CN105929455A - Device and method of multi-channel transient electromagnetic method three-dimensional detection - Google Patents

Abstract

This invention provides a device and method of multi-channel transient electromagnetic method three-dimensional detection. The device comprises an emitting electrode pair and a distributed collection station which is arranged at a position with a first preset distance to the emitting electrode pair. The distributed collection station comprises multiple electrode pairs which are arranged on multiple measurement lines, and each of the measurement lines is provided with a receiving electrode pair or multiple receiving electrode pairs. The method comprises a step of carrying out equivalent conversion of the transient electromagnetic observation data obtained by the distributed collection station into ground virtual seismic field data, a step of obtaining the virtual seismic data of any point in a ground through the ground virtual seismic field data obtained through conversion, and a step of determining the boundary surface of a ground target body to a surrounding rock according to the seismic data of any point in the ground. The practicability is strong, the data collection precision is high, a fine interpretation cross section can be obtained, and the boundary surface of the ground target body and the surrounding rock is intepreted visually.

Description

A kind of apparatus and method of multichannel transient electromagnetic method three-dimensional detection

Technical field

The present invention relates to coalfield-hydrogeology and geophysics field, be specifically related to a kind of multichannel transient electrical The apparatus and method of magnetic method three-dimensional detection.

Background technology

MTEM (Multi-channel Transient Electromagnetic Method, multichannel transient electrical Magnetic method) it is originally envisaged that be by extracting the difference estimation between the EM data that same place different time obtains The distribution situation of underground natural gas reservoirs.

As it is shown in figure 1, schematic diagram is laid in the device field for the experiment of multichannel transient electromagnetic method.On figure " point " represents each position launching limit in test, and " cross " represents the position of observation station.In test In, system carries out array multi-components transmitting along survey line, and many of array amount, multi-components are observed.Launch The bipolar square wave of dutycycle 100% launched by machine, and emitter stage spacing is 250 meters, launches.Seeing Point position, uses receiver to carry out axial type or equator to formula observation electric field and vertical magnetic field, electric field The electrode spacing of observation is 125 meters.

MTEM operation principle is as shown in Figure 2.MTEM groundwork feature is: emission electrode pair with connect Receive electrode to be pointed on same survey line, take the observation system of multicast.This device pattern and ground Seismic exploration data observation mode is more close, data processing method also with seismic prospecting basic simlarity, the most logical Cross migrated section figure, the ground electrical information of a certain depth targets body under coming speculatively altogether.

At the initial stage that MTEM method is tested, receive device record electric field level component, vertically divide Amount, and the parameter such as the derivative that vertical magnetic field is in time.Modeling Research subsequently and data processed result table Bright, except electric field level component, other component does not reflect the more information of buried target body. Therefore, the later stage takes axial type equipment as shown in Figure 2.

MTEM method uses electric dipole source to carry out signal transmitting, uses electric dipole array to record the earth Electromagnetic response, source position and the offset distance received between electric dipole are generally 2 times of objective body degree of depth To 4 times of objective body degree of depth.Whole system moves along survey line, until completing the data acquisition work of whole piece survey line Make.The peak value of the earth voltage response of each measuring point and ground resistivity value and reception and transmission range exist following near Like expression formula:

$V\≈{10}^6\·{\mathrm{\Δx}}_s\·{\mathrm{\Δx}}_r\·I\·\frac{{\mathrm{\ρ}}^2}{f_s{r}^5}$

Wherein, Δ x_s,Δx_rBe respectively source electrode away from receive electrode spacing, I is source electric current, f_sChange for source Frequency, r is offset distance, and ρ is resistivity.As can be seen from the above equation, along with the increase of offset distance r, The voltage signal that reception obtains, by sharp-decay, is difficult to obtain quality and preferably believes when offset distance is bigger Number.Additionally, conventional method is for when complex geological structure, hypsography, it is unfavorable for finely visiting Survey.

