AU2020101894A4 - A resistivity imaging method based on electrical source semi-airborne transient electromagnetic method - Google Patents
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- G01V3/165—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation specially adapted for use during transport, e.g. by a person, vehicle or boat operating with magnetic or electric fields produced or modified by the object or by the detecting device
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Abstract
The invention discloses a resistivity imaging method based on electrical source semi-airbome
transient electromagnetic method, which includes: setting observation points and detection
depths, according to which arranging emission sources and receiving devices; obtain the
voltage signal of the electrical source semi-airborne transient electromagnetic field in the
vertical direction through the receiving device, and calculate the early, late, and full-period
apparent resistivity; obtain the underground induced current distribution of the emitter.
According to the lateral and longitudinal components of the induced current, establish the
relationship between the imaging depth and the diffusion depth on the lateral and longitudinal
components of the induced current, respectively, to obtain the imaging depth when using the
transverse and longitudinal response; based on the early, late, and full-period apparent
resistivity, and the imaging depth when using the lateral response and the longitudinal
response, form a resistivity-imaging depth profile to complete resistivity imaging.
-1/8
S 1. Setting ob servation points and detection depths, according
to which arranging emission sources and receiving devices.
4;
S2. Obtain the voltage signal ofthe electrical source electrical
source semi-airborne transient electromagnetic field in the vertical
direction through the receiving device, and calculate the early,late,
andfUll-period apparent resistivity.
S3. Obtain the underground induced current distribution ofthe
emitter. According to the lateral and longitudinal components
ofthe induced current, establish the relationship between the
imaging depth and the diffusion depth on the lateral and
longitudinal components ofthe induced current, respectively,
to obtain the imaging depth when using the transverse and
longitudinal response.
J1b
S4. Based on the early, late, and fll-period apparent resistivity,
and the imaging depth when using the lateral response and the
longitudinal response, form a resistivity-imaging depth profile
to complete resistivity imaging
Figure 1
Description
-1/8
S 1. Setting ob servation points and detection depths, according to which arranging emission sources and receiving devices.
4; S2. Obtain the voltage signal ofthe electrical source electrical source semi-airborne transient electromagnetic field in the vertical direction through the receiving device, and calculate the early,late, andfUll-period apparent resistivity.
S3. Obtain the underground induced current distribution ofthe emitter. According to the lateral and longitudinal components ofthe induced current, establish the relationship between the imaging depth and the diffusion depth on the lateral and longitudinal components ofthe induced current, respectively, to obtain the imaging depth when using the transverse and longitudinal response.
J1b S4. Based on the early, late, and fll-period apparent resistivity, and the imaging depth when using the lateral response and the longitudinal response, form a resistivity-imaging depth profile to complete resistivity imaging
Figure 1
PATENTS ACT 1990
A resistivity imaging method based on electrical source semi-airborne transient
electromagnetic method
The invention is described in the following statement:-
A resistivity imaging method based on electrical source semi-airborne
transient electromagnetic method
The invention relates to the technical field of geophysical prospecting, in particular to a
resistivity imaging method based on the electrical source semi-airbome transient
electromagnetic method.
With the research of transient electromagnetic method gradually turning to high-altitude
mountain and other areas with complicated terrain and geological conditions for deep
exploration, electrical source semi-airborne transient electromagnetic method has
received more attention. The Electrical source semi-airbome transient electromagnetic
method arranges excitation sources on the ground surface, and carries the flying platform
to collect signals in the air. It combines the advantages of ground transient
electromagnetic method and aviation transient electromagnetic method. Compared with
ground transient electromagnetic method, it can effectively improve field work
effectiveness; compared with the aerial transient electromagnetic method, the exploration
depth is greater and the signal-to-noise ratio of the collected signal is higher. In recent
years, the electrical source semi-airborne transient electromagnetic method has developed
rapidly.
The electrical source semi-airborne transient electromagnetic method (SATEM) is
suitable for observation in lakes, swamps, mountainous areas and other areas with complex terrain due to its strong adaptability, large detection depth, and strong real-time performance. However, rapid detection has led to a rapid increase in the amount of received data. The rapid realization of large-scale, high-precision imaging is a key technology and problem for the wide application of the electrical source semi-airborne transient electromagnetic method, and it is also a technical problem that needs to be solved urgently.
