CN103675911A - Method for combined inversion of intercept and gradient based on compressional waves and converted shear waves - Google Patents

Abstract

The invention relates to a method for combined inversion of intercept and gradient based on compressional waves and converted shear waves. The method comprises the following steps of obtaining a compressional wave and converted shear wave angle domain gather, and meanwhile, obtaining the compressional wave and shear wave speeds and well logging interpretation result; extracting the sub-waves from the compressional wave and converted shear wave angle domain gather to obtain an angle domain reflection coefficient profile, and utilizing the obtained compressional wave and shear wave speeds to solve a shear wave and compressional wave ratio profile; utilizing the induced converted shear wave reflection coefficient formula and the compressional wave reflection parameter approximate formula using the intercept and gradient as parameters, and adopting a singular value decomposition method to realize combined inversion so as to obtain the intercept and gradient; utilizing the well logging interpretation result to calibrate the inverted intercept and gradient, establishing a fluid identification mode, and carrying out the fluid detection on the undrilled area. The method has the advantages that the received multi-component earthquake wave field information is sufficiently utilized, the multiple-solution property of the inversion process is reduced, the stability of the inversion process is improved, and a reliable method is provided for the oil and gas prediction.

Description

A kind of method based on compressional wave and converted shear wave joint inversion intercept and gradient

Technical field

The invention belongs to geophysical survey field, particularly, relate to a kind of method based on compressional wave and converted shear wave joint inversion intercept and gradient.

Background technology

Amplitude variation with Offset (Amplitude Versus Offet) is with offset distance variation relation, to carry out the lithologic parameters such as acquisition speed, density by research reflection amplitude, and then a technology of carrying out oil and gas reservoir prediction.Utilize the corresponding intercept of Shuey (1985) formulas Extraction (P) and gradient (G) or their combination parameter can effectively carry out oil-gas recognition and fluid prediction.Wherein, intercept (P) section, the incidence reflection coefficient section that directly hangs down, has higher signal to noise ratio (S/N ratio) and resolution, in approximate zero geophone offset place vertical incidence, reflection, can not produce converted shear wave, can be considered P-wave section.Gradient (G) section is relevant with Poisson ratio, the information that contains the upper and lower stratum of reflecting interface lithological change, and intercept (P) and gradient (G) they are good oil and gas indication and fluid prediction parameter.

But the method that tradition is extracted intercept (P) and gradient (G) only depends on compressional wave data, be difficult to overcome instability and the multi-solution that extracts result in leaching process; Another one aspect, multi-component seismic data has been recorded to abundant seismic wave field information, can make up the deficiency of utilizing merely compressional wave method, reduces the multi-solution of refutation process, increases the stability of inversion result, for petroleum-gas prediction provides reliable method.The present invention fully utilizes compressional wave and converted shear wave is combined extraction intercept (P) and gradient (G), make full use of the Multi-component earthquake wave field information receiving, reduced the multi-solution of refutation process, improved the stability of refutation process, for petroleum-gas prediction provides a kind of reliable method.

Summary of the invention

In order to overcome the deficiency of independent use compressional wave Data Inversion intercept (P) and gradient (G) parameter, the invention provides a kind of method based on compressional wave and converted shear wave joint inversion intercept (P) and gradient (G); Make full use of compressional wave, converted shear wave wave field information, take the longitudinal wave reflection coefficient approximate expression (Shuey that intercept (P) and gradient (G) be parameter, 1985) on basis, further derived and take the converted shear wave reflection coefficient approximate expression that intercept (P) and gradient (G) be parameter, utilize the compressional wave and the converted shear wave angle Dao Ji that obtain, adopt singular value decomposition method to carry out joint inversion, obtain intercept (P) and gradient (G).

