CN111999770A - Precise beam offset imaging method and system for converting TTI medium into PS wave - Google Patents

Abstract

The invention discloses a method and a system for precise beam migration imaging of a TTI medium converted PS wave. First, the converted PS wave common shot gather seismic record data, anisotropic medium parameters and offset of the TTI medium to be migrated and imaged are acquired. Shift ray parameters; carry out ray tracing of P-wave and S-wave in TTI medium respectively; then calculate the forward wave field of each shot point and the reverse wave field of each detection point; The forward wave field and the reverse wave field of each detection point are imaged; the converted PS wave depth migration profile of the TTI medium of each shot point is superimposed to obtain the converted PS wave depth domain migration imaging of the TTI medium profile. The invention fully considers the influence of anisotropy factors on the converted PS wave seismic wave field, can accurately migrate and reset the underground structure with TTI medium, overcome the influence of anisotropy on the converted PS wave migration, and improve the obtained Accuracy of prestack depth-migrated imaging profiles of converted PS waves in TTI media.

Description

A method and system for precise beam shifting imaging of TTI medium-converted PS wave

technical field

The invention relates to the technical field of seismic exploration, in particular to a method and system for precise beam shift imaging of TTI medium-converted PS waves.

Background technique

Compared with single P-wave seismic exploration, the combined conversion of PS-wave seismic data can obtain more subsurface medium information, and achieve better exploration results for subsurface structural imaging, lithology estimation, fluid detection and reservoir monitoring. Due to the asymmetry of the propagation path from the source to the detection point, the imaging processing of converted PS waves is very difficult, and conventional superposition processing and post-stack migration methods cannot obtain accurate imaging results. Although prestack time migration of converted PS waves can obtain relatively good imaging results, in areas with complex geological structures and large velocity changes, prestack time migration often has imaging errors, while prestack depth migration is It is an effective technical means to solve the accurate imaging of converted PS waves under the conditions of complex underground geological structures.

Seismic anisotropy exists in most subsurface sedimentary rocks, and if seismic data in anisotropic media is processed using seismic migration methods based on the isotropic assumption, significant imaging errors will result and energy will appear in the migrated profile The phenomenon of non-focusing will seriously affect the subsequent seismic interpretation work. Therefore, with the continuous improvement of seismic exploration accuracy requirements, it is more and more important to consider the influence of anisotropy on seismic migration imaging. Transversely isotropic (TI) media is a commonly used anisotropic media model in practical applications. Most sedimentary rocks can be described as TI media, and TTI media with inclined axes of symmetry are the general form of TI media. The study of migration technology in TTI medium has important application value for eliminating the influence of anisotropy in the process of seismic wave propagation and realizing high-precision imaging of complex structures. The effect of anisotropy on the S wave is more obvious than that of the P wave, and the anisotropy is more important for the migration imaging of the converted PS wave and cannot be ignored. At present, the research on prestack time migration of converted PS waves in anisotropic media is relatively mature, but the existing prestack time migration methods cannot obtain ideal imaging profiles of converted PS wave migration for complex underground structures.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method and system for precise beam offset imaging of converted PS wave in TTI medium, so as to overcome the influence of anisotropy on the offset of converted PS wave and improve the pre-stack depth offset of converted PS wave in acquired TTI medium. Accuracy of shifting imaging profiles.

For achieving the above object, the present invention provides the following scheme:

A TTI medium conversion PS wave precise beam shift imaging method, the imaging method comprises the following steps:

Obtain the converted PS wave common shot gather seismic record data, anisotropic medium parameters and migration ray parameters of the TTI medium to be migrated and imaged;

According to the parameters of the anisotropic medium and the offset ray, the two-dimensional anisotropic ray tracing equations are used to carry out the ray tracing of the P wave and the S wave in the TTI medium, respectively, and the ray tracing of the P wave emitted from each shot point is obtained. The complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam and the complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the S-wave emitted from each detection point;

According to the complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the P wave emitted from each shot, the forward wave field of each shot is constructed;

According to the complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the S-wave emitted from each detection point, the reverse continuation of the converted PS-wave common shot gather seismographic record data of each shot is performed to obtain each detection point The reverse wave field of ;

Based on the cross-correlation migration imaging conditions, the forward wavefield of each shot and the reverse wavefield of each detection point were imaged, and the converted PS wave prestack depth migration profile of the TTI medium of each shot was obtained;

The pre-stack depth migration profiles of the converted PS waves of the TTI medium of each shot are superimposed to obtain the converted PS wave depth domain migration imaging profiles of the TTI medium.

Optionally, obtain the anisotropic medium parameters of the TTI medium to be migrated for imaging, specifically including:

Obtain the Thomsen parameters (V _P0 , V _S0 ,ε,δ) of the anisotropic medium model of the TTI medium to be migrated and imaged; where V _P0 and V _P0 are the vertical velocities of the P-wave and S-wave, respectively, and ε and δ is the first dimensionless factor and the second dimensionless factor representing the anisotropic strength of the VTI medium;

计算VTI介质密度归一化弹性矩阵

中的弹性参数元素

和

According to the relationship between the Thomsen parameters and the elastic parameters of the VTI medium, using the formula

Calculation of Density Normalized Elasticity Matrix for VTI Media

Elastic parameter element in

and

利用Bond变换公式

计算TTI介质密度归一化弹性矩阵

中的各向异性弹性参数元素a₁₁,a₃₃,a₅₅,a₁₃,a₁₅和a₃₅；Normalize the elastic parameter elements in the elastic matrix according to the density of the VTI medium

Use the Bond transform formula

Calculation of Density Normalized Elasticity Matrix for TTI Media

The anisotropic elastic parameter elements a ₁₁ , a ₃₃ , a ₅₅ , a ₁₃ , a ₁₅ and a ₃₅ in ;

和

均为VTI介质密度归一化弹性矩阵中的弹性参数元素，

a₁₁、a₁₂、a₁₃、a₁₅、a₂₂、a₂₃、a₂₅、a₃₃、a₃₅、a₄₄、a₄₆、a₅₅、a₆₆均为TTI介质密度归一化弹性矩阵中的各向异性弹性参数元素，θ⁰为TTI介质的对称轴倾角。in,

and

are elastic parameter elements in the VTI medium density normalized elastic matrix,

a ₁₁ , a ₁₂ , a ₁₃ , a ₁₅ , a ₂₂ , a ₂₃ , a ₂₅ , a ₃₃ , a ₃₅ , a ₄₄ , a ₄₆ , a ₅₅ , a ₆₆ are all in the TTI medium density normalized elastic matrix Anisotropic elastic parameter element, θ ⁰ is the inclination angle of the symmetry axis of the TTI medium.

