CN104749647A - Geological interface structure detection method, device and system - Google Patents

Abstract

The invention provides a geological interface structure detection method, device and system and relates to the fields of geology and geophysics, and the reliability and resolution of interface resolution interpretation through detection by the electromagnetic method can be improved. The method includes acquiring transient electromagnetic data of detection points of a region to be estimated; establishing a relational expression between the electromagnetic field diffusion characteristics and subsurface resistivity or induction voltage according to the detection points; according to the established relational expression, acquiring the corresponded electromagnetic response diffusion time parameters; according to the acquired electromagnetic response diffusion time parameters, interpreting the geological interface and geological structure of the subsurface medium. The reliability of interpretation of detection by the transient electromagnetic method is improved, the resolution of the method is improved, the geological interface and geological structure of the subsurface medium can be segmented directly and clearly, and the interface resolution can be performed rapidly and effectively.

Description

The detection method that a kind of geology interphase constructs, device and system

Technical field

The present invention relates to geology and geophysics field, particularly relate to the detection method of a kind of geology interphase structure, device and system.

Background technology

Transient electromagnetic method (TEM, Transient Electromagnetic Method) is a kind of common geophysical method based on electromagnetic induction, can provide ground, underground telecommunications breath.In recent years, utilize transient electromagnetic method to explore for oil, the Theory and applications research work of geothermal source and various mineral resources at development, detection is embedded in the low-resistance anomalous body of underground, TEM has proved a kind of effective method.But, due to the complicacy of electromagnet phenomenon in layering, lossy medium, still very low to the interpretation level of measured data at present.

Horizontal thin plate model uniquely can resolve with elementary function the earth-electricity model represented in transient electromagnetic field forward modelling.As time goes on, transient electromagnetic field is propagated to depths, stratum, therefore, can by each instant observation to electromagnetic signal be equivalent to a certain " floating " electrically conductive layer produce field, thus be directly conductivity-depth value the perpendicular magnetic component of observation, time-derivative, matrix conversion, inverse goes out the conductivity with change in depth, and this method is the S-method of inversion.This is a kind of traditional better simply interpretation procedure, can apply at qualitative analysis interpretation phase.

By the way of optimizing, use genetic inverse transient electromagnetic field data, make theoretical data and field data reach best-fit, obtain the optimum estimate to geological information.This estimation is a kind of guestimate based on neural network, and precision is not high.Dividing underground electrical interface by transient electromagnetic method, have employed different several methods, based on the imaging of the subsurface interface of conductance differential parameter, the equation about parameter of seeking knowledge is an implicit function, have employed genetic algorithm, has uncertainty.

In electromagnetic method data interpretation, domestic and foreign literature reports the research carrying out electromagnetic wave migration imaging with reflection shooting and imaging technique, and electromagnetic pseudo-seismic interpretation has become the hot issue of current geophysics circle.Based on the plan seismic imaging technology of reflection coefficient, the system of equations of required solution is the underdetermined system of equations, and its solution has nonuniqueness; Also have a kind of method, realize the imaging of transient electromagnetic method to interface by wave-field conversion method, but wave-field conversion equation is an ill-condition equation, solves and has certain difficulty, should use more difficult.

Along with the increase of resource exploration difficulty and the raising of engineering investigation accuracy requirement, the interpretation level of further improvement TEM, the resolving power of raising method are particularly important.If can find one fast and effectively method picture is embodied as to interface, and avoid above-mentioned complex calculations, then can be promoted.

Summary of the invention

The present invention proposes detection method, device and the system that a kind of geology interphase constructs, and can improve transient electromagnetic method detection and interface be differentiated to the reliability explained, improve resolving power.

In order to solve the problems of the technologies described above, the invention provides the detection method of a kind of geology interphase structure, comprising:

Gather the transient electromagnetic data of each sensing point of region to be assessed;

The relational expression between electromagnetic field Spreading and diffusion characteristic and subsurface resistivity or induced voltage is set up for sensing point described in each;

According to set up relational expression, obtain corresponding electromagnetic response parameter diffusion time;

According to geology interphase and the tectonic structure of the electromagnetic response parameter interpretation diffusion time underground medium obtained.

