CN105487112A - Method for constructing stratum reflection coefficient - Google Patents

Abstract

The invention discloses a method for constructing a stratum reflection coefficient, and belongs to the technical field of geological exploration. The method can construct accurate stratum reflection coefficient imaging. The method includes the following steps of: acquiring a velocity field and observation gun data; performing two-way wave migration according to the velocity and the observation gun data to obtain an initial stratum reflection coefficient; and performing least square inversion migration iteration process on the initial stratum reflection coefficient to obtain the processed stratum reflection coefficient.

Description

A kind of method building stratum reflection coefficient

Technical field

The present invention relates to technical field of geological exploration, specifically, relate to a kind of method building stratum reflection coefficient.

Background technology

The process of seismic prospecting, be exactly in series of points on the ground, utilize artificial excitation's seismic event, seismic event is to underground propagation, when running into wave impedance (seismic event in stratum media to the speed of underground propagation and the product of Media density) interface (i.e. the unequal face of upper and lower stratum wave impedance), on wave impedance interface, seismic event produces reflection, seismic wave propagation direction changes, seismic event starts upwards to propagate, a series of acceptance points on the ground settle receiver, receive the seismic data upwards propagated, this is the positive process (ground observation process) of seismic prospecting.Technician needs the seismic data utilizing receiver to receive, and carrys out the reflection coefficient imaging of inverting stratum, so that understand the structure on stratum, formation is studied.

Inventor finds, the reflection coefficient imaging of existing stratum, mainly through wave equation migration, can realize engineering construction system and the relative guarantor's width based on energy compensating.But the effect of protecting width is undesirable, be unfavorable for building comparatively accurate stratum reflection coefficient.

Summary of the invention

The object of the present invention is to provide a kind of method building stratum reflection coefficient, is a kind of method that can build accurate stratum reflection coefficient.

The invention provides a kind of method building stratum reflection coefficient, comprising:

Acquisition speed field and observation big gun data;

Carry out the skew of round trip ripple according to described velocity field and described observation big gun data, obtain initial stratum reflection coefficient;

The process of Least squares inversion offset iterations is carried out to described initial stratum reflection coefficient, obtains the stratum reflection coefficient after processing.

The described imaging results to initial offset carries out the process of least-squares migration inversion iterates, obtains stratum reflection coefficient and comprises:

Step a, acquisition inverse migration operator, obtain described initial stratum reflection coefficient as current stratum reflection coefficient;

Step b, obtain the stratum reflection coefficient that upgrades according to observation big gun data, described inverse migration operator and current stratum reflection coefficient;

Step c, based on upgrade stratum reflection coefficient, obtain current artillery simulators data;

Steps d, judge whether the residual error of current artillery simulators data and described observation big gun data is less than preset value, if so, perform step e, if not, then perform step f;

The stratum reflection coefficient of the renewal that step e, acquisition obtain exports as the stratum reflection coefficient after described process;

The stratum reflection coefficient of the renewal that step f, acquisition obtain, as current stratum reflection coefficient, returns and performs step b.

In described step b:

Based on described observation big gun data, described inverse migration operator and current stratum reflection coefficient, form gradient;

Obtain upgrading step-length based on described gradient;

According to described renewal step-length and current stratum reflection coefficient, obtain the stratum reflection coefficient upgraded.

After step e, described method also comprises:

Step g, export imaging results corresponding to described stratum reflection coefficient.

After step g, described method also comprises:

Step h, wave impedance parameter inversion procedure is carried out to described stratum reflection coefficient, and export wave impedance parameter inversion result corresponding to described stratum reflection coefficient.

Utilize Sparse Pulse Inversion algorithm, wave impedance parameter inverting is carried out to exported stratum reflection coefficient, and output wave impedance parameter inversion result.

