AU2020101824A4 - A multi-source short-offset frequency domain electromagnetic detection method - Google Patents
A multi-source short-offset frequency domain electromagnetic detection method Download PDFInfo
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- 238000001514 detection method Methods 0.000 title claims abstract description 27
- 230000005684 electric field Effects 0.000 claims abstract description 6
- 238000010586 diagram Methods 0.000 claims description 15
- 238000010276 construction Methods 0.000 claims description 3
- 230000002159 abnormal effect Effects 0.000 claims description 2
- 230000000694 effects Effects 0.000 claims description 2
- 238000010187 selection method Methods 0.000 claims description 2
- 238000000034 method Methods 0.000 abstract description 7
- 230000005672 electromagnetic field Effects 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 239000010438 granite Substances 0.000 description 2
- 230000002547 anomalous effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
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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
- G01V3/12—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with electromagnetic waves
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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
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06Q—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES; SYSTEMS OR METHODS SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES, NOT OTHERWISE PROVIDED FOR
- G06Q50/00—Information and communication technology [ICT] specially adapted for implementation of business processes of specific business sectors, e.g. utilities or tourism
- G06Q50/02—Agriculture; Fishing; Forestry; Mining
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- Environmental & Geological Engineering (AREA)
- Geology (AREA)
- General Life Sciences & Earth Sciences (AREA)
- General Physics & Mathematics (AREA)
- Geophysics (AREA)
- Geophysics And Detection Of Objects (AREA)
Abstract
The invention discloses a multi-source short-offset frequency domain electromagnetic
detection method, which comprises the following steps: different transmitting sources are
sequentially arranged in different positions of the observation point, and the distance between
the transmitting source and the observation point is 1 to 3 times the detection depth, and the
transmitting signals of different frequencies are transmitted from the source, the horizontal
electric field component is observed at the receiving point, and the signals excited by
different transmitting sources observed at the same measuring point are jointly inverted to
obtain the underground electrical structure. The invention proposes a frequency domain
electromagnetic method using multiple transmitting sources for joint detection, and shortens
the observation offset to 1 to 3 times the detection depth, which can significantly improve the
strength of the observation signal and the recognition accuracy of underground targets.
Description
PATENTS ACT 1990
A multi-source short-offset frequency domain electromagnetic detection method
The invention is described in the following statement:-
A multi-source short-offset frequency domain electromagnetic detection method
The invention relates to the technical field of geophysical prospecting, in particular to a
multi-source short-offset frequency domain electromagnetic detection method.
The traditional land controlled-source electromagnetic method generally uses only one
transmitting source to emit signals, and observes a set of orthogonal horizontal electric
and magnetic field components in the far field area. This data acquisition mode will bring
the shortcomings of weak signal and low resolution, and the detection accuracy of deep
targets is low. In fact, when the observation distance is greater than 1 times the skin
depth, the electromagnetic field has the ability to sound the earth. But when it is close to
the transmitting source, electromagnetic waves cannot be approximated to plane waves,
and traditional data processing methods based on wave impedance are no longer
applicable. Therefore, the development of an inversion method based on the amplitude of
a single electromagnetic field is one of the main solutions for near-source
electromagnetic detection. In addition, using different transmitting sources to "illuminate"
anomalous bodies can produce different electromagnetic coupling relationships,
especially for grounded wire sources with a "galvanic" field. By changing the
transmitting source-anomalous body- the geometric relationship of the receiving device
can obtain more accurate positioning of the underground medium.
The present invention proposes a frequency-domain electromagnetic method based on
multi-source transmitting and short-offset observation signals. The short-offset
observation can significantly improve the signal strength, and the use of multi-source
transmitting and joint inversion data can significantly improve target detection Accuracy.
The purpose of the present invention is to provide a multi-source short-offset frequency
domain electromagnetic detection method to solve the above-mentioned background art
problems.
In order to achieve the above objective, the present invention provides the following
technical solutions: the present invention provides a multi-source short-offset frequency
domain electromagnetic detection method, which includes the following steps:
Si. Lay a survey line on the abnormal area;
S2. Arrange the first transmitting source with a long wire grounded at both ends on one
side of the survey line to form a side device;
S3. Electromagnetic signals of different frequencies are emitted from the transmitting
source, the frequency range is generally 0.1-1OOOOHz;
S4. Use the receiver to observe the horizontal electric field component Ex point by point
along the survey line;
S5. Arrange a second transmitting source in the extension area of a certain end of the
survey line to form an axial observation device;
S6. Repeat steps S3 and S4;
S7. Perform joint inversion processing on the signals excited by different transmitting
sources observed at the same survey point to obtain the resistivity-depth profile of the
entire survey line.
Preferably, the length of the survey line in the step Si should be greater than twice the
lateral dimension of the geological anomaly.
Preferably, more transmitting sources are arranged in other locations as required, and the
arrangement of the other transmitting sources is the same as that of the first transmitting
source and the second transmitting source.
Preferably, the length of the transmitting source is denoted asLo,,,,which should
satisfy that L,,,, is greater than 1/2 of the length of the survey line, that is,
Lr >Llne 2/.
