CA2363337A1 - Surveying geophysical properties in wells for expropriation of minerals and tool therefor - Google Patents
Surveying geophysical properties in wells for expropriation of minerals and tool therefor Download PDFInfo
- Publication number
- CA2363337A1 CA2363337A1 CA002363337A CA2363337A CA2363337A1 CA 2363337 A1 CA2363337 A1 CA 2363337A1 CA 002363337 A CA002363337 A CA 002363337A CA 2363337 A CA2363337 A CA 2363337A CA 2363337 A1 CA2363337 A1 CA 2363337A1
- Authority
- CA
- Canada
- Prior art keywords
- electrode
- clay
- wall surface
- displacement current
- shale
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
- G01V3/18—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for well-logging
- G01V3/26—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for well-logging operating with magnetic or electric fields produced or modified either by the surrounding earth formation or by the detecting device
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
- Y02A90/30—Assessment of water resources
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- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Remote Sensing (AREA)
- Life Sciences & Earth Sciences (AREA)
- Electromagnetism (AREA)
- Environmental & Geological Engineering (AREA)
- Geology (AREA)
- General Life Sciences & Earth Sciences (AREA)
- General Physics & Mathematics (AREA)
- Geophysics (AREA)
- Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
Abstract
A method for determining clay and shale magnitudes in pore and bore spaces of geologic formations of commercial interest, comprising the steps of suspending an insulated electrode in a pore space proximate a wall surface thereof, applying a relatively low frequency displacement current to the insulated electrode thereby producing an electric field between the electrode and the wall surface, attracting electrons from water molecules on clay particles on the wall surface and sensing the displacement current as it determines the frequency of an oscillator circuit joined to the electrode through an LC tank circuit.
Description
TITLE: Surveying Geophysical Properties In Wells For Expropriation Of Minerals And Tool Therefore BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION:
This invention relates to an electrical process by which the characteristics of earth formations are recorded for the purpose of analysis of mineral resources.
DESCRIPTION OF RELATED ART:
The following art defines the present state of this field:
Turcotte et al., U.S. 4,093,854 describes a logging sonde including a standing wave type microwave linear particle accelerator excited by a magnetron and producing bursts of high energy electrons which can selectively bombard either a neutron emitting target or a photon emitting target. Means are provided to sense the variations in the amplitude of the microwave field in the linear accelerator and to control the frequency of the magnetron so as to maintain the 2o amplitude of the accelerating field at a reference value representative of the expected maximum amplitude value at resonance. Means are also provided to sense the variations in the temperature of the linear accelerator and to control the frequency of the magnetron so as to compensate for the variations in the resonant frequency of the accelerator that result from temperature induced changes the length thereof.
Vinegar et al., U.S. 4,769,606 describes a logging means and method for distinguishing between dispersed and laminated clay in earth formations. A wireline apparatus is employed consisting of a multifrequency induced polarization logging tool operating at extremely low frequencies, combined with other logging tools which measure the total amount of clay in the formation. A determination is then made of the fraction of the total clay content in the formation which is due to laminated clay.
Coates, U.S. 5,557,200 describes an improved system for using magnetic resonance techniques to obtain information relating to geologic structures. The system of the present invention uses values of the total porosity of a formation and the porosity obtained via NMR
pulse echo techniques to derive additional information relating to the underlying geologic structures, including resistivity and water saturation. Independent estimate is provided to account for the l0 presence of clay mineral content.
Taicher et al., U.S. 5,710,511 describes an electromagnetic wellbore logging tool including an elongated sonde adapted for traversing the wellbore, a source of alternating current, an antenna connected to the source of alternating current, and a receiver circuit connected to the antenna.
