Geoelectroprospecting

 

The invention relates to the field of geophysical methods of prospecting and exploration of minerals and can be used to determine the parameters of the geological section and detect local inhomogeneities. Effect: increased resolution receiving the electromagnetic response of the earth's surface receiving dipole electromagnetic field sensors using electromagnetic sensing of the geological section. Essence: excite geological cross-section excitation signal and record the electromagnetic response to the probing signal system receiving dipole sensors. The sensors are located on the surface of the probe section of the geological section with coordinate reference with respect to the emitter of the probing signal in the circle of diameter not less than the depth zfin a two-dimensional grid with step hzfalong and across the direction of one of the horizontal components of the electric field in the sensing area. The sensors are oriented parallel to the direction of the horizontal component of the electromagnetic field. Receiving electromagnetic response aktalnye components are multiplied by weighting coefficients, obtained from the corresponding expressions. Multiplied by the values of the individual spectral components from all the receiving dipole sensors put algebraically and get the resulting spectrum of the entire system. Then perform the inverse Fourier transform of this spectrum, which is the resultant signal to the electromagnetic response of the entire system receiving dipole sensors. This signal is judged on the structure of the geological section. 4 Il.

The invention relates to the field of geophysical methods of prospecting and exploration of minerals and can be used to determine the parameters of the geological section and detect local variations.

Known methods and devices of the survey method (see, for example, and.with. The USSR 324601, IPC G 01 V 3/02, BI 2, 1972), according to which the reception of e/m response exercise one receiving probe.

The disadvantage of this method is that it cannot give information about the direction of the incoming response.

Example of a multi-array system described in the method gearside and the device, providing for and.with. The USSR 1233068, G 01 V 3/02 from 23.05.86, BI 19). According to the method of using the system several elename electric field of the Central feeding electrode while changing a spatial orientation of the lines of force by changing the ratios of the currents of the side feeding electrode. In the scanning measure the phase and magnitude of current in the circuits of all of the electrodes.

The disadvantage of this method of gearside is insufficient resolution measurement method, especially for deeply located heterogeneity of the geological section, which does not allow to obtain information about the position of the inhomogeneity on the depth of the sensed area. Or require the placement of electrodes on the depth in special wells, which in itself is a very time consuming process. When placing the probes on the surface is provided by sensing only the top layer on the square, contoured placement of the electrodes.

The prototype of the invention is a method of sounding in the near zone (TEM), described in the book Matveeva B. K. Electromagnetics: the textbook for high schools - 2nd edition, revised and enlarged. - M.: Nedra, 1990, 368 Art. p. 119, Fig. 47. According to this method using the radiating probe pulse current excite geological cross-section. As a result, in the geological cross-section is formed of e/m response of the unsteady field due to the excitation of the second kind. Reception and registration of the electromagnetic response is realized by one adoptive electromagnetic sensor the population field in the near zone is insufficient resolution receiving the electromagnetic response of the earth's surface single receiver sensor of the electromagnetic field due to the impossibility of ensuring the selection of the received signal in the direction of.

Solved technical problem of the invention is to increase the resolution receiving the electromagnetic response of the earth's surface receiving sensors of the electromagnetic field with e/m sensing geological section.

Solved technical problem in geoelectroprospecting, which consists in the excitation of the geological section of the probing signal Ucs(t) and the signal of the electromagnetic response Uc(t) on the sounding signal system M foster dipole electromagnetic field sensors located on the surface of the probe section of the geological section with coordinate reference with respect to the emitter of the probing signal, is achieved by the fact that M foster dipole sensors are oriented parallel to the direction of the horizontal component of the electromagnetic field within the study area geological section with a center pointand placed on the surface of the sensed area within a circle with diameter D is not less than the depth zf(Dzfin a two-dimensional grid with step hzfalong and across the direction of one of the ub>c(t) on the excitation signal Ucs(t) produced by the system M foster dipole sensors synchronously to each other and received signals from these sensors is decomposed in the frequency spectra, the spectral components which Um() are multiplied by the weighting factors Jm(), obtained from the expressionand multiplied the values of the individual spectral componentsall M foster dipole sensors put algebraically and get the resulting spectrum of the entire system receiving dipole sensors Uc(), then perform the inverse Fourier transform of this spectrum that is the result electromagnetic signal response Uc(t) of the entire system receiving dipole electromagnetic field sensors from the zone focus with the center pointthis signal is judged on the structure of the geological section, where M is an integer greater than or equal to one,spatial cutoff frequency associated with the step lattice ratio=xf, yf- coordinates of the focal point on the plane z=zfxm, ym- the location of the m-th dipole sensor in the plane z= 0, Efthe K factor, which characterizes the amplitude of the field at the point of focusis the wave number of the ith layer of the cut,
i- complex dielectric permittivity of the i-th layer of the cut,
i- the magnetic permeability of the i-th layer of the cut,
wave resistance of the i-th layer of the cut,
wave resistance of the air,
x,y- spatial frequency along the x and y coordinates,
the vector of spatial frequencies,
- the module of the vector of spatial frequencies,