For achieving the above object, technical scheme of the present invention is as follows:

Method based on compressional wave and converted shear wave joint inversion intercept and gradient, comprises the following steps:

Step 1: obtain compressional wave, converted shear wave angle domain road collection, obtain compressional wave and shear wave velocity and result of log interpretation simultaneously

Step 2: compressional wave and converted shear wave angle domain road collection are extracted to wavelet and obtain angle domain reflection coefficient section, and utilize the compressional wave that obtains and shear wave velocity to ask for transverse and longitudinal wave velocity and compare section

Step 3: utilize converted shear wave reflection coefficient formula and the longitudinal wave reflection coefficient approximate expression that intercept (P) and gradient (G) be parameter of take derive, employing singular value decomposition method carries out joint inversion, acquisition intercept (P) and gradient (G)

Step 4: utilize result of log interpretation to demarcate to the intercept being finally inversed by (P) and gradient (G) the fluid identification pattern of setting up, to drilling area not carrying out fluid detection

With respect to prior art, the present invention has following beneficial effect: the present invention fully utilizes compressional wave and converted shear wave is combined extraction intercept (P) and gradient (G), make full use of the Multi-component earthquake wave field information receiving, reduced the multi-solution of refutation process, improved the stability of refutation process, for petroleum-gas prediction provides a kind of reliable method.

Accompanying drawing explanation

Fig. 1 is that compressional wave and converted shear wave are combined extraction intercept (P) and gradient (G) method flow diagram;

Fig. 2 carries out compressional wave and converted shear wave to combine the stratified model data of extracting intercept (P) and gradient (G);

Fig. 3 a is by the direct synthetic compressional wave angle domain road collection (0-38 °) of Zoeppritz equation;

Fig. 3 b is by the direct synthetic converted shear wave angle domain road collection (0-38 °) of Zoeppritz equation;

Fig. 4 a removes by least square spiking deconvolution principle the compressional wave angle domain reflection coefficient that the wavelet of compressional wave angle domain road collection in Fig. 3 a obtains;

Fig. 4 b removes by least square spiking deconvolution principle the converted shear wave angle domain reflection coefficient that the wavelet of converted shear wave angle domain road collection in Fig. 3 b obtains;

Fig. 5 a is intercept (P) and the intercept (P) of only utilizing compressional wave extraction and the comparison of intercept (P) actual value that compressional wave and converted shear wave are combined extraction;

Fig. 5 b utilizes compressional wave and converted shear wave to combine the gradient of extraction (G) and only utilizes the gradient (G) of compressional wave extraction and the comparison of gradient (G) actual value;

Fig. 6 a is by the direct synthetic compressional wave angle domain road collection (0-38 °) of Zoeppritz equation and is added with 25dB ground unrest;

Fig. 6 b is by the direct synthetic converted shear wave angle domain road collection (0-38 °) of Zoeppritz equation and is added with 25dB ground unrest;

Fig. 7 a removes by least square spiking deconvolution principle the compressional wave angle domain reflection coefficient that the wavelet of compressional wave angle domain road collection in Fig. 6 a obtains;

Fig. 7 b removes by least square spiking deconvolution principle the converted shear wave angle domain reflection coefficient that the wavelet of converted shear wave angle domain road collection in Fig. 6 b obtains;

Fig. 8 a concentrates and adds in random noise situation in input angle road, and compressional wave and converted shear wave are combined the intercept (P) of extraction and only utilized the intercept (P) of compressional wave extraction and the comparison of intercept (P) actual value;

Fig. 8 b concentrates and adds in random noise situation in input angle road, utilizes compressional wave and converted shear wave to combine the gradient of extraction (G) and only utilizes the gradient (G) of compressional wave extraction and the comparison of gradient (G) actual value.