The purpose of the present invention is to provide a resistivity imaging method
based on the electrical source semi-airbome transient electromagnetic method, so as to
solve the technical problems in the prior art to significantly improve the imaging speed
and accuracy and provide great help for large-scale and rapid construction of
underground geoelectric structures.
In order to achieve the above objectives, the present invention provides the
following scheme. The present invention provides a resistivity imaging method based on
an electrical source semi-airbome transient electromagnetic method, which includes the
following steps:
Si. Setting observation points and detection depths, according to which arranging
emission sources and receiving devices.
S2. Obtain the voltage signal of the electrical source semi-airborne transient
electromagnetic field in the vertical direction through the receiving device, and calculate
the early, late, and full-period apparent resistivity.
S3. Obtain the underground induced current distribution of the emitter. According to the lateral and longitudinal components of the induced current, establish the relationship between the imaging depth and the diffusion depth on the lateral and longitudinal components of the induced current, respectively, to obtain the imaging depth when using the transverse and longitudinal response.
S4. Based on the early, late, and full-period apparent resistivity, and the imaging depth
when using the lateral response and the longitudinal response, form a resistivity-imaging
depth profile to complete resistivity imaging.
Preferably, in the step Si, the specific method of arranging the transmitting source and
the receiving device according to the observation point and the detection depth includes
that arrange grounded wires at both ends as the emission source, and mount the receiving
device on the UAV platform. The distance between the emission source and the
observation point is 0.5 to 3 times of the detection depth; the distance between the flight
altitude of the UAV and the ground is 0-1 times of the detection depth.
Preferably, in the step S2, the calculation method of early, late, and full-period
apparent resistivity includes: calculating the air response of the electrical source semi
airborne transient electromagnetic field in a uniform half-space according to the vertical
voltage signal of the electrical source semi-airborne transient electromagnetic field;
calculating the early, late, and full-period apparent resistivity based on the air response of
the electrical source semi-airborne transient electromagnetic field in a uniform half-space.
Preferably, the air response of the electrical source semi-airbome transient
electromagnetic field in a uniform half space is as formula 1:
8,(t)= 3PprS. 3E L U2U 1 2] 2 . ''''''''''''''' 1.......
3PESprz2 2 " 5 u2 u4 J R sing - 5u(u)- e u 5+-+ 2rcR' I rc 3 3
In the formula, R = r29+z2 , z is the flying height, r is the offset distance, c,(t) is the
vertical induced voltage, S is the effective area of the receiving device, PE is the
transmitting magnetic distance, p is the earth resistivity, u -+k2 , k is the
wavelength, and k is wave number, <p represents the angle between the receiving position
and the transmitting source, <p(u) represents the probability integral.
The early calculation of apparent resistivity P ris shown as formula 2:
27z R' .E,zt . . . . . . . . . . . 2 3Sr(R 5z. . in . I.. ...... 3Slr(R -5Z )sin,- I
In the formula, R = ±2 +-z2 , z is the flying height, r is the offset, S is the effective area
of the receiving device, 1 is the length of the emission source, and I is the induced
current underground.
The calculation of late apparent resistivity Pite is shown as formula 3:
po ( po SIlro,- sin? 22(p z ( 4S1lporz sin?) 2p2/3 .............. Plater 47ut 5te~o - tR tirRA ) .
In the formula, go is the magnetic permeability under vacuum, t is the time, A2 is the
difference between the induced voltage in the air and the induced voltage at the projection
position on the ground, and 8zo is the apparent resistivity of the ground.
The calculation method of the full-period apparent resistivity is to solve iteratively the early and late apparent resistivity respectively to obtain the variation curve of the early and the late apparent resistivity with u, and the full-period apparent resistivity is solved based on the turning point of the variation curve.
Preferably, the method for solving the full-period apparent resistivity based on the turning
point of the change curve comprises the following steps.
When u is greater than the turning point coordinate, the early apparent resistivity is
solved; when u is less than the turning point coordinate, the late apparent resistivity is
solved; when u is equal to the turning point coordinate, the average value of early and late
apparent resistivity is calculated to obtain the full- period apparent resistivity.
Preferably, the relationship between the imaging depth and the diffusion depth on
the lateral and longitudinal components of the induced current is a linear positive
correlation, as shown in formula 4 and formula 5:
6v = 0.816 2t .................................. 4
H = 0 .2 5 - ....................................... 5
In the formula, V2t/pu 0 - represents the diffusion depth of the induced current, t
represents the response time of the receiving device, 0- represents the electrical
conductivity of the earth, Uo represents the magnetic permeability under vacuum, and
(5y and 3 H represent the imaging depth during the lateral and the longitudinal
response, respectively.