Preferably, set up the relational expression between electromagnetic field Spreading and diffusion characteristic and subsurface resistivity or induced voltage for sensing point described in each, comprising:

The relational expression between electromagnetic field Spreading and diffusion characteristic power exponent and subsurface resistivity or induced voltage is set up for sensing point described in each.

Preferably, described electromagnetic response parameter diffusion time is electromagnetic response power exponent diffusion time.

Preferably, according to geology interphase and the tectonic structure of the electromagnetic response parameter interpretation diffusion time underground medium obtained, comprising:

When the induced voltage of described sensing point is directly proportional to-2.5 power of electromagnetic field propagation time delay, the geology interphase of described medium and tectonic structure are homogeneous half space;

When the induced voltage of described sensing point is directly proportional to-4 power of electromagnetic field propagation time delay, the geology interphase of described medium and tectonic structure are high resistant layered medium;

When the induced voltage of described sensing point and the natural Exponents of electromagnetic field propagation time delay are inversely proportional to, the geology interphase of described medium and tectonic structure are spheroidite.

In order to solve the problems of the technologies described above, the sniffer that the present invention also provides a kind of geology interphase to construct, comprising:

Acquisition module, for gathering the transient electromagnetic data of each sensing point of region to be assessed;

Relating module, sets up the relational expression between electromagnetic field Spreading and diffusion characteristic and subsurface resistivity or induced voltage for sensing point described in each;

Determination module, according to set up relational expression, obtains corresponding electromagnetic response parameter diffusion time;

Explanation module, according to geology interphase and the tectonic structure of the electromagnetic response parameter interpretation diffusion time underground medium obtained.

Preferably, relating module specifically for:

The relational expression between electromagnetic field Spreading and diffusion characteristic power exponent and subsurface resistivity or induced voltage is set up for sensing point described in each.

Preferably, described electromagnetic response parameter diffusion time in relating module is electromagnetic response power exponent diffusion time.

Preferably, explanation module comprises:

Even Interpretation unit, for when the induced voltage of described sensing point is directly proportional to-2.5 power of electromagnetic field propagation time delay, determines that the geology interphase of described medium and tectonic structure are homogeneous half space;

High resistant Interpretation unit, for when the induced voltage of described sensing point is directly proportional to-4 power of electromagnetic field propagation time delay, determines that the geology interphase of described medium and tectonic structure are high resistant layered medium;

Spherical Interpretation unit, for when the induced voltage of described sensing point and the natural Exponents of electromagnetic field propagation time delay are inversely proportional to, determines that the geology interphase of described medium and tectonic structure are spheroidite.

In order to solve the problems of the technologies described above, the present invention also provides a kind of transient electromagnetic detecting system, comprise sniffer and first loop line of above-mentioned geology interphase structure, described first loop line is connected with the acquisition module of the sniffer that described geology interphase constructs, comprise and send loop line and receiving coil, place receiving coil at transmission loop line center, carry out transient electromagnetic data measurement.

Compared with prior art, method and apparatus of the present invention, passes through observed voltage data, sets up the relational expression between electromagnetic field Spreading and diffusion characteristic power exponent and subsurface resistivity; According to set up relational expression, ask for electromagnetic response power exponent diffusion time; Tried to achieve electromagnetic response power exponent diffusion time is explained geology interphase and the tectonic structure of underground medium as new argument, improve the reliability that transient electromagnetic method detection is explained, improve the resolving power of method, intuitively clearly can divide geology interphase and the tectonic structure of underground medium, realize differentiating fast, effectively to interface, there is certain practical significance.

Accompanying drawing explanation

Fig. 1 is the process flow diagram of the detection method of a kind of geology interphase structure of the embodiment of the present invention;

Fig. 2 is the structural representation of the sniffer of a kind of geology interphase structure of the embodiment of the present invention;

Fig. 3 is the geologic model schematic diagram of the embodiment of the present invention one;

Fig. 4 is the apparent resistivity curve figure of the embodiment of the present invention one;

Fig. 5 is the decay differential parameter curve map of the embodiment of the present invention one;

Fig. 6 is the apparent resistivity section diagram of the embodiment of the present invention two;

Fig. 7 is the electromagnetic response parameter diffusion time sectional drawing of the embodiment of the present invention two;

Fig. 8 is that the geology of the embodiment of the present invention two infers interpretation results figure.