Summary of the invention

The present invention provides the apparatus and method of a kind of multichannel transient electromagnetic method three-dimensional detection, utilizes earth thing Reason method, completes the high 3-D data acquisition of precision, obtains Fine structural interpretation section.

In order to realize foregoing invention purpose, the technical scheme that the present invention takes is as follows:

A kind of device of multichannel transient electromagnetic method three-dimensional detection, including: emission electrode is adopted with distributed Collection station；

Apart from described emission electrode to arranging described distributed capture station at the first predeterminable range；

Described distributed capture station includes the multiple reception electrodes pair being arranged on a plurality of survey line, every survey line On arrange one receive electrode to or multiple reception electrode pair.

Alternatively, the spacing of two electrodes of described emission electrode pair is the second predeterminable range.

Alternatively, the line of described emission electrode pair is parallel or vertical with the survey line at described distributed capture station Directly.

For solving above-mentioned technical problem, the present invention also provides for a kind of multichannel transient electromagnetic method three-dimensional detection Method, including:

The transient electromagnetic observation data equivalency transform obtained at distributed capture station is terrestrial virtual seismic wave field Data；

The described terrestrial virtual seismic wavefield data obtained by conversion, it is thus achieved that underground any point is virtually Shake data；

According to the geological data of described underground any point, descend objective body with country rock separating surface definitely.

Alternatively, the transient electromagnetic observation data equivalency transform obtained at distributed capture station is terrestrial virtual Seismic wavefield data includes:

The transient electromagnetic observation data equivalency transform obtained at distributed capture station according to equation below is ground Virtual seismic wavefield data:

$E(x,y,z,t)=\frac{1}{2\sqrt{{\mathrm{\πt}}^3}}{\∫}_0^{\mathrm{\∞}}{\mathrm{\τe}}^{-\frac{{\mathrm{\τ}}^2}{4t}}U(x,y,x,\mathrm{\τ})d\mathrm{\τ},$

Wherein, (x, y, z, be t) distributed capture station transient electromagnetic observation data to E, and U (x, y, z, τ) is for turn The virtual seismic wavefield data changed, t is the distributed capture station transient electromagnetic data time, and τ is virtual earthquake The wavefield data time.

Alternatively, the described terrestrial virtual seismic wavefield data obtained by conversion, it is thus achieved that underground any point Geological data include:

According to the described terrestrial virtual seismic wavefield data obtained, utilize from ground to the method for underground recursion, Obtain the virtual geological data of underground any point.

Alternatively, the described terrestrial virtual seismic wavefield data obtained by conversion, it is thus achieved that underground any point Virtual earthquake packet include:

Geological data according to equation below acquisition underground any point:

$U(x,y,z,t)=-\frac{1}{4\mathrm{\π}}\underset{Q_0}{\∫\∫}\{\frac{\∂}{\∂n}\left(\frac{1}{r}\right)-\frac{1}{r}\frac{\∂}{\∂n}-\frac{1}{vr}\frac{\∂r}{\∂n}\frac{\∂}{\∂t}\}U(\mathrm{\ξ},\mathrm{\η},{\mathrm{\ζ}}_0,t+\frac{r}{v})dQ$

Wherein, U (x, y, z, t) be t underground any point (x, y, z) the virtual seismic wavefield data value at place, T is observation time, n be any point (x, y, z) normal orientation at place,It is that earth's surface is arbitrary Virtual seismic wavefield data value at Dian, Q₀It is the measured zone on earth's surface,R is certain sight of ground Survey measuring point is distance of certain point to underground.

Compared to the prior art the present invention, has the advantages that

Apparatus and method of the present invention, is modified to stereo observing system by conventional vision systems, its application Higher, accuracy of data acquisition is high；Conventional apparent resistivity processing method is modified to virtual seismic wave field explain Technology, it is thus achieved that Fine structural interpretation section, explains the separating surface of buried target body and country rock intuitively.

