CN101261327B - All-zone couple source frequency domain magnetic depth measuring method and device - Google Patents

Abstract

The invention discloses a whole-zone electric coupling source frequency domain magnetic sounding method and a device thereof; the magnetic sounding method comprises the following steps: (1) a transmission power source (generating set) is arranged, the transmission power source is connected with a multiple frequency current transmission machine and the multiple frequency current transmission machine is connected with two current-supply electrodes A and B; (2) a transmission-reception distance r is selected, a reception magnetic probe is arranged and is connected with a reception machine; (3) the transmission power source, the multiple frequency current transmission machine and the reception machine are started, the multiple frequency current transmission machine transmits the current of designated wave form, voltage, volume as well as frequency to the underground via the current-supply electrodes A and B, the reception machine measures the magnetic field responses of each frequency component from the underground simultaneously, the relevant parameters are automatically stored into a memory and the apparent resistivity of near zone, far zone and medium zone can be automatically calculated respectively according to relevant formulas, automatically drawn out and stored. The invention also comprises the corresponding devices. The whole-zone electric coupling source frequency domain magnetic sounding method is suitable to be used for underground electrical distribution observation in the whole zone (including the near zone, the medium zone and the far zone), used for investigating underground geological structure and mineral product distribution or solving other engineering, hydrological as well as environmental geological problems, and has high observation efficiency, high accuracy and simple equipment.

Description

A kind of all-zone couple source frequency domain magnetic depth measuring method and device

Technical field

The present invention relates to a kind of electromagnetic sounding method and device of reconnoitring geophysics field, especially relate to a kind of measurement magnetic field vertical component H _zAll-zone couple source frequency domain magnetic depth measuring method and device.

Background technology

Reconnoitring geophysics field, existing artificial source's frequency-domian electromagnetic sounding method, for example, all there are certain shortcoming in controllable source audio-frequency magnetotelluric magnetic method (Control Source Audio-Frequency Magnetotellurics) and magnetic couple source frequency bathymetry (MELOS method).Wherein the CSAMT method need be measured one group of mutually orthogonal electricity, magnetic field levels component E " far field " (sending out-receive apart from the 7-9 that equals skin depth doubly) _x, H _y(perhaps E _y, H _x), by calculating ratio (the being called impedance) Z of the two _Xy=E _x/ H _y(perhaps Z _Yx=E _y/ H _x), and then obtain underground apparent resistivity distribution ${\mathrm{\ρ}}_s=\frac{{\left|Z_{\mathrm{xy}}\right|}^2}{\mathrm{\ω\μ}}$ (perhaps ${\mathrm{\ρ}}_s=\frac{{\left|Z_{\mathrm{yx}}\right|}^2}{\mathrm{\ω\μ}}$ ), so as to reaching the purpose of finding out subsurface geological structure or mineral resources.Owing to need measure two mutually orthogonal electricity, magnetic field levels component E in the far field _x, H _y, the survey area that can dispose is very limited.The equipment that uses must possess both energy measurement electric field E _xEnergy measurement magnetic field H again _yFunction.When conducting a field operation, on one side need measure E _xMeasure H on one side _y, also to guarantee E simultaneously _xAnd H _yMutually orthogonal.Measure E _xAnd H _yError all be brought among the result, again by square error being amplified more.Owing to measure in " far field ", weak output signal certainly will will strengthen the transmission electric current again, makes the dispensing device heaviness.Though the MELOS method not necessarily requires to measure in " far field ", in also being only limited to-scope in far field, can not enter close-in measurement, and need carry out a series of correction the observed result in non-" far field ", formality is loaded down with trivial details, makes inefficiency.So existing CSAMT method and MELOS method all have the equipment heaviness, efficient is low, and formality is loaded down with trivial details, the not high shortcoming of precision.

Summary of the invention

At the shortcoming of existing CSAMT method and MELOS method, the object of the present invention is to provide a kind of equipment simple, efficient height, the vertical component H in the measurement magnetic field that measuring accuracy is high _zAll-zone couple source frequency domain magnetic depth measuring method and device.

