Viscous sound reverse time migration method in inclined transverse isotropic medium

Abstract

The invention relates to the field of exploration geophysics, and discloses a viscous sound reverse time migration method in an inclined transverse isotropic medium, comprising the following steps: S1, setting an observation system, and inputting model parameter fields including a velocity field, an anisotropy parameter field and an attenuation anisotropy parameter field; s2, performing grid discretization on the model parameters according to the model parameter field to obtain model parameters at each grid point; s3, setting a pure viscous sound TT I wave equation with decoupling amplitude attenuation and a phase frequency dispersion operator, and constructing a high-precision wave field propagation operator; and S4, realizing Q compensation reverse time migration by using a pure viscous sound TT I wave equation with decoupling amplitude attenuation and phase frequency dispersion operators. Therefore, a pure viscous sound TT I wave equation based on memory variable expression is deduced, separation of amplitude attenuation and phase dispersion is achieved, efficient solving is achieved through a finite difference method, and the method is suitable for industrial application.

Description

Technical Field

[0001] The invention relates to the field of exploration geophysics, and in particular to a viscoacoustic reverse time migration method in an inclined transversely isotropic medium. Background Art

[0002] The attenuation and anisotropy properties of real earth media can lead to amplitude loss and phase dispersion during the propagation of seismic waves. In order to address these effects on seismic imaging, many viscoacoustic anisotropy methods have been proposed in recent years. The anisotropy of the underground medium affects the propagation speed of seismic waves in all directions. In addition, attenuation and anisotropy often coexist in certain geological structures such as arranged fluid-filled fractures, affecting the propagation characteristics of seismic waves at the same time. Ignoring the effects of attenuation and anisotropy in migration imaging such as reverse time migration (RTM) will lead to inaccurate imaging results, thereby reducing the accuracy of geological interpretation. Therefore, in order to correct the amplitude loss and phase dispersion caused by viscous anisotropic media on seismic imaging results, a viscoacoustic anisotropic wave equation with amplitude loss and phase dispersion decoupling is important.

[0003] However, although the viscoacoustic anisotropic wave equations characterized by the traditional fractional Laplace operator have decoupled amplitude loss and phase dispersion characteristics, solving these wave equations requires multiple fast Fourier transforms, which is computationally intensive and makes them unsuitable for industrial applications, especially three-dimensional applications. In addition, the traditional viscoacoustic anisotropic wave equations that can be solved using efficient finite differences have coupled amplitude loss and phase dispersion characteristics, which is not conducive to the implementation of attenuation-compensated reverse time migration to correct the viscous effect in complex viscous anisotropic media.

[0004] In view of this, we propose a viscoacoustic reverse time migration method in inclined transversely isotropic media. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a viscoacoustic reverse time migration method in an inclined transversely isotropic medium, which solves the problem that the traditional viscoacoustic anisotropic wave equation characterized by a fractional-order Laplace operator has a huge amount of calculation, making it unsuitable for industrial applications, especially three-dimensional applications.

[0006] To achieve the above object, the present invention is implemented by the following technical solution: a viscoacoustic reverse time migration method in an inclined transversely isotropic medium, comprising the following steps:

[0007] S1, setting the observation system and inputting the model parameter field, wherein the model parameter field includes the velocity field, the anisotropy parameter field and the attenuation parameter field;

[0008] S2, according to the model parameter field, the model parameters are discretized into grids to obtain the model parameters at each grid point;

[0009] S3, setting the pure viscoacoustic TTI wave equation with decoupled amplitude attenuation and phase dispersion operators to construct a high-precision wave field propagation operator;

[0010] S4, Q-compensated reverse time migration is realized using the pure viscoacoustic TTI wave equation with decoupled amplitude decay and phase dispersion operators.

[0011] Preferably, in step S1, the velocity field includes the propagation velocity Vp of the longitudinal wave; the anisotropic parameter field includes ε, δ, Among them, ε and δ represent the strength of velocity anisotropy, is the anisotropic dip parameter; the attenuation anisotropic parameter field includes Q.