Accompanying drawing explanation

Fig. 1 is the arrangement of measuring-line schematic diagram of correlation technique；

Fig. 2 is the grounded source MTEM data acquisition modes schematic diagram of correlation technique；

Fig. 3 is the schematic diagram of the device of the multichannel transient electromagnetic method three-dimensional detection of the embodiment of the present invention；

Fig. 4 is the flow chart of the method for the multichannel transient electromagnetic method three-dimensional detection of the embodiment of the present invention；

Fig. 5 is the copper mine body Model schematic diagram of the embodiment of the present invention one；

Fig. 6 is the ore body model depth migration profile of the embodiment of the present invention one.

Detailed description of the invention

For making the goal of the invention of the present invention, technical scheme and beneficial effect of greater clarity, below in conjunction with Embodiments of the invention are illustrated by accompanying drawing, it should be noted that in the case of not conflicting, this Shen Embodiment in please and the feature in embodiment can mutual combination in any.

As it is shown on figure 3, the embodiment of the present invention provides the dress of a kind of multichannel transient electromagnetic method three-dimensional detection Put, including: emission electrode to and distributed capture station；

Apart from described emission electrode to arranging described distributed capture station at the first predeterminable range；

Described distributed capture station includes the multiple reception electrodes pair being arranged on a plurality of survey line, every survey line On arrange one receive electrode to or multiple reception electrode pair.

The spacing of two electrodes of described emission electrode pair is the second predeterminable range.

The line of described emission electrode pair is parallel or vertical with the survey line at described distributed capture station.

In implementation process, at a distance of squeezing into transmitting from two positions of ground A, B of 1000---2000 rice Electrode, and connect A, B 2 point with wire, form transmitting terminal, or the vertical direction face cloth at AB Transmitting terminal.Launch 10--50A electric current, 500-1000V voltage to underground, send the coding figure place of signal 1-4095(2¹²-1) reference frequency < 10kHz of signal, is sent；The dynamic range sending signal is 160dB.

The a plurality of survey line of the certain position of range transmission end is laid simultaneously and receives device, at most can be simultaneously Measure 1000 roads, be received signal, sample rate 64kHz simultaneously, the time synchronized essence launched and receive Spend 5 μ s.Primary emission distributed capture station receives simultaneously, can obtain the geological information of three-dimensional, more Add beneficially fine granularing scalability.This scheme can realize from earth's surface superficial part (500m) to underground deep (2000 M) more finely detection, the lifting reconnoitred to three-dimensional (3D) solid from two dimension (2D) section.

In the method that conventional apparent resistivity section is explained, the earth can be regarded as a linear time invariant system, The source signal launched by ground electrode is regarded as system input, received signal is regarded as system output letter Number, according to linear time invariant system characteristic, output signal is represented by:

a_k(x_s,x_r, t)=s (x_s,x_r,t)*g(x_s,x_r,t)+n(x_r,t)

In formula: x_s,x_rRepresent emission electrode respectively to the center with reception electrode pair, a_k(x_s,x_r, t) table Show output signal；s(x_s,x_r, t) represent the system response relevant with launching signal, reception and transmission range etc.； g(x_s,x_r, t) represent the earth impulse response from geologic objective body；T express time time delay, n (x_r, t) represent Noise.

In order to preferably record the earth impulse response relevant with geologic body, when data acquisition and processing (DAP), Have employed following 3 guardian technique: (1), when measuring induced voltage, is measured simultaneously and sent electric current, To obtain the response of measurement system；(2) by the deconvolution to observation signal with system response, it is thus achieved that big Earth pulse responds；(3) by repeatedly superposition, signal to noise ratio is increased.

According to the earth impulse response, calculate apparent resistivity value:

$\mathrm{\&rho;}=\frac{{\mathrm{\&mu;r}}^2}{10t_{peak}}$

In formula: t_peakRepresent the peak value moment of the earth impulse response；R represents reception and transmission range；μ represents Jie The pcrmeability of matter.