Preferably, the distance between the transmitting source and the survey line is an offset,
and the offset is equal to 1 to 3 times the target detection depth.
Preferably, in the step S7, the signals excited by different transmitting sources are
subjected to joint inversion processing to obtain the resistivity-depth profile.
Preferably, the selection method for deploying more transmitting sources is as follows: if
the effect of using two transmitting sources for observation is still not good, deploy more
transmitting sources in other positions.
The beneficial effects of the present invention are: the present invention sequentially
arranges different transmitting sources in different orientations of the observation point,
the distance between the transmitting source and the observation point is 1 to 3 times the
detection depth, the transmitting source emits signals of different frequencies, and the
level of observation at the receiving point electric field components are combined inversion of signals excited by different transmitting sources observed at the same measuring point to obtain the underground electrical structure. The invention proposes a frequency-domain electromagnetic method using multiple transmitting sources for joint detection, and shortens the observation offset to 1 to 3 times the detection depth, which can significantly improve the strength of the observation signal and the recognition accuracy of underground targets.
Figure 1 is a schematic diagram of the transceiver arrangement of the method of the
present invention;
Figure 2 is a graph of Ex response curves at different offsets under the side device of the
present invention;
Figure 3 is a schematic diagram of the preset wheel pressure-measured electrical signal of
the present invention.
Figure 4 is a diagram of inversion results of single-source and dual-source data according
to the present invention;
Figure 5 is a construction layout diagram of the present invention;
Figure 6 is a diagram of the measured Ex signal of the present invention;
Figure 7 is an inversion result diagram based on Si source data of the present invention;
Figure 8 is an inversion result diagram based on S2 source data of the present invention;
Figure 9 is a graph of the joint inversion result of the present invention based on S Iand
S2 source data.
The technical solutions in the embodiments of the present invention will be clearly and
completely described below in conjunction with the accompanying drawings in the
embodiments of the present invention. Obviously, the described embodiments are only a
part of the embodiments of the present invention, rather than all the embodiments. Based
on the embodiments of the present invention, all other embodiments obtained by those of
ordinary skill in the art without creative work shall fall within the protection scope of the
present invention.
Embodiment 1
Referring to Figures 1-9, the present invention discloses a frequency domain
electromagnetic detection method using multiple transmitting sources for joint detection.
The specific steps are as follows:
Carry out numerical simulation: design a five-layer earth model, the resistivity of each
layer is p =100Q , p 2 =10QF , P 3 =100QF P4=10 OQ P =100 OQ
, andthethicknessofeachlayeris hi=500m, h2=m100m, 3 =500m, h4=m100m
h5 = o . The length of the transmitting source is 1000m, the transmitting current is 1A,
and the transmitting frequency is 0.1-I0000Hz. Suppose the transmitting source of the
side device is Sl, and the transmitting source of the equatorial direction is S2.
Figure 2 shows the horizontal electric field component (Ex) response curve at different
offset distances under the condition of the side device under the above design parameters,
and Figure 3 shows the Ex response curve at different offset distances under the
equatorial device condition. It can be seen that regardless of the device type, the short
offset distance observation proposed by the present invention can significantly improve the strength of the electromagnetic field signal. Compared with traditional far-area observations, the signal amplitude can be increased by nearly two orders of magnitude.
Considering the short-offset observation (offset=2000m), Figure 4 shows the inversion
results of a single source data (Si and S2) and the joint inversion results of two source
data (S1+S2). It can be seen that inverting the data of a single source alone can only
reflect the shallow strata, but the resolution of the deep strata is lost. The joint inversion
of the data from the two transmitting sources can significantly improve the resolution of
the deep strata and successfully reveal the second low-resistance layer in the deep.
This method was used to conduct field surveys in an iron ore area in Dezhou City,
Shandong Province, China, with the purpose of detecting the location of the granite body
under the huge thickness and low resistance overburden. The construction layout is
shown in Figure 5. The parameters are: the length of the survey line is 1800 meters, the
length of the transmitting source S Iis 1600 meters, the offset distance from the survey
line is 3300 meters, the length of the transmitting source S2 is 1200 meters, the offset
distance from the survey line is 3800 meters, two launches The transmitting current of the
source is 14 amperes, the transmitting frequency range is 9600Hz-1Hz, the Ex
component of the horizontal electric field is observed, and the electrode distance MN is
meters.
One-dimensional inversion is performed on the data obtained when the two transmitting
sources Si and S2 work independently, and the resistivity-depth cross-sectional diagrams
are shown in Figure 7 and Figure 8, respectively. It can be seen that the inversion result
based on the S transmitting source only reflects the shallow strata, and the ability to
distinguish electrical changes in the formation is basically lost below the depth of about
800 meters. The inversion results based on the S2 transmitting source can reflect the deep
strata, but the electrical structure is rather messy, and there are many false anomalies
caused by sudden changes in resistivity. The data of the two transmitting sources are
jointly inverted, and the result is shown in Figure 9. It can be seen that the joint inversion
result not only reflects the deep electrical layer well, but also avoids the false anomaly
caused by the sudden change in resistivity, and the inversion result is more stable overall.