Present invention offers following beneficial effect: in the technical scheme of the embodiment of the present invention, provide a kind of method building stratum reflection coefficient, the initial stratum reflection coefficient that the method utilizes the process of Least squares inversion offset iterations to offset through round trip ripple.The process of Least squares inversion offset iterations not only realizes the structure of stratum reflection coefficient, can also carry out seismic amplitude energy process.Therefore, the process of Least squares inversion offset iterations achieves guarantor's width imaging of real meaning, namely constructs accurate stratum reflection coefficient.Ensure that researchist can make for the stratum of correspondence conscientiously to study accurately.

Other features and advantages of the present invention will be set forth in the following description, and, partly become apparent from instructions, or understand by implementing the present invention.Object of the present invention and other advantages realize by structure specifically noted in instructions, claims and accompanying drawing and obtain.

Accompanying drawing explanation

In order to be illustrated more clearly in the technical scheme in the embodiment of the present invention, accompanying drawing required in describing is done simple introduction below to embodiment:

Fig. 1 is the schematic flow sheet one of the method for the structure stratum reflection coefficient that the embodiment of the present invention provides;

Fig. 2 is the schematic flow sheet two of the method for the structure stratum reflection coefficient that the embodiment of the present invention provides;

Fig. 3 is the schematic flow sheet three of the method for the structure stratum reflection coefficient that the embodiment of the present invention provides;

Fig. 4 is the schematic diagram of the SEG_EAGE model that the embodiment of the present invention provides;

Fig. 5 is the imaging results corresponding through the stratum reflection coefficient constructed by the process of 10 Least squares inversion offset iterations based on Fig. 4 that the embodiment of the present invention provides;

Fig. 6 is the imaging results corresponding through the stratum reflection coefficient constructed by the process of 50 Least squares inversion offset iterations based on Fig. 4 that the embodiment of the present invention provides;

Fig. 7 is the wave impedance parameter inversion procedure result based on Fig. 5 that the embodiment of the present invention provides;

Fig. 8 is the wave impedance parameter inversion procedure result based on Fig. 6 that the embodiment of the present invention provides;

Fig. 9 is the schematic diagram of the simulation solution cavity model that the embodiment of the present invention provides;

Figure 10 is the imaging results that the round trip ripple based on Fig. 9 that the embodiment of the present invention provides offsets;

Figure 11 is the imaging results corresponding based on the stratum reflection coefficient obtained through the process of 20 Least squares inversion offset iterations of Fig. 9 that the embodiment of the present invention provides;

Figure 12 is the wave impedance parameter inversion procedure result based on Figure 10 that the embodiment of the present invention provides;

Figure 13 is the wave impedance parameter inversion procedure result based on Figure 11 that the embodiment of the present invention provides.

Embodiment

Describe embodiments of the present invention in detail below with reference to drawings and Examples, to the present invention, how application technology means solve technical matters whereby, and the implementation procedure reaching technique effect can fully understand and implement according to this.It should be noted that, only otherwise form conflict, each embodiment in the present invention and each feature in each embodiment can be combined with each other, and the technical scheme formed is all within protection scope of the present invention.

Embodiments provide a kind of method building stratum reflection coefficient, as shown in Figure 1, the method comprises:

Step S101, acquisition speed field and observation big gun data.

Step S102, carry out the skew of round trip ripple according to described velocity field and described observation big gun data, obtain initial stratum reflection coefficient.

Step S103, the process of Least squares inversion offset iterations is carried out to described stratum reflection coefficient, obtain the stratum reflection coefficient after processing.

In the prior art, the expression formula of observation big gun data is:

P _obs＝L·m………………………………(1)

Wherein, P _obsfor observation big gun data, i.e. m characterizing formation reflection coefficient herein; L characterizes and linearly just drills matrix operator.

