CN113156523A - Carrier transient electromagnetic system and test method thereof - Google Patents

Carrier transient electromagnetic system and test method thereof Download PDF

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Publication number
CN113156523A
CN113156523A CN202110598458.1A CN202110598458A CN113156523A CN 113156523 A CN113156523 A CN 113156523A CN 202110598458 A CN202110598458 A CN 202110598458A CN 113156523 A CN113156523 A CN 113156523A
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host
mobile terminal
data
coil
carrier
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胡雄武
陈人峻
孔冰清
徐标
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Anhui University of Science and Technology
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Anhui University of Science and Technology
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    • 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
    • G01V3/08—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices
    • G01V3/10—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices using induction coils

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Abstract

The invention discloses a carrier transient electromagnetic system and a test method thereof, belonging to the field of coal mining. The amplitude of the primary field of the carrier wave section is greatly reduced by reasonably arranging the transmitting coil and the receiving coil, the primary field keeps constant by transmitting linear turn-off current, the interference of the primary field of the carrier wave section is thoroughly eliminated, a carrier wave section pure secondary field signal is obtained, the fine detection of the geoelectrical information of shallow geology is realized by calculating and imaging the apparent resistivity, and the problem of exploration blind areas existing in the traditional transient electromagnetic method is solved.

Description

Carrier transient electromagnetic system and test method thereof
Technical Field
The invention relates to the field of transient electromagnetism, in particular to a carrier transient electromagnetic system and a test method thereof.
Background
Transient electromagnetism has significant advantages for underground medium detection as an important geophysical prospecting method. At present, the method observes signals (attenuation sections) of secondary fields after emission current is cut off to obtain electrical characteristics of underground media, but the secondary fields of the attenuation sections cannot accurately reflect the electrical characteristics of the media due to early data distortion caused by primary field interference, and detection blind areas are caused. Although the existing transient electromagnetic technology is greatly improved in the aspects of transmitting current turn-off, coil devices and the like, the problem of blind areas is not completely solved, and the actual shallow layer detection capability is still insufficient. Research shows that the secondary field in the carrier band (in the process of switching off the emission current) is more sensitive to the response of the electric information of the shallow layer and has high response amplitude compared with the secondary field in the attenuation band.
Disclosure of Invention
The invention aims to provide a carrier transient electromagnetic system and a test method thereof, so as to improve the detection capability of a transient electromagnetic method on shallow geological information.
The invention is realized by the following technical scheme:
a carrier transient electromagnetic system includes a support, a transmitting coil, a receiving coil, a host, a connecting wire, and a mobile terminal.
Further, the support piece comprises a box body, a connecting rod, a main frame, a roller and a distance measuring wheel. The box body is made of insulating plastic materials and is used for fixing the transmitting coil and the receiving coil and installing rollers on two sides; the connecting rod is used for installing a connecting wire and fixing the main frame and the box body; the main frame is used for fixing the main machine, and two sides of the main frame are respectively provided with a distance measuring wheel and a roller; measuring and recording the moving distance by the distance measuring wheel; the box, connecting rod and main frame can be dismantled.
Furthermore, the transmitting coil and the receiving coil are circular and have adjustable turns, the ratio of the radius a of the transmitting coil to the radius C of the receiving coil is 1 (0.1-0.9), the distance from the center O of the transmitting coil to the center O' of the receiving coil is L, and the ratio of a to L is 1 (2.452-2.675).
Furthermore, the transmitting coil and the receiving coil are coplanar and are connected with a host through a connecting wire, and the vertical distance from the host to OO' is more than or equal to 3.5 m; the host establishes communication and data transmission with the mobile terminal through the built-in Wi-Fi; the host machine measures geodetic coordinates through a built-in GPS; the host is used for emitting linear turn-off current, and the turn-off time is adjustable.
Furthermore, the mobile terminal is provided with acquisition software which has the functions of setting instructions, receiving and processing data, imaging and the like.
A carrier transient electromagnetic test method, comprising the steps of:
s1: laying exploration measuring lines and measuring points according to detection requirements;
s2: carrying out test work and determining the optimal acquisition parameters;
s3: implementing data acquisition and transmitting data to the mobile terminal in real time; the mobile terminal preprocesses, processes and images data in real time;
s4: and analyzing the electrical characteristics of the underground medium according to the apparent resistivity image.
Further, the test in S2 is used as a test for determining observation parameters such as current turn-off time and emission current intensity, and a carrier segment primary field U1And (4) measuring and testing.
Further, in the step S3, the data acquisition is to set acquisition parameters at the mobile terminal, transmit an instruction to the host, and the host performs data acquisition on each measurement point according to the instruction. The preprocessing is to subtract U from the actually measured data U of the carrier segment1Obtaining the secondary field U of the carrier segment2And is paired with U2And performing smooth filtering. The processing and imaging are to calculate apparent resistivity and generate a contour image.
The invention has the beneficial effects that:
1. the method can effectively observe the carrier segment secondary field signal, realize the fine detection of the shallow geological information, and thoroughly solve the problem that the shallow geological information cannot be distinguished by the traditional transient electromagnetic method;
2. the invention can control the detection depth by adjusting the linear turn-off time of the emission current, and is more accurate than the traditional transient electromagnetic method;
