probes;

[0010] In terms of core samples, core samples are taken and measured and calibrated using nuclear magnetic resonance (NMR) detection methods to qualitatively and quantitatively detect the enrichment of hazardous water.

[0011] Preferably, in the aerospace dimension, the steps of using nuclear magnetic resonance detection methods to lay out transmission lines on the ground and use receiving coils in the air to quickly scan and detect in order to delineate the range of underground hazardous water are as follows:

[0012] S1. Measure the geomagnetic field strength at the site using a magnetometer. The local Larmor frequency is calculated according to the following formula. :

[0013] ;

[0014] In the formula, The gyromagnetic ratio of hydrogen protons;

[0015] S2. Lay the transmitting coil on the ground;

[0016] S3. Measure the inductance of the laid transmitting coil. The value of the harmonic capacitor is calculated according to the following formula. :

[0017] ;

[0018] S4. Based on the calculated tuning capacitor value, connect the transmitting coil, tuning capacitor, transmitter and power supply to transmit the excitation pulse. In the air, use a drone equipped with a receiving coil to scan and detect the framed area.

[0019] S5. Process the data received from the host computer and delineate the scope of underground water hazards.

[0020] Preferably, on the ground level, within the delineated area of ​​underground hazardous water, the specific steps of using nuclear magnetic resonance (NMR) detection methods to lay ground-based transmission and reception loops to delineate the exact location of the underground hazardous water include the following process:

[0021] S1. Lay a transmitting coil on the ground within the demarcated area of ​​underground water hazard;

[0022] S2. Lay a pre-polarized coil and a receiving coil of the same size as the transmitting coil on the ground;

[0023] S3. Measure the geomagnetic field strength at the site using a magnetometer. The local Larmor frequency is calculated according to the following formula. :

[0024] ;

[0025] In the formula, The gyromagnetic ratio of hydrogen protons;

[0026] S4. Measure the inductance of the laid transmitting coil. The value of the harmonic capacitor is calculated according to the following formula. :

[0027] ;

[0028] S5. Based on the calculated tuning capacitor value, connect the transmitting coil, tuning capacitor, AC control module, pre-polarization coil and pre-polarization control module, and receiving coil and receiving control module.

[0029] S6. Connect the power supply and use the host computer to control the transmission and reception of prepolarization pulses and AC pulses, process the returned data, and determine the location and corresponding water content of underground disaster water.

[0030] Preferably, in the shaft dimension, the steps of using nuclear magnetic resonance (NMR) detection to detect hazardous water at the working face in underground engineering tunnels using vertical detection loops are as follows:

[0031] S1. Determine the side length of the transmitting coil based on the size of the tunnel face in the underground engineering project, and lay pre-polarized coils and receiving coils of the same size.

[0032] S2. Measure the geomagnetic field strength at the site using a magnetometer. The local Larmor frequency is calculated according to the following formula. :

[0033] ;

[0034] In the formula, The gyromagnetic ratio of hydrogen protons;

[0035] S3. Measure the inductance of the laid transmitting coil. The value of the harmonic capacitor is calculated according to the following formula. :

[0036] ;

[0037] S4. Based on the calculated tuning capacitor value, connect the transmitting coil, tuning capacitor, AC control module, pre-polarization coil and pre-polarization control module, and receiving coil and receiving control module.

[0038] S5. Connect to the power supply and use the host computer to control the transmission and reception of pre-polarized pulses and AC pulses, process the returned data, and detect the occurrence of disaster water in the unknown area in front of the roadway.

[0039] Preferably, in the borehole dimension, the step of using nuclear magnetic resonance (NMR) detection to detect the direction of fracture water around the borehole in the underground engineering area with a logging probe is as follows:

[0040] S1. In underground engineering areas with boreholes, use an RF cable to connect the probe to the well logging surface workstation and lower the probe into the borehole;

[0041] S2. Configure the transmission frequency, transmission pulse width, number of pulses, sampling time, and number of superpositions on the host computer, and perform the transmission and reception process.

[0042] S3. Perform noise reduction and inversion on the received signal data returned by the host computer to determine the water content and direction of the water around the well.