- two-dimensional radius-vector of the point of focus,
two-dimensional radius-vector of the point of placement of the m-th sensor,
- the scalar product of vectors,
- funk is anticolana the plane of incidence, in the i-th layer of the geological section, containing the focus plane (zi-1< zf< zi), where
- transfer coefficients of the components of the spatial spectrum,
the reflection coefficients determined using iterative procedure, starting with j = N and





In Fig. 1 shows the geometry for solving the problem of finding the weights {Jm()} geoelectroprospecting.

In Fig. 2 shows the results of calculating the field distribution in the focal plane along the Y axis for a flat 3x3 grid electric dipole geometry according to Fig.1.

In Fig. 3 shows the results of calculation of the field distribution in the focal plane along the x axis.

In Fig. 4 shows a functional diagram of the device that implements the proposed geoelectroprospecting.

Geometry for solving the problem of geoelectroprospecting in Fig. 1 includes a coordinate system XYZ with origin at the point X=0, Y=0, Z=0 located at the daily feed Vinormal to the surface S. the Material environment of the sensed region Vicharacterized electrical parametersi,i,i. On the surface S of the sensed region Viin the plane Z=0 are M electric dipoles characterized by the amplitudes of electric currents JmwhereThese electric dipoles in accordance with the principle of reciprocity (see, for example, Semenov N. A. Technical electrodynamics. - M.: "Link", 1973, page 151) meet in the apparatus of the geoelectroprospecting, foster dipole sensors electromagnetic field induced on them by the electromagnetic signal response amplitudes of the currents Jm. These dipoles are located on the surface S with a step h on the X-axis and Y-axis with the polarization vector oriented along the axis X. the Amplitude of the currents Jmobtained from the solution of the expression (1) are in the proposed method, the weights in the allocation of the signal response from the zone of focus.

At a depth of Zfin the probing region Viis located in the focal plane Z=Zf,- radius-vactm> is the radius - vector of the m-th electric dipole, rf- two-dimensional radius-vector in the focal point in a focal plane Zf. The field distribution in the plane of focus when the solution isfunctions in the focus point.

On the graph (Fig. 2) shows the results of a calculation example of the focus along the y-axis at a depth of Zf=1000 m in Fig. 1 for a grid of nine electric dipoles (grid 33), located on the step n=100 m, the signal frequency of 1 MHz curve 11 and the calculation result field in the same plane for a single electric dipole in accordance with the prototype curve 12. The environment in the sensed region is characterized by the parameters: the relative permittivity= 10, conductivity= 10-5SIM/m, the magnetic permeability=1. These graphs characterize the distribution of the tangential components of the electric field Exin the focal plane Zfalong the y axis.

On the graph (Fig. 3) shows the calculation results of the same field as in Fig. 2, but along the x axis.

A device that implements the proposed method GE the receiving dipole electromagnetic field sensors 3, each of which is connected to the receiver 4, M recording units 5, each of which is connected to the output of the corresponding receiver 4. All registration blocks 5 and the probing signal generator 1 is connected to the synchronization unit 6. The outputs of the recording unit 5 via a wired or dial-up communication line 7 is connected to the input of the interface block 8 with a computer 9, geological section 10, where M1, a natural number sequence.

Emitting probe 2 and the receivers of the e/m field 3 are placed on the surface S of the geological section 10 with a coordinate binding to each other in a circle of diameter Dzfwhere probing depth zfcorresponds to the depth of the location of the focal plane, the spacing of the receiving dipole sensors h electromagnetic fields selected from the condition hzf. All foster dipole sensors are installed with the same orientation of the polarization vector.

The distribution of the electric field Exin the focal plane zfin Fig.2, generated with a grid of nine electric dipoles with the currents Jmfound from the solution of equation (1) has a pronounced global maximum at the point Fok the th plane ZX and ZY 2.53 times less than in the same field distribution for a single electric dipole curves 12 on the same figures, and in both planes, this win is the width of the zone response, respectively 6,259 times.

The calculation results suggest that the signal passed by the grating with the distribution of the currents Jmat the receiving dipole electromagnetic field sensors, will be compared with the prototype greater spatial selection in the direction of a point focus xf, yf, zfthan in the case of a single transducer, as is the case in the prototype.