The all-zone couple source frequency domain magnetic depth measuring method that the present invention proposes is only measured the magnetic field vertical component H that electric dipole source produces _z, measurement is set out-is received apart from r, calculates by the formula and the method for the present invention's proposition, can obtain to send out-receive apart from the apparent resistivity that is the whole district of any size.

According to Theory of Electromagnetic Field, the magnetic field vertical component expression formula that electric dipole source produces on the homogeneous half space is

By induction number p (p=r/ δ, $\mathrm{\δ}=\sqrt{\frac{2\mathrm{\ρ}}{\mathrm{\ω\μ}}}$ Being the skin depth of electromagnetic wave in medium) following formula can be expressed as

1, for " far field " of p 〉=9, can omit in (2) $e^{-p}{e}^{-\mathrm{ip}}[1+p+i\frac{1}{3}(p+2P^2)],$ The error that causes thus can not surpass 1% (the present invention is " far field " to the zone definitions that satisfies p 〉=9).At this moment (2) formula is reduced to

Its absolute value is

In the formula, r is for sending out-receive distance, and I is an electric current of supplying with electric dipole source, and dL is the dipole moment of power supply, and ω is the circular frequency of electric current, and μ is the magnetoconductivity of underground medium, Be r and the angle (position angle) that sends electric dipole moment (two transmitting electrodes distance) forward, ρ is the resistivity of the earth that is detected.I wherein, dL, ω, μ (desirable μ for the nonferromagnetic medium=4 π * 10 ^-7H/m) all be known quantity, measure r and H _z, according to formula

Just descend the apparent resistivity of material extractedly.

2, for sending out-receive, by induction number p formula (3) is rewritten into equally apart from very little near region

(6) can be divided into real part

And imaginary part

For measuring H _zReal part, we are defined as the scope of p≤0.008 to " near region ", at this moment omit the error that the item more than four times and four times of p causes and be no more than 1% in (7), (7) are reduced to

Under the prerequisite of r (this r is artificially to arrange and is known), send and receive the real component ReH of the vertical magnetic field of any two frequency currents generation known-receipts _z(ω _h), ReH _z(ω _l) (ω wherein _hBe the frequency of high-frequency current, ω _lBe the frequency of low-frequency current, the ratio s of the two is called frequency ratio, s=ω _h/ ω _l),

According to formula

${\mathrm{\ρ}}_a={\left\{\frac{\mathrm{IdLr}{\left(\frac{{\mathrm{\ω}}_l\mathrm{\μ}}{2}\right)}^{\frac{3}{2}}(s^{\frac{3}{2}}-1)}{\mathrm{\π}15[\mathrm{Re}{H}_z\left({\mathrm{\ω}}_l\right)-\mathrm{Re}{H}_z\left({\mathrm{\ω}}_h\right)]}\right\}}^{\frac{2}{3}}---\left(10\right)$

Can calculate (extraction) apparent resistivity.

Also can measure H _zImaginary part, at this moment " near region " is defined as p≤0.18, make the error that causes of item more than five times and five times of in (8), omitting p be no more than 1%.(8) formula becomes

Send and receive the imaginary part of the magnetic field vertical component of any two frequency currents generation

The low frequency imaginary component is subtracted each other with frequency ratio s weighting and with the high frequency imaginary component

According to formula

Can extract (calculating) apparent resistivity equally.

Neither satisfy " far field " for those, also do not satisfy the intermediate area (transitional zone) of " near region ", by formula (4)

Can get

(17)

Wherein $f\left(p\right)=\{1-e^{-p}{e}^{-\mathrm{ip}}[1+p+i\frac{1}{3}(p+2P^2)\left]\right\}---\left(18\right)$

Measure the absolute value of magnetic field vertical component | H _z|, at first by formula (5) calculate

Because

$p=r/\mathrm{\δ}=r\sqrt{\frac{\mathrm{\ω\μ}}{2\mathrm{\ρ}}}---\left(20\right)$

With ρ _A1P is tried to achieve in substitution (20) ₁, substitution again (18) obtains

$f\left(p_1\right)=\{1-e^{{-p}_1}{e}^{{-\mathrm{ip}}_1}[1+p_1+i\frac{1}{3}(p_1+2P_1^2)\left]\right\}---\left(21\right)$

Then by formula

Try to achieve ρ _aTwo stage approach value ρ _A2Continuation is with ρ _A2Substitution (20) and (18) obtain p ₂And f (p ₂), obtain three grades of approximate value ρ then _A3

So proceed down,, approach one by one, up to ρ through the several times iteration _{A (n-1)}With ρ _AnDifference little till the satisfied degree.The ρ that obtains _AnIt is exactly the apparent resistivity of intermediate area (transitional zone).