The receiver circuit provides an output corresponding to electromagnetic signals induced in the antenna. The invention includes at least one insulating insert disposed in an annular space between the exterior of the sonde and the wall of the wellbore. The insert extends in a direction so as to segment the paths of eddy current which would otherwise flow in the annular space. In a preferred embodiment, the logging tool includes a nuclear magnetic resonance apparatus having a longitudinal dipole antenna. The insulating inserts extend along the longitudinal axis of the tool so as to segment eddy current paths perpendicular to the longitudinal axis of the tool.
The prior art teaches the use of pulse echo techniques, microwave fields in linear accelerators, induced polarization, and nuclear magnetic resonance but does not teach the relatively simple use of an electrode introduced into a bore or core so as to form a displacement current with the walls of the bore, said current magnitude being inversely proportional to the frequency of an oscillator circuit joined to the electrode through an LC tank circuit. The present invention fulfills these needs and provides further related advantages as described in the following summary.
SUMMARY OF THE INVENTION
The present invention teaches certain benefits in construction and use which give rise to the objectives described below.
It is common to use tools for detecting clay and shale in the pore spaces of formations such as coal deposits, where the clay and shale content affect the value of the product. The invention to provides a tool attached to a cable with a core of insulated conductors for the two-fold purpose of lowering the tool into a well, and also providing electrical instrumentation interconnection to the tool from recording equipment at the surface. A constant electrical current is achieved by providing an electromotive force, and this measurable current changes in magnitude depending on the characteristics of the mineral formation. The results are recorded at the surface. In prior art techniques, the well must be filled with a conductive fluid or a radioactive isotope must be used, both approaches having severe logistical problems.
The present invention uses an electric field to dissociate hydrogen causing electron movement on the walls of the well. The hydrogen is present in polar water molecules which cling to clay 2o and shale particles deposited in pore spaces by migrating ground waters.
These seem to be present in most natural formations.
The present invention is a method for determining clay magnitudes in pore spaces within geologic formations such as coal and other natural deposits. The method comprising the steps of suspending an insulated electrode in a pore space proximate a wall surface thereof, applying a positively charged ion current to the insulated electrode thereby producing an electric field between the electrode and the wall surface, attracting electrons from water molecules on clay particles on the wall surface and sensing the ion current to determine the magnitude of clay in the wall surface.
A primary objective of the present invention is to provide an apparaW s and method of use of such apparatus that provides advantages not taught by the prior art.
Another objective is to provide such an invention capable of overcoming spurious readings due to eddy currents.
A further objective is to provide such an invention capable of detecting clay and shale 1 o magnitudes in geologic formations of coal, oil, shales, oil sands, potash and other deposits. , A still further objective is to provide an invention for determining clay and shale magnitudes in mineral deposits which is not unduly affected by conditions in the pore holes of use.
Other features and advantages of the present invention will become apparent from the following more detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings illustrate the present invention. In such drawings:
Figure 1 is an elevational view of the invention in cross-section; and Figure 2 is an electrical schematic diagram of an oscillator circuit thereof.
DETAILED DESCRIPTION OF THE INVENTION
FIELD OF THE INVENTION:
This invention relates to an electrical process by which the characteristics of earth formations are recorded for the purpose of analysis of mineral resources.
DESCRIPTION OF RELATED ART:
The following art defines the present state of this field:
Turcotte et al., U.S. 4,093,854 describes a logging sonde including a standing wave type microwave linear particle accelerator excited by a magnetron and producing bursts of high energy electrons which can selectively bombard either a neutron emitting target or a photon emitting target. Means are provided to sense the variations in the amplitude of the microwave field in the linear accelerator and to control the frequency of the magnetron so as to maintain the 2o amplitude of the accelerating field at a reference value representative of the expected maximum amplitude value at resonance. Means are also provided to sense the variations in the temperature of the linear accelerator and to control the frequency of the magnetron so as to compensate for the variations in the resonant frequency of the accelerator that result from temperature induced changes the length thereof.
