CN109541695A - Artificial field source frequency domain electric-force gradient far-zone apparent resistivity fast imaging method - Google Patents
Artificial field source frequency domain electric-force gradient far-zone apparent resistivity fast imaging method Download PDFInfo
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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
- G01V3/083—Controlled source electromagnetic [CSEM] surveying
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R29/00—Arrangements for measuring or indicating electric quantities not covered by groups G01R19/00 - G01R27/00
- G01R29/08—Measuring electromagnetic field characteristics
- G01R29/0864—Measuring electromagnetic field characteristics characterised by constructional or functional features
- G01R29/0892—Details related to signal analysis or treatment; presenting results, e.g. displays; measuring specific signal features other than field strength, e.g. polarisation, field modes, phase, envelope, maximum value
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- 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
- G01V3/083—Controlled source electromagnetic [CSEM] surveying
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Abstract
The present invention relates to a kind of artificial field source frequency domain electric-force gradient far-zone apparent resistivity fast imaging methods, including data prediction, electric-force gradient calculates, electric-force gradient computation of apparent resistivity, aerial image, it is view depth by measurement frequency corresponding conversion, draws apparent resistivity-view depth pseudosection map on survey line.The present invention promotes the responding ability of anomalous body horizontal boundary, by seeking longitudinal gradient to electric field, promotes the responding ability of anomalous body longitudinal boundary by seeking transverse gradients to electric field.It can accurately reflect out variation tendency electrical greatly, there is higher anomaly resolution rate, anomalous body position, size, boundary can more accurately be positioned.Calculation amount is small, and calculating speed is fast, and in the practical exploration in field, scene can tentatively judge that geological information judges after extracting data, can be applied to the live fast imaging in practical field detection, improves ground observation efficiency, realizes accurately identifying for subsurface anomaly body.
Description
Technical field:
Horizontal, longitudinal edge circle recognition capability that the present invention relates to a kind of electromagnetic survey imaging method, especially promotion subsurface anomaly bodies
Artificial field source frequency domain electric-force gradient apparent resistivity imaging method.
Background technique:
Electromagnetic prospecting is based on being detected electrical property and the magnetic contrast of medium by underground, by observing artificial or day
The changing rule for the alternating electromagnetic field that right field source excites in the earth, obtains the electrical property and magnetic parameter of underground medium, to reach
To a kind of geophysical exploration method for reconnoitring purpose.By its electromagnetic field with the changing rule of frequency and time can crossover rate domain and
Time domain electromagnetic method.Wherein, frequency domain electromagnetic methods are to utilize frequency and detection by the electromagnetic field response under acquisition different frequency
Relationship between depth obtains the earth electrical property information under different depth, compared with time domain electromagnetic method, frequency domain electromagnetic methods tool
There are bigger investigation depth and higher detection efficient.In frequency domain electromagnetic methods, natural field source frequency can be divided into again according to field source
Rate domain electromagnetic method and artificial field source frequency domain electromagnetic method, artificial field source frequency domain electromagnetic method have emission parameter known, anti-interference
The advantages such as ability is stronger have been widely used in the fields such as resource exploration, hydrology prospecting and engineering, geologic survey.
CSAMT is typical, common artificial field source frequency domain electromagnetic exploration method, passes through the electromagnetic field under different frequency
Component recycles mutually orthogonal electromagnetic field component ratio calculation card release Buddhist nun Asian TV Station resistivity, obtains finally by inversion interpretation
Obtain the earth electrical property information under different depth.But it need to be measured in far field for calculating the electromagnetic field component of apparent resistivity.Work as receipts
When hair is away from certain threshold value is greater than with the ratio of investigation depth, far zone condition is just satisfied.And it receives and dispatches away from strong with reception signal
Degree has a direct relation again, transmitting-receiving away from it is too big when, received signal strength can reduce, and signal quality will receive negative effect, be unfavorable for
Exploration effects.In order to realize the detection under big depth, there is scholar to propose WFEM, this method only measures single component, Ji Ketong
It crosses corresponding apparent resistivity formula and calculates apparent resistivity, can be measured in non-far field, since it only measures single component, so only
Single component is needed to meet far zone condition, this makes its far zone condition looser compared with CSAMT method.