Optionally, according to the anisotropic medium parameters and the offset ray parameters, the two-dimensional anisotropic ray tracing equations are used to carry out the ray tracing of the P wave and the S wave in the TTI medium, respectively, to obtain each shot. The complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the P-wave emitted from the point and the complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the S-wave emitted from each detection point, including:

获得初始的第一射线参数p₁₀和第三射线参数p₃₀，作为二维各向异性射线追踪方程组的初始的慢度矢量的第一分量p₁和第三分量p₃；Using Newton's Iterative Method to Solve the Function Equation

obtaining the initial first ray parameter p ₁₀ and the third ray parameter p ₃₀ as the first component p ₁ and the third component p ₃ of the initial slowness vector of the two-dimensional anisotropic ray tracing equation system;

Among them, κ ₁ , κ ₂ , κ ₃ , κ ₄ , κ ₅ represent the first coefficient, the second coefficient, the third coefficient, the fourth coefficient and the fifth coefficient of the function equation, respectively,

Input the first component p ₁ and the third component p ₃ of the initial slowness vector and the initial ray position coordinates into the two-dimensional anisotropic ray tracing equation system, and use the Runge-Kutta method to solve the two-dimensional anisotropic ray tracing equation group, to obtain the path information and travel time information of the central rays of the P-wave and S-wave emitted from each shot point and each detection point;

According to the path information and travel time information of the central ray of the P-wave and S-wave emitted from each shot point and each receiver point, solve the anisotropic dynamic ray equation, and obtain the P wave emitted from each shot point and each receiver point. Dynamic parameters of the center ray of waves and S-waves;

Calculate the complex-valued amplitude of the anisotropic Gaussian beam of the P-wave emitted from each shot point according to the path information, travel time information and dynamic parameters of the central ray of the P-wave and S-wave emitted from each shot point and each detection point and complex-valued time and the complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the S-wave emitted from each detection point.

Optionally, the forward wave field of each shot point is constructed according to the complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the P wave emitted from each shot point, specifically including:

According to the complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the P wave emitted from each shot point, the forward wave field of each shot source is constructed as:

和

分别为炮点x_s出射的P波各向异性高斯束的复值振幅和复值时间，ω为角频率，

为炮点x_s出射的P波射线偏移参数矢量，

为P波射线偏移参数矢量的水平分量；

为P波射线偏移参数矢量的垂直分量；x表示地下任意一点的位置矢量。Among them, G(x,x _s ,ω) is the forward wave field of the shot point x _s ,

and

are the complex-valued amplitude and complex-valued time of the P-wave anisotropic Gaussian beam emitted from the shot x _s , respectively, ω is the angular frequency,

is the offset parameter vector of the P-wave ray emitted from the shot point x _s ,

is the horizontal component of the P-wave ray migration parameter vector;

is the vertical component of the P-wave ray migration parameter vector; x represents the position vector of any point underground.

Optionally, according to the complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the S-wave emitted from each detection point, reverse continuation is performed on the converted PS-wave common shot gather seismic record data of each shot. , obtain the reverse wave field of each detection point, including:

对每炮所述转换PS波共炮点道集地震记录数据进行反向延拓，获得每个检波点的反向波场；According to the complex-valued amplitude and complex-valued time of the S-wave emitted from each detection point, the

Carry out reverse continuation of the converted PS wave common shot gather seismic record data of each shot to obtain the reverse wave field of each detection point;

和

分别为检波点x_r出射的S波各向异性高斯束的复值振幅和复值时间，

为检波点x_r出射的S波射线偏移参数矢量，

为S波射线偏移参数矢量的水平分量；

为S波射线偏移参数矢量的垂直分量；x表示地下任意一点的位置矢量。Among them, R(x,x _r ,ω) represents the reverse wave field of the detection point x _r , u ^PS (x _r ,x _s ,ω) is the converted PS wave common shot point of the shot point x _s and the detection point x _r Gather seismic record data,

and

are the complex-valued amplitude and complex-valued time of the S-wave anisotropic Gaussian beam emitted from the detection point x _r , respectively,

is the S-wave ray migration parameter vector from the detection point x _r ,

is the horizontal component of the S-wave ray migration parameter vector;

is the vertical component of the S-wave ray migration parameter vector; x represents the position vector of any point underground.

Optionally, based on the cross-correlation migration imaging conditions, image the forward wave field of the source and the reverse wave field of the detection point for each shot, and obtain the converted PS wave pre-stack depth migration profile of the TTI medium of each shot. , including:

对每个炮点的正向波场和每个检波点的反向波场进行成像，获得每个炮点的TTI介质的转换PS波叠前深度偏移剖面；Based on the cross-correlation migration imaging conditions, using the formula

Image the forward wavefield of each shot and the reverse wavefield of each detection point to obtain the converted PS wave prestack depth migration profile of the TTI medium of each shot;

表示炮点x_s的转换PS波偏移剖面；sgn(x_r-x_s)表示校正转换PS波地震记录的极性反转现象的符号函数，

u^PS(x_r,x_s,ω)为炮点x_s和检波点x_r的转换PS波共炮点道集地震记录数据，

和

分别为检波点x_r出射的S波各向异性高斯束的复值振幅和复值时间，

和

分别为炮点x_s出射的P波各向异性高斯束的复值振幅和复值时间，i表示复数单位，

为P波射线偏移参数矢量的水平分量，

为S波射线偏移参数矢量的水平分量；x表示地下任意一点的位置矢量，ω为角频率。in,

represents the converted PS-wave migration profile at shot x _s ; sgn(x _r -x _s ) represents the sign function to correct the polarity inversion phenomenon of the converted PS-wave seismic records,

u ^PS (x _r , x _s , ω) is the converted PS wave common shot gather seismic record data of shot x _s and detection point x _r ,

and

are the complex-valued amplitude and complex-valued time of the S-wave anisotropic Gaussian beam emitted from the detection point x _r , respectively,

and

are the complex-valued amplitude and complex-valued time of the P-wave anisotropic Gaussian beam emitted from the shot x _s , respectively, i represents the complex unit,

is the horizontal component of the P-wave ray migration parameter vector,

is the horizontal component of the S-wave ray migration parameter vector; x represents the position vector of any point underground, and ω is the angular frequency.

Optionally, superimposing the converted PS wave pre-stack depth migration profile of the TTI medium of each shot point to obtain the converted PS wave depth domain migration imaging profile of the TTI medium, specifically including:

将每个炮点的TTI介质的转换PS波叠前深度偏移剖面进行叠加，获得TTI介质的转换PS波深度域偏移成像剖面；Use the formula

Superimpose the converted PS wave prestack depth migration profile of each shot point in the TTI medium to obtain the converted PS wave depth domain migration imaging profile of the TTI medium;

Among them, N represents the number of shot points recorded by the converted PS wave common shot gather, I ^PS (x) represents the final TTI medium converted PS wave depth domain migration imaging profile, and x represents the position vector of any point underground.