Implementation of geoelectroprospecting with the device assembled according to the circuit of Fig. 4, is as follows.

Electromagnetic pulse Ucs(t) coming from the probing signal generator 1 for emitting probe 2, excites geological section 10 (region Vi).

In geological section 10 is formed by the electromagnetic response Uc(t) on the excitation signal Ucs(t), which is M foster dipole electromagnetic field sensors 3 with their amplitudes and phases determined by the geological features of the cut and melting units 5 values Um(t), where
The signal processing is performed as follows. Received signals {Um(t)} is digitized and stored in all M recording units 5 synchronously at time tZapdetermined by the signal synchronization unit 6. Then the signals {Um(t)} are transmitted over the communication line 7 to the connection unit 8 computer 9 and from there to the computer 9. The computer 9 is processed signals {Um(t)}. In the process the signals { Um(t)} is decomposed into frequency spectra {Um()} (direct Fourier transform), calculate the amplitudes of the currents Jm() the ratio of (1) for the spectral components {Um()}, multiply the spectral components {Um()} with weights Jm(and get the value of the spectral component signaladopted by the m-th receiving sensor 3
Then multiplied by the values of the individual spectral components {U'm()}, respectively, with all receiving dipole sensors 3 fold algebraically and get D/chr/969.gif">)}. With this range of {U'm()} perform the inverse Fourier transform and get the resulting signal of the electromagnetic response of the entire system receiving dipole sensors of the electromagnetic field U'c(t) from the zone of focus. This resulting signal U'c(t) and its spectrum { Um()} is correlated with the data Bank of the models obtained, for example, the results of the analysis of the local excitation source of a multilayer structure (see, for example, the book of O. W. Dautov. Modeling fields when designing electronic equipment. (Tutorial). Kazan: publishing house of Kazan State technical University, 1997, sec. 1.2, page 11. The distribution of the local field source through a layered structure). Thus, judged on the structure of the geological section and, in particular, the electric density of the species included in the layers that make up this section.

The results of example mathematical modeling of the process of focusing the system of nine (3x3) receiving dipole sensors show that the proposed geoelectroprospecting compared with the prototype provides increased RA is tchikov electromagnetic fields in electromagnetic sounding of the geological section in the order of six nine times.


Claims

Geoelectroprospecting, which consists in the excitation of the geological section of the probing signal Ucs(t) and the signal of the electromagnetic response Uwith(t) on the sounding signal system M foster dipole electromagnetic field sensors located on the surface of the probe section of the geological section with coordinate reference with respect to the emitter of the probing signal, wherein M foster dipole sensors are oriented parallel to the direction of the horizontal component of the electromagnetic field within the study area geological section with a center pointand placed on the surface of the sensed area within a circle with diameter D is not less than the depth zf(Dzfin a two-dimensional grid with step hzfalong and across the direction of one of the horizontal components of the electric field within the study area sensing and receiving electromagnetic response Uwith(t) on the excitation signal Ucs(t) produced by the system M foster dipole sensors electromagn the performance communications components which Um() are multiplied by the weighting factors Jm(), obtained from the expression

and multiplied the values of the individual spectral componentsall M foster dipole sensors put algebraically and get the resulting spectrum of the entire system receiving dipole sensors Uc(), then perform the inverse Fourier transform of this spectrum that is the result electromagnetic signal response Uwith(t) of the entire system receiving dipole electromagnetic field sensors from the zone focus with the center pointthis signal is judged on the structure of the geological section,
where M is a small number greater than or equal to one;
spatial cutoff frequency associated with the step lattice ratio=/h;
the x-axis is oriented along the horizontal component of the electric field at the point of focus
xf,f- coordinates of the focal point on the plane z = zf;
xm,is the wave number of the ith layer of the incision;
i- complex dielectric permittivity of the i-th layer of the incision;
i- the magnetic permeability of the i-th layer of the incision;
the wave resistance of the i-th layer of the incision;
wave resistance of the air;
x,y- spatial frequency along the coordinates x and y;
the vector of spatial frequencies;
- the module of the vector of spatial frequencies;


- two-dimensional radius-vector of the point of focus;
- two-dimensional radius-vector of the point of placement of the m-th sensor;
- the scalar product of vectors;
function characterizing the passage of components of the spatial spectrum, polarized parallel and perpendicular to the plane of incidence, in the i-th layer containing the focus plane (zi-1< zf< zi),
sub>j,l11,1the reflection coefficients near the upper boundary of the i-th layer, which is defined by the recurrent procedure starting with j = N and R11,lN+1,l0:




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