But currently, the artificial field source frequency domain electromagnetic exploration method including the above method generallys use absolute fields
Measurement and processing, and absolutely field measurement has deficiency in terms of Boundary Recognition, the electromagnetic signal of receiving point is around certain space
The comprehensive contribution of medium in range, wherein the effect of superficial part medium is larger, and superficial part would generally copy to deep extremely.This leads to ground
Reflection that electromagnetic response electrically changes local geologic body is simultaneously insensitive, also relatively fuzzyyer to the reflection of anomalous body boundary, usually only
Position, the size that can substantially determine anomalous body, can not accurately identify.So above-mentioned computation of apparent resistivity method is for anomalous body side
The recognition capability on boundary has deficiency, need to be by the accurate acquisition anomalous body boundary information of inverting ability, and inverting needs to consume
It is a large amount of to calculate time and resource, it is unfavorable for exploring live fast imaging, and live fast imaging method is explored in practical field
In detection, especially it is of great significance in the monitoring of the quality of data and the acquisition of geologic aspects.
Summary of the invention
It is an object of the invention to be directed to the deficiency of above-mentioned existing apparent resistivity imaging method, a kind of artificial field source frequency is provided
Rate domain electric-force gradient apparent resistivity fast imaging method.
The purpose of the present invention is what is be achieved through the following technical solutions:
A kind of artificial field source frequency domain electric-force gradient apparent resistivity fast imaging method, which is characterized in that including following step
It is rapid:
A, data prediction reads the E of system acquisitionxTime series data, to ExTime series data does Fourier's change
It changes, time-domain signal is transformed into frequency domain, then extract the Ex amplitude at launching frequency；
B, electric-force gradient calculates, and utilizes ExAmplitude Value Data calculates electric field transverse gradientsLongitudinal gradientAnd joint
Gradient
C, electric-force gradient computation of apparent resistivity calculates lateral change in apparent resistivity amount using electric-force gradient dataIt is longitudinal
Change in apparent resistivity amountWith joint change in apparent resistivity amountIn conjunction with the apparent resistivity value for surveying some measuring point in area, root
It is calculated according to electric-force gradient calculation formula of apparent resistivity and surveys apparent resistivity value of any point under any tranmitting frequency in area；
D, aerial image, according to skin depth formula δ=503* (ρ/f)1/2, it is view depth by measurement frequency corresponding conversion,
Draw apparent resistivity-view depth pseudosection map on survey line.
In step A, ExTime series data refers to the E that instrument system is acquired and storedxInitial data, ExAmplitude refers to frequency
The E in rate domainxAmplitude, specific processing method are to number according to the measuring point surveyed in area successively to the E of each measuring pointxTime series number
According to the processing for carrying out following (1)~(3) step, the E surveyed in area on all measuring points under different measurement frequencies is obtainedxFrequency domain amplitude:
(1) the Ex time series data of the measuring point is read；
(2) Fourier transformation is carried out to the Ex time series data, it, can be to Ex time series when carrying out Fourier transformation
Data carry out integral transformation, or choose wherein a certain section of Ex time series data and carry out Partial Transformation, carry out Fourier transformation
The selection of Ex time series data range be by setting Fourier transformation at the beginning of t1, end time t2, sample frequency
F, the parameters such as sampling number n are come what is realized, and after carrying out Fourier transformation, the Ex initial data of instrument system acquisition is from the time
Sequence transformation is frequency sequence, which is Ex frequency domain data, it includes one-to-one frequency values and Ex amplitude；
(3) the corresponding Ex amplitude of launching frequency is extracted, and launching frequency refers to a series of collection of specific electromagnetic wave tranmitting frequencies
It closes, such as in certain detection, transmits the electromagnetic wave of six frequencies of 32Hz, 64Hz, 128Hz, 256Hz, 512Hz, 1024Hz, that
In this step, then the Ex amplitude in above-mentioned six frequencies is extracted.