The present invention discloses the following technical effects.
-'7
The present invention defines the apparent resistivity and imaging depth based on
the analysis of the diffusion law of the transverse and longitudinal induced currents in the
electromagnetic field construction process and the uniform half-space electrical source
SATEM's magnetic field and induced voltage in the air, and proposes a resistivity
imaging method based on electrical source semi-airborne transient electromagnetic
method. Complete the resistivity imaging by the combination of early and late accurate
solution of electrical source semi-airborne transient electromagnetic method with
horizontal and vertical imaging depth can significantly improve the imaging speed and
accuracy, and provide great help for large-scale and rapid construction of underground
geoelectric structure.
In order to explain the embodiments of the present invention or the technical solutions in
the prior art more clearly, the following will briefly introduce the drawings needed in the
embodiments. Obviously, the drawings in the following description are only some
embodiments of the present invention. For those of ordinary skill in the art, other
drawings can be obtained based on these drawings without creative labour.
Fig. 1 is a flow chart of resistivity imaging method based on electrical source ground-air
transient electromagnetic method.
Fig. 2 is a position diagram of an observation point, a transmitting source and a receiving
device of the present invention.
Fig. 3 is a graph showing the relationship between imaging depth and diffusion depth
wherein fig. 3(a) shows the relationship between imaging depth and induced current
diffusion depth in lateral response, and fig. 3(b) shows the relationship between imaging
depth and induced current diffusion depth in longitudinal response.
Fig. 4 is an early apparent resistivity comparison diagram calculated by the traditional
resistivity imaging method of six models and the resistivity imaging method in the
embodiment 1 of the present invention, wherein fig. 4(a) shows the comparison of early
apparent resistivity in model D, fig. 4(b) shows the comparison of early apparent
resistivity in model G, fig. 4(c) shows the comparison of early apparent resistivity in
model H, fig. 4(d) shows the comparison of early apparent resistivity in model K, fig.
4(e) shows the comparison of early apparent resistivity in model A and fig. 4(f) shows the
comparison of early apparent resistivity in model Q.
Fig. 5 is a comparison diagram of the change of early apparent resistivity with flight
altitude calculated by traditional resistivity imaging method and resistivity imaging
method of the invention in the embodiment 1.
Fig. 6 is a late apparent resistivity comparison diagram calculated by the traditional
resistivity imaging method of six models and the resistivity imaging method in the
embodiment 1 of the present invention, wherein fig. 6(a) shows the comparison of late
apparent resistivity in model D, fig. 6(b) shows the comparison of late apparent resistivity
in model G, fig. 6(c) shows the comparison of late apparent resistivity in model H, fig.
6(d) shows the comparison of late apparent resistivity in model K, fig. 6(e) shows the comparison of late apparent resistivity in model A and fig. 6(f) shows the comparison of late apparent resistivity in model Q.
Fig. 7 is a comparison diagram of the change of late apparent resistivity with flight
altitude calculated by traditional resistivity imaging method and resistivity imaging
method of the invention in the embodiment 1.
Fig. 8 is an imaging comparison diagram between the conventional resistivity imaging
method and the resistivity imaging method of the present invention in the embodiment 2
of the present invention, wherein, fig. 8(a) is an imaging diagram of the conventional
resistivity imaging method, and fig. 8(b) is an imaging diagram of the resistivity imaging
method of the present invention.
The technical scheme in the embodiments of the present invention will be described
clearly and completely with reference to the drawings in the embodiments of the present
invention. Obviously, the described embodiments are only part of the present invention
embodiments, not all of them. Based on the embodiments, all other embodiments
obtained by ordinary technicians in the field without creative labour belong to the scope
of protection of the present invention.
In order to make the above objects, features and advantages of the present invention more
obvious and easier to understand, the present invention will be further explained in detail
with reference to the drawings and specific embodiments.
Referring to fig. 1, this embodiment provides a resistivity imaging method based on
electrical source semi-airborne transient electromagnetic method, which includes the
following steps:
Si. Setting observation points and detection depths, according to which arranging
emission sources and receiving devices.