[0012] Preferably, in order to achieve a stable wave field continuation result in step S2, the parameter field needs to be reasonably meshed, specifically including: the spacing Ad between the meshes obtained by meshing satisfies the condition: where ν pmax represents the maximum longitudinal wave velocity, and Δt represents the time sampling interval.

[0013] Preferably, the pure viscoacoustic TTI wave equation in step S3 has decoupled amplitude attenuation and phase dispersion operators. In theory, the pure viscoacoustic TTI wave propagation operator W vis It can generally be expressed as

[0014] W νis =W ac +W phase +W amp (1)

[0015] Where W ac is the pure sound TTI wave propagation operator, W phase is the phase dispersion control operator, W amp is the amplitude loss control operator, W ac and W phase The combination of forms a pure viscoacoustic TTI wave propagation operator W dominated by phase dispersion. νpd (i.e. W νpd =W ac +W phase ), and W ac and W amp The combination of forms a pure viscoacoustic TTI wave propagation operator W dominated by amplitude loss. vamp (i.e. W vamp =W ac +W amp ). In addition, the viscoacoustic wave equation can be decoupled by adding and subtracting these three operators, and the decoupled SLS-based viscoacoustic wave equation can be derived. According to this method, the pure viscoacoustic TTT wave propagation operator w dominated by phase dispersion is first derived. νpd(i.e. W νpd =W ac +W phase ), then from the pure viscoacoustic TTI wave propagation operator W vis Subtract the phase dispersion control operator W from phase , we can indirectly obtain the pure viscoacoustic TTI wave propagation operator dominated by amplitude loss:

[0016] W vamp =W vis -W phase , (2)

[0017] Therefore, we can derive the phase dispersion-dominated and amplitude loss-dominated pure viscoacoustic TTI wave propagation operators respectively. Using these two derived wave propagation operators, we can further derive the pure viscoacoustic TTI wave equation containing the decoupled amplitude loss and phase dispersion terms. On this basis, starting from the single SLS model, we first derive the phase dispersion-dominated pure viscoacoustic TTI wave equation W νpd :

[0018]

[0019] In equation (3), the term related to 2 / A-1 is the phase dispersion control operator W phase Then, according to Equation 2, the phase W is subtracted from the pure viscoacoustic TTI wave equation phase , we can indirectly obtain the pure viscoacoustic TTI wave equation dominated by amplitude loss W νamp :

[0020]

[0021] Based on equations (3) and (4), we derive a new pure viscoacoustic TTI wave equation with amplitude loss and phase dispersion decoupled, which is expressed as

[0022]

[0023] When κ1=0, κ2=0, Equation 5 is the acoustic anisotropic wave equation; when κ1=1, κ2=0, Equation 5 becomes the pure viscoacoustic TTI wave equation dominated by phase dispersion (Equation 3); when κ1=0, κ2=1, Equation 5 becomes the pure viscoacoustic TTI passive equation dominated by amplitude loss (Equation 4); when κ1=1, κ2=1, Equation 5 is the pure viscoacoustic TTI wave equation.

[0024] A computer device comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the aforementioned method is implemented when the processor executes the program.

[0025] A computer-readable storage medium stores a computer program, which implements the above-mentioned method when executed by a processor.

[0026] A viscoacoustic reverse time migration method in an inclined transversely isotropic medium, wherein the specific process of using the pure viscoacoustic TTI wave equation with decoupled amplitude attenuation and phase dispersion operators to realize Q-compensated reverse time migration in step S4 is as follows: forward propagating the source wave field according to the set pure viscoacoustic TTI wave equation, reverse propagating the receiving wave field according to its conjugate equation, and then obtaining the migration imaging result through the cross-correlation imaging condition.

[0027] Preferably, ε, δ, The parameters are obtained by conducting multi-dimensional physical property testing and analysis on geological samples in the actual seismic exploration area, and are determined by combining the anisotropic feature extraction algorithm of seismic wave field data.