The present invention's all-zone couple source frequency domain magnetic depth measuring method may further comprise the steps: (1) is arranged and is sent power supply (genset), to send power supply is connected with multifrequency electric current transmitter, multifrequency electric current transmitter is connected with B with two electrodes of A, and the distance between electrodes of A and the B (i.e. Gong Dian dipole moment) dL determines according to reconnoitring needs; (2), arranging at a distance of the place of r and receive magnetic probe with sending power supply, and the output terminal that will receive magnetic probe is connected with receiver according to the purpose of reconnoitring with reconnoitre selected the sending out of concrete condition in area-receive apart from r; (3) start the transmission power supply, according to voltage, size and the frequency of reconnoitring the selected multifrequency electric current transmitter transmission of needs electric current, start multifrequency electric current transmitter and receiver, it is underground that multifrequency electric current transmitter will specify the electric current of waveform, voltage, size and frequency to be sent to by electrodes of A and B, and receiver is once measured the magnetic responsiveness vertical magnetic field component H from each underground frequency content simultaneously _z(magnetic responsiveness is little of 10 usually ^-6Each parameter (I, dL, r, the H that A/m even littler), will send and receive in the receiver _z) deposit internal memory automatically in and respectively by formula (5), (10), (15), (24) calculate the apparent resistivity ρ in far field, near region, middle district automatically _a, automatic drafting pattern and data and map are stored in the internal memory of receiver.

The dark device of the present invention's magnetic survey comprises transmission power supply (genset), with send two electrodes of A and the B that multifrequency electric current transmitter that power supply is electrically connected links to each other with multifrequency electric current transmitter, 1-3 receives magnetic probe, and each output terminal that receives magnetic probe is connected with a receiver.

Sending power supply is a genset.

Multifrequency electric current transmitter is a multifrequency electric current transmitter by central processing unit (CPU) commander, control, and it can produce and send simultaneously by the electric current of specifying waveform work (height of the frequency that it contains and the number n of frequency can be determined and manual shift in advance according to the needs of reconnoitring).The voltage that its produces, the size and the frequency of electric current all can be according to the needs of reconnoitring, by manually regulating and selecting.

Receiver is an intelligent broadband multi-frequency potential difference measurement device that central processing unit (CPU) is housed.The frequency of operation of receiver is corresponding one by one with the frequency of operation of multifrequency electric current transmitter.

The present invention has overcome the E that CSAMT method in the past can only be measured one group of quadrature in the far field respectively _xAnd H _y, thereby making weak output signal, equipment is heavy, complicated, and the field survey formality is complicated, efficient is low, and the squared a series of shortcomings such as error of having amplified when calculating.Also can overcome the MELOS method need proofread and correct measurement result, loaded down with trivial details, the inefficient shortcoming of data compilation.

Distance at the zone adopts different formulas Extraction apparent resistivities, only need pre-deposit corresponding program in the CPU of receiver, does not increase the formality of field work amount and correction.

Good effect of the present invention: (1) can sent out-received apart from r is that the vast zone of arbitrary value is measured, and has greatly expanded the area that can carry out electromagnetic sounding, has reduced the number of times of mobile dispensing device, has improved work efficiency; (2) do not need to possess measurement E simultaneously _xAnd H _yFunction, the surveying instrument of use only need possess measurement H _zFunction, instrument and equipment reduce half than CSAMT method; Owing to only need measure H during field work _z, do not need to measure E _xAnd H _y, work efficiency doubles; (3) measure H with horizontal coil in the open air _z, with measurement H _yCompare, the probe coil size of its use can be bigger, and the number of turn can be more, and orientation can be more accurate, and sensitivity is higher; Direct H from measuring _zObtain underground apparent resistivity, its accuracy of observation only with an observed quantity H _zRelevant, can not introduce the error of two observed quantities, also can be through square error being amplified; Can obtain the precision higher than existing CSAMT method; The present invention does not need measurement result is carried out any correction yet, and the area that can survey than MELOS method is bigger, and formality is easier, and precision is higher; (4) can send out-receiving apart from the whole district that (observation station is to the distance at dipole center far away) gets any size and observing, only surveying a magnetic field vertical component H of galvanic couple source frequency domain electromagnetic field _z, just can obtain underground electrical distribution.

