CN104122578A - Earthquake excitation simulation method based on rock microstructure and medium elastic parameters - Google Patents

Abstract

The invention provides an earthquake excitation simulation method based on a rock microstructure and medium elastic parameters and belongs to the field of geophysical prospecting. The method includes the following steps: (1) investigating the rock microstructure and obtaining the medium elastic parameters; (2) establishing a near-surface speed model, a deep-layer speed model and a structure model of a research area; (3) realizing a numerical simulation algorithm and establishing a near-centrum wave field function which includes an elastic medium; and (4) carrying out earthquake excitation simulation based on the rock microstructure and the medium elastic parameters. Through use of the method, earthquake excitation simulation based on the rock microstructure and the medium elastic parameters can be carried out and a surrounding-rock excitation characteristic database is established so that selection of excitation parameters of different areas is completed indoor to the largest degree.

Description

A kind of earthquake stimulation analogy method based on rock microstructure and medium elastic parameter

Technical field

The invention belongs to geophysical survey field, be specifically related to a kind of earthquake stimulation analogy method based on rock microstructure and medium elastic parameter.

Background technology

For special tectonic area (as mountain front limestone exposure district), improving data signal to noise ratio (S/N ratio) is the matter of utmost importance that must solve, and excite, is one of principal element of the single big gun quality of impact.The nearly source wavefield research of elastic medium shows: earthquake stimulation is relevant to elastic parameter and the structure of medium, the mechanical properties of rock of exciting media and physical arrangement determine the amplitude characteristic and the frequency characteristic that excite, so the characteristic of epicenter excitation seismic wavelet how, largely affect the quality of seismic data.Wave-field simulation technology is all to use Ricker wavelet to simulate as source wavelet at present, again analog result is analyzed, so just analyze simply the impact of tectonic structure on wave field characteristics, not from the impact of different lithology stratum on excitation wavelet is discussed in essence, and then the impact on seismic data, cause in the actual acquisition construction of field, the selection of explosive shooting parameter (dose, well depth, combination and explosion velocity etc.) must be carried out a large amount of tests and determine, certainly will cause the loss of manpower, financial resources and material resources, also dangerous.Therefore be necessary to carry out the earthquake stimulation analogue technique based on rock microstructure and medium elastic parameter, and set up modular country rock and excite property data base, at utmost in the indoor selection that completes different regions shooting parameter, finally effectively instruct field earthquake to produce.

Summary of the invention

The object of the invention is to solve the difficult problem existing in above-mentioned prior art, a kind of earthquake stimulation analogy method based on rock microstructure and medium elastic parameter is provided, by simulating at the indoor earthquake stimulation of different special tectonics area based on rock microstructure and medium elastic parameter of carrying out, carry out rock microstructure investigation and application rock physics and test to measure the elastic parameter of medium, and then the earthquake stimulation carrying out based on rock microstructure and medium elastic parameter is simulated, each department earthquake-capturing explosive source shooting parameter (dose in the actual formation of the uncertain definite field quantitatively of analog result, well depth, combination and explosion velocity etc.), make the seismic wavelet amplitude and the frequency characteristic optimization that excite, finally make the quality of the geological data that collects be greatly improved.

The present invention is achieved by the following technical solutions:

An earthquake stimulation analogy method based on rock microstructure and medium elastic parameter, comprising:

(1) medium elastic parameter is investigated and asked for to rock microstructure;

(2) set up study area near-surface velocity model, deep layer rate pattern and tectonic model;

(3) the nearly source wavefield function that comprises elastic medium is realized and set up to numerical simulation algorithm;

(4) carry out the earthquake stimulation simulation based on rock microstructure and medium elastic parameter.

Described step (1) comprising:

(11) to collect the actual rock sample coming from study area, carry out the microstructure investigation that electron-microscope scanning completes rock sample;

(12) experiment and the analysis of medium elastic parameter relations under the experiment of medium elastic parameter relations and analysis and different saturation condition under different confined pressure conditions.

Described step (12) is achieved in that

P-and s-wave velocity and the Poisson ratio of institute's coring under different confined pressure conditions measured in chamber by experiment, and the elastic parameter of medium, obtains the relation between p-and s-wave velocity and Poisson ratio and medium elastic parameter;

P-and s-wave velocity and the Poisson ratio of institute's coring under different saturation condition measured in chamber by experiment, and the elastic parameter of medium, obtains the relation between p-and s-wave velocity and Poisson ratio and medium elastic parameter;

And then the medium velocity under the applicable this area of foundation near surface condition and the mathematical model of elastic parameter.