Setting observation points and detection depths, arranging grounding wires at both ends
as emission sources, mounting a receiving device on the unmanned aerial vehicle
platform, and receiving magnetic fields or voltage signals in three directions of X, Y and
Z axes through the receiving device, wherein the X axis is the emission source direction
and the distance between the emission source and the observation point is 0.5-3 times of
the detection depth. The distance between the flying height of the UAV and the ground is
-1 times of the detection depth, as shown in Figure 2.
S2. Acquiring the voltage signal of the electrical source semi-airbome transient
electromagnetic field in the vertical direction through the receiving device, calculating
the air response of the electrical source semi-airborne transient electromagnetic field in a
uniform half space according to the voltage signal, and calculating the early, late and full
term apparent resistivity of the receiving device according to the air response.
The flying height of UAV has a great influence on the response strength of electrical
source semi-airborne transient electromagnetic field in the air. It is unreasonable to
calculate the apparent resistivity of the ground by traditional method. Therefore, the
resistivity imaging based on electrical source semi-airborne transient electromagnetic method should first consider the influence of flying height of UAV and solve the definition of apparent resistivity.
In a uniform half-space, the response of the electrical source semi-airborne transient
electromagnetic field in the air is shown in formula (1):
3PEprS 2 _ U 2
,t=sin P ©(u)- -Te 2 3
2 3PESprz r sin~p 5©D(u)- -e ) 2u 2r 5+-+ 52 (1 2rcR' rcz 3 3
, In the formula, R = ±9r2+ 2 , z is the flying height, r is the offset distance, 6,(t) is the
vertical induced voltage, S is the effective area of the receiving device, PE is the
transmitting magnetic distance, p is the earth resistivity, u = 2+k2 , X is the
wavelength, and k is wave number, <p represents the angle between the receiving position
and the transmitting source, <p(u) represents the probability integral.
The early calculation of apparent resistivity p ,is shown as formula 2:
6 ~ 27z R' Cz t ...... P early =2 ....... (2) 2 3Slr(R -5z )sinqp I
Intheformula, R= +z2 , z is the flying height, r is the offset, S is the effective area
of the receiving device, 1 is the length of the emission source, and I is the induced
current underground.
The calculation of late apparent resistivity ptEr is shown as formula 3:
Po S1rp. sin 2 poz 4Sp .rz sin(P)23 Plae = ( - ) _ ( )(3) P 47t 5teso 7rtR treRAs_,
In the formula, go is the magnetic permeability under vacuum, t is the time, A6, is the
difference between the induced voltage in the air and the induced voltage at the projection
position on the ground, and 8z is the apparent resistivity of the ground.
The calculation method of the full-period apparent resistivity is to solve iteratively the
early and late apparent resistivity respectively to obtain the variation curve of the early
and the late apparent resistivity with u, and the full-period apparent resistivity is solved
based on the turning point of the variation curve.
When u is greater than the turning point coordinate, the early apparent resistivity is
solved; when u is less than the turning point coordinate, the late apparent resistivity is
solved; when u is equal to the turning point coordinate, the average value of early and late
apparent resistivity is calculated to obtain the full- period apparent resistivity.
S3. Obtain the underground induced current distribution of the emitter. According to the
lateral and longitudinal components of the induced current, establish the relationship
between the imaging depth and the diffusion depth on the lateral and longitudinal
components of the induced current, respectively, as shown in 3(a) and 3(b). According to
the relationship between the imaging depth and the diffusion depth of the transverse and
the longitudinal component of the induced current, the imaging depth with the transverse
and longitudinal response is obtained respectively.
The imaging depth is the depth when the induced current energy is the maximum.
The relationship between the imaging depth and the diffusion depth on the lateral and
longitudinal components of the induced current is a linear positive correlation, as shown in formula 4 and formula 5:
6r = 0.816 .................................. 4
8H = 0 .25 ....................................... 5
In the formula, 2t/peo- represents the diffusion depth of the induced current, t
represents the response time of the receiving device, U- represents the electrical
conductivity of the earth, PO represents the magnetic permeability under vacuum, and
5. and 6H represent the imaging depth during the lateral and the longitudinal
response, respectively. According to formula (4) and (5), when selecting the lateral
response, the imaging depth is 0.816 times of the diffusion depth, and when selecting the
longitudinal response, the imaging depth is 0.25 times of the diffusion depth.