Vinegar et al., U.S. 4,769,606 describes a logging means and method for distinguishing between dispersed and laminated clay in earth formations. A wireline apparatus is employed consisting of a multifrequency induced polarization logging tool operating at extremely low frequencies, combined with other logging tools which measure the total amount of clay in the formation. A determination is then made of the fraction of the total clay content in the formation which is due to laminated clay.
Coates, U.S. 5,557,200 describes an improved system for using magnetic resonance techniques to obtain information relating to geologic structures. The system of the present invention uses values of the total porosity of a formation and the porosity obtained via NMR
pulse echo techniques to derive additional information relating to the underlying geologic structures, including resistivity and water saturation. Independent estimate is provided to account for the l0 presence of clay mineral content.
Taicher et al., U.S. 5,710,511 describes an electromagnetic wellbore logging tool including an elongated sonde adapted for traversing the wellbore, a source of alternating current, an antenna connected to the source of alternating current, and a receiver circuit connected to the antenna.
The receiver circuit provides an output corresponding to electromagnetic signals induced in the antenna. The invention includes at least one insulating insert disposed in an annular space between the exterior of the sonde and the wall of the wellbore. The insert extends in a direction so as to segment the paths of eddy current which would otherwise flow in the annular space. In a preferred embodiment, the logging tool includes a nuclear magnetic resonance apparatus having a longitudinal dipole antenna. The insulating inserts extend along the longitudinal axis of the tool so as to segment eddy current paths perpendicular to the longitudinal axis of the tool.
The prior art teaches the use of pulse echo techniques, microwave fields in linear accelerators, induced polarization, and nuclear magnetic resonance but does not teach the relatively simple use of an electrode introduced into a bore or core so as to form a displacement current with the walls of the bore, said current magnitude being inversely proportional to the frequency of an oscillator circuit joined to the electrode through an LC tank circuit. The present invention fulfills these needs and provides further related advantages as described in the following summary.
SUMMARY OF THE INVENTION
The present invention teaches certain benefits in construction and use which give rise to the objectives described below.
It is common to use tools for detecting clay and shale in the pore spaces of formations such as coal deposits, where the clay and shale content affect the value of the product. The invention to provides a tool attached to a cable with a core of insulated conductors for the two-fold purpose of lowering the tool into a well, and also providing electrical instrumentation interconnection to the tool from recording equipment at the surface. A constant electrical current is achieved by providing an electromotive force, and this measurable current changes in magnitude depending on the characteristics of the mineral formation. The results are recorded at the surface. In prior art techniques, the well must be filled with a conductive fluid or a radioactive isotope must be used, both approaches having severe logistical problems.
The present invention uses an electric field to dissociate hydrogen causing electron movement on the walls of the well. The hydrogen is present in polar water molecules which cling to clay 2o and shale particles deposited in pore spaces by migrating ground waters.
These seem to be present in most natural formations.
The present invention is a method for determining clay magnitudes in pore spaces within geologic formations such as coal and other natural deposits. The method comprising the steps of suspending an insulated electrode in a pore space proximate a wall surface thereof, applying a positively charged ion current to the insulated electrode thereby producing an electric field between the electrode and the wall surface, attracting electrons from water molecules on clay particles on the wall surface and sensing the ion current to determine the magnitude of clay in the wall surface.
A primary objective of the present invention is to provide an apparaW s and method of use of such apparatus that provides advantages not taught by the prior art.
Another objective is to provide such an invention capable of overcoming spurious readings due to eddy currents.
A further objective is to provide such an invention capable of detecting clay and shale 1 o magnitudes in geologic formations of coal, oil, shales, oil sands, potash and other deposits. , A still further objective is to provide an invention for determining clay and shale magnitudes in mineral deposits which is not unduly affected by conditions in the pore holes of use.
Other features and advantages of the present invention will become apparent from the following more detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings illustrate the present invention. In such drawings:
Figure 1 is an elevational view of the invention in cross-section; and Figure 2 is an electrical schematic diagram of an oscillator circuit thereof.