Described step (2) is achieved in that by the earthquake poststack data of study area sets up tectonic model, drilling well, VSP well-log information by study area are set up deep layer rate pattern, and near-surface velocity model is set up in the microstructure investigation of the rock sample that the medium velocity obtaining by step (1) and the mathematical model of elastic parameter and step (1) obtain; Finally near surface formation speed and deep layer speed model combination are obtained to final rate pattern.

In described step (3), numerical simulation algorithm is realized and being comprised:

(31) set up the one-order velocity-stress equation of wave equation;

(32) realize the numerical simulation algorithm of staggered-mesh method of finite difference: on the one-order velocity-stress equation basis in step (31), obtain corresponding Difference Schemes with Staggered, and then form numerical simulation algorithm.

The nearly source wavefield function that comprises elastic medium that described step (3) is set up is:

$u_r(r,t)=\frac{p_{0}a}{{\mathrm{\ρr}}^2{[m^2+{(n-b)}^2]}^{\frac{1}{2}}}\{\frac{e^{-\mathrm{b\τ}}}{{[m^2+{(n-b)}^2]}^{\frac{1}{2}}}-\frac{e^{-\mathrm{n\τ}}}{m}\cos [\mathrm{m\τ}-\arctan \left(\frac{n-b}{m}\right)\left]\right\}$

In formula $m=\frac{v_p\sqrt{1-2v}}{a(1-v)},$ $n=\frac{v_p(1-2v)}{a(1-v)},$ $\mathrm{\τ}=t-\frac{r-a}{v_p}>0,$ V is Poisson ratio, and r is ripple propagation distance;

U _r(r, t) is nearly source wavefield displacement, and ρ is density, v _pfor velocity of longitudinal wave, a is the cavity radius producing after explosive source blast, P ₀for the initial pressure that blast produces, the damped expoential that b is initial pressure, t is seismic travel time, and τ is for to start seismic travel time from cavity wall.

Described step (4) comprising:

(41) complete the loading of the nearly source wavefield function that comprises elastic medium;

(42) carry out the earthquake stimulation simulation based on rock microstructure and medium elastic parameter: the numerical simulation algorithm that uses step (3) to obtain obtains the analog record that excites based on medium elastic parameter.

Described step (41) comprising:

(411): the final rate pattern that step (2) is obtained carries out mesh generation, according to horizontal and vertical net point coordinate, determine source location (NXs, NZs);

(412): on four net points of the surrounding centered by source location (NXs, NZs), load the source wavelet with the nearly source wavefield function representation of described elastic medium.

Compared with prior art, the invention has the beneficial effects as follows:

Utilize the inventive method can carry out the earthquake stimulation simulation based on rock microstructure and medium elastic parameter, and set up country rock and excite property data base, at utmost in the indoor selection that completes different regions shooting parameter, save on the one hand a large amount of human and material resources and financial resources, allow the requirement of field construction As soon as possible Promising Policy QHSE simultaneously, make on the other hand the quality of field acquisition data be greatly improved, finally effectively instruct field earthquake to produce.

Accompanying drawing explanation

Fig. 1 is the step block diagram of the inventive method.

Fig. 2 is cavity focus schematic diagram.In figure, outer rim irregular portion is divided near the country rock shape that means that focus is.

Fig. 3 (a) is limestone medium microstructure investigation schematic diagram, and Fig. 3 (b) is sandstone medium microstructure investigation schematic diagram;

Table 1 (a) is speed and the elastic parameter that one group of sample of sandstone records under certain condition; Table 1 (b) is speed and the elastic parameter that one group of limestone sample records under certain condition;

Fig. 4 (a) is the relation of nearly source wavelet maximum displacement and speed; Fig. 4 (b) comes from the relation of ripple dominant frequency and speed near earthquake;

Fig. 5 (a) is limestone model, and Fig. 5 (b) is sandstone model;

Fig. 6 (a) distributes for limestone model excites in 0.02s vertical component particle displacement constantly, and Fig. 6 (b) distributes for limestone model excites in 0.1s vertical component particle displacement constantly;

Fig. 7 (a) distributes for sandstone model excites in 0.02s vertical component particle displacement constantly, and Fig. 7 (b) distributes for sandstone model excites in 0.1s vertical component particle displacement constantly.

Table 2 is different lithology shooting parameter;

Fig. 8 is rate pattern;

Fig. 9 (a) excites single shot record for sandstone; Fig. 9 (b) excites single shot record for limestone.