[0028] Preferably, the quality factor Q is obtained by performing multi-scale and multi-angle inversion calculations on the attenuation data of seismic waves in the medium, and optimizing and adjusting the data in combination with prior information on the geological structure to ensure that the Q value can accurately reflect the attenuation characteristics of the medium.

[0029] Preferably, in the process of constructing a high-precision wave field propagation operator in step S3, a finite difference method is used to discretize the pure viscoacoustic TTI wave equation, and the difference format of the finite difference method is a high-order precision format and has an adaptive stability adjustment mechanism.

[0030] The present invention provides a viscoacoustic reverse time migration method in an inclined transversely isotropic medium. It has the following beneficial effects:

[0031] 1. The present invention derives a pure viscoacoustic TTI wave equation based on memory variable representation, realizes the separation of amplitude attenuation and phase dispersion, and efficiently solves it through the finite difference method, which is suitable for industrial applications. Numerical tests show that the proposed wave equation can simulate the independent behavior of amplitude loss and phase dispersion, and provide a wave field without S-wave artifacts and numerically stable.

[0032] 2. Based on the wave equation, the present invention develops a Q-compensated RTM algorithm in TTI media, and introduces a regularization operator in the wave field simulation process to suppress high-frequency noise and ensure the stability of wave field propagation. The experimental results of synthetic data and measured data show that the Q-compensated TTI RTM method can effectively correct anisotropy and attenuation effects to obtain high-resolution imaging results. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a flow chart of the viscoacoustic reverse time migration method in inclined transversely isotropic media;

[0034] Figure 2 A schematic diagram of wave field snapshot comparison of the method provided by the present invention;

[0035] Figure 3 (a) is a comparison diagram of seismic records of the method provided in the embodiment of this specification, and (b) is an amplitude spectrum of (a);

[0036] Figure 4 A schematic diagram of a wave field snapshot at 0.7s of simulating a uniform model using different wave equations provided by the present invention;

[0037] Figure 5 A schematic diagram of a model parameter field of a Marmousi attenuation TTI model of the present invention;

[0038] Figure 6 It is a schematic diagram of the offset result of the Marmousi attenuation TTI model of the present invention;

[0039] Figure 7 The embodiment of the present invention provides Figure 6 Schematic diagram of the comparison of vertical slices extracted at x = 3.0 km (a) and x = 5.0 km (b). DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the specification of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] Example:

[0042] Please see attached Figure 1 - Attachment Figure 7 The embodiment of the present invention provides a viscoacoustic reverse time migration method in an inclined transversely isotropic medium, comprising:

[0043] S1, set up the observation system, input the model parameter field, these parameter fields include velocity field, anisotropy parameter field and quality factor Q. Get the initial parameter field, where the parameters in the initial parameter field include viscosity parameters and anisotropy parameters. Viscosity parameters include, where vp0 represents the propagation velocity of longitudinal waves in the medium, Q represents the quality factor, the size of Q determines the strength of seismic wave energy attenuation, anisotropy parameters include ε, δ, Among them, ε and δ are Thomsen anisotropy parameters used to characterize the intensity of velocity anisotropy. is the anisotropic dip parameter, which describes the directional characteristics of velocity anisotropy;

[0044] Its main method is to draw geological and geophysical models based on data obtained from field geological surveys, mechanical drilling analysis, geophysical inversion and logging detection, and then fill the model with viscosity and anisotropy parameter values ​​to obtain the required parameter field for computer numerical simulation.

[0045] S2, according to the model parameter field, the model parameters are discretized on the grid to obtain the model parameters at each grid point. During the extension process, the model can be divided into regular grids or irregular grids according to actual needs. Generally, irregular grid division is performed for the situation where undulating surfaces need to be processed. For the horizontal surface, simple regular grid division is sufficient, that is, the grid is divided into rectangles. In actual industrial production, in order to reduce the computing cost, the smaller the amount of calculation and the less memory required, the better, which means that the fewer the number of subdivided grids, the better. At the same time, in order to ensure the stable simulation of the finite difference method, the time sampling interval and the grid spacing need to meet certain conditions. Therefore, in order to ensure efficient, accurate, and stable finite difference numerical simulation, under the conditions of satisfying stability simulation and minimum numerical dispersion, the velocity, time sampling interval, and grid spacing should satisfy the following relationship: where ν pmax represents the maximum longitudinal wave velocity, Δt represents the time sampling interval, and Δd represents the grid size.