S4. Based on the early, late, and full-period apparent resistivity, and the imaging depth
when using the lateral response and the longitudinal response, form a resistivity-imaging
depth profile to complete resistivity imaging.
In order to further verify the effectiveness of the resistivity imaging method based on the
electrical source semi-airborne transient electromagnetic method, the imaging effects of
the traditional resistivity imaging method and the resistivity imaging method of the
present invention are compared through experimental simulation and measured data
respectively.
Embodiment 1
Set six models: D, G, H, K, A, and Q, with flying altitude of 50m, PE=OOOOAm, r=500m
and equatorial reception. Comparison diagrams of early apparent resistivity calculated by
the traditional resistivity imaging method and the resistivity imaging method of the
present invention for the six models are shown in Figure 4 respectively.
In fig. 4, the solid line is the early apparent resistivityP early-ground calculated by the
traditional resistivity imaging method, the dashed line is the early apparent resistivity
-oe calculated by the resistivity imaging method of the present invention, and the lower
part of fig. 4 is the relative error of ''-'o""d and -.
According to the G and D two-layer model in fig. 4, when /R <1.8,the early apparent resistivity is more accurate and conforms to the real model. With the time delay, the error
between the apparent resistivity and the real model becomes larger and the real resistivity
cannot be reflected. In the H, K, A, Q four-layer model, the response of P early-ground and
to the model is similar, andPear'risesto parallel to e,'-'°""d so the relative error
curve of the two is unchanged. When using early apparent resistivity to calculate late
data, there will be great errors.
Set 20Mm uniform half-space model with PE=1OOOOAm, r=500m, equatorial reception.
Select early time track (t=0.0001s). Fig. 5 is the curve of early apparent resistivity
changing with flying height, dotted line is the curve of early apparent resistivity changing
with flying height in the apparent resistivity imaging method of the present invention,
solid line is the curve of early apparent resistivity changing with flying height in the traditional resistivity imaging method, and histogram is the relative error curve between them. In theory, there is no relationship between real resistivity and flying height, but according to fig. 5, the traditional resistivity imaging method has errors, and the errors gradually increase with the height change. When the flying height changes from 5m to
100m, the early apparent resistivity decreases by 25.6%, which greatly affects the
imaging results. According to the method, when the early apparent resistivity considering
the flying height is used for calculation, a more accurate result can be obtained, and the
maximum change rate is 2.7%, which is far smaller than the former, and the change of the
apparent resistivity is ignored within a height of less than 50m. The relative error of
apparent resistivity obtained by the two methods increases monotonously with the change
of height, and the maximum error is 15%.
Comparison diagrams of the late apparent resistivity calculated by the traditional
resistivity imaging method and the resistivity imaging method of the present invention for
the six models D, G, H, K, A and Q are shown in fig. 6 respectively:
The solid line shows the late apparent resistivity Plater-groundcalculated by the traditional
resistivity imaging method, the short dashed line shows the late apparent resistivity P/1
calculated by the resistivity imaging method of the present invention, and the long dashed
line shows the difference between the late apparent resistivity calculated by the
traditional resistivity imaging method and the late apparent resistivity calculated by the
resistivity imaging method of the present invention. The lower part of fig. 6 shows the
relative error ofPlater-ground and P-.
According to the G and D two-layer model in fig. 6, when r/R > 4.5, the late apparent
resistivity is more in line with the real resistivity, and with the time delay, the apparent
resistivity is gradually close to the base resistivity. The response of Plater-groundandg Sier
to the model is similar, but will be slightly higher, and the relative error Plaer-ground
between them is between 8% and 9%. When r/R<4 5 , the difference of late apparent
resistivity is bigger, and the extreme value can reach 40%. In the four-layer model of H,
K, A and Q, when r/R>3.1, it is closer to the real resistivity, and when the intermediate
layer appears, the apparent resistivity will change. From the change, it can be seen that
the electrical source semi-airbome transient electromagnetic method reflects the low
resistivity layer more strongly; when using the late apparent resistivity to calculate the
early data, there will be a great error. When calculating the late data, although the relative
error is reduced, this error can not be ignored.
Fig. 7 shows the variation curve of late apparent resistivity with flying height. Although
the late apparent resistivity without considering the signal receiving height is similar to
the real resistivity near the surface, it changes with the height and does not change
monotonously. Before zO=90m, the apparent resistivity decreases with the increase of
height, and then increases again. Therefore, when using the ground-air data to calculate
the traditional apparent resistivity, there will be an error with the real apparent resistivity,
which will increase with the height before zO.