Figure 10 is sound wave staggered-mesh difference schematic diagram.

Figure 11 is elastic wave staggered-mesh difference schematic diagram.

Figure 12 is that single source loads schematic diagram.

Embodiment

Below in conjunction with accompanying drawing, the present invention is described in further detail:

The present invention is from rock sample and the seismic data of field reality, by setting up the relation between study area medium velocity and Poisson ratio and elastic parameter, and then set up elastic parameter model and the rate pattern of study area, carry out the earthquake stimulation simulation based on rock microstructure and medium elastic parameter, and set up country rock and excite property data base, at utmost in the indoor selection that completes different regions shooting parameter, the quality of field acquisition data is greatly improved, finally effectively instructs field earthquake to produce.

Innovation of the present invention is to consider the impact of wall rock condition on earthquake stimulation wavelet, and successfully the nearly source wavefield function that comprises medium elastic parameter is loaded in numerical simulation algorithm as focus item, analog result is more conformed to field actual conditions.

(1) the inventive method as shown in Figure 1, comprising:

1) rock microstructure investigation and medium elastic parameter are asked for

On actual rock sample basis, collection research district, by electron-microscope scanning, rock sample is carried out to microstructure investigation; By rock sample being measured in laboratory, obtain the elastic parameter of medium.

1. microstructure investigation:

By rock sample electron-microscope scanning being completed to the microstructure of rock sample, investigate

2. medium elastic parameter is asked for (Lame&1& constants λ, modulus of shearing μ, Young modulus E, Poisson ratioσ and density p):

◆ experiment and the analysis of medium elastic parameter relations under different confined pressure conditions

P-and s-wave velocity and the Poisson ratio of institute's coring under different confined pressure conditions measured in chamber by experiment, and the elastic parameter of medium, relation between research p-and s-wave velocity and Poisson ratio and medium elastic parameter, the medium velocity under the applicable this area of foundation near surface condition and the mathematical model of elastic parameter.

◆ the experiment of medium elastic parameter relations and analysis under different saturation condition

P-and s-wave velocity and the Poisson ratio of institute's coring under different saturation condition measured in chamber by experiment, and the elastic parameter of medium, relation between research p-and s-wave velocity and Poisson ratio and medium elastic parameter, the medium velocity under the applicable this area of foundation near surface condition and the mathematical model of elastic parameter.

2) earth formation deep interval velocity model is set up

On the basis of the drilling well of collection research district, VSP well logging and earthquake poststack data, set up the deep interval velocity model corresponding with position, reflection horizon.

3) the nearly source wavefield function that comprises elastic medium is realized and set up to numerical simulation algorithm;

Numerical simulation algorithm is realized and being comprised:

(31) set up the one-order velocity-stress equation of wave equation

(32) realize the numerical simulation algorithm of staggered-mesh method of finite difference

Specific as follows:

(31) set up the one-order velocity-stress equation of wave equation:

1. sound wave

In isotropic medium, the one-order velocity one stress equation form of two-dimentional ACOUSTIC WAVE EQUATION can be expressed as:

$\left\{\begin{array}{c}\frac{\∂u}{\∂t}=-\mathrm{\ρ}{v_p}^2(\frac{{\∂v}_x}{\∂x}+\frac{{\∂v}_z}{\∂z})\\ \frac{{\∂v}_x}{\∂t}=-\frac{1}{\mathrm{\ρ}}\frac{\∂u}{\∂x}\\ \frac{{\∂v}_z}{\∂t}=-\frac{1}{\mathrm{\ρ}}\frac{\∂u}{\∂z}\end{array}---\left(7\right)\right.$

In formula: v _x, v _zparticle velocity, u method uniaxial stress, ρ is density, v _pit is velocity of longitudinal wave.

2. elastic wave

In isotropic medium, one-order velocity-stress equation form of two-dimension elastic ripple can be expressed as:

$\left\{\begin{array}{c}\frac{{\∂v}_x}{\∂t}=\frac{1}{\mathrm{\ρ}(x,z)}(\frac{{\∂\mathrm{\τ}}_{\mathrm{xx}}}{\∂x}+\frac{{\∂\mathrm{\τ}}_{\mathrm{xz}}}{\∂z})\\ \frac{{\∂v}_z}{\∂t}=\frac{1}{\mathrm{\ρ}(x,z)}(\frac{{\∂\mathrm{\τ}}_{\mathrm{xz}}}{\∂x}+\frac{{\∂\mathrm{\τ}}_{\mathrm{zz}}}{\∂z})\\ \frac{{\∂\mathrm{\τ}}_{\mathrm{xx}}}{\∂t}=(\mathrm{\λ}+2\mathrm{\μ})\frac{{\∂v}_x}{\∂x}+\mathrm{\λ}\frac{{\∂v}_z}{\∂z}\\ \frac{{\∂\mathrm{\τ}}_{\mathrm{zz}}}{\∂t}=\mathrm{\λ}\frac{{\∂v}_x}{\∂x}+(\mathrm{\λ}+2\mathrm{\μ})\frac{{\∂v}_z}{\∂z}\\ \frac{{\∂\mathrm{\τ}}_{\mathrm{xz}}}{\∂t}=\mathrm{\μ}\frac{{\∂v}_x}{\∂z}+\mathrm{\μ}\frac{{\∂v}_z}{\∂x}\end{array}---\right.\left(8\right)$

In formula: be respectively the component of Particle Vibration Velocity in x and z direction; u _x, u _zbe respectively the component of displacement components u in x and z direction; τ _xxand τ _zzfor the normal stress of particle in x and z direction; τ _xzfor the shearing force of particle in xz plane; ρ is Media density;

(32) the numerical simulation algorithm of realizing staggered-mesh method of finite difference (obtains corresponding Difference Schemes with Staggered on the one-order velocity-stress equation basis in step (31), and then forms modeling algorithm.Concrete Difference Schemes with Staggered is as follows:

1. sound wave

Adopt staggered-mesh, as shown in figure 10, in Figure 10, the wave field of each figure representative and elastic parameter are as shown in table 1 in the locus of corresponding acoustic wavefield component and elastic parameter.Can obtain space, 2N rank difference accuracy, the high-order limited difference scheme of second order time difference precision staggered-mesh, the difference scheme of equation (7) is:

$u^{t+}(i,j)=u^{t-}(i,j)-\frac{\mathrm{\Δt\ρ}{v}_p^2}{\mathrm{\Δx}}\left\{L_x^{-}\right[v_x^t(i^{+},j)\left]\right\}-\frac{\mathrm{\Δt\ρ}{v}_p^2}{\mathrm{\Δz}}\left\{L_z^{-}\right[v_x^t(i,j^{+})\left]\right\}---\left(9a\right)$

$v_x^t(i^{+},j)=v_x^{t-1}(i^{+},j)-\frac{\mathrm{\Δt}}{\mathrm{\Δx\ρ}}\left\{L_x^{+}\right[u^{t-}(i,j)\left]\right\}---\left(9b\right)$

$v_z^t(i,j^{+})=v_z^{t-1}(i+j^{+})-\frac{\mathrm{\Δt}}{\mathrm{\Δz\ρ}}\left\{L_z^{+}\right[u^{t-}(i,j)\left]\right\}---\left(9c\right)$

In formula: represent x direction forward difference; represent x direction backward difference; Δ x, Δ z represents x, the mesh spacing of z direction; Δ t represents time step; other in like manner.

$u^{t+}(i,j)=u(i,j,t+\frac{\mathrm{\Δt}}{2})$

$u^{t-}(i,j)=u(x,z,t-\frac{\mathrm{\Δt}}{2})$

$L_x^{-}\left[v_x^t(i^{+},j)\right]=\underset{m-1}{\overset{N}{\mathrm{\Σ}}}{a}_m^{\left(N\right)}[v_x(i+(2m-1)\frac{\mathrm{\Δx}}{2},z,t)-v_x(i-(2m-1)\frac{\mathrm{\Δx}}{2},z,t)]$

Table 1

2. elastic wave

Various wave field components and physical parameter distribute according to Figure 11, wave field and the parameter of each figure representative in Figure 11 are as shown in table 2, again in conjunction with the difference thinking of staggered-mesh, can obtain space, 2N rank difference accuracy, the high-order limited difference scheme of second order time difference precision staggered-mesh of equation (8),

$v_x^t(i^{+},j)=v_x^{t-1}(i^{+},j)+\frac{\mathrm{\Δt}}{\mathrm{\Δx\ρ}}\left\{L_x^{+}\right[{\mathrm{\τ}}_{\mathrm{xx}}^{t-}(i,j)\left]\right\}-\frac{\mathrm{\Δt}}{\mathrm{\Δz\ρ}}\left\{L_z^{-}\right[{\mathrm{\τ}}_{\mathrm{zz}}^{t-}(i^{+},j^{+})\left]\right\}---\left(10a\right)$