DETAILED DESCRIPTION OF THE INVENTION
The above described drawing figures illustrate the invention in at least one of its preferred embodiments, which is further defined in detail in the following description.
In geologic formations of clay and shale, it is highly useful to determine the percent of clay and shale present prior to exploration. Such formations generally have porous cavities or spaces into which instruments may be lowered to provide testing. Bores may be made into the deposits to provide entry to instrumentation. The present invention is such an instrument and is capable of accurately determining the magnitude of clay and shale present in such formations. It does this by applying an electric field of sufficient strength to ionize hydrogen gas molecules on the surfaces of the walls of the bores and pores. Thus a capacitance charging cLUrent (displacement current) is produced between the wall surfaces and the electrode and its magnitude is an indication of the quantity of clay and/or shale in the aggregate of the wall surfaces.
The present invention is an apparatus for determining clay magnitudes in pore spaces of clay and shale geologic formations. The apparatus comprises an insulated electrode formed as a rod wrapped with a dialectic and electrically interconnected by an insulated conductor through an inductance-capacitance (LC) tank circuit to an oscillator circuit. The oscillator is preferably a Meissner oscillator as shown in Fig. 2. An elongated suspension tube engages the insulated electrode so that it may be placed adjacent to, or in contact with a selected wall surface in the pore space of the geologic formation. This is shown in Fig. 1.
As shown in Fig. 1, the invention comprises a cylindrical body 10, preferably 7.5 cm in diameter and 700 meters in length, and may contain several sections fitted together as shown, although these dimensions may be changed to fit each particular situation. A
copper cylindrical electrode 20 is fitted about the cylindrical body 10 and is wired by conductors 25 to capacitor C2 (Fig. 2). The electrode 20 is insulated by dielectric material 30 surrounding the electrode 20. Electrode 20 acts as one plate of a capacitor C4 with the surrounding formation wall 40 acting as the other plate, in a coaxial plate capacitor arrangement shown in Fig. 1. The plates 20, 40 are separated by material 30 forming capacitor C4. Clay is a natural ion exchanger, water molecules are polar bonded so that the positive hydrogen ion is displaced from its associated electron. This allows the electrons to be dissociated by a relatively small force electric field so that in a liquid medium these polar molecules align to present the negative and then the positive portions of the molecule toward the electrode 20 in each cycle of the alternating voltage presented at the electrode 20. Such a force may be equivalent to between one and ten thousand calories of energy. Since the force used in the present invention is insufficient to dissociate covalently bonded electrons, the present method is only able to generate a current related to clay particles with their polarized water molecules and hydrogen 1 o atoms. The oscillator shown in Fig. 2 provides a regulated pulsating voltage at the electrode 20.
The frequency is controlled by the time constant associated with the LC
combination C2 and L2 and C4. This frequency therefore depends upon the number of electrons available on the deposit wall surface, which, in W rn, depends upon the amount of polarized water molecule and thus, the amount of clay present. As the voltage applied to C4 is increased, the associated electric field strength increases as well. As the displacement clurent increases due to additional electron flow at the wall surface, the time constant in the LC circuit becomes longer and the frequency in the oscillator drops. The frequency of the oscillator is recorded at the secondary of transformer Tl and is inversely proportional to the quantity of clay and shale in the formation.
The active element in the oscillator circuit is a pentode vacuum tube having anode, control grid, screen grid, suppressor grid and cathode, the control grid is biased through a leak resistance to ground, the screen grid is joined through a primary winding of a test transformer, and the suppressor grid is shorted to the cathode.
The present invention method determines clay magnitudes in pore spaces of clay and shale inn geologic formations such as coal and comprises the steps of suspending an insulated electrode in a pore space proximate a wall slu-face thereof; applying a positively charged ion current to the insulated electrode; producing an electric field between the electrode and the wall surface;
attracting electrons from water molecules on the wall surfaces; and sensing the oscillator frequency to determine relative clay and shale magnitudes in the wall surface.