A TTI medium conversion PS wave precise beam shifting imaging system, the imaging system includes:

The parameter acquisition module is used to acquire the converted PS wave common shot gather seismic record data, anisotropic medium parameters and migration ray parameters of the TTI medium to be migrated and imaged;

The ray tracing module is used to carry out the ray tracing of the P wave and the S wave in the TTI medium respectively by using the two-dimensional anisotropic ray tracing equation system according to the anisotropic medium parameters and the offset ray parameters, and obtain each shot The complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the P-wave exiting from the point and the complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the S-wave exiting from each detection point;

The forward wave field building module is used to construct the forward wave field of each shot point according to the complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the P wave emitted from each shot point;

The inverse wave field building module is used to invert the common shot gather seismogram data of the converted PS waves of each shot according to the complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the S-wave emitted from each detection point. Continue in the direction to obtain the reverse wave field of each detection point;

The single-shot conversion PS wave prestack depth migration profile calculation module is used to image the forward wave field of each shot and the reverse wave field of each detection point based on the cross-correlation migration imaging conditions, and obtain each Prestack depth migration profile of converted PS wave in TTI medium of 1 shot;

The converted PS wave depth domain migration imaging profile calculation module is used to superimpose the converted PS wave prestack depth migration profile of each shot point of the TTI medium to obtain the converted PS wave depth domain migration imaging profile of the TTI medium.

Optionally, the parameter acquisition module specifically includes:

The Thomsen parameter acquisition sub-module is used to acquire the Thomsen parameters (V _P0 , V _S0 , ε, δ) of the anisotropic medium model of the TTI medium to be migrated for imaging; wherein, V _P0 and V _P0 are the P wave and S, respectively the vertical velocity of the wave, ε and δ are the first dimensionless factor and the second dimensionless factor representing the anisotropic strength of the VTI medium;

计算VTI介质密度归一化弹性矩阵

中的弹性参数元素

和

The elastic parameter calculation sub-module of the VTI medium is used to calculate the relationship between the Thomsen parameter and the elastic parameter of the VTI medium by using the formula

Calculation of Density Normalized Elasticity Matrix for VTI Media

Elastic parameter element in

and

利用Bond变换公式

计算TTI介质密度归一化弹性矩阵

中的各向异性弹性参数元素a₁₁,a₃₃,a₅₅,a₁₃,a₁₅和a₃₅；Elastic parameter calculation sub-module for VTI media to normalize elastic parameter elements in the elastic matrix according to the density of the VTI media

Use the Bond transform formula

Calculation of Density Normalized Elasticity Matrix for TTI Media

The anisotropic elastic parameter elements a ₁₁ , a ₃₃ , a ₅₅ , a ₁₃ , a ₁₅ and a ₃₅ in ;

和

均为VTI介质密度归一化弹性矩阵中的弹性参数元素，

a₁₁、a₁₂、a₁₃、a₁₅、a₂₂、a₂₃、a₂₅、a₃₃、a₃₅、a₄₄、a₄₆、a₅₅、a₆₆均为TTI介质密度归一化弹性矩阵中的各向异性弹性参数元素，θ⁰为TTI介质的对称轴倾角。in,

and

are elastic parameter elements in the VTI medium density normalized elastic matrix,

a ₁₁ , a ₁₂ , a ₁₃ , a ₁₅ , a ₂₂ , a ₂₃ , a ₂₅ , a ₃₃ , a ₃₅ , a ₄₄ , a ₄₆ , a ₅₅ , a ₆₆ are all in the TTI medium density normalized elastic matrix Anisotropic elastic parameter element, θ ⁰ is the inclination angle of the symmetry axis of the TTI medium.

Optionally, the ray tracing module specifically includes:

获得初始的第一射线参数p₁₀和第三射线参数p₃₀，作为二维各向异性射线追踪方程组的初始的慢度矢量的第一分量p₁和第三分量p₃；Initial parameter acquisition submodule for two-dimensional anisotropic ray-tracing equations for solving function equations using Newton's iteration method

obtaining the initial first ray parameter p ₁₀ and the third ray parameter p ₃₀ as the first component p ₁ and the third component p ₃ of the initial slowness vector of the two-dimensional anisotropic ray tracing equation system;

Among them, κ ₁ , κ ₂ , κ ₃ , κ ₄ , κ ₅ represent the first coefficient, the second coefficient, the third coefficient, the fourth coefficient and the fifth coefficient of the function equation, respectively,

The path information and travel time information acquisition sub-module is used to input the first component p ₁ and the third component p ₃ of the initial slowness vector and the initial ray position coordinates into the two-dimensional anisotropic ray tracing equation system, using the Runge library The tower method solves the two-dimensional anisotropic ray tracing equation system, and obtains the path information and travel time information of the central ray of the P-wave and S-wave emitted from each shot point and each detection point;

The dynamic parameter acquisition sub-module is used to solve the dynamic ray equation system according to the path information and travel time information of the central rays of the P-wave and S-wave emitted from each shot point and each detection point, and obtain each shot point and each Dynamic parameters of the central rays of the P-wave and S-wave emitted from each detection point;

The complex-valued amplitude and complex-valued time calculation sub-module is used to calculate each shot point according to the path information, travel time information and dynamic parameters of the central rays of the P-wave and S-wave emitted from each shot point and each receiver point The anisotropic Gaussian beam complex-valued amplitude and complex-valued time of the outgoing P-wave and the anisotropic Gaussian-beam complex-valued amplitude and complex-valued time of the S-wave outgoing from each detection point.

According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

The invention discloses a precise beam migration imaging method of a TTI medium converted PS wave. The imaging method includes the following steps: acquiring the converted PS wave common shot gather seismic record data, anisotropy and imaging of the TTI medium to be migrated and imaged Medium parameters and migration ray parameters; according to the anisotropic medium parameters and migration ray parameters, using the two-dimensional anisotropic ray tracing equations, respectively carry out the ray tracing of the P wave and the S wave in the TTI medium, and obtain each The anisotropic Gaussian beam complex-valued amplitude and complex-valued time of the P-wave emitted from each shot point and the anisotropic Gaussian-beam complex-valued amplitude and complex-valued time of the S-wave emitted from each detection point; The complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the P wave are used to construct the forward wave field of each shot point; Perform reverse continuation of the converted PS wave common shot gather seismic record data of each shot to obtain the reverse wave field of each detection point; based on the cross-correlation migration imaging conditions, the forward wave of each shot point The field and the reverse wave field of each detection point are imaged to obtain the converted PS wave prestack depth migration profile of the TTI medium of each shot point; the converted PS wave prestack depth migration of the TTI medium of each shot point The profiles are superimposed to obtain the converted PS wave depth domain migration imaging profile of the TTI medium. The invention fully considers the influence of anisotropy factors on the converted PS wave seismic wave field, can accurately migrate and reset the underground structure with TTI medium, overcome the influence of anisotropy on the converted PS wave migration, and improve the obtained Accuracy of prestack depth-migrated imaging profiles of converted PS waves in TTI media.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings required in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some of the present invention. In the embodiments, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without creative labor.