[0046] S3, set the pure viscoacoustic TTI wave equation with decoupled amplitude decay and phase dispersion operators. The calculation method of the pure viscoacoustic TTI wave equation with decoupled amplitude decay and phase dispersion operators is as follows:

[0047] In order to describe the intrinsic attenuation of underground media, the standard linear solid (SLS) model is one of the widely used attenuation theories. It is known that the viscoacoustic wave equation with a single SLS in the frequency wavenumber domain can be expressed as

[0048]

[0049] Among them, P and denote the spatial Fourier transform of p and r respectively, r is the memory variable, p is the longitudinal wave field, k x , k y , k z are the wave numbers in the x, y, and z directions respectively. and represents the stress relaxation time and strain relaxation time respectively, where Q is the quality factor and ω0 is the reference angular frequency. In addition, anisotropy is another important factor affecting the propagation characteristics of seismic waves in underground media. In order to accurately characterize the characteristics of seismic waves in anisotropic media, the precise dispersion relationship between longitudinal and transverse waves is established, which is expressed as

[0050]

[0051] Where Equations 3 and 4 represent the dispersion relations of longitudinal and shear waves, respectively, vp0 and vs0 are the longitudinal and shear wave velocities along the symmetry axis, respectively. ε and δ are Thomsen anisotropy parameters.

[0052] To simplify Equation 3, the shear wave phase velocity (vs0) at all phase angles is set to 0 (i.e., ωsv = 0), thereby obtaining a pure qP wave dispersion relation with only three parameters, expressed as:

[0053]

[0054] in:

[0055]

[0056] Then, to incorporate viscosity into the pure qP-wave dispersion relation, replace Substitute into Equation 6 The pure viscoacoustic wave equation in the frequency-wavenumber domain is obtained:

[0057]

[0058] Based on equations 8 and 9, the propagation characteristics of seismic waves in attenuation anisotropic media can be simulated. Transforming equations 8 and 9 into the time domain, the pure viscoacoustic VTI wave equation is obtained:

[0059]

[0060] In the equation, Equation 12 is the spatial domain representation of Equation 7. Equations 10 and 11 can be easily solved using the finite difference method, while Equation 12 can only be solved using a spectral-based method. Using the finite difference method to solve Equation 12, the equivalent form of Equation 7 can be expressed as:

[0061]

[0062] In the equation, n=(n x ,n y ,n z )=k / |k|=(k x ,k y ,k z ) / |k| is the propagation direction of seismic waves, where based on The asymptotic approximation of , equation (13) can be approximately represented in the spatial domain as:

[0063]

[0064] Therefore, by replacing S with Sn in equations (10) and (11), we can obtain a new pure viscoacoustic VTI wave equation in the time and space domain:

[0065]

[0066] The finite difference method can effectively solve equations 15 and 16, significantly improving the computational efficiency of wave field simulation. In addition, the coordinate transformation relationship between VTI and TTI media is expressed as:

[0067]

[0068] where θ and φ represent the tilt angle and azimuth angle, respectively. and is the new wave number in the rotated coordinate system. In the context of Eq. 17, the two-dimensional pure viscoacoustic TTI wave equation can be expressed as

[0069]

[0070]

[0071] in:

[0072]

[0073] It is worth noting that Equation 20 contains coupled amplitude loss and phase dispersion operators, which poses a challenge to the implementation of Q-compensated RTM. Therefore, it is necessary to derive the pure viscoacoustic TTI wave equation containing decoupled amplitude loss and phase dispersion operators.