$v_z^t(i,j^{+})=v_z^{t-1}(i,j^{+})+\frac{\mathrm{\Δt}}{\mathrm{\Δx\ρ}}\left\{L_x^{-}\right[{\mathrm{\τ}}_{\mathrm{xz}}^{t-}(i^{+},j^{+})\left]\right\}-\frac{\mathrm{\Δt}}{\mathrm{\Δz\ρ}}\left\{L_z^{+}\right[{\mathrm{\τ}}_{\mathrm{zz}}^{t-}(i,j)\left]\right\}---\left(10b\right)$

${\mathrm{\τ}}_{\mathrm{xx}}^{t+}(i,j)={\mathrm{\τ}}_{\mathrm{xx}}^{t-}(i,j)+\frac{\mathrm{\Δt}(\mathrm{\λ}+2\mathrm{\μ})}{\mathrm{\Δx}}\left\{L_x^{-}\right[v_x^t(i^{+},j)\left]\right\}+\frac{\mathrm{\Δt\λ}}{\mathrm{\Δx}}\left\{L_z^{-}\right[v_z^t(i,j^{+})\left]\right\}---\left(10c\right)$

${\mathrm{\τ}}_{\mathrm{zz}}^{t+}(i,j)={\mathrm{\τ}}_{\mathrm{zz}}^{t-}(i,j)+\frac{\mathrm{\Δt\λ}}{\mathrm{\Δx}}\left\{L_x^{-}\right[v_x^t(i^{+},j)\left]\right\}+\frac{\mathrm{\Δt}(\mathrm{\λ}+2\mathrm{\μ})}{\mathrm{\Δx}}\left\{L_z^{-}\right[v_z^t(i,j^{+})\left]\right\}---\left(10d\right)$

${\mathrm{\τ}}_{\mathrm{xz}}^{t+}(i,j)={\mathrm{\τ}}_{\mathrm{xx}}^{t-}(i,j)+\frac{\mathrm{\Δt\μ}}{\mathrm{\Δx}}\left\{L_z^{+}\right[v_x^t(i^{+},j)\left]\right\}+\frac{\mathrm{\Δt\μ}}{\mathrm{\Δx}}\left\{L_x^{+}\right[v_z^t(i,j^{+})\left]\right\}---\left(10e\right)$

In formula: represent to do in the x-direction forward difference; represent to do in the x-direction backward difference; Δ x, Δ z represents x, the mesh spacing of z direction; Δ t represents time step; other representation in like manner.

Table 2

The nearly source wavefield function that comprises elastic medium is set up:

In seismic prospecting, conventional explosive source is as excitaton source.In infinite medium, on the inwall of the spherical hollow space that the radius of take is a, homogeneous radiation pressure pulse (as shown in Figure 2), represents symmetrical explosive source.

Time Migration of Elastic Wave Equation is:

$\mathrm{\ρ}\frac{{\∂}^{2}q}{{\∂t}^2}=(\mathrm{\λ}+2\mathrm{\μ})\▿\▿\·q-\mathrm{\μ}\▿\×\▿\×q$

In above formula, q is displacement, and λ and μ are Lame elastic constants.The solution that represents compressional wave fluctuation is:

$q=\▿\mathrm{\Φ}---\left(1\right)$

Due to bit shift, Φ meets wave equation:

${\∂}^2\mathrm{\Φ}/{\∂t}^2=v^2{\▿}^2\mathrm{\Φ}---\left(2\right)$

In formula for longitudinal wave propagation speed.Spherical coordinate system is applicable to the research of this problem, and ball chamber internal pressure all equates, and all motions and pressure and angle have nothing to do.Given this, (1) and (2) formula can be written as:

${\∂}^2\left(\mathrm{r\Φ}\right)/{\∂t}^2=v^2{\∂}^2\left(\mathrm{r\Φ}\right)/{\∂r}^2---\left(3\right)$

$u_r=\∂\mathrm{\Φ}/\∂r,v_r=0,w_r=0,---\left(4\right)$

In medium, the volume breathing at any some place has in accordance with boundary condition:

${[(\mathrm{\λ}+2\mathrm{\μ})\frac{{\∂u}_r}{\∂r}+2\mathrm{\λ}\frac{u_r}{r}]|}_{r=a}=-p\left(t\right)---\left(5\right)$

This boundary condition is that medium will produce spherically symmetric irrotational wave due under the effect at spherically symmetric pressure p (t), and does not produce without loose ripple, and displacement is only relevant with r.