3. compared with the traditional transient electromagnetic method, the invention has the advantages that the signal intensity of the primary field is greatly reduced, the stability is kept unchanged in the carrier wave section, and the interference of the primary field to the secondary field can be thoroughly eliminated.
Drawings
The invention will be further described with reference to the accompanying drawings.
FIG. 1 is a schematic diagram of a carrier transient electromagnetic system of the present invention;
FIG. 2 is a side view of a carrier transient electromagnetic system of the present invention;
FIG. 3 is a schematic diagram of a transmit coil and a receive coil of the present invention;
FIG. 4 is a graph of the variation of the magnetic flux of the receiver coil of the present invention;
FIG. 5 is a graph of the variation of the emission current of the present invention;
Detailed Description
The technical scheme of the invention is clearly and completely described below with reference to the accompanying drawings.
As shown in fig. 1 and 2, a carrier transient electromagnetic system includes a support 1, a transmitting coil 2, a receiving coil 4, a host 3, a connecting wire 5, and a mobile terminal 8. The support 1 comprises a case 11, a connecting rod 12, a main frame 13, rollers 7 and a distance measuring wheel 6. The box body 11 is made of insulating plastic and is used for fixing the transmitting coil 2 and the receiving coil 4, and rollers 7 are arranged on two sides of the box body; the connecting rod 12 is used for installing the connecting wire 5 and fixing the main frame 13 and the box body 11; the main frame 13 is used for fixing the main machine 3, and two sides of the main frame are respectively provided with a distance measuring wheel 6 and a roller 7; the distance measuring wheel 6 measures and records the moving distance; the box body 11, the connecting rod 12 and the main frame 13 can be detached. The transmitting coil 2 and the receiving coil 4 are circular and have adjustable turns, the ratio of the radius a of the transmitting coil 2 to the radius C of the receiving coil 4 is 1 (0.1-0.9), the distance from the center O of the transmitting coil 2 to the center O' of the receiving coil 4 is L, and the ratio of a to L is 1 (2.452-2.675). The transmitting coil 2 and the receiving coil 4 are coplanar and are connected with the host 2 through a connecting wire 5, and the vertical distance from the host 2 to OO' is more than or equal to 3.5 m; the host 2 establishes communication and data transmission with the mobile terminal 8 through the built-in Wi-Fi; the host machine 2 measures geodetic coordinates through a built-in GPS; the host 2 is used to emit a linear off current and the off time is adjustable. The mobile terminal 8 is configured with acquisition software, and the acquisition software has the functions of setting instructions, receiving and processing data, imaging and the like.
Carrier transient electromagnetic system principle: as shown in FIG. 3, the xoy plane has a single-turn current-carrying circular coil with radius a, the center of the circle is coincident with the origin of coordinates, the current is I, and the vacuum permeability is μ0Arbitrarily take a point in space
Figure BDA0003092052680000041
(
Figure BDA0003092052680000042
For the length of the point vector, theta is the tilt angle,
Figure BDA0003092052680000043
is the azimuth angle), the magnetic induction B is:
Figure BDA0003092052680000044
in the formula:
Figure BDA0003092052680000045
Figure BDA0003092052680000046
Figure BDA0003092052680000047
simplifying to obtain:
Figure BDA0003092052680000048
in the formula:
Figure BDA0003092052680000049
wherein:
Figure BDA00030920526800000410
respectively, the magnetic induction per unit vector on the xoy plane.
According to the symmetry of the current-carrying coil magnetic field, the spatial arbitrary point B is only related to r and theta, i.e.
Figure BDA00030920526800000411
In the formula
Figure BDA00030920526800000412
I.e. sin θ is 1, the obtained xoy plane is
Figure BDA0003092052680000051
The key of the carrier transient electromagnetic system is the primary field magnetic flux phi in the carrier segment receiving coilTTending towards 0. Suppose that
Figure BDA0003092052680000052
Can receive phiTThe expression is as follows:
Figure BDA0003092052680000053
simple and easy to obtain
Figure BDA0003092052680000054
In the formula
Figure BDA0003092052680000055
He Wei
Figure BDA0003092052680000056
Full elliptic integrals of the first and second type, respectively.
The above formula (6) is numerically solved, and when a is 1m, I is 1A, C is 0.1m, and L is 3m, phi isT＝2.79394832438472e-10T·m。
In FIG. 4, phi is given when a is 1m and C is 0.1mTThe L/a relationship curve shows that phi exists when L/a is 1 (2-3.5)TL value of 0. Through calculation, the actual values of a, C and L are in accordance with the following table.
C/a, L/a and phimTable of the corresponding relationship between the three
C/a L/a φT
0.1 2.452～2.453 -4.89890224422383e-13～4.10623155119736e-13
0.2 2.461～2.462 -1.46944181622529e-12～2.14042733671610e-12
0.3 2.476～2.477 -6.66723092024184e-13～7.47963802419011e-12
0.4 2.496～2.497 -6.21697362437416e-12～8.35124167983244e-12
0.5 2.522～2.523 -5.76102960694360e-12～1.71359978814257e-11
0.6 2.553～2.554 -1.09026014350474e-11～2.23209950844902e-11
0.7 2.589～2.590 -1.81333421030043e-11～2.74771354015583e-11
0.8 2.630～2.631 -1.08242285324587e-11～4.92671407725993e-11
0.9 2.675～2.676 -2.95485023725695e-11～4.73048955191273e-11
A carrier transient electromagnetic test method is based on the following principle: during the turn-off of the linear turn-off current 9 (see fig. 5), the carrier segment primary field
Figure BDA0003092052680000061
It can be seen that U1And current off time t0Is inversely proportional and constant, so U1Can be eliminated.
The method comprises the following specific steps:
(1) laying exploration measuring lines and measuring points as required;
(2) determining a, C and L according to the exploration target, and firstly determining the off-time t of the emission current through field test0And current intensity and other observation parameters; secondly, inMeasuring primary field U of carrier segment by suspension test of carrier transient system1；
(3) Setting parameters such as emission current, turn-off time and point distance at the mobile terminal 8, sending an acquisition instruction to the host 3 through Wi-Fi, and acquiring data by the host 3 according to the instruction, wherein the acquired data comprises the moving distance of the distance measuring wheel, GPS coordinates and carrier data U; when data acquisition of one measuring point is completed, the host 3 sends the data to the mobile terminal 8 in real time, and acquisition software is arranged in the mobile terminal 8 to carry out real-time preprocessing, processing and imaging on the data; by analogy, the acquisition, pretreatment, processing and imaging of all the measuring point data are completed; wherein the preprocessing is to subtract U from U1Obtaining a carrier segment secondary field U2And is paired with U2Carrying out smooth filtering; the processing and imaging are to the pre-processed U2Performing apparent resistivity calculation and generating a contour image;
(4) and evaluating the geoelectric characteristics of the underground medium according to the apparent resistivity image to achieve the geological exploration target.