[0074] Theoretically, the pure viscoacoustic TTI wave propagation operator W vis It can generally be expressed as:

[0075] W vis =W ac +W phase +W amp (twenty one)

[0076] Where W ac is the pure sound TTI propagation operator, W phase is the phase dispersion control operator, W amp is the amplitude loss control operator. ac and W phase The combination of forms a pure viscoacoustic TTI wave propagation operator W dominated by phase dispersion. vpd (i.e. W vpd =W ac +W phase ), and w ac and W amp The combination of forms a pure viscoacoustic TTI wave propagation operator W dominated by amplitude loss.vamp (i.e. W vamp =W ac +W amp ). In addition, the viscoacoustic wave equation can be decoupled by adding and subtracting these three operators, and the decoupled SLS-based viscoacoustic wave equation can be derived. According to this method, the pure viscoacoustic TTI wave propagation operator W dominated by phase dispersion is first derived. vpd , then from the pure viscoacoustic TTI wave propagation operator W vis Subtract the phase dispersion control operator W from phase , we can indirectly obtain the pure viscoacoustic TTI wave propagation operator W dominated by amplitude loss vamp :

[0077] W vamp =W vis -W phase (twenty two)

[0078] Therefore, we can derive the phase dispersion-dominated and amplitude loss-dominated pure viscoacoustic TTI wave propagation operators respectively. Using these two derived wave propagation operators, we can further derive the pure viscoacoustic TTI wave equation containing the decoupled amplitude loss and phase dispersion terms. On this basis, starting from a single SLS model, we first derive the phase dispersion-dominated pure viscoacoustic TTI wave equation W vpd :

[0079]

[0080] In equation (23), the term related to 2 / A-1 is the phase dispersion control operator W phase Then, according to Equation 22, subtract the phase W from Equation 18 phase , we can get the pure viscoacoustic TTI wave equation dominated by amplitude loss W vamp :

[0081]

[0082] Based on equations (23) and (24), we derive a new pure viscoacoustic TTI wave equation with amplitude loss and phase dispersion decoupled, which is expressed as:

[0083]

[0084] When κ1=0, κ2=0, Equation 25 is an acoustic anisotropic wave equation; when κ1=1, κ2=0, Equation 25 becomes a pure viscoacoustic TTI wave equation dominated by phase dispersion (Equation 23); when κ1=0, κ2=1, Equation 25 becomes a pure viscoacoustic TTI wave equation dominated by amplitude loss (Equation 24); when κ1=1, κ2=1, Equation 25 is a pure viscoacoustic TTI wave equation;

[0085] S4. Q-compensated reverse time migration is realized by using the pure viscoacoustic TTI wave equation with decoupled amplitude attenuation and phase dispersion operators. The wave equation describing seismic wave propagation is the basis of migration imaging. The newly derived wave equation has decoupled amplitude loss and phase dispersion characteristics, which facilitates the realization of Q-compensated RTM. In order to realize attenuation compensation, the sign of the amplitude attenuation term in equation 25 (i.e., κ1=1, κ2=-1) is reversed to obtain the attenuation compensation wave field modeling operator:

[0086]

[0087] However, directly reversing the sign of the amplitude attenuation term may lead to an unstable wave field, which is attributed to the amplification of high-frequency components. In order to suppress these high-frequency components, some methods have been developed, such as low-pass filtering, stabilization factor method, and regularization method. Based on the regularization method, the attenuation compensation wave field simulation operator with regularization term can be expressed as:

[0088]

[0089] Where ζ is the regularization parameter, which is generally a small positive value. In addition, imaging conditions are another important component in the Q-compensated RTM workflow. This paper adopts the source normalized correlation (SNC) imaging condition proposed by Fathalian et al. (2020). This is because the SNC imaging condition has two advantages: First, in viscoacoustic anisotropic media, the image calculated by the SNC imaging condition is theoretically equivalent to the image in the case of non-attenuation of acoustic anisotropy. Secondly, for Q-compensated imaging, the SNC imaging condition only needs to compensate for the backward received wavefield, unlike the zero-lag correlation imaging condition, which requires simultaneous compensation of the forward source and backward received wavefields. Therefore, the SNC imaging condition is more convenient and more suitable for Q-compensated RTM, which is expressed as:

[0090]