If the functional form of p (t) is

$p\left(t\right)=\left\{\begin{array}{cc}{P}_0{e}^{-\mathrm{bt}}(b>0)& t>0\\ 0& t<=0\end{array}\right.---\left(6\right)$

The nearly source wavefield function that comprises elastic medium of finally asking through a series of conversion is:

$u_r(r,t)=\frac{p_{0}a}{{\mathrm{\&rho;r}}^2{[m^2+{(n-b)}^2]}^{\frac{1}{2}}}\{\frac{e^{-\mathrm{b\&tau;}}}{{[m^2+{(n-b)}^2]}^{\frac{1}{2}}}-\frac{e^{-\mathrm{n\&tau;}}}{m}\cos [\mathrm{m\&tau;}-\arctan \left(\frac{n-b}{m}\right)\left]\right\}$

In formula $m=\frac{v_p\sqrt{1-2v}}{a(1-v)},$ $n=\frac{v_p(1-2v)}{a(1-v)},$ $\mathrm{\&tau;}=t-\frac{r-a}{v_p}>0,$ V is Poisson ratio, and r is ripple propagation distance.

This function is that the present invention is with reference to obtaining after series is derived in the situation of pertinent literature and books, but most important is exactly through deriving, this function can provide the nearly source wavefield function under different blast impulse modes (seeing formula (6)), more approaching with actual conditions.

4) the earthquake stimulation analogue technique based on rock microstructure and medium elastic parameter realizes

1. complete the loading that contains the nearly source wavefield function of medium elastic parameter;

2. carry out the earthquake stimulation simulation based on rock microstructure and medium elastic parameter

Specific as follows:

1. complete the loading that contains the nearly source wavefield function of medium elastic parameter

Loading procedure is as follows: what in the present invention, load is single source, i.e. pure p-wave source (explosive source).

The first step: rate pattern is carried out to mesh generation, determine source location (NXs, NZs) according to horizontal and vertical net point coordinate;

Second step: on four net points of surrounding centered by source location (NXs, NZs), by the loading (source wavelet is the time dependent near source wavefield function that contains medium elastic parameter) of carrying out focus shown in Figure 12;

Specific as follows:

1. four net points around of the source location shown in Figure 12 are respectively (NXs-1, NZs-1), (NXs-1, NZs+1), (NXs+1, NZs-1), (NXs+1, NZs+1);

2. the total external force direction acting on these four points is as consistent in F direction in Figure 12, practical operation is exactly at every bit, to load the acting force (as shown in f in Figure 12) of horizontal and vertical direction, by the synthetic result that obtains every some F of power, the horizontal component that regulation loads is to the right for just, left for negative; Vertical component is downwards for just, upwards for negative.

2. carry out the earthquake stimulation simulation based on rock microstructure and medium elastic parameter.

Described method is in step 4) after further comprise:

5) set up country rock and excite property data base: the rate pattern of model study area, carry out again the earthquake stimulation simulation based on medium elastic parameter, obtain the seismic data exciting under different surrounding rock condition, by the analysis of seismic data (as data dominant frequency, energy etc.) and then set up different surrounding rock and excite property data base;

6) optimization selection field construction parameter: high according to the seismic data signal to noise ratio (S/N ratio) that makes to collect, dominant frequency is high and energy is strong and operating efficiency etc. because of usually select field construction parameter (dose, well depth, combination and explosion velocity etc.) (can be with reference to pertinent literature: 1. high and steep etc. based on explosive shooting sub-wave characteristic selective excitation well depth [J]. geophysical prospecting for oil; 2. Zhang Fusheng etc. land earthquake stimulation selecting factors method is inquired into [J]. petroleum exploration; 3. reach the clouds. excite dose and Types of Medicine analysis [J]. geophysical prospecting for oil) and effectively instruct field earthquake to produce.

The effect of the inventive method is described with two embodiment below.