In step B, transverse gradientsIt is E of the adjacent measuring point under same measurement frequency on same survey linexAmplitude is done
Apart from difference coefficient, longitudinal gradientIt is the E of side frequency on same survey line, same observation stationxAmplitude does frequency difference coefficient, joint ladder
DegreeBe longitudinal gradient in same survey line, adjacent measuring point is done apart from difference coefficient, specific formula is as follows:
--- the measuring point j on survey line i is f in frequencyκWhen transverse gradients are as follows:
In formula, Δ LxFor the distance between adjacent measuring point on same survey line；
--- the measuring point j on survey line i is f in frequencyκWhen longitudinal gradient are as follows:
In formula, fκAnd fκ-1For adjacent frequency values；
--- the measuring point j on survey line i is f in frequencyκWhen joint gradient are as follows:
In step C, lateral change in apparent resistivity amountLongitudinal change in apparent resistivity amountWith joint change in apparent resistivity
AmountFormula is that existing far-zone apparent resistivity calculation formula and transverse gradients, longitudinal gradient, to combine gradient public by combining
Formula derives and goes out, in which:
--- the measuring point j on survey line i is f in frequencyκWhen lateral change in apparent resistivity amount are as follows:
In formula, PeTo emit electric moment, rjFor measuring point j transmitting-receiving away from αjLine between artificial field source center and measuring point with
Angle between the perpendicular bisector of artificial field source；
--- the measuring point j on survey line i is f in frequencyκWhen longitudinal change in apparent resistivity amount are as follows:
--- the measuring point j on survey line i is f in frequencyκWhen joint change in apparent resistivity amount are as follows:
In step C, the apparent resistivity value for surveying some measuring point in area can be provided according to known geological information, not any
In the case where known geological information, pass through ExData are calculated using far-zone apparent resistivity calculation formula and survey some measuring point of area
Apparent resistivity value, the measuring point j on survey line i, frequency be fκWhen far-zone apparent resistivity calculation formula are as follows:
In step C, any point j in area is surveyedLIt is f in measurement frequencykWhen, electric-force gradient far-zone apparent resistivity calculation formula
Are as follows:
In formula, ρ (i, j0,f0) it is to survey in area, the measuring point j on survey line i is f in frequency0When apparent resistivity value.
The utility model has the advantages that compared with prior art, it is horizontal to promote anomalous body by seeking transverse gradients to electric field by (1) present invention
The responding ability of anomalous body longitudinal boundary is promoted by seeking longitudinal gradient to electric field to the responding ability on boundary.(2) artificial
Field source frequency domain electric-force gradient apparent resistivity fast imaging method can be more accurate reflect the electrical variation tendency of the earth, have
Higher anomaly resolution rate can more accurately position anomalous body position, size, boundary.(3) this method calculation amount
Small, calculating speed is fast, requires allocation of computer low.(4) artificial field source frequency domain electric-force gradient apparent resistivity quickly calculate with
Imaging method is expected to provide more accurate initial model for inverting, promotes inversion accuracy and efficiency.(5) this method is for field reality
For the acquisition methods of border data without particular/special requirement, electric field need to be only realized using the electromagnetic method instrument, of mainstream in the market synchronizes distribution
Detection, strong applicability are conducive to promote.(6) for this method in the practical exploration in field, scene can be preliminary after extracting data
Judge that geological information judges, can be applied to the live fast imaging in practical field detection, especially in the monitoring of the quality of data and
It is of great significance in the acquisition of geologic aspects, it, can further inversion interpretation or joint other methods be (such as key position
CSAMT etc.) efforts will be concentrated on prospecting are carried out, to improve ground observation efficiency, realize accurately identifying for subsurface anomaly body.
Detailed description of the invention
Fig. 1: gradient apparent resistivity fast imaging method flow chart
Fig. 2: transverse gradients response characteristic figure
Fig. 2 (a) transversal inhomogeneity the earth schematic diagram；
Fig. 2 (b) ExAmplitude response curve graph；
Fig. 2 (c)Response curve
Fig. 3: longitudinal gradient response characteristic figure
Fig. 3 (a) ExRelative anomalies curve graph varying with frequency
Fig. 3 (b)Relative anomalies curve graph varying with frequency.
Fig. 4: 3-D model gradient fields apparent resistivity pseudosection map
Fig. 4 (a) 3-D Earth model front view；
Fig. 4 (b) combines change in apparent resistivity amountPseudosection map；
Fig. 4 (c) gradient fields apparent resistivity pseudosection map；
Fig. 4 (d) absolute fields apparent resistivity pseudosection map.