[0091] Where α and L are the attenuation coefficient and propagation length, respectively. The subscripts up and down represent the upgoing wave and the downgoing wave, respectively. Where S(x, t) and R(x, t) are the source wave field and the receiving wave field in the non-attenuating anisotropic medium, respectively. and They are the attenuated source wavefield and the attenuated receiving wavefield in the attenuated anisotropic medium, respectively. is the compensated receiver wave field in the attenuating anisotropic medium. After simple mathematical operations, Equation 29 can be rewritten as

[0092]

[0093] Where I is the imaging condition in a non-attenuating anisotropic medium. From equation 30, it can be seen that using the SNC imaging condition in Q-compensated TTI RTM, compensating the received wavefield alone is sufficient to obtain the compensated RTM image. In addition, the migration results obtained using the imaging condition described in equation 29 are consistent with those obtained in a non-attenuating medium.

[0094] In order to demonstrate the behavior of decoupled amplitude loss and phase dispersion of the newly derived pure viscoacoustic TTI wave equation, a uniform model is designed for forward simulation. The model is discretized into 401×401 grids with a grid spacing of 10m. A Ricker wavelet with a peak frequency of 20Hz is used as the source and is excited at the point (2km, 2km). The reference frequency is the same as the main frequency of the source wavelet.

[0095] Figure 2 Snapshots of the wave field under the uniform model. (a) Acoustic TTI wave equation, (b) Phase dispersion dominated TTI wave equation, (c) Amplitude attenuation dominated TTI wave equation, (d) Viscoacoustic wave TTI wave equation; from Figure 2 It can be clearly seen from the figure that the proposed wave equation can simulate the amplitude attenuation and phase dispersion effects respectively. In addition, the waveforms simulated by different wave equations are as follows Figure 3 a, the corresponding spectrum is Figure 3 As shown in b. Figure 3 It is shown that the wave field dominated by amplitude decay and the wave field dominated by phase dispersion exhibit attenuated amplitude and phase delay, respectively, compared with the acoustic case. The waveform of the viscoacoustic wave field shows both amplitude decay and phase shift. This observation indicates that the newly derived pure viscoacoustic TTI wave equation is able to simulate the amplitude decay and phase dispersion characteristics, respectively. This characteristic facilitates the realization of Q-compensated RTM in TTI media.

[0096] Since the wave field simulated by the coupled viscoacoustic TTI wave equation presents S-wave artifacts and cannot remain stable when ε<δ, in order to show that the newly derived pure viscoacoustic TTI wave square motion equation has the same characteristics as the pure qP wave TTI wave equation, we simulated the wave field in a uniformly attenuated TTI model. The model consists of a 401×401 grid with a spatial spacing of 10m. The source is a Ricker wavelet with a main frequency of 25 Hz, which is excited at the center of the model. Figure 4 The wave fields simulated by the proposed pure viscoacoustic TTI wave equation and the coupled pseudo-viscoacoustic TTI wave equation. Figure 4 It can be clearly seen in Figure c that compared with the wave field calculated by the coupled pseudo-viscoacoustic TTI wave equation, the wave field simulated by the proposed pure viscoacoustic TTI wave equation has no shear wave artifacts and remains numerically stable when the anisotropy parameter ε < δ ( Figure 4 d).

[0097] also, Figure 4ef describes Figure 4 ab and Figure 4 The comparison of cd shows that the proposed wave equation is in good agreement with the simulation results of the coupled pseudo-viscoacoustic TTI wave equation. This observation shows that the proposed wave equation can accurately simulate the propagation of seismic waves in attenuating anisotropic media.

[0098] A synthetic data set is used to test the feasibility and effectiveness of the proposed Q-compensated TTI RTM. For the synthetic examples, the proposed pure viscoacoustic TTI wave equation is used to calculate the observed data. In all numerical examples, the reference frequency is equal to the dominant frequency of the source wavelet, and the newly derived pure viscoacoustic TTI wave equation is solved using an efficient finite difference method.