The earth impulse response is processed further, the section of 3 kinds of multi-forms can be obtained.(1) pulse Response common offset from section, the greatly resistivity of the peak value of impulse response and peak value moment with underground medium Relevant, the earth impulse response under same offset distance is organized into common offset section, underground can be reflected The ground electrical information of the same degree of depth.(2) CMP apparent resistivity section, according to regarding that formula (3) defines Resistivity, obtains the apparent resistivity of CMP----offset distance section.This section reflection different measuring points electricity Resistance rate is with the variation relation of the degree of depth.(3) concentrically point set 1D inverting section, by under different offset distances After the reverse simulation of pulse respond, it is thus achieved that the apparent resistivity of CMP---degree of depth two dimensional cross-section..

The embodiment of the present invention utilizes multiple tracks transient electromagnetic method acquisition mode, and the present invention is for the solution of metal copper mine Method of releasing compares similar with seismic prospecting, uses for reference the data processing technique of seismic prospecting.Electric current is in the earth formation Circulation way different from seismic wave circulation way in same formation, first observation signal equivalence is turned Change virtual seismic signal into, explain the most again.

As shown in Figure 4, the embodiment of the present invention provides the side of a kind of multichannel transient electromagnetic method three-dimensional detection Method, including:

S101, the transient electromagnetic observation data equivalency transform obtained at distributed capture station are terrestrial virtual ground Seismic wave field data；

S102, the described terrestrial virtual seismic wavefield data obtained by conversion, it is thus achieved that underground any point Virtual geological data；

S103, geological data according to described underground any point descend the boundary of objective body and country rock definitely Face.

S101 includes:

The transient electromagnetic observation data equivalency transform obtained at distributed capture station according to equation below is ground Virtual seismic wavefield data:

$E(x,y,z,t)=\frac{1}{2\sqrt{{\mathrm{\&pi;t}}^3}}{\&Integral;}_0^{\mathrm{\&infin;}}{\mathrm{\&tau;e}}^{-\frac{{\mathrm{\&tau;}}^2}{4t}}U(x,y,x,\mathrm{\&tau;})d\mathrm{\&tau;};$

Wherein, (x, y, z, be t) distributed capture station transient electromagnetic observation data to E, and U (x, y, z, τ) is for turn The virtual seismic wavefield data changed, t is the distributed capture station transient electromagnetic data time, and τ is virtually The seismic wave field data time.

S102 includes:

According to the described terrestrial virtual seismic wavefield data obtained, use from ground to the method for underground recursion, From ground to underground back-extrapolate, it is thus achieved that the virtual geological data of underground any point.

Field in exploring due to transient electromagnetic is propagated with diffusion mode in underground, and this diffusion mode is propagated Electromagnetic field does not have the character of reflection and refraction on the objective body separating surface with country rock, thus to objective body Insensitive with the reflection of the separating surface of country rock；And the field in seismic prospecting is propagated with wave in underground, this The field that the form of kind is propagated has reflection and the character of refraction, quick with the reflection of the separating surface of country rock to objective body Sense.

If data Processing and Interpretation Technology ripe in seismic prospecting to be used for reference, must be become by mathematic integral Change, be meet wave equation virtual by the time domain transient electromagnetic field data equivalency transform meeting diffusion equation Wavefield data, followed by the formation method technology of some comparative maturities grown up in earthquake, than Solve the separating surface being visited objective body more intuitively.The physical significance of virtual seismic wavefield data is: with ground The Equivalent Elasticity characteristic that the lower real electrical characteristics data of objective body is corresponding.