Specific embodiment
The present invention is described in further detail with reference to the accompanying drawings and examples:
Artificial field source frequency domain electric-force gradient far-zone apparent resistivity fast imaging method, comprising the following steps:
A, data prediction reads the E of system acquisitionxTime series data, to ExTime series data does Fourier's change
It changes, time-domain signal is transformed into frequency domain, then extract the E at launching frequencyxAmplitude；
B, electric-force gradient calculates, and utilizes ExAmplitude Value Data calculates electric field transverse gradientsLongitudinal gradientAnd joint
Gradient
C, electric-force gradient computation of apparent resistivity calculates lateral change in apparent resistivity amount using electric-force gradient dataIt is longitudinal
Change in apparent resistivity amountWith joint change in apparent resistivity amountIn conjunction with the apparent resistivity value for surveying some measuring point in area, root
It is calculated according to electric-force gradient calculation formula of apparent resistivity and surveys apparent resistivity value of any point under any tranmitting frequency in area；
D, aerial image, according to skin depth formula δ=503* (ρ/f)1/2, it is view depth by measurement frequency corresponding conversion,
Draw apparent resistivity-view depth pseudosection map on survey line.
Fig. 1 quickly calculates for gradient apparent resistivity and imaging method flow chart, mainly includes data prediction, electric-force gradient
It calculates, four major part of electric-force gradient computation of apparent resistivity and aerial image.It is specific as follows:
Ex time series data refers to the E that instrument system is acquired and storedxInitial data, ExAmplitude refers to the Ex of frequency domain
Amplitude.ExE of the time series data to frequency domainxAmplitude transformation through the following steps that implement:
Firstly, numbering according to the measuring point surveyed in area successively to the E of each measuring pointxTime series data is read out.ExWhen
Between sequence data should be the E for being acquired and being stored by instrument system under following measuring conditionxInitial data: area is surveyed by artificial source
Side, positioned at using the midpoint of long conducting wire emission source as starting point, with regional scope of the emission source perpendicular bisector at ± 45° angle in, survey line edge
The direction parallel with artificial source lay, the electric field of different spatial takes the mode of synchronous recording.
Secondly, reading the E measured under the above conditionsxAfter time series data, to the ExTime series data carries out in Fu
Leaf transformation.It, can be to E when carrying out Fourier transformationxTime series data carries out integral transformation, can also choose wherein a certain section
Ex time series data carries out Partial Transformation.Carry out the E of Fourier transformationxThe selection of time series data range is to pass through setting
T at the beginning of Fourier transformation1, end time t2, sample frequency f, the parameters such as sampling number n realize.
Third, after carrying out Fourier transformation, the E of instrument system acquisitionxInitial data is transformed to frequency from time series
Rate sequence, the data are ExFrequency domain data, it includes one-to-one frequency values and ExAmplitude.
Finally, extracting the corresponding E of launching frequencyxAmplitude.Launching frequency refers to a series of specific electromagnetic wave tranmitting frequencies
In set, such as certain detection, the electromagnetic wave of six frequencies of 32Hz, 64Hz, 128Hz, 256Hz, 512Hz, 1024Hz is transmitted,
So in this step, then the E in above-mentioned six frequencies is extractedxAmplitude.
Obtain corresponding E under each launching frequencyxAfter amplitude, by the way that on same survey line, adjacent measuring point is in same measurement
E under frequencyxAmplitude is done apart from difference coefficient, and transverse gradients are obtained.By on same side line, same observation station, the E of side frequencyxWidth
Value does frequency difference coefficient, obtains longitudinal gradient.By doing longitudinal gradient in same survey line, adjacent measuring point apart from difference coefficient, obtain
Joint gradient, in which:
--- the measuring point j on survey line i is f in frequencyκWhen transverse gradients are as follows:
In formula, Δ LxFor the distance between adjacent measuring point on same survey line；
--- the measuring point j on survey line i is f in frequencyκWhen longitudinal gradient are as follows:
In formula, fκAnd fκ-1For adjacent frequency values.