Therefore, the exact solution of stratum reflection coefficient is expressed as:

m＝(L ^TL) ^-1·L ^T·P _obs…………………………(2)

Wherein, L ^tl is Hessian matrix (HessianMatrix).Offset method common at present, as ray class, one-way wave skew and the skew of round trip ripple all suppose (L ^tl) ^-1≈ I, wherein, I is unit matrix.The conjugate transpose of direct propagation operator carrys out approximate inverse operator and acts on observational record and offset, then obtained by formula (2):

m＝L ^T·P _obs………………………………(3)

But, in most cases, L ^tl is not a unit matrix I.Its main manifestations is: LTL entry of a matrix element is unequal on the diagonal, or the element on off-diagonal is not 0.Therefore the imaging value obtained is one of legitimate reading and is similar to, and more lays particular emphasis on and realizes the imaging of reflecting interface geometry, do not comprise the process to seismic event amplitude energy.

The process of Least squares inversion offset iterations is the exact solution that will solve the stratum reflection coefficient characterized such as formula (2), and it is the inverse matrix adding Hessian matrix on the basis of conventional migration technique (i.e. formula (3)).And the cornerwise element of Hessian matrix characterizes seismic amplitude energy.Therefore, the process of Least squares inversion offset iterations not only realizes the accurately image of stratum reflecting interface, can also carry out seismic amplitude energy process.Therefore, the process of Least squares inversion offset iterations achieves guarantor's width imaging of real meaning, namely constructs accurate stratum reflection coefficient.

Therefore, in embodiments of the present invention, a kind of method building stratum reflection coefficient is provided, the initial stratum reflection coefficient that the method utilizes the process of Least squares inversion offset iterations to offset through round trip ripple.The process of Least squares inversion offset iterations not only realizes the structure of stratum reflection coefficient, can also carry out seismic amplitude energy process.Therefore, the process of Least squares inversion offset iterations achieves guarantor's width imaging of real meaning, namely constructs accurate stratum reflection coefficient.Ensure that researchist can make for the stratum of correspondence conscientiously to study accurately.

Concrete, as shown in Figure 2, step S103 comprises:

Step S201, acquisition inverse migration operator, obtain described initial stratum reflection coefficient as current stratum reflection coefficient.

Concrete, inverse migration operator can be obtained by following Procedure Acquisition:

According to prior art, known two-dimentional Chang Midu Acoustic Wave-equation is as shown in the formula shown in (4):

$s^2\left(x\right)\frac{{\∂}^{2}p(x,t,x_s)}{{\∂}^{2}t}-{\▿}^{2}p(x,t,x_s)=\mathrm{\δ}(x-x_s)f\left(t\right)...\left(4\right)$

Wherein, p (x, t, x _s) characterize actual wave field; S (x) characterizes acoustic slowness field; F (t) characterizes source wavelet; x _scharacterize focal point coordinate; X characterizes locus coordinate.

Concrete, acoustic slowness field, relation between background slowness field and disturbance slowness field three are as shown in the formula shown in (5):

$s^2\left(x\right)=s_0^2\left(x\right)+{\mathrm{\Δs}}^2\left(x\right)...\left(5\right)$

Wherein, characterize background slowness field, Δ s ²x () characterizes disturbance slowness field.

Then corresponding, actual wave field p (x, t, x _s) be formed by stacking by the background wave field propagated in background media and disturbance wave field,

p(x,t,x _s)＝p ₀(x,t,x _s)+p _s(x,t,x _s)…………………………(6)

Wherein, p ₀(x, t, x _s) characterize background wave field, p _s(x, t, x _s) characterize disturbance wave field.

Formula (5) and formula (6) are substituted in formula (4), and utilizes Born-Oppen-heimer approximation (Born-Oppenheimerapproximation) can about disturbance wave field p _s(x, t, x _s) expression formula as follows:

$s_0^2\left(x\right)\frac{{\∂}^2{p}_s(x,t,x_s)}{{\∂}^{2}t}-{\▿}^2{p}_s(x,t,x_s)={-\mathrm{\Δs}}^2\left(x\right)\frac{{\∂}^2{p}_0(x,t,x_s)}{{\∂}^{2}t}...\left(7\right)$

Background wave field p in formula (7) ₀(x, t, x _s) meet following formula:

$s_0^2\left(x\right)\frac{{\∂}^2{p}_0(x,t,x_s)}{{\∂}^{2}t}-{\▿}^2{p}_0(x,t,x_s)=f\left(t\right)...\left(8\right)$