Specifically, according to the virtual geological data of equation below acquisition underground any point:

$U(x,y,z,t)=-\frac{1}{4\mathrm{\&pi;}}\underset{Q_0}{\&Integral;\&Integral;}\{\frac{\&part;}{\&part;n}\left(\frac{1}{r}\right)-\frac{1}{r}\frac{\&part;}{\&part;n}-\frac{1}{vr}\frac{\&part;r}{\&part;n}\frac{\&part;}{\&part;t}\}U(\mathrm{\&xi;},\mathrm{\&eta;},{\mathrm{\&zeta;}}_0,t+\frac{r}{v})dQ$

Wherein, U (x, y, z, t) be t underground any point (x, y, z) the virtual seismic wavefield data value at place, T is observation time, n be any point (x, y, z) normal orientation at place,It is that earth's surface is arbitrary Virtual seismic wavefield data value at Dian, Q₀It is the measured zone on earth's surface,R is certain sight of ground Survey measuring point is distance of certain point to underground.

According to this formula above, can be the virtual seismic data of arbitrfary point on groundThrough integral and calculating, integral domain Q₀It is transient electromagnetic observation area, ground, To the virtual geological data U of position, arbitrfary point, underground, (x, y, z, t), the underground according to integration gained is any The virtual geological data of point, can preferably judge the electrical separating surface of buried target body and country rock.

Embodiment

When certain survey district carries out transient electromagnetic work, its ore body buried depth is about 1000m, and tax is deposited In Carboniferous System HUANGLONG group-group layer position, ship mountain, in like stratiform output, its occurrence and form and country rock one Cause.Ore body spread in the plane is wider, and changes less in the degree of depth.Ore body is mainly by cupric silicon card Rock, cupriferous pyrite, cupric serpentinite, copper-bearing pyrrhotite etc. are constituted.The direct country rock in ore body chassis is System mountain, Koryo group rock and quartz diorite under the Carboniferous System, based on horn stone siltstone.Ore body directly pushes up Dish rock is HUANGLONG group griotte, and top is the rocks such as Xi-Xia group griotte.Ore body simple structure, research Degree is higher.Having preferable electrical property feature difference between ore body and country rock, ore body itself has good Electric conductivity, and country rock mainly shows as high resistant feature, is suitable for electromagnetic exploration.Early stage is through repeatedly surveying Visit, it is thus achieved that ore body model (Fig. 5).

Country rock is according to being electrically divided into three layers, and ground floor resistivity is 1000 Ω m, second layer resistivity Being 500 Ω m, substrate resistance rate is 5000 Ω m.Ground floor ore body resistivity value is 100 Ω m, Compose along the interface between ground floor and second layer country rock and deposit, run through whole survey region；Second layer ore body Compose along the interface between the second layer and substrate and deposit, in the range of being distributed mainly on 300m--1100m.Two-layer ore deposit Body thickness is each about 50m--100m, is about 600m--800m along its extension moving towards direction.Ore body has Having certain fluctuating, the vertical characteristics scope of ground floor ore body is about between 300m--1000m, the second layer Ore body is distributed between 800m--1000m.

According to described survey district copper mine ore body, carry out modelling and multiple tracks transient electromagnetic data is just drilling meter Calculating, the method then proposed by the embodiment of the present invention carries out seismic wavefield data conversion and process.Fig. 6 is Depth migration section after seismic processing, is analyzed it follows that (1) processing profiles according to figure Electrical interface and the rolling shape of two-layer ore body are substantially reflected.Reflection according to virtual seismic wave field Rule with the phase property of reflection line-ups it is inferred that Article 1 and Article 2 lineups are the most corresponding The end face of ground floor ore body, bottom surface and first country rock aspect, Article 3 lineups correspond to the second layer The end face of ore body；(2) the model average resistivity value used is relatively big, owing to high frequency is become by high resistance medium The filter action divided is relatively weak, and when the degree of depth is bigger, the radio-frequency component of wave field is still the abundantest, has Higher resolution, still has significantly reflection for deeper second layer ore body end face；(3) due to second The laterally continuity scope of layer ore body is less, and the lineups of its end face corresponding amplitude in section both sides has subtracted Little.