--- the measuring point j on survey line i is f in frequencyκWhen joint gradient are as follows:
Acquire each measuring point under each frequency point transverse gradients, longitudinal gradient, after joint gradient, in conjunction with emission current, artificial
The actual measurements parameter such as relative position between field source length, transmitting-receiving, can acquire the measuring point j on survey line i, be in frequency
fkWhen lateral change in apparent resistivity amountLongitudinal change in apparent resistivity amountWith joint change in apparent resistivity amountFormula,
Wherein:
--- the measuring point j on survey line i is f in frequencyκWhen lateral change in apparent resistivity amount are as follows:
--- the measuring point j on survey line i is f in frequencyκWhen longitudinal change in apparent resistivity amount are as follows:
--- the measuring point j on survey line i is f in frequencyκWhen joint change in apparent resistivity amount are as follows:
In above-mentioned formula, in formula, PeTo emit electric moment, rjFor measuring point j transmitting-receiving away from αjFor artificial field source center and measuring point it
Between line and artificial field source perpendicular bisector between angle.
Calculate lateral change in apparent resistivity amountLongitudinal change in apparent resistivity amountWith joint change in apparent resistivity amountAfterwards, speculate further according to known geological information, or pass through ExData utilize far-zone apparent resistivity calculation formulaCalculate the view electricity for surveying some measuring point of area under specific frequency
Values of resistivity, finally can be by surveying any point j in areaLIt is f in measurement frequencyKWhen electric-force gradient far-zone apparent resistivity calculate
FormulaIt calculates to survey in area and arbitrarily survey
Apparent resistivity value of the point under any measurement frequency, in formula, ρ (i, j0,f0) it is to survey in area, the measuring point j on survey line i, in frequency
Rate is f0When apparent resistivity value.It is view depth by measurement frequency corresponding conversion, the apparent resistivity-view depth drawn on survey line is quasi-
Cross-section diagram.
Using transverse gradients calculation formula, calculating transversal inhomogeneity Earth model in low-resistance slice width is respectively w=
E when 1000m, w=1500m, w=2000mxWithAs shown in Fig. 2 (a), artificial source is located at model x/y plane origin, along x
Direction arrangement；Survey line is arranged at distance sources 8500m in the y-direction.ExShown in response curve such as Fig. 2 (b),Response curve such as Fig. 2
(c) shown in.Under different low resistivity layer width, ExResponse curve is at electrical interface all without apparent abnormal response, peak
Value fails to indicate electrical interface position, andResponse curve produces apparent extreme value, three models at electrical interface
Under electrical interface location withThe extreme value place of response curve is corresponding good, as shown in Figure 2.Simultaneously as can be seen that with
The increase of abnormal layer width,Extreme value place becomes larger therewith,Extreme value amplitude is increased.Therefore,To horizontal boundary
Responding ability be better than electric field absolute fields, and with the increase of abnormal layer width,Responding ability is promoted.
Using longitudinal gradient calculation formula, the longitudinal gradient of the standard of three layers of Earth model is calculated, intermediate low resistivity layer
Buried depth be 600m, with a thickness of 400m, low-resistance layer resistivity is 20 Ω .m, and background resistivity is 100 Ω .m, and measuring point is located at x=
0, at y=8000, z=0.E is calculated separatelyxWithRelative anomalies curve varying with frequency, respectively such as Fig. 3 (a), 3 (b)
Shown, red dotted rectangle indicates exception response frequency range in figure, it can be seen that ExIt is influenced by bulk effect brighter
Aobvious, the exception response of superficial part can copy to deep, and relative anomalies is caused to continue to lower frequency, this will lead to later use and becomes
When skin depth formula calculates apparent resistivity-view depth pseudosection map, occurs biggish false anomaly in depth.ButIt is abnormal
It responds corresponding frequency range more to concentrate, is conducive to the reflection of the bottom boundary of local anomalous body.And depth where low resistivity layer
Near corresponding frequency,Relative anomalies amplitude is bigger, sensitiveer to abnormal response.