Embodiment

As shown in Figure 1, the method based on compressional wave and converted shear wave joint inversion intercept (P) and gradient (G), comprises the steps:

(1), obtain compressional wave, converted shear wave angle domain road collection, obtain compressional wave and shear wave velocity and result of log interpretation simultaneously; Concrete grammar is as follows:

Seismic data based on field acquisition utilizes seismic imaging method to extract road, pre-stack seismic angle collection data;

Well-log information based on field logging obtains compressional wave and shear wave velocity and result of log interpretation;

(2), compressional wave, converted shear wave angle domain road collection extracted to wavelet obtain angle domain reflection coefficient section, and utilize the compressional wave that obtains and shear wave velocity to ask for transverse and longitudinal wave velocity and compare section; Concrete grammar is as follows:

Utilize pre-stack seismic geology scaling method (careful Guoqiang. prestack seismic inversion method and Study on influencing factors [J] .2013) obtain compressional wave and the concentrated wavelet in road, converted shear wave angle, then adopt least square spiking deconvolution principle to remove the wavelet of compressional wave, converted shear wave angle domain road collection, obtain compressional wave, converted shear wave angle domain reflection coefficient.

By Zoeppritz equation (referring to < < theory of earthquake wave and method > >, Sun Chengyu, the 65th page of formula 3-2-7), utilize well logging velocity of longitudinal wave, shear wave velocity and density parameter, can obtain the other angle domain seismic trace of the compressional wave of just drilling and converted shear wave well, the prestack compressional wave that this compressional wave and road, converted shear wave angle collection and reality obtain and road, converted shear wave angle set pair are than the wavelet that can estimate inside actual acquisition Jiao road collection.Then under wavelet known case, adopt least square spiking deconvolution method (the 67th page of the < < seismic data processing technique > > of Li Zhenchun) to remove the wavelet of compressional wave, converted shear wave angle domain road collection, obtain compressional wave, converted shear wave angle domain reflection coefficient.

Utilize shear wave that well-log information obtains and velocity of longitudinal wave to be divided by obtain transverse and longitudinal wave velocity and compare section.

(3), utilize converted shear wave reflection coefficient formula (formula 1.5) and Shuey (1985) the longitudinal wave reflection coefficient approximate expression (formula 1.1) that intercept (P) and gradient (G) be parameter of take derive, adopt singular value decomposition method to carry out joint inversion, obtain intercept (P) and gradient (G); Concrete grammar is as follows:

The longitudinal wave reflection coefficient approximate expression that Shuey (1985) derives Aki and Richard (1980) is rewritten as take the formula that intercept (P) and gradient (G) be parameter:

$R_{\mathrm{pp}}\left(\mathrm{\&theta;}\right)=P+G{\sin }^2\mathrm{\&theta;}+\frac{1}{2}\frac{\mathrm{\&Delta;}{V}_p}{V_p}({\tan }^2\mathrm{\&theta;}-{\sin }^2\mathrm{\&theta;})---\left(1.1\right)$

Wherein, $P=\frac{1}{2}(\frac{\mathrm{\&Delta;}{v}_p}{v_p}+\frac{\mathrm{\&Delta;\&rho;}}{\mathrm{\&rho;}}),$ $G=\frac{1}{2}\frac{\mathrm{\&Delta;}{v}_p}{v_p}-2(2\frac{\mathrm{\&Delta;}{v}_p}{v_p}+\frac{\mathrm{\&Delta;\&rho;}}{\mathrm{\&rho;}})+\frac{\mathrm{\&Delta;\&sigma;}}{{(1-\mathrm{\&sigma;})}^2};$ V _p, Δ V _pbe respectively that upper and lower layer compressional wave average velocity and upper and lower layer velocity of longitudinal wave are poor, θ is the average of incident compressional angle, angle of transmission.

Take intercept (P) and gradient (G) is parameter, derivation converted shear wave reflection coefficient approximate formula (formula 1.5).Aki and Richard etc. (1980) have provided converted shear wave reflection coefficient approximate expression:

Wherein θ, be respectively the mean value of mean value, transformed wave reflection angle and the angle of transmission of incident compressional angle and angle of transmission, V _p, V _s, ρ is respectively the mean value of levels velocity of longitudinal wave, shear wave velocity, density, Δ V _p, Δ V _s, Δ ρ is that levels velocity of longitudinal wave is poor, shear wave velocity is poor, density difference.