Embodiment

For making the object, technical solutions and advantages of the present invention clearly understand, hereinafter will be described in detail to embodiments of the invention by reference to the accompanying drawings.It should be noted that, when not conflicting, the embodiment in the application and the feature in embodiment can combination in any mutually.

Loop source transient electromagnetic method is being carried out in the production application of theoretical research, in conventional data process, underground medium is all idealized as homogeneous half space, and like this, the voltage parameter observed becomes following relation with electromagnetic field in the travel-time of underground medium:

$V=\frac{{{\mathrm{\μ}}_0}^{5/2}\mathrm{Mq}}{20{\mathrm{\π}}^{3/2}{\mathrm{\ρ}}^{3/2}{t}^{5/2}}---\left(1\right)$

In formula, V is the induced voltage of actual observation, and M sends magnetic moment, and size is the product of transmitter current and transmitting loop area, and q is the area of receiving coil, μ ₀it is the magnetic permeability in vacuum.

And for the horizontal electrically conductive layer in high resistance medium, the voltage parameter observed becomes following relation with electromagnetic field in the travel-time of underground medium:

$V\≈\frac{3\mathrm{Mq}{{\mathrm{\μ}}_0}^4{S}^3}{16\mathrm{\π}{t}^4}---\left(2\right)$

In formula, S is conductance.

For plastid spherically, the electromagnetic response under Genter loop is:

$V\left(t\right)={3\mathrm{\π}}^{-1}{\mathrm{\μ}}_0\frac{{\mathrm{Ia}}^3{R}^2{r}^2}{{(R^2+h^2)}^{3/2}}\underset{k=1}{\overset{\∞}{\mathrm{\Σ}}}\exp ({-k}^{2}t/\mathrm{\τ})---\left(3\right)$

In formula, r is the radius of receiving coil, and a is the radius of ground lower sphere, and h is the center depth of burial of spheroid, and τ is time constant.

As can be seen from formula (1), under homogeneous half space, late period transient electromagnetic field evanescent voltage and time delay between pass be time delay power exponent is-2.5; As can be seen from formula (2), in high resistant layered medium, for any one observation station, response reduces along with passage of time, until be zero, late period transient electromagnetic field evanescent voltage and time delay between pass be time delay power exponent is-4; As can be seen from formula (3): when detected object is spheroidite, late period transient electromagnetic field evanescent voltage and time delay between pass be V (t) ∝ exp (-t), electromagnetic field inducing voltage is exponentially decayed.Namely electromagnetic field response attenuation is relevant with multiple response sum exponentially decayed.From (1), (2), (3), in different medium situation, the exponential size of electromagnetic field decay is not identical.Why there will be this situation, is the result changed because of underground medium.

Due to the difference of characteristics of underground media, time delay power exponent is change, under other complex dielectrics, the expression responded of showing up of having no idea to obtain, but can think for certain: the decay power exponent value of field can change to some extent along with medium character change.If this characteristic parameter can be extracted from observed electromagnetic field response numerical value, the electrical structure of underground medium so just can be inferred according to the situation of change of this parameter, and the electrical interphase of Further Division.

By the characteristic of electromagnetic field response analytic expression analysis of Electromagnetic diffusive transport, the embodiment of the present invention is passed through: (1), according to observed voltage data, sets up the relational expression between electromagnetic field Spreading and diffusion characteristic power exponent and subsurface resistivity; (2) according to set up relational expression, electromagnetic response power exponent diffusion time is asked for; (3) tried to achieve electromagnetic response power exponent diffusion time is explained geology interphase and the tectonic structure of underground medium as new argument.

As shown in Figure 1, the embodiment of the present invention proposes the detection method of a kind of geology interphase structure, comprising:

S101, gather the transient electromagnetic data of each sensing point of region to be assessed;

S102, to set up relational expression between electromagnetic field Spreading and diffusion characteristic and subsurface resistivity or induced voltage for sensing point described in each;

S103, according to set up relational expression, obtain corresponding electromagnetic response parameter diffusion time;

S104, according to the geology interphase of electromagnetic response parameter interpretation diffusion time underground medium obtained and tectonic structure.