According to this result, a high-resistance granite body located in the depth of the survey
line 1200~1800 was discovered.
For those skilled in the art, it is obvious that the present invention is not limited to the
details of the foregoing exemplary embodiments, and the present invention can be
implemented in other specific forms without departing from the spirit or basic
characteristics of the present invention. Therefore, no matter from which point of view,
the embodiments should be regarded as exemplary and non-limiting. The scope of the
present invention is defined by the appended claims rather than the above description,
and therefore it is intended that all changes falling within the meaning and scope of
equivalent elements of the claims are included in the present invention. Any reference
signs in the claims should not be regarded as limiting the claims involved.
Claims (7)
1. A multi-source short-offset frequency domain electromagnetic detection method is
characterized in that it comprises the following steps:
Sl. Lay a survey line on the abnormal area;
S2. Arrange the first transmitting source with a long wire grounded at both ends on one
side of the survey line to form a side device;
S3. Electromagnetic signals of different frequencies are emitted from the transmitting
source, the frequency range is generally 0.1-1OOOOHz;
S4. Use the receiver to observe the horizontal electric field component Ex point by point
along the survey line;
S5. Arrange a second transmitting source in the extension area of a certain end of the
survey line to form an axial observation device;
S6. Repeat steps S3 and S4;
S7. Perform joint inversion processing on the signals excited by different transmitting
sources observed at the same survey point to obtain the resistivity-depth profile of the
entire survey line.
2. The multi-source short-offset frequency domain electromagnetic detection method
according to claim 1 is characterized in that the length of the survey line in the step SI
should be greater than twice the lateral size of the geological anomaly.
3. The multi-source short-offset frequency domain electromagnetic detection method
according to claim 1 is characterized in that more transmitting sources are arranged in
other positions as required. The arrangement of the other transmitting sources is the same
as the arrangement of the first transmitting source and the second transmitting source.
4. The multi-source short-offset frequency domain electromagnetic detection method
according to claim 1 is characterized in that the length of the transmitting source is
denoted as , and the requirement that L_, is greater than 1/2 of the length of the
survey line, namely L_, > L,, /2.
5. The multi-source short-offset frequency domain electromagnetic detection method
according to claim 1 is characterized in that the distance between the transmitting source
and the survey line is an offset, and the offset is equal to 1 to 3 times the target detection
depth.
6. The multi-source short-offset frequency domain electromagnetic detection method
according to claim 1 is characterized in that in the step S7, the signals excited by different
transmitting sources are subjected to joint inversion processing to obtain the resistivity
depth profile.
7. The multi-source short-offset frequency-domain electromagnetic detection method
according to claim 3 is characterized in that the selection method for deploying more
transmitting sources is that if two transmitting sources are used for observation, the effect
is still not good, then deploy more transmitting sources in other locations.
-1/5- 14 Aug 2020 2020101824
Figure 1. A schematic diagram of the transceiver arrangement
Figure 2. A graph of Ex response curves at different offsets under the side device
-2/5- 14 Aug 2020 2020101824
Figure 3.
A schematic diagram of the preset wheel pressure-measured electrical signal
Figure 4. A diagram of inversion results of single-source and dual-source data
-3/5- 14 Aug 2020 2020101824
Figure 5. A construction layout diagram
-4/5- 14 Aug 2020 2020101824
Figure 6. A diagram of the measured Ex signal
Figure 7. An inversion result diagram based on S1 source data
-5/5- 14 Aug 2020 2020101824
Figure 8. An inversion result diagram based on S2 source data
Figure 9. A graph of the joint inversion result based on S1 and S2 source data.
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| AU2020101824A AU2020101824A4 (en) | 2020-08-14 | 2020-08-14 | A multi-source short-offset frequency domain electromagnetic detection method |
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| AU2020101824A AU2020101824A4 (en) | 2020-08-14 | 2020-08-14 | A multi-source short-offset frequency domain electromagnetic detection method |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113406707A (en) * | 2021-06-10 | 2021-09-17 | 应急管理部国家自然灾害防治研究院 | Magnetotelluric multi-scale and multi-time-period detection method |
| CN113960684A (en) * | 2021-09-29 | 2022-01-21 | 江苏大学 | Apparent resistivity-depth profile generation method for short offset electromagnetic exploration |
-
2020
- 2020-08-14 AU AU2020101824A patent/AU2020101824A4/en active Active
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113406707A (en) * | 2021-06-10 | 2021-09-17 | 应急管理部国家自然灾害防治研究院 | Magnetotelluric multi-scale and multi-time-period detection method |
| CN113960684A (en) * | 2021-09-29 | 2022-01-21 | 江苏大学 | Apparent resistivity-depth profile generation method for short offset electromagnetic exploration |
| US20230341579A1 (en) * | 2021-09-29 | 2023-10-26 | Jiangsu University | Apparent resistivity-depth section generating method for short-offset electromagnetic exploration |
| CN113960684B (en) * | 2021-09-29 | 2024-03-19 | 江苏大学 | Apparent resistivity-depth profile generation method for short offset electromagnetic exploration |
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