Using gradient fields calculation formula of apparent resistivity, the gradient fields apparent resistivity of 3-D Earth model is calculated.3-
Shown in D Earth model front view such as Fig. 4 (a).Long conducting wire source is laid along the direction x in model, and the midpoint in source is located at x-y plane
At origin.Survey line is placed along the direction parallel with source, and the vertical range with source is 8500m.The background resistance of 3-D Earth model
Rate is 100 Ω .m, and the resistivity of objective body is 1 Ω .m.Calculate gradient fields joint change in apparent resistivity amount, gradient fields apparent resistance
Rate and absolute fields apparent resistivity, respectively as shown in Fig. 4 (b), Fig. 4 (c), Fig. 4 (d).In order to intuitively show gradient fields view electricity
The advantage of resistance rate in Fig. 4, utilizes skin depth formula δ=503* (ρ/f)1/2, it is view depth by look-in frequency corresponding conversion.Figure
In 4 (b), combine change in apparent resistivity amountIn x1'=- 500m and x2Occur two obvious extreme values at '=500m, in figure
It is marked by solid white line, the two positions are the horizontal boundary position of anomalous body in 3-D Earth model.So utilizing joint view
Resistivity variationThe horizontal boundary position of anomalous body can be recognized accurately.Meanwhile paired observation Fig. 4 (c), 4 (d) two
Width figure it can be found that the calculated result of Fig. 4 (c) can reflect horizontal, the vertical boundary position of anomalous body, and boundary isopleth compared with
Intensively, the abnormal area in the Yi Dingwei abnormal position result is with the size and location of anomalous body in 3-D Earth model (by scheming
Middle white rectangle frame indicates) it is closer to.And Fig. 4 (d) can not reflect the bottom boundary position of anomalous body, and in boundary equivalence
Line is sparse, and fade effect is presented, is not easy to position, can only substantially delineation abnormality lateral extent, be unable to respond the vertical of anomalous body
To bottom boundary position.It is 100 Ω .m, anomalous body using the calculated background apparent resistivity value of gradient fields and in Fig. 4 (c)
Apparent resistivity value is 78 Ω .m, and the difference of the two is larger, is easy to embody electrical property difference；And Fig. 4 (d) is calculated using absolute fields
Background apparent resistivity value be 98 Ω .m, anomalous body apparent resistivity value be 90 Ω .m, the difference of the two is smaller, is not easy to embody electricity
Sex differernce.Above-mentioned modeling computation the result shows that, gradient fields apparent resistivity have higher anomaly resolution rate, can more accurately reflect
Electrical variation tendency, positioning abnormal position greatly out.
Claims (6)
1. a kind of artificial field source frequency domain electric-force gradient apparent resistivity fast imaging method, which comprises the following steps:
A, data prediction reads the E of system acquisitionxTime series data, to ExTime series data does Fourier transformation, will
Time-domain signal transforms to frequency domain, then extracts the Ex amplitude at launching frequency；
B, electric-force gradient calculates, and utilizes ExAmplitude Value Data calculates electric field transverse gradientsLongitudinal gradientWith joint gradient
C, electric-force gradient computation of apparent resistivity calculates lateral change in apparent resistivity amount using electric-force gradient dataLongitudinal view electricity
Resistance rate variable quantityWith joint change in apparent resistivity amountIn conjunction with the apparent resistivity value for surveying some measuring point in area, according to electricity
Field gradient calculation formula of apparent resistivity, which calculates, surveys apparent resistivity value of any point under any tranmitting frequency in area；
D, aerial image, according to skin depth formula δ=503* (ρ/f)1/2, it is view depth by measurement frequency corresponding conversion, draws
Apparent resistivity-view depth pseudosection map on survey line.
2. artificial field source frequency domain electric-force gradient apparent resistivity fast imaging method described in accordance with the claim 1, feature exist
In, in step A, ExTime series data refers to the E that instrument system is acquired and storedxInitial data, ExAmplitude refers to frequency domain
ExAmplitude, specific processing method are to number according to the measuring point surveyed in area successively to the E of each measuring pointxTime series data carries out
The processing of (1)~(3) step as follows obtains the E surveyed in area on all measuring points under different measurement frequenciesxFrequency domain amplitude:
(1) E of the measuring point is readxTime series data；
(2) to the ExTime series data carries out Fourier transformation, can be to E when carrying out Fourier transformationxTime series data
Integral transformation is carried out, or chooses wherein a certain section of ExTime series data carries out Partial Transformation, carries out the E of Fourier transformationxTime
The selection of sequence data range be by setting Fourier transformation at the beginning of t1, end time t2, sample frequency f, sampled point
The parameters such as n are counted to realize, after carrying out Fourier transformation, the E of instrument system acquisitionxInitial data is converted from time series
For frequency sequence, which is ExFrequency domain data, it includes one-to-one frequency values and ExAmplitude；
(3) the corresponding E of launching frequency is extractedxAmplitude, launching frequency refer to a series of set of specific electromagnetic wave tranmitting frequencies, example
In certain detection, the electromagnetic wave of six frequencies of 32Hz, 64Hz, 128Hz, 256Hz, 512Hz, 1024Hz is transmitted, then
In the step, then the E in above-mentioned six frequencies is extractedxAmplitude.