Example one:

Performing step:

1) investigation of rock sample microstructure and medium elastic parameter are asked for

Fig. 3 (a) is limestone medium microstructure investigation schematic diagram, and Fig. 3 (b) is sandstone medium microstructure investigation schematic diagram; Can find out that limestone inner structure is for block, sandstone inner structure is stratiform;

Table 3 (a) is speed and the elastic parameter that one group of sample of sandstone records under certain condition; Table 3 (b) is speed and the elastic parameter that one group of limestone sample records under certain condition;

Table 3 (a)

Table 3 (b)

2) elastic medium parameter is to the field function impact analysis of near earthquake source

Fig. 4 (a) is dissimilar limestone and the corresponding maximum displacement of nearly source wavelet and the relation of speed of sandstone elastic parameter; Fig. 4 (b) is dissimilar limestone and the corresponding dominant frequency of nearly source wavelet and the relation of speed of sandstone elastic parameter; Two figure results are all to record under the prerequisite of rock sample elastic parameter, use nearly source wavefield function to try to achieve.Can find out limestone dominant frequency 120Hz, sandstone 70Hz, cryptite, 100Hz, peak swing: sandstone be limestone 3-5 doubly, in limestone, excite the dominant frequency will be higher than dominant frequency in sandstone, bandwidth is slightly wide; In sandstone, excitation energy is higher than limestone.In sandstone and limestone, excite as can be seen here the impact of the energy of seismic event and dominant frequency greatlyr, analog result is also that the selection for shooting parameter in different lithology provides foundation.

3) carry out the earthquake stimulation simulation based on rock microstructure and elastic parameter

1. the foundation of model

According to the elastic parameter of above-mentioned sandstone and limestone microstructure and mensuration, the model of foundation is as follows: Fig. 5 (a) is limestone model, and Fig. 5 (b) is sandstone model.The size of two models is all 1000m*500m, and limestone model is uniform dielectric, and sandstone is two-layer up and down, and top 200m is thick is overlayer, and bottom 300m is thick is ground.With reference to table 1 result, the elastic parameter value in limestone model: young modulus of material E=68GPa, Poisson ratioσ=0.30 and density p=2430kg/m3; Upper cover layer elastic parameter value in sandstone model: young modulus of material E=41GPa, Poisson ratioσ=0.18 and density p=2000kg/m3, bottom ground elastic parameter is the same with limestone; Simulated time is 1.1s.

2. earthquake stimulation simulation realizes

The two is all to excite at below ground 20m place, center, earth's surface.Fig. 6 (a) distributes for limestone model excites in 0.02s vertical component particle displacement constantly, and Fig. 6 (b) distributes for limestone model excites in 0.1s vertical component particle displacement constantly; Fig. 7 (a) distributes for sandstone model excites in 0.02s vertical component particle displacement constantly, and Fig. 7 (b) distributes for sandstone model excites in 0.1s vertical component particle displacement constantly.From the contrast of result up and down, be easy to find out that limestone area excites, produce the energy of propagating along earth's surface in a large number, and sandstone region excites, mostly seismic energy is propagated to earth formation deep, along surface energy, propagate seldom (as arrow in figure indicates), like this when earth's surface, study area is very complicated when, the interference (scattering wave of grey petrographic province earth's surface generation, ground roll etc.) just very severe, have a strong impact on seismic data quality.

Example two:

1. model is set up

Or the same with example one, the stimulation effect of research in sandstone and limestone medium.Therefore sandstone with in limestone, excite elastic parameter the same with the parameter recording in example one.Table 4 is different lithology shooting parameter; The complicated rate pattern of simplification that Fig. 8 sets up for the source book by collecting, model size is 1000m*1000m, shot point position is (500m, 4m).

Table 4

2. shock excitation is sent out simulation realization

By loading nearly source wave field function as explosive source excitation wavelet, use staggered-mesh Wave Equation Numerical algorithm to carry out earthquake stimulation simulation, finally obtain the analog record that excites based on medium elastic parameter.Fig. 9 (a) excites single shot record for sandstone; Fig. 9 (b) excites single shot record for limestone.From single shot record, can find out that quality of seismic data that limestone excites is than excite quality of seismic data poor (black rectangle frame marked position) in sandstone, noise jamming is strong, consistent with field physical record, therefore the impact that explosive shooting produces has not only been simulated in the earthquake stimulation simulation based on medium elastic parameter of carrying out well, has also simulated the communication process of seismic event after exciting simultaneously.

Technique scheme is one embodiment of the present invention, for those skilled in the art, the invention discloses on the basis of application process and principle, be easy to make various types of improvement or distortion, and be not limited only to the described method of the above-mentioned embodiment of the present invention, therefore previously described mode is just preferred, and does not have restrictive meaning.

Claims (8)

1. the earthquake stimulation analogy method based on rock microstructure and medium elastic parameter, is characterized in that: described method comprises:

(1) medium elastic parameter is investigated and asked for to rock microstructure;

(2) set up study area near-surface velocity model, deep layer rate pattern and tectonic model;

(3) the nearly source wavefield function that comprises elastic medium is realized and set up to numerical simulation algorithm;

(4) carry out the earthquake stimulation simulation based on rock microstructure and medium elastic parameter.