From formula (7) and formula (8), background wave field p ₀(x, t, x _s) and disturbance wave field p _s(x, t, x _s) be the wave field propagated in background media, wherein disturbance wave field p _s(x, t, x _s) be with medium disturbance and background wave field p ₀(x, t, x _s) interaction as secondary focus formed and the wave field propagated in background media, there is clear and definite physical significance.Definition stratum reflection coefficient m (x) is Δ s ²x (), then can utilize Green function (Green ' sfunction) explicit representation disturbance wave field p _s(x, t, x _s), that is:

$p_s(x,t,x_s)=-\∫{\mathrm{dx}}^{\′}{G}_0(x_r,t;x^{\′},0)*\left[m\left(x^{\′}\right)\frac{{\∂}^2{p}_0(x^{\′},t,x_s)}{{\∂t}^2}\right]...\left(9\right)$

Wherein, G ₀(x _r, t; X', 0) characterize background wave field, x' characterizes locus coordinate, x _rcharacterize wavefield reception coordinate.

As can be seen from formula (9), disturbance wave field p _s(x, t, x _s) and stratum reflection coefficient m (x) between linear.Be expressed as follows with operational form:

p _s＝Lm(x)……………………………(10)

In formula, L is just calculation of disturbance wave field.So far, approximate by wave equation linearization based on Born, just calculation of disturbance wave field of having derived, this operator is also the inverse migration operator corresponding to reverse-time migration.

Further, as shown in Figure 2, also comprise in the embodiment of the present invention:

Step S202, obtain the stratum reflection coefficient that upgrades according to observation big gun data, described inverse migration operator and current stratum reflection coefficient;

Concrete, as shown in Figure 3, described step S202 comprises:

Step S301, based on described observation big gun data, described inverse migration operator and current stratum reflection coefficient, formed gradient;

Namely gradient g is formed according to following formula (13) ^(k+1):

g ^(k+1)＝L ^T[Lm ^(k)-P _obs]……………………………(11)

Wherein, k is natural number, characterize the number of times of Least squares inversion offset iterations process of process.

It should be noted that, suppose that the m in formula (11) is initial stratum reflection coefficient now for first time carries out the process of Least squares inversion offset iterations, then k=0.

Step S302, based on described gradient obtain upgrade step-length;

Concrete, for upgrading step-length α z according to obtaining with following formula (12) to (14) ^(k+1):

$\mathrm{\β}=\frac{g^{(k+1)}{g}^{(k+1)}}{g^{\left(k\right)}{g}^{\left(k\right)}}...\left(12\right)$

z ^(k+1)＝g ^(k+1)+βZ ^(k)…………………………(13)

$\mathrm{\α}=\frac{{\left[z^{(k+1)}\right]}^T{g}^{(k+1)}}{{\left[{\mathrm{Lz}}^{(k+1)}\right]}^T{\mathrm{Lz}}^{(k+1)}}...\left(14\right)$

Step S303, according to described renewal step-length and current stratum reflection coefficient, obtain upgrade stratum reflection coefficient.

Concrete, for according to the stratum reflection coefficient obtaining with following formula (15) upgrading:

m ^(k+1)＝m ^(k)-αz ^(k+1)………………………(15)

It should be noted that, the method for the stratum reflection coefficient that the acquisition of step S301 to step S303 upgrades, is commonly referred to method of conjugate gradient.

Further, as shown in Figure 2, also comprise in the embodiment of the present invention:

Step S203, based on upgrade stratum reflection coefficient, obtain current artillery simulators data.

Concrete, can according to the stratum reflection coefficient m upgraded ^(k+1)with inverse migration operator L, convolution (1) can obtain current artillery simulators data P _cal.

Step S204, judge whether the residual error of current artillery simulators data and described observation big gun data is less than preset value.If so, step S205 is performed; If not, then step S206 is performed.