FIG. 1 is a flow chart of a method for precise beam shift imaging of TTI medium conversion PS wave provided by the present invention;

2 is a model diagram of a horizontal layered TTI medium provided by Embodiment 1 of the present invention;

Fig. 3 is the single shot conversion PS wave seismic record diagram of the horizontal layered TTI medium model provided by the specific embodiment one of the present invention;

Fig. 4 is the single shot conversion PS wave prestack depth migration profile of the horizontal layered TTI medium model provided by the specific embodiment of the present invention; wherein, Fig. 4(a) uses the isotropic migration method to obtain the horizontal layered TTI The migration profile of the medium model, Fig. 4(b) is the migration profile of the horizontal layered TTI medium model obtained by the method of the present invention;

5 is a diagram of a thrust TTI medium model provided by Embodiment 2 of the present invention;

Fig. 6 is the multi-shot superposition transformation PS wave prestack depth migration profile of the thrust TTI medium model provided by the specific embodiment 2 of the present invention; wherein, Fig. 6(a) is the thrust obtained by utilizing the isotropic migration method The migration profile of the TTI medium model, Fig. 6(b) is the migration profile of the thrust TTI medium model obtained by the method of the present invention.

Detailed ways

The purpose of the present invention is to provide a precise beam migration imaging method and system for converted PS wave in TTI medium, so as to overcome the influence of anisotropy on the migration of converted PS wave and improve the pre-stack depth migration of converted PS wave in acquired TTI medium Accuracy of imaging profiles.

In order to make the above objects, features and advantages of the present invention more clearly understood, the invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

As shown in FIG. 1 , the present invention provides a TTI medium-converted PS wave precise beam shift imaging method, and the imaging method includes the following steps:

Step 101: Acquire the converted PS wave common shot gather seismic record data, anisotropic medium parameters and migration ray parameters of the TTI medium to be migrated and imaged.

The obtaining of the anisotropy parameters of the TTI medium to be migrated and imaging specifically includes:

中的弹性参数元素

具体为：Read the Thomsen parameters (V _P0 , V _S0 , ε, δ) of the anisotropic medium model to be migrated and imaged. According to the relationship between the Thomsen parameters and the elastic parameters of the VTI medium, the VTI medium characterized by the Thomsen parameters can be obtained. Density Normalized Elasticity Matrix

Elastic parameter element in

Specifically:

In formula (1), the Thomsen parameters V _P0 and V _P0 are the vertical velocities of the P-wave and S-wave respectively, and ε and δ are dimensionless factors representing the anisotropic strength of the VTI medium;

中的各向异性弹性参数元素a₁₁,a₃₃,a₅₅,a₁₃,a₁₅,a₃₅，具体为：According to the elastic parameters normalized by the density of the VTI medium, through Bond transformation, the normalized elastic matrix of the density of the TTI medium is obtained

The anisotropic elastic parameter elements a ₁₁ ,a ₃₃ ,a ₅₅ ,a ₁₃ ,a ₁₅ ,a ₃₅ in , specifically:

In formula (2), θ ⁰ is the inclination angle of the symmetry axis of the TTI medium.

和

均为VTI介质密度归一化弹性矩阵中的弹性参数元素，

a₁₁、a₁₂、a₁₃、a₁₅、a₂₂、a₂₃、a₂₅、a₃₃、a₃₅、a₄₄、a₄₆、a₅₅、a₆₆均为TTI介质密度归一化弹性矩阵中的各向异性弹性参数元素，θ⁰为TTI介质的对称轴倾角。本发明的运算中只用到了

和

a₁₁、a₃₃、a₅₅、a₁₃、a₁₅和a₃₅，无需其他元素的计算。in,

and

are elastic parameter elements in the VTI medium density normalized elastic matrix,

a ₁₁ , a ₁₂ , a ₁₃ , a ₁₅ , a ₂₂ , a ₂₃ , a ₂₅ , a ₃₃ , a ₃₅ , a ₄₄ , a ₄₆ , a ₅₅ , a ₆₆ are all in the TTI medium density normalized elastic matrix Anisotropic elastic parameter element, θ ⁰ is the inclination angle of the symmetry axis of the TTI medium. In the operation of the present invention, only the

and

a ₁₁ , a ₃₃ , a ₅₅ , a ₁₃ , a ₁₅ and a ₃₅ , without calculation of other elements.

Step 102, according to the parameters of the anisotropic medium and the offset ray parameters, using the two-dimensional anisotropic ray tracing equations, respectively carry out the ray tracing of the P wave and the S wave in the TTI medium, and obtain the ray tracing of each shot point. The complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the P-wave and the complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the S-wave emitted from each detection point.

Step 102, according to the parameters of the anisotropic medium and the offset ray parameters, using the two-dimensional anisotropic ray tracing equations, respectively carry out the ray tracing of the P wave and the S wave in the TTI medium, and obtain the ray tracing of each shot point. The complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the P-wave and the complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the S-wave emitted from each detection point, including:

The two-dimensional anisotropic ray tracing equations are:

是慢度矢量的分量，a_kl＝c_kl/ρ(k,l＝1,3,or 5)为TTI介质密度归一化的弹性参数，

为Christoffel矩阵特征向量的分量。所述二维各向异性射线追踪方程组(式(3))对于TTI介质中P波和S波具有相同的形式，m＝1和m＝2分别表示P波和S波；In formula (3), τ is the travel time along the ray, x _i (i=1,3) is the coordinate in the Cartesian coordinate system,

is the component of the slowness vector, a _kl =c _kl /ρ(k,l=1,3,or 5) is the elastic parameter normalized by the density of the TTI medium,

are the components of the eigenvectors of the Christoffel matrix. The two-dimensional anisotropic ray tracing equations (equation (3)) have the same form for P-wave and S-wave in TTI medium, and m=1 and m=2 represent P-wave and S-wave respectively;

The ray tracing of the P-wave and S-wave in the TTI medium is respectively realized, and then the complex-valued amplitude and complex-valued time of the corresponding P-wave and S-wave anisotropic Gaussian beams are obtained, specifically including:

(a) According to the functional equation G _m (x _i0 , p _i0 )=1 of the P-wave and S-wave in the anisotropic medium, the following relational expressions are obtained between the initial ray parameters p ₁₀ and p ₃₀ of the corresponding wave modes:

In formula (4)

κ ₂ =(a ₁₅ a ₃₃ -a ₁₃ a ₃₅ )p ₁₀

(b) For the quartic equations (equation (4)) of the initial ray parameters p ₁₀ and p ₃₀ described in (a), use the Newton iteration method to solve, and for each initial ray parameter p ₁₀ , obtain the corresponding initial ray parameter p ₃₀ , and then obtain the corresponding initial conditions of P-wave and S-wave anisotropic ray tracing, specifically:

The initial conditions of the two-dimensional anisotropic ray tracing equations are as follows:

In formula (6), (x ₁₀ , x ₃₀ ) are the coordinates of the initial position of the ray tracing, and the initial positions of the P-wave and S-wave ray tracing are known;

(c) According to the corresponding initial conditions of the P-wave and S-wave anisotropic ray tracing described in (b), use the Runge-Kutta method to calculate the two-dimensional anisotropic ray tracing equations, and solve the corresponding P wave in the TTI medium and S-wave ray tracing to obtain the path and travel time information of the corresponding P-wave and S-wave central rays;

(d) On the central ray paths of the P-wave and S-wave described in (c), use the anisotropic dynamical ray equations to obtain the dynamic parameters of the corresponding rays, specifically:

The dynamic ray equations in anisotropic medium are:

In formula (7), P and Q are the dynamic parameters of the ray, and B ₁ , B ₂ , and B ₃ are the derivatives of the Christoffel matrix eigenvalue G _m of the corresponding wave mode to the ray normal direction n and the ray parameter p _n in the normal direction. ;

(e) Based on the travel time information of the P-wave and S-wave central rays described in (c) and the dynamic parameters of the corresponding rays described in (d), obtain the corresponding P-wave and S-wave anisotropic Gaussian beams Complex-valued amplitude A and complex-valued time T, specifically:

是初始振幅，其中V₀是射线初始位置相应波型的群速度，L₀是相应波型各向异性高斯束的初始束宽，ω_r是参考频率；V是沿射线路径相应波型的群速度，n是射线附近位置到中心射线的垂直距离。In formula (8),

is the initial amplitude, where V0 is the group velocity of the corresponding mode at the initial position of the ray, _L0 is the initial _beamwidth of the corresponding mode anisotropic Gaussian beam, _ωr is the reference frequency; V is the group of the corresponding mode along the ray path Velocity, n is the vertical distance from the position near the ray to the center ray.

Step 103 , construct the forward wave field of each shot point according to the complex-valued amplitude and complex-valued time of the P-wave emitted from each shot point.

In step 103, the forward wave field of each shot is constructed according to the complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the P wave emitted from each shot, specifically including:

According to the converted PS wave common shot gather seismic records, read the source position coordinates of each shot, and determine the source position;

The forward wave field at the source position is constructed by using the anisotropic Gaussian beam of the P wave emitted at the source position, which is specifically:

和

分别为震源出射的P波各向异性高斯束的复值振幅和复值时间，ω为角频率，

为震源出射的P波射线参数矢量。In formula (9), G(x,x _s ,ω) is the forward wave field at the source position x _s ,

and

are the complex-valued amplitude and complex-valued time of the P-wave anisotropic Gaussian beam emitted from the source, respectively, ω is the angular frequency,

is the parameter vector of the P-wave rays emitted by the source.

Step 104, according to the complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the S-wave emitted from each detection point, reversely extend the converted PS-wave common shot gather seismic record data of each shot to obtain each shot. The reverse wavefield of a receiver point.

In step 104, according to the complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the S-wave emitted from each detection point, reverse continuation is performed on the converted PS-wave common shot gather seismic record data of each shot to obtain: The reverse wave field of each detection point, including:

The exact beam field reverse extension formula of the detection point is:

和

分别为检波点x_r出射的S波各向异性高斯束的复值振幅和复值时间，

为检波点出射的S波射线参数矢量。In formula (10), R(x, x _r , ω) represents the reverse continuation wave field, u ^PS (x _r , x _s , ω) is the converted PS wave common shot gather seismic record spectrum in TTI medium,

and

are the complex-valued amplitude and complex-valued time of the S-wave anisotropic Gaussian beam emitted from the detection point x _r , respectively,

is the S-wave ray parameter vector emitted from the detection point.

Step 105, based on the cross-correlation migration imaging conditions, image the forward wave field of each shot and the reverse wave field of each detection point, and obtain the converted PS wave prestack depth migration of the TTI medium of each shot. Move the profile.

The precise beam offset imaging formula of single-shot converted PS wave in TTI medium is:

表示单炮转换PS波偏移剖面；利用符号函数sgn(x_r-x_s)校正转换PS波地震记录的极性反转现象，符号函数满足如下关系：In formula (11),

Represents the single-shot converted PS wave migration profile; the sign function sgn(x _r -x _s ) is used to correct the polarity inversion phenomenon of the converted PS wave seismic records, and the sign function satisfies the following relationship:

Step 106 , superimposing the converted PS wave prestack depth migration profiles of the TTI medium of each shot point to obtain the converted PS wave depth domain migration imaging profile of the TTI medium.

Specifically, all single shot migration profiles are superimposed to obtain the final converted PS wave depth domain migration imaging profile in TTI medium, which is as follows:

In Equation (13), N represents the number of shots recorded in the converted PS wave common shot gather seismic record, and I ^PS (x) represents the final TTI medium converted PS wave depth domain migration imaging profile.

The present invention also provides a TTI medium-converted PS-wave precise beam shift imaging system, the imaging system comprising:

The parameter acquisition module is used to acquire the converted PS wave common shot gather seismic record data, anisotropic medium parameters and migration ray parameters of the TTI medium to be migrated and imaged.

The parameter acquisition module specifically includes:

The Thomsen parameter acquisition sub-module is used to acquire the Thomsen parameters (V _P0 , V _S0 , ε, δ) of the anisotropic medium model of the TTI medium to be migrated for imaging; wherein, V _P0 and V _P0 are the P wave and S, respectively The vertical velocity of the wave, ε and δ are the first and second dimensionless factors representing the anisotropic strength of the VTI medium.

计算VTI介质密度归一化弹性矩阵

中的弹性参数元素

和

The elastic parameter calculation sub-module of the VTI medium is used to calculate the relationship between the Thomsen parameter and the elastic parameter of the VTI medium by using the formula

Calculation of Density Normalized Elasticity Matrix for VTI Media

Elastic parameter element in

and

利用Bond变换公式

计算TTI介质密度归一化弹性矩阵

中的各向异性弹性参数元素a₁₁,a₃₃,a₅₅,a₁₃,a₁₅和a₃₅。Elastic parameter calculation sub-module for VTI media to normalize elastic parameter elements in the elastic matrix according to the density of the VTI media

Use the Bond transform formula

Calculation of Density Normalized Elasticity Matrix for TTI Media

The anisotropic elastic parameters in the elements a ₁₁ , a ₃₃ , a ₅₅ , a ₁₃ , a ₁₅ and a ₃₅ .

和

均为VTI介质密度归一化弹性矩阵中的弹性参数元素，

a₁₁、a₁₂、a₁₃、a₁₅、a₂₂、a₂₃、a₂₅、a₃₃、a₃₅、a₄₄、a₄₆、a₅₅、a₆₆均为TTI介质密度归一化弹性矩阵中的各向异性弹性参数元素，θ⁰为TTI介质的对称轴倾角。本发明的运算中只用到了

和

a₁₁、a₃₃、a₅₅、a₁₃、a₁₅和a₃₅，无需其他元素的计算。in,

and

are elastic parameter elements in the VTI medium density normalized elastic matrix,

a ₁₁ , a ₁₂ , a ₁₃ , a ₁₅ , a ₂₂ , a ₂₃ , a ₂₅ , a ₃₃ , a ₃₅ , a ₄₄ , a ₄₆ , a ₅₅ , a ₆₆ are all in the TTI medium density normalized elastic matrix Anisotropic elastic parameter element, θ ⁰ is the inclination angle of the symmetry axis of the TTI medium. In the operation of the present invention, only the

and

a ₁₁ , a ₃₃ , a ₅₅ , a ₁₃ , a ₁₅ and a ₃₅ , without calculation of other elements.