Use the present invention,, can find out subsurface geological structure and distribution of mineral deposits or solve other engineering, the hydrology and The problems of geo-environment by observing underground electrical distribution.

The present invention is for theory and the development of method and the open-air efficient and the accuracy of observation that improves electromagnetic prospecting of electromagnetic prospecting, thereby it is faster, provide mineral resources and geological foundation data efficiently for development of economic construction more accurately, both had important significance for theories, had important practical value again.

Description of drawings

Fig. 1 is the synoptic diagram of apparatus of the present invention and observation procedure embodiment.

Embodiment

The invention will be further described below in conjunction with drawings and Examples.

With reference to accompanying drawing, apparatus of the present invention embodiment comprises transmission power supply (genset) 1, the multifrequency electric current transmitter 2 that is electrically connected with transmission power supply 1, two electrodes of A and the B that link to each other with multifrequency electric current transmitter 2, place reception magnetic probe 3-1,3-2, the 3-3 near region, Zhong Qu, far field respectively, the output terminal that receives magnetic probe 3-1,3-2,3-3 is connected with receiver 4-1, the 4-2, the 4-3 that place near region, Zhong Qu, far field respectively.

Multifrequency electric current transmitter 2 is the multifrequency electric current transmitters by central processing unit (CPU) commander, control, and it can produce and send simultaneously by the electric current of specifying waveform work (height of the frequency that it contains and the number n of frequency can be determined and manual shift in advance according to the needs of reconnoitring); The voltage that its produces, the size and the frequency of electric current all can be according to the needs of reconnoitring, by manually regulating and selecting.

Receiver 4-1,4-2,4-3 be one by the broadband multi-frequency potential difference measurement device under central processing unit (CPU) control.The frequency of operation of receiver 4 is corresponding one by one with the frequency of operation of transmitter 2.

Principle of work is as follows: the power delivery that sends power supply 1 generation is to multifrequency electric current transmitter 2, the electric current of the characteristic frequency that multifrequency electric current transmitter 2 produces is sent into underground via electrodes of A and B, receive magnetic probe 3-1,3-2,3-3 respectively the vertical component H of the magnetic responsiveness of the earth generation that is positioned near region, Zhong Qu, far field _z(this response contains the information of the electrical distribution of subsurface material) is converted into the voltage signal ε that is directly proportional with variation rate of magnetic flux $(\mathrm{\ϵ}=-\frac{\mathrm{d\φ}}{\mathrm{dt}}),$ Be sent to receiver 4-1,4-2, the 4-3 near region, Zhong Qu, far field, under the control of CPU separately, commander, receiver 4-1,4-2,4-3 once measure from the near region respectively simultaneously, (magnetic responsiveness is little of 10 usually for the magnetic responsiveness of each underground frequency content in Zhong Qu, far field ^-6A/m even littler); Each parameter (I, dL, r, H that micro computer in receiver 4-1,4-2, the 4-3 will send and receive _z) deposit internal memory automatically in and calculate the apparent resistivity ρ near region, Zhong Qu, far field automatically according to formula (10), (15), (24), (5) _a, automatic drafting pattern and data and map are stored in the internal memory of receiver.