While the invention has been described with reference to at least one preferred embodiment, it is to be clearly understood by those skilled in the art that the invention is not limited thereto.
Rather, the scope of the invention is to be interpreted only in conjunction with the appended claims.
In geologic formations of clay and shale, it is highly useful to determine the percent of clay and shale present prior to exploration. Such formations generally have porous cavities or spaces into which instruments may be lowered to provide testing. Bores may be made into the deposits to provide entry to instrumentation. The present invention is such an instrument and is capable of accurately determining the magnitude of clay and shale present in such formations. It does this by applying an electric field of sufficient strength to ionize hydrogen gas molecules on the surfaces of the walls of the bores and pores. Thus a capacitance charging cLUrent (displacement current) is produced between the wall surfaces and the electrode and its magnitude is an indication of the quantity of clay and/or shale in the aggregate of the wall surfaces.
The present invention is an apparatus for determining clay magnitudes in pore spaces of clay and shale geologic formations. The apparatus comprises an insulated electrode formed as a rod wrapped with a dialectic and electrically interconnected by an insulated conductor through an inductance-capacitance (LC) tank circuit to an oscillator circuit. The oscillator is preferably a Meissner oscillator as shown in Fig. 2. An elongated suspension tube engages the insulated electrode so that it may be placed adjacent to, or in contact with a selected wall surface in the pore space of the geologic formation. This is shown in Fig. 1.
As shown in Fig. 1, the invention comprises a cylindrical body 10, preferably 7.5 cm in diameter and 700 meters in length, and may contain several sections fitted together as shown, although these dimensions may be changed to fit each particular situation. A
copper cylindrical electrode 20 is fitted about the cylindrical body 10 and is wired by conductors 25 to capacitor C2 (Fig. 2). The electrode 20 is insulated by dielectric material 30 surrounding the electrode 20. Electrode 20 acts as one plate of a capacitor C4 with the surrounding formation wall 40 acting as the other plate, in a coaxial plate capacitor arrangement shown in Fig. 1. The plates 20, 40 are separated by material 30 forming capacitor C4. Clay is a natural ion exchanger, water molecules are polar bonded so that the positive hydrogen ion is displaced from its associated electron. This allows the electrons to be dissociated by a relatively small force electric field so that in a liquid medium these polar molecules align to present the negative and then the positive portions of the molecule toward the electrode 20 in each cycle of the alternating voltage presented at the electrode 20. Such a force may be equivalent to between one and ten thousand calories of energy. Since the force used in the present invention is insufficient to dissociate covalently bonded electrons, the present method is only able to generate a current related to clay particles with their polarized water molecules and hydrogen 1 o atoms. The oscillator shown in Fig. 2 provides a regulated pulsating voltage at the electrode 20.
The frequency is controlled by the time constant associated with the LC
combination C2 and L2 and C4. This frequency therefore depends upon the number of electrons available on the deposit wall surface, which, in W rn, depends upon the amount of polarized water molecule and thus, the amount of clay present. As the voltage applied to C4 is increased, the associated electric field strength increases as well. As the displacement clurent increases due to additional electron flow at the wall surface, the time constant in the LC circuit becomes longer and the frequency in the oscillator drops. The frequency of the oscillator is recorded at the secondary of transformer Tl and is inversely proportional to the quantity of clay and shale in the formation.
The active element in the oscillator circuit is a pentode vacuum tube having anode, control grid, screen grid, suppressor grid and cathode, the control grid is biased through a leak resistance to ground, the screen grid is joined through a primary winding of a test transformer, and the suppressor grid is shorted to the cathode.
The present invention method determines clay magnitudes in pore spaces of clay and shale inn geologic formations such as coal and comprises the steps of suspending an insulated electrode in a pore space proximate a wall slu-face thereof; applying a positively charged ion current to the insulated electrode; producing an electric field between the electrode and the wall surface;
attracting electrons from water molecules on the wall surfaces; and sensing the oscillator frequency to determine relative clay and shale magnitudes in the wall surface.