[0043] Preferably, in the core dimension, core sampling is performed, and nuclear magnetic resonance (NMR) is used for measurement and calibration to qualitatively and quantitatively detect the enrichment of hazardous water. The specific steps are as follows:

[0044] S1. Use a drilling rig to take soil or rock samples at the test site and use a low-field indoor nuclear magnetic resonance instrument to test the samples.

[0045] S2. Set the pulse type, relaxation waiting time, number of echoes, and number of superpositions in the host computer, and start the measurement calibration.

[0046] S3. Perform inversion on the measured results and analyze the specific porosity and water content of the rock core based on the results.

[0047] Compared with the prior art, the specific beneficial effects of the present invention are as follows:

[0048] The embodiments of the present invention rely on nuclear magnetic resonance detection technology, which has the advantages of in-situ, non-invasive, and direct detection. It can avoid damage to the strata while obtaining detection results, which is of great significance to environmental protection and engineering safety.

[0049] The embodiments of the present invention have multi-dimensional detection advantages, which can cover the entire process of underground engineering from site selection to construction. It can detect hazardous water for different environments and needs, and directly promote the simplification of engineering-related processes, cost reduction and efficiency improvement.

[0050] The embodiments of the present invention cover a wide range of detection areas, from broad to precise, and from coarse to fine in terms of detection accuracy, which can meet the multifaceted requirements of underground disaster water detection, making it both comprehensive and flexible. Attached Figure Description

[0051] Figure 1 A flowchart of a method for detecting underground hazardous water using multi-dimensional nuclear magnetic resonance (NMR) in borehole cores, provided in an embodiment of the present invention;

[0052] Figure 2 A schematic diagram illustrating the layout of a multi-dimensional nuclear magnetic resonance (NMR) method for detecting underground hazardous water using borehole cores, provided in an embodiment of the present invention.

[0053] Figure 3 A flowchart of nuclear magnetic resonance detection transmission and reception provided for embodiments of the present invention;

[0054] Figure 4 This is a partial schematic diagram of a nuclear magnetic resonance detection system provided in an embodiment of the present invention, wherein (a) is a schematic diagram of a prepolarization subsystem, (b) is a schematic diagram of a transmitting subsystem, and (c) is a schematic diagram of a receiving subsystem. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0056] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0057] like Figure 1 The diagram shown is a flowchart of a method for detecting underground hazardous water using multi-dimensional nuclear magnetic resonance (NMR) in borehole cores, according to an embodiment of the present invention. The layout is illustrated in the diagram. Figure 2 As shown, the specific implementation method includes the following steps:

[0058] S1. Using nuclear magnetic resonance detection, a large area of ​​transmission lines is laid on the ground, and small receiving coils are used in the air to quickly scan and detect to delineate the approximate range of underground water hazards.

[0059] This step is typically applied in the site selection phase of underground engineering projects. It is suitable for areas with unclear geological data, and involves a relatively rough and rapid scanning and exploration to roughly delineate the extent of underground hazardous water. The specific workflow includes:

[0060] Due to the influence of geographical location and surrounding electromagnetic environment, the intensity of the geomagnetic field varies from place to place. A magnetometer is used to measure the intensity of the geomagnetic field at the site. ;

[0061] The strength of the Earth's magnetic field directly affects the Larmor frequency of hydrogen protons in water (Lammor frequency: the frequency of the applied magnetic field that causes hydrogen protons to exhibit nuclear magnetic resonance). Therefore, the local Larmor frequency can be calculated using the following formula. :

[0062] ;

[0063] In the formula, The gyromagnetic ratio of hydrogen protons is typically taken as 0.04258;

[0064] A large area of ​​transmission loops is laid on the ground in the area to be tested, usually a 100m*100m square coil or a figure-eight coil;

[0065] To transmit Larmor frequency excitation pulses underground and most effectively excite hydrogen protons in the water, a capacitor is added to the transmitting circuit for tuning. Essentially, this capacitor acts as a frequency selector, converting the square wave into a Larmor frequency sine wave to concentrate the energy. An LCR meter is used to measure the inductance of the transmitting coil. The value of the harmonic capacitor is calculated according to the following formula. :

[0066] ;

[0067] Based on the calculated tuning capacitor value, the transmitting coil, tuning capacitor box, transmitter and power supply are connected on the ground. After the transmitting host computer sets the parameters such as the frequency, duration and number of superpositions of the transmitting pulse, the transmission of the excitation pulse begins.