Claims (8)

1. A carrier transient electromagnetic system, comprising: the carrier transient electromagnetic system comprises a support piece, a transmitting coil, a receiving coil, a host, a connecting wire and a mobile terminal.
2. The system of claim 1, wherein: the supporting piece comprises a box body, a connecting rod, a main frame, a roller and a distance measuring wheel; the box body is made of insulating plastic materials and is used for fixing the transmitting coil and the receiving coil and installing rollers on two sides; the connecting rod is used for installing a connecting wire and fixing the main frame and the box body; the main frame is used for fixing the main machine, and two sides of the main frame are respectively provided with a distance measuring wheel and a roller; measuring and recording the moving distance by the distance measuring wheel; the box body, the connecting rod and the main frame are detachable.
3. The system of claim 1, wherein: the transmitting coil and the receiving coil are circular and adjustable in turn number, the radius ratio of the radius a of the transmitting coil to the radius C of the receiving coil is 1 (0.1-0.9), the distance from the center O of the transmitting coil to the center O' of the receiving coil is L, and the ratio of a to L is 1 (2.452-2.675).
4. The system of claim 1, wherein: the transmitting coil and the receiving coil are coplanar and are connected with a host through a connecting wire, and the vertical distance from the host to OO' is more than or equal to 3.5 m; the host establishes communication and data transmission with the mobile terminal through the built-in Wi-Fi; the host machine measures geodetic coordinates through a built-in GPS; the host is used for emitting linear turn-off current, and the turn-off time is adjustable.
5. The system of claim 1, wherein: the mobile terminal is provided with acquisition software, and the acquisition software has the functions of setting instructions, receiving and processing data and imaging.
6. A test method based on the system of any one of claims 1 to 5, characterized in that: the test method comprises the following steps:
s1: laying exploration measuring lines and measuring points according to detection requirements;
s2: carrying out test work and determining the optimal acquisition parameters;
s3: implementing data acquisition and transmitting data to the mobile terminal in real time; the mobile terminal preprocesses, processes and images data in real time;
s4: and analyzing the electrical characteristics of the underground medium according to the apparent resistivity image.
7. The test method of claim 6, wherein: in the S2, the test is used as a test for determining observation parameters such as current turn-off time, emission current intensity and the like and a carrier segment primary field U1And (4) measuring and testing.
8. The test method of claim 6, wherein: in the step S3, data acquisition is to set acquisition parameters at the mobile terminal, transmit an instruction to the host, and the host acquires data at each measurement point according to the instruction; the preprocessing is to subtract U from the actually measured data U of the carrier segment1Obtaining the secondary field U of the carrier segment2And is paired with U2Carrying out smooth filtering; the processing and imaging are to calculate apparent resistivity and generate a contour image.
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117148454A (en) * 2023-08-29 2023-12-01 合肥工业大学 Measurement device and method based on electromagnetic field receiving and transmitting synchronization

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117148454A (en) * 2023-08-29 2023-12-01 合肥工业大学 Measurement device and method based on electromagnetic field receiving and transmitting synchronization

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