The ray tracing module is used to carry out the ray tracing of the P wave and the S wave in the TTI medium respectively by using the two-dimensional anisotropic ray tracing equation system according to the anisotropic medium parameters and the offset ray parameters, and obtain each shot The complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the P-wave emitted from the point and the complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the S-wave emitted from each detection point.

The ray tracing module specifically includes:

获得初始的第一射线参数p₁₀和第三射线参数p₃₀，作为二维各向异性射线追踪方程组的初始的慢度矢量的第一分量p₁和第三分量p₃。Initial parameter acquisition submodule for two-dimensional anisotropic ray-tracing equations for solving function equations using Newton's iteration method

The initial first ray parameter p ₁₀ and the third ray parameter p ₃₀ are obtained as the first component p ₁ and the third component p ₃ of the initial slowness vector of the two-dimensional anisotropic ray tracing equation system.

Among them, κ ₁ , κ ₂ , κ ₃ , κ ₄ , κ ₅ represent the first coefficient, the second coefficient, the third coefficient, the fourth coefficient and the fifth coefficient of the function equation, respectively,

The path information and travel time information acquisition sub-module is used to input the first component p ₁ and the third component p ₃ of the initial slowness vector and the initial ray position coordinates into the two-dimensional anisotropic ray tracing equation system, using the Runge library The tower method solves the two-dimensional anisotropic ray tracing equation system, and obtains the path information and travel time information of the central ray of the P-wave and S-wave emitted from each shot point and each detection point.

The dynamic parameter acquisition sub-module is used to solve the anisotropic dynamic ray equation system according to the path information and travel time information of the central ray of the P-wave and S-wave emitted from each shot point and each detection point, and obtain each shot Dynamic parameters of the center ray of the P- and S-waves at each detection point.

The complex-valued amplitude and complex-valued time calculation sub-module is used to calculate each shot point according to the path information, travel time information and dynamic parameters of the central rays of the P-wave and S-wave emitted from each shot point and each receiver point The anisotropic Gaussian beam complex-valued amplitude and complex-valued time of the outgoing P-wave and the anisotropic Gaussian-beam complex-valued amplitude and complex-valued time of the S-wave outgoing from each detection point.

The forward wavefield building block is used to construct the forward wavefield of each shot based on the complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the P-wave emitted from each shot.

The inverse wave field building module is used to invert the common shot gather seismogram data of the converted PS waves of each shot according to the complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the S-wave emitted from each detection point. Continue in the direction to obtain the reverse wave field of each detection point.

The single-shot conversion PS wave prestack depth migration profile calculation module is used to image the forward wave field of each shot and the reverse wave field of each detection point based on the cross-correlation migration imaging conditions, and obtain each Converted PS-wave prestack depth-migration profile of a TTI medium for one shot.

The converted PS wave depth domain migration imaging profile calculation module is used to superimpose the converted PS wave prestack depth migration profile of each shot point of the TTI medium to obtain the converted PS wave depth domain migration imaging profile of the TTI medium.

Specific implementation one:

Fig. 2 is a horizontal layered TTI medium model provided by the present invention, the model anisotropy parameters are shown in Fig. 2, the model grid is 301ⅹ301, and the vertical and horizontal grid spacings are both 10m. A single explosion source (shot point) is set in the middle of the surface of this model, the source wavelet is Ricker wavelet, the main frequency is 30Hz, the sampling time of seismic recording is set to 3s, and the sampling interval is 2ms. The receiver and observation system on both sides of the middle shot is adopted, and the track spacing is 10m. Fig. 3 is the single-shot converted PS wave seismic record of the horizontal layered TTI medium model shown in Fig. 2. From Fig. 3, the polarity reversal phenomenon of the converted PS wave can be clearly seen. Fig. 4 is the single-shot converted PS wave prestack depth migration profile of the horizontal layered TTI medium model shown in Fig. 2, in which Fig. 4(a) is the migration profile obtained by the isotropic migration method, and Fig. 4(b) ) is the offset profile obtained by the method of the present invention. As can be seen from Fig. 4(a), since the influence of anisotropy is ignored, the isotropic migration method cannot accurately locate the reflection interface in the model, and there are obvious imaging errors in the section. It can be seen from Fig. 4(b) that the method of the present invention can completely return the reflection interface to obtain an accurate offset imaging section. The effectiveness of the method of the present invention is verified by performing a single-shot conversion PS wave migration test on a horizontal layered TTI medium model.

Specific implementation two:

Fig. 5 is the thrust TTI medium model provided by the present invention, the model anisotropy parameter is shown in Fig. 5, the model grid is 401 × 201, the vertical and horizontal grid spacing is 10m, and the model has thrust with different symmetry axis inclination angles rock structure. On the surface of this model, 77 explosion sources are set, the distance between the guns is 50m, the source wavelet is Ricker wavelet with the main frequency of 25Hz, and 401 channels are received for each gun, and the distance between the channels is 10m. Fig. 6 is the multi-shot superposition converted PS wave prestack depth migration profile of the thrust TTI medium model shown in Fig. 5, in which Fig. 6(a) is the migration profile obtained by the isotropic migration method, Fig. 6(b) ) is the offset profile obtained by the method of the present invention. It can be seen from Fig. 6 that for the isotropic migration profile shown in Fig. 6(a), the imaging position of the horizontal interface under the thrust slat structure is lifted upward, and the imaging position of the inclined interface in the thrust slat structure is not It is accurate, and there is obvious divergent energy and strong noise interference near the reflection interface, as shown by the arrow in Fig. 6(a). It can be seen from Fig. 6(b) that the method of the present invention obtains accurate focusing imaging for the thrust TTI medium model and eliminates noise interference. Compared with the isotropic method shown in Fig. 6(a), the method of the present invention The migration imaging effect is obviously improved, which further verifies that the method of the present invention is an accurate and effective migration method suitable for TTI medium-converted PS wave seismic data.

The invention includes: acquiring the seismic recording data of the TTI medium converted PS wave common shot gather, the anisotropy parameter of the TTI medium and the migration ray parameter; realizing the ray tracing of the P wave and the S wave in the TTI medium, and obtaining the corresponding P wave and The complex-valued amplitude and complex-valued time of the S-wave anisotropic Gaussian beam; the obtained P-wave anisotropic Gaussian beam complex-valued amplitude and complex-valued time are used to construct the forward wave field at the source of each shot; for each shot TTI The medium-converted PS wave seismic record is reversely extended to obtain the precise beam reverse extension wavefield of each shot corresponding to the detection point; the forward wavefield of each shot source and the reverse wavefield of the detection point are imaged, The pre-stack depth migration profile of each shot of the TTI medium converted PS wave is obtained; all single shot migration profiles are superimposed to obtain the final converted PS wave depth domain migration imaging profile in the TTI medium. By adopting the method of the invention, the influence of anisotropy on the migration of the converted PS wave can be effectively solved, and a high-precision pre-stack depth migration imaging section of the converted PS wave in the TTI medium can be obtained.