Although disclosed embodiment is as above, but its content is only to facilitate understand the present invention Technical scheme and the embodiment that uses, be not intended to limit the present invention.Technology belonging to any present invention Skilled person, on the premise of without departing from disclosed core technology scheme, permissible The form implemented and details make any amendment and change, but the protection domain that the present invention is limited, still Must limit in the range of standard with appending claims.

Claims (7)

1. the device of a multichannel transient electromagnetic method three-dimensional detection, it is characterised in that including: launch Electrode to and distributed capture station；

Apart from described emission electrode to arranging described distributed capture station at the first predeterminable range；

Described distributed capture station includes the multiple reception electrodes pair being arranged on a plurality of survey line, every survey line On arrange one receive electrode to or multiple reception electrode pair.

2. device as claimed in claim 1, it is characterised in that: two electricity of described emission electrode pair The spacing of pole is the second predeterminable range.

3. device as claimed in claim 1, it is characterised in that: the line of described emission electrode pair with The survey line at described distributed capture station is parallel or vertical.

4. the method for a multichannel transient electromagnetic method three-dimensional detection, it is characterised in that including:

The transient electromagnetic observation data equivalency transform obtained at distributed capture station is terrestrial virtual seismic wave field Data；

The described terrestrial virtual seismic wavefield data obtained by conversion, it is thus achieved that underground any point is virtually Shake data；

According to the geological data of described underground any point, descend objective body with country rock separating surface definitely.

5. method as claimed in claim 4, it is characterised in that: the wink that distributed capture station is obtained Become electromagnetic observation data equivalency transform to include into terrestrial virtual seismic wavefield data:

The transient electromagnetic observation data equivalency transform obtained at distributed capture station according to equation below is ground Virtual seismic wavefield data:

$E(x,y,z,t)=\frac{1}{2\sqrt{{\mathrm{\&pi;t}}^3}}{\&Integral;}_0^{\mathrm{\&infin;}}{\mathrm{\&tau;e}}^{-\frac{{\mathrm{\&tau;}}^2}{4t}}U(x,y,z,\mathrm{\&tau;})d\mathrm{\&tau;};$

Wherein, (x, y, z, be t) distributed capture station transient electromagnetic observation data to E, and U (x, y, z, τ) is for turn The virtual seismic wavefield data changed, t is the distributed capture station transient electromagnetic data time, and τ is virtual earthquake The wavefield data time.

6. method as claimed in claim 4, it is characterised in that: the described ground obtained by conversion Virtual seismic wavefield data, it is thus achieved that the geological data of underground any point includes:

According to the described terrestrial virtual seismic wavefield data obtained, utilize from ground to the method for underground recursion, Obtain the virtual geological data of underground any point.

7. method as claimed in claim 6, it is characterised in that: the described ground obtained by conversion Virtual seismic wavefield data, it is thus achieved that the virtual earthquake packet of underground any point includes:

Geological data according to equation below acquisition underground any point:

$U(x,y,z,t)=-\frac{1}{4\mathrm{\&pi;}}\underset{Q_0}{\&Integral;\&Integral;}\{\frac{\&part;}{\&part;n}\left(\frac{1}{r}\right)-\frac{1}{r}\frac{\&part;}{\&part;n}-\frac{1}{vr}\frac{\&part;r}{\&part;n}\frac{\&part;}{\&part;t}\}U(\mathrm{\&xi;},\mathrm{\&eta;},{\mathrm{\&xi;}}_0,t+\frac{r}{v})dQ$

Wherein, U (x, y, z, t) be t underground any point (x, y, z) the virtual seismic wavefield data value at place, T is observation time, n be any point (x, y, z) normal orientation at place,It is that earth's surface is arbitrary Virtual seismic wavefield data value at Dian, Q₀It is the measured zone on earth's surface,R is certain sight of ground Survey measuring point is distance of certain point to underground.