Wherein step S102 comprises:

The relational expression between electromagnetic field Spreading and diffusion characteristic power exponent and subsurface resistivity or induced voltage is set up for sensing point described in each;

Described electromagnetic response parameter diffusion time is electromagnetic response power exponent diffusion time.

Wherein step S104 comprises:

When the induced voltage of described sensing point is directly proportional to-2.5 power of electromagnetic field propagation time delay, the geology interphase of described medium and tectonic structure are homogeneous half space;

When the induced voltage of described sensing point is directly proportional to-4 power of electromagnetic field propagation time delay, the geology interphase of described medium and tectonic structure are high resistant layered medium;

When the induced voltage of described sensing point and the natural Exponents of electromagnetic field propagation time delay are inversely proportional to, the geology interphase of described medium and tectonic structure are spheroidite.

As shown in Figure 2, the embodiment of the present invention proposes the sniffer of a kind of geology interphase structure, comprising:

Acquisition module, for gathering the transient electromagnetic data of each sensing point of region to be assessed;

Relating module, sets up the relational expression between electromagnetic field Spreading and diffusion characteristic and subsurface resistivity or induced voltage for sensing point described in each;

Determination module, according to set up relational expression, obtains corresponding electromagnetic response parameter diffusion time;

Explanation module, according to geology interphase and the tectonic structure of the electromagnetic response parameter interpretation diffusion time underground medium obtained.

Relating module specifically for:

The relational expression between electromagnetic field Spreading and diffusion characteristic power exponent and subsurface resistivity or induced voltage is set up for sensing point described in each.

Described electromagnetic response parameter diffusion time in relating module is electromagnetic response power exponent diffusion time.

Explanation module comprises:

Even Interpretation unit: for when the induced voltage of described sensing point is directly proportional to-2.5 power of electromagnetic field propagation time delay, determines that the geology interphase of described medium and tectonic structure are homogeneous half space;

High resistant Interpretation unit: for when the induced voltage of described sensing point is directly proportional to-4 power of electromagnetic field propagation time delay, determines that the geology interphase of described medium and tectonic structure are high resistant layered medium;

Spherical Interpretation unit: for when the induced voltage of described sensing point and the natural Exponents of electromagnetic field propagation time delay are inversely proportional to, determine that the geology interphase of described medium and tectonic structure are spheroidite.

The embodiment of the present invention also proposes a kind of transient electromagnetic detecting system, comprise sniffer and first loop line of above-mentioned geology interphase structure, described first loop line is connected with the acquisition module of the sniffer that described geology interphase constructs, comprise and send loop line and receiving coil, place receiving coil at transmission loop line center, carry out transient electromagnetic data measurement.

With reference to formula (1), (2), (3), suppose that the pass between observation signal voltage and time attenuation parameter is:

V＝Dρ ^-3/2t ^k(4)

D is the coefficient relevant with device, and k is the attenuation variable parameter relevant with fading propagation, and ρ is the resistivity of medium.

Following derivation can be done: order by (4)

V ₁＝Dρ ₁ ^-3/2t ₁ ^k(5)

V ₂＝Dρ ₂ ^-3/2t ₂ ^k(6)

Then $\frac{V_2}{V_1}=\frac{{{\mathrm{\ρ}}_2}^{-3/2}{t_2}^k}{{{\mathrm{\ρ}}_1}^{-3/2}{t_1}^k}---\left(7\right)$

$\log \frac{V_2}{V_1}=\log \frac{{{\mathrm{\ρ}}_2}^{-3/2}{t_2}^k}{{{\mathrm{\ρ}}_1}^{-3/2}{t_1}^k}=-\frac{3}{2}\log \frac{{\mathrm{\ρ}}_2}{{\mathrm{\ρ}}_1}+k\log \frac{t_2}{t_1}---\left(8\right)$

Then $k=(\log \frac{V_2}{V_1}+\frac{3}{2}\log \frac{{\mathrm{\ρ}}_2}{{\mathrm{\ρ}}_2})/\log \frac{t_2}{t_1}---\left(9\right)$

When log intervals such as times

Order $\log \frac{t_2}{t_1}=C,$ Then

$k=(\log \frac{V_2}{V_1}+\frac{3}{2}\log \frac{{\mathrm{\ρ}}_2}{{\mathrm{\ρ}}_1})/C---\left(10\right)$

Again because: $\stackrel{\‾}{B}\left(t\right)=\frac{V\left(t\right)/I\·I}{S_{R}N}---\left(11\right)$

for magnetic induction density, V (t) is induced voltage, and I is transmitter current, S _rfor coil receiving area, N is coil turn.