Therefore, compared with the traditional resistivity imaging method, the resistivity
calculation error is significantly reduced, and the imaging result is more accurate, which
proves the effectiveness of the method.
Embodiment 2
The traditional resistivity imaging method and the resistivity imaging method of the
present invention are respectively used for field measurement in a certain place in Shanxi,
China. The construction parameters are as follows: the emitter length is 1000m, the offset
distance is 300m, the survey line length is 600m, and the point distance is 5 m. The
comparison diagram of the bottom layer electrical structure obtained by resistivity
inversion is shown in fig. 8. When the apparent resistivity is calculated considering the
flying height, compared with the traditional apparent resistivity, the overall amplitude
increases, which reduces the "assimilation" influence of the low-resistance target on the
surrounding area and the target position is more accurate and the difference with deep
bedrock is strengthened. At the same time, considering that the vertical magnetic field is
generated by transverse induced current, the imaging depth will be more in line with the
actual depth position of the target. Comparing the two imaging methods, it is easy to find
that the imaging depth calculated by transverse induced current will "increase", and the
minimum point of apparent resistivity in the result is at the depth of 250 m-270 m.
Compared with the result in fig. 8(a), its minimum position is between 300 m and 400 m.
According to the lithologic distribution of logging data, the depth of water level is 267.96
m, and the thickness is 2.25 M. the result is more consistent with fig. 8(b). The imaging results are consistent with the known borehole results in the survey area, which proves the effectiveness of the imaging method of the invention.
The above embodiments only describe the preferred mode of the invention, but do not
limit the scope of the invention. On the premise of not departing from the design spirit of
the invention, various modifications and improvements made by ordinary technicians in
the field to the technical scheme of the invention shall fall within the protection scope
determined by the claims of the invention.
Claims (6)
1. A resistivity imaging method based on electrical source electrical source semi
airborne transient electromagnetic method is characterized in that it comprises the
following steps:
Si. Setting observation points and detection depths, according to which arranging
emission sources and receiving devices.
S2. Obtain the voltage signal of the electrical source electrical source semi-airborne
transient electromagnetic field in the vertical direction through the receiving device,
and calculate the early, late, and full-period apparent resistivity.
S3. Obtain the underground induced current distribution of the emitter. According to
the lateral and longitudinal components of the induced current, establish the
relationship between the imaging depth and the diffusion depth on the lateral and
longitudinal components of the induced current, respectively, to obtain the imaging
depth when using the transverse and longitudinal response.
S4. Based on the early, late, and full-period apparent resistivity, and the imaging depth
when using the lateral response and the longitudinal response, form a resistivity
imaging depth profile to complete resistivity imaging.
2. The resistivity imaging method based on electrical source electrical source semi
airborne transient electromagnetic method according to claim 1 is characterized in
that, in the step S1, the specific method for arranging the transmitting source and
receiving device according to the observation point and the detection depth includes
that arrange grounded wires at both ends as the emission source, and mount the receiving device on the UAV platform. The distance between the emission source and the observation point is 0.5 to 3 times of the detection depth; the distance between the flight altitude of the UAV and the ground is 0-1 times of the detection depth.
3. The resistivity imaging method based on electrical source electrical source semi
airborne transient electromagnetic method according to claim 1 is characterized in
that, in the step S2, the early, late, and full-period apparent resistivity calculation
methods include: calculating the air response of the electrical source semi-airborne
transient electromagnetic field in a uniform half-space according to the vertical
voltage signal of the electrical source semi-airborne transient electromagnetic field;
calculating the early, late, and full-period apparent resistivity based on the air
response of the electrical source semi-airborne transient electromagnetic field in a
uniform half-space.
4. The resistivity imaging method based on the electrical source semi-airborne
transient electromagnetic method according to claim 3 is characterized in that the air
response of the electrical source semi-airborne transient electromagnetic field in a
uniform half space is as formula 1:
3PE -u 2 Ce (t) = 3pSsinfo ©1(u)- - e2u 1+ 3P~S~f -9s 2 ~~ 2 . ........... 1
3 3PSp P 2 sinto 5(u)- e -U22 u 5+55U2 + U4 2rcR' Irc/ 3 3
In the formula, R = r2+ z2 , z is the flying height, r is the offset distance, c,(t) is
the vertical induced voltage, S is the effective area of the receiving device, PE is the
transmitting magnetic distance, p is the earth resistivity, u= 2j2+k2 , k is the wavelength, and k is wave number, <p represents the angle between the receiving position and the transmitting source, <p(u) represents the probability integral.