While the invention has been described with reference to at least one preferred embodiment, it is to be clearly understood by those skilled in the art that the invention is not limited thereto.
Rather, the scope of the invention is to be interpreted only in conjunction with the appended claims.
Claims (9)
1. A method for determining clay and shale magnitudes in pore spaces of geologic formations comprising the steps of: suspending an insulated electrode in a pore space proximate a wall surface thereof; applying a positive pulsating charge to the insulated electrode thereby producing an electric field between the electrode and the wall surface;
establishing a displacement current between the wall surface and the electrode; and sensing the displacement current to determine clay and shale magnitude in the wall surface.
establishing a displacement current between the wall surface and the electrode; and sensing the displacement current to determine clay and shale magnitude in the wall surface.
2. The method of claim 1 further comprising the step of applying an oscillator dependent on the displacement current for establishing an oscillator frequency and monitoring said frequency as an indication of clay and shale magnitudes.
3. An apparatus for determining clay magnitudes in pore spaces of clay and shale geologic formations comprising: an insulated electrode electrically interconnected through a tuned circuit to an oscillator circuit adapted for establishing an oscillator frequency dependent on a displacement current at the insulated electrode; and an elongated suspension tube engaging the insulated electrode adjacent to a selected wall surface in a pore space of a geologic formation.
4. The apparatus of claim 3 wherein the oscillator circuit provides an active element;
the active element providing a pentode vacuum tube with anode, control grid, screen grid, suppressor grid and cathode, the control grid biased through a leak resistance to ground, the screen grid joined through a primary winding of a test transformer, and the suppressor grid shorted to the cathode.
the active element providing a pentode vacuum tube with anode, control grid, screen grid, suppressor grid and cathode, the control grid biased through a leak resistance to ground, the screen grid joined through a primary winding of a test transformer, and the suppressor grid shorted to the cathode.
5. The apparatus of claim 4 wherein the oscillator circuit tuned circuit is a parallel connection of an inductance and a capacitance.
6. An apparatus for determining relative amounts of clay and shale in mineral deposits comprising an oscillator circuit adapted for applying a pulsating voltage to a suspended electrode placed in proximity to a cavity wall of the mineral deposit.
7. The apparatus of claim 6 further comprising means for measuring a displacement current in the electrode.
8. The apparatus of claim 7 further comprising means for controlling a frequency of the oscillator relative to the displacement current in the electrode.
9. The apparatus of claim 8 further comprising means for limiting an electric field strength associated with the displacement current in the electrode.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002363337A CA2363337A1 (en) | 2001-12-04 | 2001-12-04 | Surveying geophysical properties in wells for expropriation of minerals and tool therefor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002363337A CA2363337A1 (en) | 2001-12-04 | 2001-12-04 | Surveying geophysical properties in wells for expropriation of minerals and tool therefor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2363337A1 true CA2363337A1 (en) | 2002-04-14 |
Family
ID=4170581
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002363337A Abandoned CA2363337A1 (en) | 2001-12-04 | 2001-12-04 | Surveying geophysical properties in wells for expropriation of minerals and tool therefor |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2363337A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110736422A (en) * | 2019-09-12 | 2020-01-31 | 中国地质大学（武汉） | prefabricated magnetic field layout system and deformation state response method |
-
2001
- 2001-12-04 CA CA002363337A patent/CA2363337A1/en not_active Abandoned
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110736422A (en) * | 2019-09-12 | 2020-01-31 | 中国地质大学（武汉） | prefabricated magnetic field layout system and deformation state response method |
| CN110736422B (en) * | 2019-09-12 | 2020-09-29 | 中国地质大学（武汉） | Prefabricated magnetic field layout system and deformation state response method |
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| EEER | Examination request | ||
| FZDE | Dead |