On homogeneous half space surface, the analytic expression of transient electromagnetic field is:

$\stackrel{\‾}{B}\left(t\right)=\frac{3I_{\mathrm{\ρ}}}{a^3}[\mathrm{\Φ}\left(u\right)-\sqrt{\frac{2}{\mathrm{\π}}{\mathrm{ue}}^{-u^2/2}}(1+\frac{1}{3}{u}^2)]---\left(12\right)$

for magnetic induction density, I is transmitter current, and ρ is formation resistivity, and a is transmitting loop radius, and Φ (u) is probability integral.

Can know from (5) and (6) formula:

So (10) become

$k=\left(\frac{5}{2}\log \frac{{\mathrm{\ρ}}_2}{{\mathrm{\ρ}}_1}\right)/C---\left(13\right)$

According to (13) formula, then continue to derive, order

$k_1=\left(\frac{5}{2}\log \frac{{\mathrm{\ρ}}_2}{{\mathrm{\ρ}}_1}\right)/C---\left(14\right)$

$k_2=\left(\frac{5}{2}\log \frac{{\mathrm{\ρ}}_3}{{\mathrm{\ρ}}_1}\right)/C---\left(15\right)$

Then $\mathrm{\Δk}=k_2-k_1=\left(\frac{5}{2}\log \frac{{\mathrm{\ρ}}_3}{{\mathrm{\ρ}}_2}\right)/C-\left(\frac{5}{2}\log \frac{{\mathrm{\ρ}}_2}{{\mathrm{\ρ}}_1}\right)/C---\left(16\right)$

After letter: $\mathrm{\Δk}=\left(\frac{5}{2}\log \frac{{\mathrm{\ρ}}_3{\mathrm{\ρ}}_1}{{\mathrm{\ρ}}_2{\mathrm{\ρ}}_2}\right)/C---\left(17\right)$

Order $\mathrm{\Δ}{k}^{\′}=\log \frac{{\mathrm{\ρ}}_3{\mathrm{\ρ}}_1}{{\mathrm{\ρ}}_2{\mathrm{\ρ}}_2}---\left(18\right)$

(18) formula is exactly electromagnetic response parameter diffusion time in embodiment of the present invention step S103; Parameter reflects the attenuation characteristic of electromagnetic field in underground medium.This parameter can be calculated according to apparent resistivity value.

Embodiment one

First geologic model (Fig. 3) is designed, (wherein, ρ ₁=100 Ω m, h ₁=100m, ρ ₂=160 Ω m), send electric current 10A, send the length of side 100 meters, time road 20, time delay scope is 0.087ms-7.ms (table 1).Fig. 4 is forward modelling apparent resistivity curve, and horizontal ordinate is the time road waiting log intervals, and ordinate is apparent resistivity value.

The each time road of table 1 and corresponding diffusion time

Fig. 5 is calculated decay new argument curve map, and horizontal ordinate is still the time road waiting log intervals, and ordinate is immeasurable firm differential parameter value.As can be seen from Figure 5, a spike is had in the 7th time road, corresponding geological interface.

Embodiment two

The method utilizing the embodiment of the present invention to provide processes somewhere transient electromagnetic method detection data, its objective is to determine subsurface geologic structures and tectonic structure better.Fig. 6 is the apparent resistivity section diagram under regular situation.In figure, horizontal ordinate represents measurement point position, and ordinate represents depth of exploration.The computing formula of depth of exploration is as follows:

in formula, μ ₀=4 π × 10 ^-7h/m

When making a decision geological condition according to Fig. 6, depending on the working experience of professional and technical personnel to a great extent, often easily causing erroneous judgement.Fig. 7 is the electromagnetic response parameter diffusion time sectional drawing made according to the embodiment of the present invention, and this figure provides subsurface geology information and tectonic information more intuitively.In sectional top and bottom, the sudden change of new argument curve illustrates that shallow stratum and deep formation all exist interphase, No. 150 measuring points in the horizontal direction and No. 650 point position places, new argument curvilinear motion and big rise and fall, illustrate to there is tomography in these two positions.