The early calculation of apparent resistivity r is shown as formula 2:
3SerrR 2 - z si ....................... . 2 P S~rrRY - 5Z()2s2). I
In the formula, R = 2 , z +r2+ is the flying height, r is the offset, S is the effective
area of the receiving device, I is the length of the emission source, and I is the
induced current underground.
The calculation of late apparent resistivity Per is shown as formula 3:
po SMlr p sinP 21 poz 4S~lporz sin? 2/3 Pla = (i ) ( )s...............3 lt 4 xt 5tsco 7tR trcRAs,
In the formula, Uo is the magnetic permeability under vacuum, t is the time, Asz is
the difference between the induced voltage in the air and the induced voltage at the
projection position on the ground, and Ezo is the apparent resistivity of the ground.
The calculation method of the full-period apparent resistivity is to solve iteratively the
early and late apparent resistivity respectively to obtain the variation curve of the
early and the late apparent resistivity with u, and the full-period apparent resistivity is
solved based on the turning point of the variation curve.
5. The resistivity imaging method based on the electrical source semi-airborne
transient electromagnetic method according to claim 4 is characterized in that the
method for solving the full-period apparent resistivity based on the turning point of
the change curve comprises the following steps.
When u is greater than the turning point coordinate, the early apparent resistivity is
solved; when u is less than the turning point coordinate, the late apparent resistivity is
solved; when u is equal to the turning point coordinate, the average value of early and
late apparent resistivity is calculated to obtain the full- period apparent resistivity.
6. The resistivity imaging method based on the electrical source semi-airborne
transient electromagnetic method according to claim 1 is characterized in that the
relationship between the imaging depth and the diffusion depth on the lateral and
longitudinal components of the induced current is a linear positive correlation, as
shown in formula 4 and formula 5:
9v = 0 .8 16 - ....................................... 4
8H = 0 .25 - - ....................................... 5
In the formula, 2t/pieo- represents the diffusion depth of the induced current, t
represents the response time of the receiving device, - represents the electrical
conductivity of the earth, /1 represents the magnetic permeability under vacuum,
and 6, and eH represent the imaging depth during the lateral and the
longitudinal response, respectively.
-1/8-
Figure 1
-2/8-
Figure 2
(a) -3/8-
Figure 3 (b)
-4/8- 19 Aug 2020 2020101894
(a) (b)
(c) (d)
(e) (f)
Figure 4
-5/8-
Figure 5
-6/8- 19 Aug 2020 2020101894
（a） （b）
（c） （d）
（e） （f）
Figure 6
-7/8-
Figure 7
-8/8-
Figure 8
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| CN113655532A (en) * | 2021-09-03 | 2021-11-16 | 山东大学 | Method and system for removing motion noise of non-full-time semi-aviation transient electromagnetic data |
| CN113791450A (en) * | 2021-07-30 | 2021-12-14 | 天地科技股份有限公司 | Transient electromagnetic whole-course apparent resistivity calculation method and system |
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| CN115201922A (en) * | 2022-06-28 | 2022-10-18 | 中国科学院地质与地球物理研究所 | Semi-aeroelectromagnetic apparent resistivity measurement system and method |
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| CN113791450A (en) * | 2021-07-30 | 2021-12-14 | 天地科技股份有限公司 | Transient electromagnetic whole-course apparent resistivity calculation method and system |
| CN113791450B (en) * | 2021-07-30 | 2024-03-15 | 天地科技股份有限公司 | Transient electromagnetic whole-course apparent resistivity calculation method and system |
| CN113655532A (en) * | 2021-09-03 | 2021-11-16 | 山东大学 | Method and system for removing motion noise of non-full-time semi-aviation transient electromagnetic data |
| CN114460654A (en) * | 2022-02-22 | 2022-05-10 | 成都理工大学 | Semi-aviation transient electromagnetic data inversion method and device based on L1L2 mixed norm |
| CN115201922A (en) * | 2022-06-28 | 2022-10-18 | 中国科学院地质与地球物理研究所 | Semi-aeroelectromagnetic apparent resistivity measurement system and method |
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