In isotropic medium, the relational expression of Poisson ratio and p-and s-wave velocity ratio:

$\frac{V_s^2}{V_p^2}=\frac{1-2\mathrm{\&sigma;}}{2(1-\mathrm{\&sigma;})}---\left(1.3\right)$

Wherein, V _p, V _s, σ is respectively the mean value of levels velocity of longitudinal wave, shear wave velocity, Poisson ratio, σ is V _p, V _sfunction.To 1.2 formula both sides differential arrangement, can obtain:

$\frac{\mathrm{\&Delta;}{V}_s}{V_s}=\frac{\mathrm{\&Delta;}{V}_p}{V_p}-\frac{1}{4}\frac{V_p^2}{V_s^2}\frac{\mathrm{\&Delta;\&sigma;}}{{(1-\mathrm{\&sigma;})}^2}---\left(1.4\right)$

By in 1.4 formula substitution 1.2 formulas and arrange to obtain following formula:

In order to overcome the deficiency of independent use compressional wave Data Inversion intercept (P) and gradient (G) parameter, make full use of compressional wave, converted shear wave wave field information, simultaneous formula 1.1 formulas and formula 1.5 formulas, by SVD (svd) method, carry out joint inversion intercept and gradient:

$\left[\begin{array}{c}{R}_{\mathrm{pp}}\left({\mathrm{\&theta;}}_1\right)\\ .\\ .\\ .\\ R_{\mathrm{pp}}\left({\mathrm{\&theta;}}_n\right)\\ R_{\mathrm{ps}}\left({\mathrm{\&theta;}}_1\right)\\ .\\ .\\ .\\ R_{\mathrm{ps}}\left({\mathrm{\&theta;}}_n\right)\end{array}\right]\left[\begin{array}{ccc}1& B\left({\mathrm{\&theta;}}_1\right)& C\left({\mathrm{\&theta;}}_1\right)\\ .& .& .\\ .& .& .\\ .& .& .\\ 1& B\left({\mathrm{\&theta;}}_n\right)& C\left({\mathrm{\&theta;}}_n\right)\\ D\left({\mathrm{\&theta;}}_1\right)& E\left({\mathrm{\&theta;}}_1\right)& F\left({\mathrm{\&theta;}}_1\right)\\ .& .& .\\ .& .& .\\ .& .& .\\ D\left({\mathrm{\&theta;}}_n\right)& E\left({\mathrm{\&theta;}}_n\right)& F\left({\mathrm{\&theta;}}_n\right)\end{array}\right]\left[\begin{array}{c}\\ P\\ G\\ \frac{\mathrm{\&Delta;}{V}_p}{V_p}\end{array}\right]$

Wherein, B (θ _i), C (θ _i) (i=1,2,3......n) be respectively different angles θ _i(i=1,2,3......n) G, Δ V in Rpp equation _p/ V _pfront coefficient, D (θ _i), E (θ _i), F (θ _i) (i=1,2,3...n) be respectively different angles θ _i(i=1,2,3......n) P, G, Δ V in Rps equation _p/ V _pfront coefficient, Rpp (θ _i), Rps (θ _i) (i=1,2,3.....n) be respectively different angles θ _i(i=1,2, compressional wave 3......n) and converted shear wave reflection coefficient.

The expression formula of above-mentioned inverting intercept and gradient can be summarized as:

y＝Ax

Wherein, y is angle domain quasi-reflection matrix of coefficients, the property parameters matrix of x for needing to extract, and A is matrix of coefficients before property parameters x.

Utilize Matrix Singular Value to carry out AVO inverting and can try to achieve property parameters x matrix,

x＝UΛ ^-1V ^Ty

Wherein, U, V carry out to matrix A the AA that svd obtains ^teigenwert, Λ carries out to matrix A the AA that svd obtains ^tsingular value matrix.