According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

1) The present invention fully considers the influence of anisotropy factors on the converted PS wave seismic wave field, and can accurately offset and reset the underground structures with TTI medium; 2) The method of the present invention is not limited by the strength of anisotropy, and is suitable for strong anisotropic medium; 3) the present invention adopts the precise beam reverse continuation wave field formula, does not do approximation processing in the wave field continuation calculation process, and can obtain a high-precision converted PS wave migration imaging profile; 4) this The inventive method is not limited by the observation system, and is suitable for irregularly collected converted PS wave seismic data; 5) the present invention can be widely used in the field of converted PS wave seismic exploration, and has more obvious effects on complex structures with anisotropic media. Imaging effect.

The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the various embodiments can be referred to each other.

The principles and implementations of the invention are described herein by using specific examples. The descriptions of the above embodiments are only used to help understand the method and the core idea of the present invention, and the described embodiments are only a part of the embodiments of the present invention. , rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

Claims (10)

1. a TTI medium conversion PS wave precise beam shift imaging method, is characterized in that, described imaging method comprises the steps: Obtain the converted PS wave common shot gather seismic record data, anisotropic medium parameters and migration ray parameters of the TTI medium to be migrated and imaged; According to the parameters of the anisotropic medium and the offset ray, the two-dimensional anisotropic ray tracing equations are used to carry out the ray tracing of the P wave and the S wave in the TTI medium, respectively, and the ray tracing of the P wave emitted from each shot point is obtained. The complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam and the complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the S-wave emitted from each detection point; According to the complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the P wave emitted from each shot, the forward wave field of each shot is constructed; According to the complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the S-wave emitted from each detection point, the reverse continuation of the converted PS-wave common shot gather seismographic record data of each shot is performed to obtain each detection point The reverse wave field of ; Based on the cross-correlation migration imaging conditions, the forward wavefield of each shot and the reverse wavefield of each detection point were imaged, and the converted PS wave prestack depth migration profile of the TTI medium of each shot was obtained; The pre-stack depth migration profiles of the converted PS waves of the TTI medium of each shot are superimposed to obtain the converted PS wave depth domain migration imaging profiles of the TTI medium. 2. The TTI medium-converted PS-wave precise beam shifting imaging method according to claim 1, wherein acquiring the anisotropic medium parameters of the TTI medium to be shifted and imaging specifically comprises: Obtain the Thomsen parameters (V _P0 , V _S0 , ε, δ) of the anisotropic medium model of the TTI medium to be migrated and imaged; where, V _P0 and V _S0 are the vertical velocities of the P-wave and S-wave, respectively, ε and δ is the first dimensionless factor and the second dimensionless factor representing the anisotropic strength of the VTI medium; According to the relationship between the Thomsen parameters and the elastic parameters of the VTI medium, using the formula

Calculation of Density Normalized Elasticity Matrix for VTI Media

Elastic parameter element in

and

Normalize the elastic parameter elements in the elastic matrix according to the density of the VTI medium

Use the Bond transform formula

Calculation of Density Normalized Elasticity Matrix for TTI Media

The anisotropic elastic parameter elements a ₁₁ , a ₃₃ , a ₅₅ , a ₁₃ , a ₁₅ and a ₃₅ in ; in,

and

are elastic parameter elements in the VTI medium density normalized elastic matrix,

a ₁₁ , a ₁₂ , a ₁₃ , a ₁₅ , a ₂₂ , a ₂₃ , a ₂₅ , a ₃₃ , a ₃₅ , a ₄₄ , a ₄₆ , a ₅₅ , a ₆₆ are all in the TTI medium density normalized elastic matrix Anisotropic elastic parameter element, θ° is the inclination angle of the symmetry axis of the TTI medium. 3. The TTI medium conversion PS wave precise beam migration imaging method according to claim 2, wherein, according to the anisotropic medium parameters and the migration ray parameters, a two-dimensional anisotropic ray tracing equation is used ray tracing of the P-wave and S-wave in the TTI medium, respectively, to obtain the complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the P-wave emitted from each shot point, as well as the difference of the S-wave output from each detection point. Anisotropic Gaussian beam complex-valued amplitude and complex-valued time, including: Using Newton's Iterative Method to Solve the Function Equation

obtaining the initial first ray parameter p ₁₀ and the third ray parameter p ₃₀ as the first component p ₁ and the third component p ₃ of the initial slowness vector of the two-dimensional anisotropic ray tracing equation system; Among them, κ ₁ , κ ₂ , κ ₃ , κ ₄ , κ ₅ respectively represent the first coefficient, second coefficient, third coefficient, fourth coefficient and fifth coefficient of the function equation,

Input the first component p ₁ and the third component p ₃ of the initial slowness vector and the initial ray position coordinates into the two-dimensional anisotropic ray tracing equation system, and use the Runge-Kutta method to solve the two-dimensional anisotropic ray tracing equation group, to obtain the path information and travel time information of the central rays of the P-wave and S-wave emitted from each shot point and each detection point; According to the path information and travel time information of the central ray of the P-wave and S-wave emitted from each shot point and each receiver point, solve the anisotropic dynamic ray equation, and obtain the P wave emitted from each shot point and each receiver point. Dynamic parameters of the center ray of waves and S-waves; Calculate the complex-valued amplitude of the anisotropic Gaussian beam of the P-wave emitted from each shot point according to the path information, travel time information and dynamic parameters of the central ray of the P-wave and S-wave emitted from each shot point and each detection point and complex-valued time and the complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the S-wave emitted from each detection point. 4. TTI medium conversion PS wave precise beam shift imaging method according to claim 1, is characterized in that, described according to the anisotropic Gaussian beam complex-valued amplitude and complex-valued time of the P wave that each shot point exits, Construct the forward wavefield for each shot, including: According to the complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the P wave emitted from each shot point, the forward wave field of each shot source is constructed as:

Among them, G(x,x _s ,ω) is the forward wave field of the shot point x _s ,

and

are the complex-valued amplitude and complex-valued time of the P-wave anisotropic Gaussian beam emitted from the shot x _s , respectively, ω is the angular frequency,

is the offset parameter vector of the P-wave ray emitted from the shot point x _s ,

is the horizontal component of the P-wave ray migration parameter vector;

is the vertical component of the P-wave ray migration parameter vector; x represents the position vector of any point underground, and i is a complex unit. 5. The TTI medium-converted PS-wave precise beam-shift imaging method according to claim 1, wherein the anisotropic Gaussian beam complex-valued amplitude and complex-valued time of the S-wave emitted from each detection point, Perform reverse continuation of the converted PS wave common shot gather seismic record data of each shot to obtain the reverse wave field of each detection point, specifically including: According to the complex-valued amplitude and complex-valued time of the S-wave emitted from each detection point, the