Fig. 8 is that the geology made according to Fig. 7 infers result map.On this map, mark the electrical interphase in underground and tectonic structure, clearly mark three stratum and two tomographies of underground.Like this, before geological drilling, for relevant departments provide necessary out-of-the way position and reliable bore position.

Above embodiment only in order to technical scheme of the present invention and unrestricted to be described, only with reference to preferred embodiment to invention has been detailed description.Those of ordinary skill in the art should be appreciated that and can modify to technical scheme of the present invention or equivalent replacement, and does not depart from the spirit and scope of technical solution of the present invention, all should be encompassed in the middle of right of the present invention.

Claims (9)

1. a detection method for geology interphase structure, is characterized in that: comprising:

Gather the transient electromagnetic data of each sensing point of region to be assessed;

The relational expression between electromagnetic field Spreading and diffusion characteristic and subsurface resistivity or induced voltage is set up for sensing point described in each;

According to set up relational expression, obtain corresponding electromagnetic response parameter diffusion time;

According to geology interphase and the tectonic structure of the electromagnetic response parameter interpretation diffusion time underground medium obtained.

2. the method for claim 1, is characterized in that: set up the relational expression between electromagnetic field Spreading and diffusion characteristic and subsurface resistivity or induced voltage for sensing point described in each, comprising:

The relational expression between electromagnetic field Spreading and diffusion characteristic power exponent and subsurface resistivity or induced voltage is set up for sensing point described in each.

3. method as claimed in claim 2, is characterized in that: described electromagnetic response parameter diffusion time is electromagnetic response power exponent diffusion time.

4. method as claimed in claim 2, is characterized in that: according to geology interphase and the tectonic structure of the electromagnetic response parameter interpretation diffusion time underground medium obtained, comprising:

When the induced voltage of described sensing point is directly proportional to-2.5 power of electromagnetic field propagation time delay, the geology interphase of described medium and tectonic structure are homogeneous half space;

When the induced voltage of described sensing point is directly proportional to-4 power of electromagnetic field propagation time delay, the geology interphase of described medium and tectonic structure are high resistant layered medium;

When the induced voltage of described sensing point and the natural Exponents of electromagnetic field propagation time delay are inversely proportional to, the geology interphase of described medium and tectonic structure are spheroidite.

5. a sniffer for geology interphase structure, is characterized in that: comprising:

Acquisition module, for gathering the transient electromagnetic data of each sensing point of region to be assessed;

Relating module, sets up the relational expression between electromagnetic field Spreading and diffusion characteristic and subsurface resistivity or induced voltage for sensing point described in each;

Determination module, according to set up relational expression, obtains corresponding electromagnetic response parameter diffusion time;

Explanation module, according to geology interphase and the tectonic structure of the electromagnetic response parameter interpretation diffusion time underground medium obtained.

6. device as claimed in claim 5, is characterized in that: relating module specifically for:

The relational expression between electromagnetic field Spreading and diffusion characteristic power exponent and subsurface resistivity or induced voltage is set up for sensing point described in each.

7. device as claimed in claim 6, is characterized in that: described electromagnetic response parameter diffusion time in relating module is electromagnetic response power exponent diffusion time.

8. device as claimed in claim 6, is characterized in that: explanation module comprises:

Even Interpretation unit, for when the induced voltage of described sensing point is directly proportional to-2.5 power of electromagnetic field propagation time delay, determines that the geology interphase of described medium and tectonic structure are homogeneous half space;

High resistant Interpretation unit, for when the induced voltage of described sensing point is directly proportional to-4 power of electromagnetic field propagation time delay, determines that the geology interphase of described medium and tectonic structure are high resistant layered medium;

Spherical Interpretation unit, for when the induced voltage of described sensing point and the natural Exponents of electromagnetic field propagation time delay are inversely proportional to, determines that the geology interphase of described medium and tectonic structure are spheroidite.

9. a transient electromagnetic detecting system, it is characterized in that: the sniffer and the first loop line that comprise the arbitrary described geology interphase structure of claim 5 to 8, described first loop line is connected with the acquisition module of the sniffer that described geology interphase constructs, comprise and send loop line and receiving coil, place receiving coil at transmission loop line center, carry out transient electromagnetic data measurement.