3. artificial field source frequency domain electric-force gradient apparent resistivity fast imaging method described in accordance with the claim 1, feature exist
In, in step B, transverse gradientsIt is E of the adjacent measuring point under same measurement frequency on same survey linexAmplitude does range difference
Quotient, longitudinal gradientIt is the E of side frequency on same survey line, same observation stationxAmplitude does frequency difference coefficient, combines gradient
Be longitudinal gradient in same survey line, adjacent measuring point is done apart from difference coefficient, specific formula is as follows:
--- the measuring point j on survey line i is f in frequencyκWhen transverse gradients are as follows:
In formula, Δ LxFor the distance between adjacent measuring point on same survey line；
--- the measuring point j on survey line i is f in frequencyκWhen longitudinal gradient are as follows:
In formula, fκAnd fκ-1For adjacent frequency values；
--- the measuring point j on survey line i is f in frequencyκWhen joint gradient are as follows:
4. artificial field source frequency domain electric-force gradient apparent resistivity fast imaging method described in accordance with the claim 1, feature exist
In, in step C, lateral change in apparent resistivity amountLongitudinal change in apparent resistivity amountWith joint change in apparent resistivity amount
Formula is by combining existing far-zone apparent resistivity calculation formula and transverse gradients, longitudinal gradient, combining gradient formula derivation
And go out, in which:
--- the measuring point j on survey line i is f in frequencyκWhen lateral change in apparent resistivity amount are as follows:
In formula, PeTo emit electric moment, rjFor measuring point j transmitting-receiving away from αjLine between artificial field source center and measuring point and artificial
Angle between the perpendicular bisector of field source；
--- the measuring point j on survey line i is f in frequencyκWhen longitudinal change in apparent resistivity amount are as follows:
--- the measuring point j on survey line i is f in frequencyκWhen joint change in apparent resistivity amount are as follows:
5. artificial field source frequency domain electric-force gradient apparent resistivity fast imaging method described in accordance with the claim 1, feature exist
In in step C, the apparent resistivity value for surveying some measuring point in area can be provided according to known geological information, not any known
In the case where geological information, pass through ExData calculate the view for surveying some measuring point of area using far-zone apparent resistivity calculation formula
Resistivity value, the measuring point j on survey line i are f in frequencyκWhen far-zone apparent resistivity calculation formula are as follows:
6. artificial field source frequency domain electric-force gradient apparent resistivity fast imaging method described in accordance with the claim 1, feature exist
In, in step C, any point j in survey areaLIt is f in measurement frequencykWhen, electric-force gradient far-zone apparent resistivity calculation formula are as follows:
In formula, ρ (i, j0,f0) it is to survey in area, the measuring point j on survey line i is f in frequency0When apparent resistivity value.
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|---|---|---|---|---|
| CN113484920A (en) * | 2021-08-17 | 2021-10-08 | 成都理工大学 | Two-dimensional structured inversion method for frequency domain electromagnetic sounding data |
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| CN113504574A (en) * | 2021-04-30 | 2021-10-15 | 青海省第三地质勘查院 | Electromagnetic data quasi-seismic profile display method and system based on normalization function |
| CN113504574B (en) * | 2021-04-30 | 2022-07-01 | 青海省第三地质勘查院 | Electromagnetic data quasi-seismic profile display method and system based on normalization function |
| CN113484920A (en) * | 2021-08-17 | 2021-10-08 | 成都理工大学 | Two-dimensional structured inversion method for frequency domain electromagnetic sounding data |
| CN113484920B (en) * | 2021-08-17 | 2023-05-19 | 成都理工大学 | Two-dimensional structured inversion method for frequency domain electromagnetic sounding data |
| WO2023050496A1 (en) * | 2021-09-29 | 2023-04-06 | 江苏大学 | Apparent resistivity-depth profile generation method for short-offset electromagnetic exploration |
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