Concrete, the residual error E (m) of current artillery simulators data and described observation big gun data is calculated according to following formula (16).

$E\left(m\right)=\frac{1}{2}{\left|\right|P_{\mathrm{cal}}-P_{\mathrm{obs}}\left|\right|}_2^2=\frac{1}{2}{\left|\right|\mathrm{Lm}-P_{\mathrm{obs}}\left|\right|}_2^2...\left(16\right)$

After obtaining residual error E (m), need judge whether residual error E (m) is less than preset value, such as, whether be less than if meet this preset value, then the stratum reflection coefficient of now obtained renewal exports, otherwise again will carry out iterative processing.

The stratum reflection coefficient of the renewal that step S205, acquisition obtain exports as described stratum reflection coefficient.

The stratum reflection coefficient of the renewal that step S206, acquisition obtain, as current stratum reflection coefficient, returns and performs step S202.

Obviously, after step S206, need to carry out least-squares migration inversion iterates process at least one times again, till satisfied " residual error of current artillery simulators data and described observation big gun data is less than preset value " this condition.

Further, as shown in Figure 2, after step S205, described method also comprises:

Step S207, export imaging results corresponding to described stratum reflection coefficient.

The imaging results that the stratum reflection coefficient formed by this method is corresponding exports, and personnel for deliberation carry out observing, studying.

In order to the application prospect of the inventive method in lithological reservoir exploration is described better, as shown in Figure 2, after step S207, described method also comprises:

Step S208, wave impedance parameter inversion procedure is carried out to described stratum reflection coefficient, and export wave impedance parameter inversion result corresponding to described stratum reflection coefficient.

Concrete, Sparse Pulse Inversion algorithm can be utilized, wave impedance parameter inversion procedure is carried out to exported stratum reflection coefficient, and output wave impedance parameter inversion result.Obviously, method for distinguishing also can be utilized to carry out wave impedance parameter inversion procedure, and the embodiment of the present invention does not limit this.

In order to further illustrate the guarantor's width building stratum reflection coefficient based on the method disclosed in the invention described above, make concrete example respectively by SEG_EAGE modeling and simulation solution cavity model below:

Be illustrated in figure 4 the disclosed international public master pattern of SEG_EAGE, this model lateral velocity variation is violent, ruptures containing steep dip.Utilize this cover normal data.Test in conjunction with the method disclosed in the present, Figure 5 shows that through imaging results corresponding to the stratum reflection coefficient constructed by the process of 10 Least squares inversion offset iterations, Figure 6 shows that through imaging results corresponding to the stratum reflection coefficient constructed by the process of 50 Least squares inversion offset iterations.Can find out, along with iterations increases, salt dome flank and bottom imaging effect are more and more accurate, and resolution is also more and more higher, and the overall amplitude equalization of imaging results increases.

Width is protected in order to test above-mentioned two imaging results further, on the basis of the imaging results corresponding with the stratum reflection coefficient shown in Fig. 6 shown in Fig. 5, carry out wave impedance parameter inversion procedure respectively, Fig. 7 and Fig. 8 is based on wave impedance parameter inversion procedure result corresponding to the stratum reflection coefficient constructed by 10 times and the process of 50 Least squares inversion offset iterations respectively.Comparison diagram 7 and Fig. 8 can know, iterations is larger, and wave impedance parameter inversion procedure result is all the more close to real model.Illustrate along with successive iteration, the imaging results of Least squares inversion offset iterations process is more and more accurate, more and more protects width, approaches real strata condition gradually.

In addition, be the model of the geological phenomenon design of simulation solution cavity as Fig. 9, wherein comprising radius is 10m, 20m, 30m, 40m and 50m different scale scatterer.This model has four main layers, and the speed of top-down each main layer is respectively 2000m/s, 2200m/s, 2500m/s and 2800m/s, and in the model, the speed of each scatterer is 2000m/s.