Carry out reverse continuation of the converted PS wave common shot gather seismic record data of each shot to obtain the reverse wave field of each detection point; Among them, R(x,x _r ,ω) represents the reverse wave field of the detection point x _r , u ^PS (x _r ,x _s ,ω) is the converted PS wave common shot point of the shot point x _s and the detection point x _r Gather seismic record data,

and

are the complex-valued amplitude and complex-valued time of the S-wave anisotropic Gaussian beam emitted from the detection point x _r , respectively,

is the S-wave ray migration parameter vector from the detection point x _r ,

is the horizontal component of the S-wave ray migration parameter vector;

is the vertical component of the S-wave ray migration parameter vector; x represents the position vector of any point underground, i is a complex unit, and ω is the angular frequency. 6. TTI medium conversion PS wave precise beam migration imaging method according to claim 1, is characterized in that, described based on cross-correlation migration imaging condition, to the forward wave field of each shot point and each detection point The reversed wavefield of the TTI medium is imaged to obtain the converted PS wave prestack depth migration profile of each shot point, including: Based on the cross-correlation migration imaging conditions, using the formula

Image the forward wavefield of each shot and the reverse wavefield of each detection point to obtain the converted PS wave prestack depth migration profile of the TTI medium of each shot; in,

represents the converted PS-wave migration profile at shot x _s ; sgn(x _r -x _s ) represents the sign function to correct the polarity inversion phenomenon of the converted PS-wave seismic records,

u ^PS (x _r , x _s , ω) is the converted PS wave common shot gather seismic record data of shot x _s and detection point x _r ,

and

are the complex-valued amplitude and complex-valued time of the S-wave anisotropic Gaussian beam emitted from the detection point x _r , respectively,

and

are the complex-valued amplitude and complex-valued time of the P-wave anisotropic Gaussian beam emitted from the shot x _s , respectively, i represents the complex unit,

is the horizontal component of the P-wave ray migration parameter vector,

is the horizontal component of the S-wave ray migration parameter vector, x represents the position vector of any point underground, and ω is the angular frequency. 7. TTI medium conversion PS wave precise beam migration imaging method according to claim 6, is characterized in that, described by the conversion PS wave prestack depth migration profile of the TTI medium of each shot point is superimposed, obtains TTI The converted PS wave depth domain migration imaging profile of the medium, including: Use the formula

Superimpose the converted PS wave prestack depth migration profile of each shot point in the TTI medium to obtain the converted PS wave depth domain migration imaging profile of the TTI medium; Among them, N represents the number of shot points recorded by the converted PS wave common shot gather, I ^PS (x) represents the final TTI medium converted PS wave depth domain migration imaging profile, and x represents the position vector of any point underground. 8. A TTI medium converted PS wave precise beam shift imaging system, wherein the imaging system comprises: The parameter acquisition module is used to acquire the converted PS wave common shot gather seismic record data, anisotropic medium parameters and migration ray parameters of the TTI medium to be migrated and imaged; The ray tracing module is used to carry out the ray tracing of the P wave and the S wave in the TTI medium respectively by using the two-dimensional anisotropic ray tracing equation system according to the anisotropic medium parameters and the offset ray parameters, and obtain each shot The complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the P-wave exiting from the point and the complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the S-wave exiting from each detection point; The forward wave field building module is used to construct the forward wave field of each shot point according to the complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the P wave emitted from each shot point; The inverse wave field building module is used to invert the common shot gather seismogram data of the converted PS waves of each shot according to the complex-valued amplitude and complex-valued time of the anisotropic Gaussian beam of the S-wave emitted from each detection point. Continue in the direction to obtain the reverse wave field of each detection point; The single-shot conversion PS wave prestack depth migration profile calculation module is used to image the forward wave field of each shot and the reverse wave field of each detection point based on the cross-correlation migration imaging conditions, and obtain each Prestack depth migration profile of converted PS wave in TTI medium of 1 shot; The converted PS wave depth domain migration imaging profile calculation module is used to superimpose the converted PS wave prestack depth migration profile of each shot point of the TTI medium to obtain the converted PS wave depth domain migration imaging profile of the TTI medium. 9. The TTI medium conversion PS wave precise beam offset imaging system according to claim 8, wherein the parameter acquisition module specifically comprises: The Thomsen parameter acquisition sub-module is used to acquire the Thomsen parameters (V _P0 , V _S0 , ε, δ) of the anisotropic medium model of the TTI medium to be migrated for imaging; wherein, V _P0 and V _P0 are the P wave and S, respectively the vertical velocity of the wave, ε and δ are the first dimensionless factor and the second dimensionless factor representing the anisotropic strength of the VTI medium; The elastic parameter calculation sub-module of the VTI medium is used to calculate the relationship between the Thomsen parameter and the elastic parameter of the VTI medium by using the formula

Calculation of Density Normalized Elasticity Matrix for VTI Media

Elastic parameter element in

and

Elastic parameter calculation sub-module for VTI media to normalize elastic parameter elements in the elastic matrix according to the density of the VTI media

Use the Bond transform formula

Calculation of Density Normalized Elasticity Matrix for TTI Media

The anisotropic elastic parameter elements a ₁₁ , a ₃₃ , a ₅₅ , a ₁₃ , a ₁₅ and a ₃₅ in ; in,

and

are elastic parameter elements in the VTI medium density normalized elastic matrix,

a ₁₁ , a ₁₂ , a ₁₃ , a ₁₅ , a ₂₂ , a ₂₃ , a ₂₅ , a ₃₃ , a ₃₅ , a ₄₄ , a ₄₆ , a ₅₅ , a ₆₆ are all in the TTI medium density normalized elastic matrix Anisotropic elastic parameter element, θ° is the inclination angle of the symmetry axis of the TTI medium. 10. The TTI medium-converted PS-wave precise beam shifting imaging system according to claim 8, wherein the ray tracing module specifically comprises: Initial parameter acquisition submodule for two-dimensional anisotropic ray-tracing equations for solving function equations using Newton's iteration method

obtaining the initial first ray parameter p ₁₀ and the third ray parameter p ₃₀ as the first component p ₁ and the third component p ₃ of the initial slowness vector of the two-dimensional anisotropic ray tracing equation system; Among them, κ ₁ , κ ₂ , κ ₃ , κ ₄ , κ ₅ represent the first coefficient, the second coefficient, the third coefficient, the fourth coefficient and the fifth coefficient of the function equation, respectively,

The path information and travel time information acquisition sub-module is used to input the first component p ₁ and the third component p ₃ of the initial slowness vector and the initial ray position coordinates into the two-dimensional anisotropic ray tracing equation system, using the Runge library The tower method solves the two-dimensional anisotropic ray tracing equation system, and obtains the path information and travel time information of the central ray of the P-wave and S-wave emitted from each shot point and each detection point; The dynamic parameter acquisition sub-module is used to solve the anisotropic dynamic ray equation system according to the path information and travel time information of the central ray of the P-wave and S-wave emitted from each shot point and each detection point, and obtain each shot Dynamic parameters of the center rays of the P-wave and S-wave emitted from the point and each detection point; The complex-valued amplitude and complex-valued time calculation sub-module is used to calculate each shot point according to the path information, travel time information and dynamic parameters of the central rays of the P-wave and S-wave emitted from each shot point and each receiver point The anisotropic Gaussian beam complex-valued amplitude and complex-valued time of the outgoing P-wave and the anisotropic Gaussian-beam complex-valued amplitude and complex-valued time of the S-wave outgoing from each detection point.

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