(4), utilize result of log interpretation to demarcate to the intercept being finally inversed by (P) and gradient (G) the fluid identification pattern of setting up, to drilling area not carrying out fluid detection; Concrete grammar is as follows:

First the intercept of inverting (P) and gradient (G) section are demarcated with the result of log interpretation of crossing this section well, according to result of log interpretation, the hydrocarbon zone on intercept (P) and gradient (G) section and water layer corresponding demarcation on the intercept (P) of inverting and gradient (G) section, can be according to oil gas and water layer the demonstration phenomenon on this intercept (P) and gradient (G) section, oil reservoir and gas-bearing formation on not drilling area intercept and gradient profile are predicted, obtained favourable drilling area.

By four layer models that Mahmoudian and Margrave (2004) is proposed, test, Fig. 5 is that associating compressional wave and converted shear wave extract intercept (P) and gradient (G) attribute and utilize single compressional wave to extract the comparison diagram of intercept (P) and gradient (G) attribute and intercept (P) and gradient (G) actual value, contrast finds that intercept (P) and the gradient (G) of joint inversion have higher precision, particularly gradient (G) attribute; Fig. 8 is in the noisy situation of input Jiao road collection data, associating compressional wave and converted shear wave extract intercept (P) and gradient (G) attribute and utilize single compressional wave to extract the comparison diagram of intercept (P) and gradient (G) attribute and intercept (P) and gradient (G) actual value, contrast finds that intercept (P) and the gradient (G) of joint inversion have higher precision, gradient (G) attribute particularly, and combine ground unrest is had to certain compacting.

Claims (5)

1. the method based on compressional wave and converted shear wave joint inversion intercept and gradient, is characterized in that, comprises the following steps:

Step 1: obtain compressional wave, converted shear wave angle domain road collection, obtain compressional wave and shear wave velocity and result of log interpretation simultaneously;

Step 2: compressional wave and converted shear wave angle domain road collection are extracted to wavelet and obtain angle domain reflection coefficient section, and utilize the compressional wave that obtains and shear wave velocity to ask for transverse and longitudinal wave velocity and compare section;

Step 3: utilize and take converted shear wave reflection coefficient formula and the longitudinal wave reflection coefficient approximate expression that intercept (P) and gradient (G) be parameter, employing singular value decomposition method carries out joint inversion, acquisition intercept (P) and gradient (G);

Step 4: utilize result of log interpretation to demarcate to the intercept being finally inversed by (P) and gradient (G) the fluid identification pattern of setting up, to drilling area not carrying out fluid detection.

2. the method based on compressional wave and converted shear wave joint inversion intercept and gradient according to claim 1, is characterized in that, the concrete grammar of step 1 is as follows:

Seismic data based on field acquisition, utilizes seismic imaging method to extract road, pre-stack seismic angle collection data;

Well-log information based on field logging, obtains compressional wave and shear wave velocity and result of log interpretation.

3. according to the method based on compressional wave and converted shear wave joint inversion intercept and gradient described in claim 1-2, it is characterized in that, the concrete grammar of step 2 is as follows:

Utilize pre-stack seismic geology scaling method to obtain compressional wave and the concentrated wavelet in converted shear wave angle domain road, then utilize least square spiking deconvolution method to remove the wavelet of compressional wave, converted shear wave angle domain road collection, obtain compressional wave, converted shear wave angle domain reflection coefficient;

Utilize shear wave that well-log information obtains and velocity of longitudinal wave to be divided by obtain transverse and longitudinal wave velocity and compare section.

4. according to the method based on compressional wave and converted shear wave joint inversion intercept and gradient described in claim 1-3, it is characterized in that, step 3 concrete grammar is as follows:

Take the longitudinal wave reflection coefficient approximate formula that intercept (P) and gradient (G) be parameter:

$R_{\mathrm{pp}}\left(\mathrm{\&theta;}\right)=P+G{\sin }^2\mathrm{\&theta;}+\frac{1}{2}\frac{\mathrm{\&Delta;}{V}_p}{V_p}({\tan }^2\mathrm{\&theta;}-{\sin }^2\mathrm{\&theta;})---\left(1.1\right)$