Concrete, Figure 10 is the imaging results offset based on the round trip ripple of the simulation solution cavity model shown in Fig. 9, Figure 11 be based on the simulation solution cavity model shown in Fig. 9, through imaging results corresponding to the stratum reflection coefficient constructed by the process of 20 Least squares inversion offset iterations.From the imaging effect contrast shown in Figure 10 and Figure 11, the imaging results that the stratum reflection coefficient constructed by the process of Least squares inversion offset iterations is corresponding is that horizontal or longitudinal energy is all more balanced, and it is more clear that solution cavity border is portrayed.Describe the process of Least squares inversion offset iterations, in the imaging of western carbonate rock fractured cave Reservoir Body reservoir, there is application potential.

Further, on the basis of the imaging results shown in Figure 10 and Figure 11, carry out wave impedance parameter inversion procedure respectively, form the wave impedance parameter inversion procedure result shown in Figure 12 and Figure 13.Obviously, the inversion procedure result shown in Figure 13, compared with the inversion procedure result shown in Figure 12, can have better consistance with the master pattern shown in Fig. 9.That is, the stratum reflection coefficient of the structure of Least squares inversion offset iterations process has better amplitude and protects width effect, can meet the aspects such as follow-up layer description better to the demand of protecting width imaging.

Can illustrate from above imaging results, the advantage of Least squares inversion offset iterations result is not construction location imaging roughly, but more careful small scale body and border of accurately portraying stratigraphic structure, and obtain more reliable more accurate parametric inversion on this basis, for carrying out lithology exploration better and reservoir portrays service.

Although embodiment disclosed in this invention is as above, the embodiment that described content just adopts for the ease of understanding the present invention, and be not used to limit the present invention.Technician in any the technical field of the invention; under the prerequisite not departing from spirit and scope disclosed in this invention; any amendment and change can be done what implement in form and in details; but scope of patent protection of the present invention, the scope that still must define with appending claims is as the criterion.

Claims (6)

1. build a method for stratum reflection coefficient, it is characterized in that, comprising:

Acquisition speed field and observation big gun data;

Carry out the skew of round trip ripple according to described velocity field and described observation big gun data, obtain initial stratum reflection coefficient;

The process of Least squares inversion offset iterations is carried out to described initial stratum reflection coefficient, obtains the stratum reflection coefficient after processing.

2. method according to claim 1, is characterized in that, describedly carries out the process of least-squares migration inversion iterates to initial stratum reflection coefficient, obtains stratum reflection coefficient and comprises:

Step a, acquisition inverse migration operator, obtain described initial stratum reflection coefficient as current stratum reflection coefficient;

Step b, obtain the stratum reflection coefficient that upgrades according to observation big gun data, described inverse migration operator and current stratum reflection coefficient;

Step c, based on upgrade stratum reflection coefficient, obtain current artillery simulators data;

Steps d, judge whether the residual error of current artillery simulators data and described observation big gun data is less than preset value, if so, perform step e, if not, then perform step f;

The stratum reflection coefficient of the renewal that step e, acquisition obtain exports as the stratum reflection coefficient after described process;

The stratum reflection coefficient of the renewal that step f, acquisition obtain, as current stratum reflection coefficient, returns and performs step b.

3. method according to claim 2, is characterized in that, in described step b:

Based on described observation big gun data, described inverse migration operator and current stratum reflection coefficient, form gradient;

Obtain upgrading step-length based on described gradient;

According to described renewal step-length and current stratum reflection coefficient, obtain the stratum reflection coefficient upgraded.

4. method according to claim 2, is characterized in that, after step e, described method also comprises:

Step g, export imaging results corresponding to described stratum reflection coefficient.

5. method according to claim 4, is characterized in that, after step g, described method also comprises:

Step h, wave impedance parameter inversion procedure is carried out to described stratum reflection coefficient, and export wave impedance parameter inversion result corresponding to described stratum reflection coefficient.

6. method according to claim 5, is characterized in that, described step h comprises:

Utilize Sparse Pulse Inversion algorithm, wave impedance parameter inverting is carried out to exported stratum reflection coefficient, and output wave impedance parameter inversion result.