[0068] After receiving the corresponding receiving parameters set by the host computer, a drone carrying a small receiving coil is used in the air to quickly scan and detect the area defined by the transmitting coil. The overall transmission and reception process is as follows: Figure 3 As shown;

[0069] Based on the transmission and reception timestamps recorded by the GPS module, the received signal data returned by the host computer is denoised and inverted to delineate the approximate range of underground water hazards.

[0070] S2. Within the approximate area of ​​the delineated underground hazardous water, nuclear magnetic resonance detection method is used to lay out small-area ground-based transmission and reception loops to determine the specific location of the underground hazardous water with high resolution.

[0071] This step is typically applied in the site selection phase of underground engineering projects, where further refined exploration is conducted after the area has been delineated using S1. It can also be applied in areas with relatively clear geological data, skipping the S1 exploration step and directly performing high-resolution nuclear magnetic resonance (NMR) detection of hazardous water at the surface level. The specific workflow includes:

[0072] First, the local geomagnetic field strength is measured using a magnetometer. The measurement process and reasons are the same as described in S1. The Larmor frequency is then calculated using the same method.

[0073] In areas with abnormal underground water hazards where the location is roughly determined, a small area of ​​AC transmission loop is laid, usually a 5m*5m square coil. The side length can be appropriately increased or decreased depending on the terrain.

[0074] Perform the tuning process using the same method as in step S1;

[0075] A DC pre-polarization coil and a receiving coil of the same size as the AC transmitting coil are laid. The DC pre-polarization is to pass a strongly polarized DC current into the ground before the AC transmission process, which strengthens the geomagnetic field and can effectively increase the amplitude of the nuclear magnetic resonance signal, thereby improving the resolution and accuracy of the detection.

[0076] Connecting the transmitting coil, harmonic capacitor, AC control module, prepolarization coil and prepolarization control module, and receiving coil and receiving control module constitutes a nuclear magnetic resonance detection system, as shown in the partial schematic diagram below. Figure 4 As shown, the prepolarization subsystem is as follows: Figure 4 As shown in (a), the launch subsystem is as follows Figure 4 As shown in (b), the receiving subsystem is as follows Figure 4 As shown in (c);

[0077] Connect the power supply and set experimental parameters such as AC excitation pulse frequency, excitation duration, pre-polarization time, and superposition number on the host computer to carry out the transmission and reception process;

[0078] The received signal data transmitted back from the host computer is denoised and inverted to determine the specific location and corresponding water content of underground disaster water;

[0079] S3. Using nuclear magnetic resonance detection methods, vertical detection loops are used to conduct advanced detection of hazardous water at the working face in specific underground engineering tunnels;

[0080] This step is typically applied in underground engineering environments, such as tunnels and mines, to conduct advance detection of the potential for hazardous water when the geological conditions ahead are unknown. The specific workflow includes:

[0081] First, the geomagnetic field strength is measured using a magnetometer. The measurement process and reasons are the same as described in S1. The Larmor frequency is then calculated using the same method.

[0082] Because it is necessary to conduct advance detection in front of the tunnel face in the underground space, it is necessary to lay vertical coils. Specifically, first fix the telescopic coil frame, and then wind the transmitting and receiving coils on the coil frame, which is perpendicular to the ground and leans against the tunnel face.

[0083] Perform the tuning process using the same method as in step S1;

[0084] Connect the transmitting coil, harmonic capacitor, AC control module, receiving coil, and receiving control module;

[0085] Connect the power supply, set the experimental parameters such as AC excitation pulse frequency, excitation duration, and number of superpositions on the host computer, and carry out the transmission and reception process;

[0086] The received signal data transmitted back from the host computer is denoised and inverted to determine the occurrence of disaster water in front of the tunnel face in the underground space;

[0087] S4. Using nuclear magnetic resonance detection methods, a well logging probe is used to conduct refined detection of the direction of fracture water around the well in underground engineering areas with boreholes.