Operation steps: (1) is arranged and is sent power supply 1, will send power supply 1 and be connected with multifrequency electric current transmitter 2, and multifrequency electric current transmitter 2 is connected with B with two electrodes of A, and the distance between electrodes of A and the B (i.e. Gong Dian dipole moment) dL determines according to reconnoitring needs; (2) according to the purpose of reconnoitring with reconnoitre the sending out-receive of the selected respectively near region of concrete condition, Zhong Qu, far field in area apart from r _Closely, r _In, r _Far, with send power supply at a distance of r _Closely, r _In, r _FarThe place arrange reception magnetic probe 3-1,3-2, the 3-3 near region, Zhong Qu, far field respectively, and the output terminal that will receive magnetic probe 3-1,3-2,3-3 is connected with receiver 4-1, the 4-2, the 4-3 that place near region, Zhong Qu, far field respectively; (3) start the transmission power supply, according to voltage, size and the frequency of reconnoitring the selected multifrequency electric current transmitter transmission of needs electric current, start multifrequency electric current transmitter and receiver, it is underground that multifrequency electric current transmitter will specify the electric current of waveform, voltage, size and frequency to be sent to by electrodes of A and B, and subsequent step is then carried out automatically by receiver.

Claims (2)

1. all-zone couple source frequency domain magnetic depth measuring method, it is characterized in that, may further comprise the steps: (1) is arranged and is sent power supply, to send power supply is connected with multifrequency electric current transmitter, multifrequency electric current transmitter is connected determining according to reconnoitring needs between electrodes of A and the B apart from dL with B with two electrodes of A; (2), arranging at a distance of the place of r and receive magnetic probe with sending power supply, and the output terminal that will receive magnetic probe is connected with receiver according to the purpose of reconnoitring with reconnoitre selected the sending out of concrete condition in area-receive apart from r; (3) start the transmission power supply, according to voltage, size and the frequency of reconnoitring the selected multifrequency electric current transmitter transmission of needs electric current, start multifrequency electric current transmitter and receiver, it is underground that multifrequency electric current transmitter will specify the electric current of waveform, voltage, size and frequency to be sent to by electrodes of A and B, and receiver is once measured the magnetic responsiveness vertical magnetic field component H from each underground frequency content simultaneously _z, receiver is interior with the correlation parameter I that receives, dL, r, H _zAutomatically deposit internal memory and difference by formula (5), (10), (15), (24) in:

${\mathrm{\ρ}}_a={\left\{\frac{\mathrm{IdLr}{\left(\frac{{\mathrm{\ω}}_l\mathrm{\μ}}{2}\right)}^{3/2}(s^{3/2}-1)}{\mathrm{\π}15[\mathrm{Re}{H}_z\left({\mathrm{\ω}}_l\right)-\mathrm{Re}{H}_z\left({\mathrm{\ω}}_h\right)]}\right\}}^{2/3}---\left(10\right)$

In the formula, r is for sending out-receive distance, and I is an electric current of supplying with electrodes of A and B, and dL is the distance between electrodes of A and the B, and ω is the circular frequency of electric current, and μ is the magnetoconductivity of underground medium,

Be the angle of r and transmitting electrode forward, ρ is the resistivity of the earth that is detected, calculates the apparent resistivity ρ in far field, near region, middle district automatically _a, automatic drafting pattern and data and map are stored in the internal memory of receiver.

2. all-zone couple source frequency domain magnetic depth measuring device, it is characterized in that, comprise that one sends power supply (1), the multifrequency electric current transmitter (2) that is electrically connected with transmission power supply (1), two electrodes of A and the B that link to each other with multifrequency electric current transmitter (2), place 3 reception magnetic probes (3-1,3-2,3-3) near region, Zhong Qu, far field respectively, 3 receive magnetic probe (3-1,3-2,3-3) output terminals and are connected with 3 receivers (4-1,4-2,4-3) that place near region, Zhong Qu, far field respectively; Multifrequency electric current transmitter (2) is a multifrequency electric current transmitter by central processing unit commander, control, this multifrequency electric current transmitter (2) can produce and send simultaneously by the electric current of specifying waveform work, and the height of the frequency that this multifrequency electric current transmitter (2) contains and the number n of frequency can be determined and manual shift in advance according to the needs of reconnoitring; The voltage that its produces, the size and the frequency of electric current all can be according to the needs of reconnoitring, by manually regulating and selecting; Receiver (4-1,4-2,4-3) be one by the broadband multi-frequency potential difference measurement device under the central processing unit control; The frequency of operation of receiver (4-1,4-2,4-3) is corresponding one by one with the frequency of operation of transmitter (2).