2. the earthquake stimulation analogy method based on rock microstructure and medium elastic parameter according to claim 1, is characterized in that: described step (1) comprising:

(11) to collect the actual rock sample coming from study area, carry out the microstructure investigation that electron-microscope scanning completes rock sample;

(12) experiment and the analysis of medium elastic parameter relations under the experiment of medium elastic parameter relations and analysis and different saturation condition under different confined pressure conditions.

3. the earthquake stimulation analogy method based on rock microstructure and medium elastic parameter according to claim 2, is characterized in that: described step (12) is achieved in that

P-and s-wave velocity and the Poisson ratio of institute's coring under different confined pressure conditions measured in chamber by experiment, and the elastic parameter of medium, obtains the relation between p-and s-wave velocity and Poisson ratio and medium elastic parameter;

P-and s-wave velocity and the Poisson ratio of institute's coring under different saturation condition measured in chamber by experiment, and the elastic parameter of medium, obtains the relation between p-and s-wave velocity and Poisson ratio and medium elastic parameter;

And then the medium velocity under the applicable this area of foundation near surface condition and the mathematical model of elastic parameter.

4. the earthquake stimulation analogy method based on rock microstructure and medium elastic parameter according to claim 3, it is characterized in that: described step (2) is achieved in that by the earthquake poststack data of study area sets up tectonic model, drilling well, VSP well-log information by study area are set up deep layer rate pattern, and near-surface velocity model is set up in the microstructure investigation of the rock sample that the medium velocity obtaining by step (1) and the mathematical model of elastic parameter and step (1) obtain; Finally near surface formation speed and deep layer speed model combination are obtained to final rate pattern.

5. the earthquake stimulation analogy method based on rock microstructure and medium elastic parameter according to claim 4, is characterized in that: in described step (3), numerical simulation algorithm is realized and being comprised:

(31) set up the one-order velocity-stress equation of wave equation;

(32) realize the numerical simulation algorithm of staggered-mesh method of finite difference: on the one-order velocity-stress equation basis in step (31), obtain corresponding Difference Schemes with Staggered, and then form numerical simulation algorithm.

6. the earthquake stimulation analogy method based on rock microstructure and medium elastic parameter according to claim 5, is characterized in that: the nearly source wavefield function that comprises elastic medium that described step (3) is set up is:

$u_r(r,t)=\frac{P_{0}a}{\mathrm{\&rho;}{r}^2{[m^2+{(n-b)}^2]}^{\frac{1}{2}}}\{\frac{e^{-\mathrm{b\&tau;}}}{{[m^2+{(n-b)}^2]}^{\frac{1}{2}}}-\frac{e^{-\mathrm{n\&tau;}}}{m}\cos [\mathrm{m\&tau;}-\arctan \left(\frac{n-b}{m}\right)\left]\right\}$

In formula $m=\frac{v_P\sqrt{1-2v}}{a(1-v)},$ $n=\frac{v_P\sqrt{1-2v}}{a(1-v)},$ $\mathrm{\&tau;}=t-\frac{r-a}{v_P}>0,$ ν is Poisson ratio, and r is ripple propagation distance;

U _r(r, t) is nearly source wavefield displacement, and ρ is density, v _pfor velocity of longitudinal wave, a is the cavity radius producing after explosive source blast, P ₀for the initial pressure that blast produces, the damped expoential that b is initial pressure, t is seismic travel time, and τ is for to start seismic travel time from cavity wall.

7. the earthquake stimulation analogy method based on rock microstructure and medium elastic parameter according to claim 6, is characterized in that: described step (4) comprising:

(41) complete the loading of the nearly source wavefield function that comprises elastic medium;

(42) carry out the earthquake stimulation simulation based on rock microstructure and medium elastic parameter: the numerical simulation algorithm that uses step (3) to obtain obtains the analog record that excites based on medium elastic parameter.

8. the earthquake stimulation analogy method based on rock microstructure and medium elastic parameter according to claim 7, is characterized in that: described step (41) comprising:

(411): the final rate pattern that step (2) is obtained carries out mesh generation, according to horizontal and vertical net point coordinate, determine source location (NXs, NZs);

(412): on four net points of the surrounding centered by source location (NXs, NZs), load the source wavelet with the nearly source wavefield function representation of described elastic medium.