[0088] This step is typically applied when there are geological boreholes in the engineering area. It allows for the detection of the content and direction of fracture water around the borehole. The specific workflow includes:

[0089] A steel tape measure was used to detect the depth of water accumulation in the borehole and determine the distance at which the probe could be lowered, preventing water accumulation in the well from affecting the detection results of fracture water around the well.

[0090] The probe is connected to the logging surface workstation using an RF cable, and the probe is slowly lowered into the wellbore using a suspension bracket structure.

[0091] Configure parameters such as transmission frequency, transmission pulse width, number of pulses, sampling time, and number of superpositions on the host computer to carry out the transmission and reception process;

[0092] The received signal data transmitted back from the host computer is denoised and inverted to determine the water content and general direction of the water around the well.

[0093] S5. Based on project requirements, core samples will be taken and measured and calibrated using nuclear magnetic resonance detection methods to accurately and quantitatively detect the enrichment of hazardous water.

[0094] This step is typically applied when it is necessary to specifically calibrate and quantitatively analyze the porosity and moisture content of the soil or rock in the engineering area. The specific workflow includes:

[0095] The soil or rock samples are taken from the test site using a drilling rig, wrapped in Teflon film, and then placed in a Teflon container (the core component of Teflon is polytetrafluoroethylene, which does not contain hydrogen atoms and will not interfere with the nuclear magnetic resonance test results).

[0096] After calibrating the temperature of the low-field nuclear magnetic resonance instrument, a standard sample is placed in the instrument to precisely determine the center frequency and scan for 90° / 180° pulse widths.

[0097] After completing the preliminary preparations for the instrument, place the sample in the designated position in the sample slot, and set parameters such as pulse type, relaxation waiting time, number of echoes, and number of superpositions in the host computer for measurement calibration.

[0098] The measured results are inverted to obtain schematic diagrams of magnetic resonance parameters such as T2 and T1 times, which can then be further processed and analyzed to determine the specific porosity and water content of the rock core.

[0099] In summary, the embodiments of the present invention propose a comprehensive, multi-dimensional magnetic resonance groundwater detection method, which solves the problem that existing technologies often only detect a single dimension and cannot be implemented throughout the entire project, thereby achieving improvements in the direction of simplifying the engineering process and reducing costs and increasing efficiency.

[0100] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for detecting underground hazardous water using multi-dimensional nuclear magnetic resonance (NMR) of borehole core samples from open-pit wells, characterized in that... Includes the following steps: In the aerospace dimension, nuclear magnetic resonance detection method is used to lay transmission loops on the ground and use receiving coils in the air to scan and detect to delineate the range of underground hazardous water; On the ground level, within the delineated area of ​​underground hazardous water, nuclear magnetic resonance detection is used to lay ground-based transmission and reception loops to pinpoint the specific location of underground hazardous water. In the shaft dimension, nuclear magnetic resonance detection method is used to detect hazardous water at the working face in underground engineering tunnels using vertical detection loops; In terms of borehole dimension, nuclear magnetic resonance detection method is used to detect the direction of fracture water around the well in underground engineering areas with boreholes using well logging probes; In terms of core samples, core samples are taken and measured and calibrated using nuclear magnetic resonance (NMR) detection methods to qualitatively and quantitatively detect the enrichment of hazardous water.

2. The method for detecting underground water hazards using multi-dimensional nuclear magnetic resonance in borehole cores according to claim 1, characterized in that, In the aerospace dimension, the process of using nuclear magnetic resonance (NMR) detection methods, laying out transmission lines on the ground, and using receiving coils in the air to rapidly scan and detect to delineate the extent of underground hazardous water, is as follows: S1. Measure the geomagnetic field strength at the site using a magnetometer. The local Larmor frequency is calculated according to the following formula. : ； In the formula, The gyromagnetic ratio of hydrogen protons; S2. Lay the transmitting coil on the ground; S3. Measure the inductance of the laid transmitting coil. The value of the harmonic capacitor is calculated according to the following formula. : ； S4. Based on the calculated tuning capacitor value, connect the transmitting coil, tuning capacitor, transmitter and power supply to transmit the excitation pulse. In the air, use a drone equipped with a receiving coil to scan and detect the framed area. S5. Process the data received from the host computer and delineate the scope of underground water hazards.