Wherein, $P=\frac{1}{2}(\frac{\mathrm{\&Delta;}{v}_p}{v_p}+\frac{\mathrm{\&Delta;\&rho;}}{\mathrm{\&rho;}}),$ $G=\frac{1}{2}\frac{\mathrm{\&Delta;}{v}_p}{v_p}-2(2\frac{\mathrm{\&Delta;}{v}_p}{v_p}+\frac{\mathrm{\&Delta;\&rho;}}{\mathrm{\&rho;}})+\frac{\mathrm{\&Delta;\&sigma;}}{{(1-\mathrm{\&sigma;})}^2};$

V _p, Δ V _pbe respectively that upper and lower layer compressional wave average velocity and upper and lower layer velocity of longitudinal wave are poor, θ is the average of incident compressional angle, angle of transmission;

Take the converted shear wave reflection coefficient approximate formula that intercept (P) and gradient (G) be parameter:

Wherein θ,

be respectively the mean value of mean value, transformed wave reflection angle and the angle of transmission of incident compressional angle and angle of transmission, V _p, V _s, ρ is respectively the mean value of levels velocity of longitudinal wave, shear wave velocity, density, V _p, V _s, ρ is that levels velocity of longitudinal wave is poor, shear wave velocity is poor, density difference;

By utilizing the compressional wave and the converted shear wave angle domain reflection coefficient that obtain after grape ripple to compare section with the transverse and longitudinal wave velocity calculating, adopt singular value decomposition method (SVD) solution system equation below to carry out joint inversion, obtain intercept (P) and gradient (G):

$\left[\begin{array}{c}{R}_{\mathrm{pp}}\left({\mathrm{\&theta;}}_1\right)\\ .\\ .\\ .\\ R_{\mathrm{pp}}\left({\mathrm{\&theta;}}_n\right)\\ R_{\mathrm{ps}}\left({\mathrm{\&theta;}}_1\right)\\ .\\ .\\ .\\ R_{\mathrm{ps}}\left({\mathrm{\&theta;}}_n\right)\end{array}\right]\left[\begin{array}{ccc}1& B\left({\mathrm{\&theta;}}_1\right)& C\left({\mathrm{\&theta;}}_1\right)\\ .& .& .\\ .& .& .\\ .& .& .\\ 1& B\left({\mathrm{\&theta;}}_n\right)& C\left({\mathrm{\&theta;}}_n\right)\\ D\left({\mathrm{\&theta;}}_1\right)& E\left({\mathrm{\&theta;}}_1\right)& F\left({\mathrm{\&theta;}}_1\right)\\ .& .& .\\ .& .& .\\ .& .& .\\ D\left({\mathrm{\&theta;}}_n\right)& E\left({\mathrm{\&theta;}}_n\right)& F\left({\mathrm{\&theta;}}_n\right)\end{array}\right]\left[\begin{array}{c}\\ P\\ G\\ \frac{\mathrm{\&Delta;}{V}_p}{V_p}\end{array}\right]$

Wherein, B (θ _i), C (θ _i) (i=1,2,3......n) be respectively different angles θ _i(i=1,2,3......n) G in Rpp equation, front coefficient,

D (θ _i), E (θ _i), F (θ _i) (i=1,2,3...n) be respectively different angles θ _i(i=1,2,3......n) P, G in Rps equation,

front coefficient,

Rpp (θ _i), Rps (θ _i) (i=1,2,3.....n) be respectively different angles θ _i(i=1,2, compressional wave 3......n) and converted shear wave reflection coefficient.

5. according to the method based on compressional wave and converted shear wave joint inversion intercept and gradient described in claim 1-4, it is characterized in that, step 4 concrete grammar is as follows:

First the intercept of inverting (P) and gradient (G) section are demarcated with the result of log interpretation of crossing this section well, according to result of log interpretation, the hydrocarbon zone on intercept (P) and gradient (G) section and water layer corresponding demarcation on the intercept (P) of inverting and gradient (G) section, can be according to oil gas and water layer the demonstration phenomenon on this intercept (P) and gradient (G) section, oil reservoir and gas-bearing formation on not drilling area intercept and gradient profile are predicted, obtained favourable drilling area.

Images