3. The method for detecting underground water hazards using multi-dimensional nuclear magnetic resonance in borehole cores according to claim 1, characterized in that, On the ground level, within the delineated area of ​​underground hazardous water, the specific steps for determining the location of underground hazardous water using nuclear magnetic resonance (NMR) detection methods and laying ground-based transmission and reception loops are as follows: S1. Lay a transmitting coil on the ground within the demarcated area of ​​underground water hazard; S2. Lay a pre-polarized coil and a receiving coil of the same size as the transmitting coil on the ground; S3. Measure the geomagnetic field strength at the site using a magnetometer. The local Larmor frequency is calculated according to the following formula. : ； In the formula, The gyromagnetic ratio of hydrogen protons; S4. Measure the inductance of the laid transmitting coil. The value of the harmonic capacitor is calculated according to the following formula. : ； S5. Based on the calculated tuning capacitor value, connect the transmitting coil, tuning capacitor, AC control module, pre-polarization coil and pre-polarization control module, and receiving coil and receiving control module. S6. Connect the power supply and use the host computer to control the transmission and reception of prepolarization pulses and AC pulses, process the returned data, and determine the location and corresponding water content of underground disaster water.

4. The method for detecting underground water hazards using multi-dimensional nuclear magnetic resonance in borehole cores according to claim 1, characterized in that, In terms of shaft dimensions, the steps for detecting hazardous water at the working face in underground engineering tunnels using nuclear magnetic resonance (NMR) detection methods and vertical probe loops are as follows: S1. Determine the side length of the transmitting coil based on the size of the tunnel face in the underground project, and lay pre-polarized coils and receiving coils of the same size. S2. Measure the geomagnetic field strength at the site using a magnetometer. The local Larmor frequency is calculated according to the following formula. : ； In the formula, The gyromagnetic ratio of hydrogen protons; S3. Measure the inductance of the laid transmitting coil. The value of the harmonic capacitor is calculated according to the following formula. : ； S4. Based on the calculated tuning capacitor value, connect the transmitting coil, tuning capacitor, AC control module, pre-polarization coil and pre-polarization control module, and receiving coil and receiving control module. S5. Connect to the power supply and use the host computer to control the transmission and reception of pre-polarized pulses and AC pulses, process the returned data, and detect the occurrence of disaster water in the unknown area in front of the roadway.

5. The method for detecting underground water hazards using multi-dimensional nuclear magnetic resonance in borehole cores according to claim 1, characterized in that, In terms of borehole dimensions, the steps for detecting the direction of fracture water around the well using a well logging probe in underground engineering areas with boreholes using nuclear magnetic resonance detection methods are as follows: S1. In underground engineering areas with boreholes, use an RF cable to connect the probe to the well logging surface workstation and lower the probe into the borehole; S2. Configure the transmission frequency, transmission pulse width, number of pulses, sampling time, and number of superpositions on the host computer, and perform the transmission and reception process. S3. Perform noise reduction and inversion on the received signal data returned by the host computer to determine the water content and direction of the water around the well.

6. The method for detecting underground water hazards using multi-dimensional nuclear magnetic resonance in borehole cores according to claim 1, characterized in that, In terms of core samples, the process of taking core samples and using nuclear magnetic resonance (NMR) for measurement and calibration to qualitatively and quantitatively detect the enrichment of hazardous water involves the following steps: S1. Use a drilling rig to take soil or rock samples at the test site and use a low-field indoor nuclear magnetic resonance instrument to test the samples. S2. Set the pulse type, relaxation waiting time, number of echoes, and number of superpositions in the host computer, and start the measurement calibration. S3. Perform inversion on the measured results and analyze the specific porosity and water content of the rock core based on the results.

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