[0099] The adaptability of the proposed Q-compensated TTI RTM is verified using the improved attenuated Marmousi TTI model. Figure 5 are the model parameters of the Marmousi TTI model. Figure 6 a is the acoustic TTI RTM imaging result with acoustic TTI data as reference. Figure 6 bd respectively describe the imaging results of viscoacoustic TTI data by acoustic TTI RTM, Q-compensated ISO RTM and Q-compensated TTI RTM. Figure 6 b, compared with the reference figure ( Figure 6 Compared with a), since no compensation is performed during the migration process, the imaging result obviously has weak energy, especially in the area below the strong attenuation structure. However, when ISO parameters are used for compensation, Figure 6 The imaging result of c shows the displacement of geological structures and deformation of fault planes, highlighting the importance of anisotropic effects. Considering the anisotropy and attenuation during the migration process, the image amplitude is consistent with the reference image ( Figure 6 a), the location of geological structures was accurately imaged, such as Figure 6 As shown in d.

[0100] For a clear comparison, we also Figure 6 Vertical slices were extracted from Figure 7 As shown in Figure 7 As shown, compared with the reference trace (shown by the solid grey line), Figure 6The traces extracted in bc show obvious amplitude attenuation and phase shift. However, the traces extracted from the Q-compensated TTI RTM image (indicated by the black dashed line) are in good agreement with the reference traces. This example shows that the proposed Q-compensated TTI RTM can provide high-quality imaging results in complex attenuation anisotropic media. This result indicates that simultaneously correcting the anisotropy and attenuation effects of the subsurface medium is crucial to improving the quality of seismic imaging. Therefore, we can conclude that the proposed Q-compensated TTI RTM effectively corrects the attenuation and anisotropy effects simultaneously and can be used as a reliable attenuation imaging technique for TTI media.

[0101] Correspondingly, an embodiment of the present application also provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the aforementioned efficient Q-compensated pure viscoacoustic reverse time migration method for tilted anisotropic media is implemented.

[0102] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device, equipment and medium embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiments, and will not be repeated here.

[0103] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A viscoacoustic reverse time migration method in an inclined transversely isotropic medium, characterized in that: The following steps are involved: S1, setting the observation system and inputting the model parameter field, wherein the model parameter field includes the velocity field, the anisotropy parameter field and the attenuation parameter field; S2, according to the model parameter field, the model parameters are discretized into grids to obtain the model parameters at each grid point; S3, setting the pure viscoacoustic TTI wave equation with decoupled amplitude attenuation and phase dispersion operators to construct a high-precision wave field propagation operator; S4, Q-compensated reverse time migration is realized using the pure viscoacoustic TTI wave equation with decoupled amplitude decay and phase dispersion operators.

2. The viscoacoustic reverse time migration method in an inclined transversely isotropic medium according to claim 1, characterized in that: The velocity field in step S1 includes the propagation velocity Vp of the longitudinal wave; the anisotropic parameter field includes ε, δ, Among them, ε and δ represent the strength of velocity anisotropy, is the anisotropic dip parameter; the attenuation anisotropic parameter field includes Q.

3. The viscoacoustic reverse time migration method in an inclined transversely isotropic medium according to claim 2, characterized in that: In order to achieve a stable wave field extension result in step S2, the parameter field needs to be reasonably meshed, specifically including: the spacing Ad between the meshes obtained by meshing satisfies the condition: where ν pmax represents the maximum longitudinal wave velocity, and Δt represents the time sampling interval.

4. The viscoacoustic reverse time migration method in an inclined transversely isotropic medium according to claim 3, characterized in that: The pure viscoacoustic TTI wave equation with decoupled amplitude attenuation and phase dispersion operators in step S3 is in the form of: When κ1=0, κ2=0, the equation is an acoustic anisotropic wave equation; when κ1=1, κ2=0, the equation is a pure viscoacoustic TTI wave equation dominated by phase dispersion; when κ1=0, κ2=1, the equation is a pure viscoacoustic TTI wave equation dominated by amplitude loss; when κ1=1, κ2=1, the equation is a pure viscoacoustic TTI wave equation.

5. The viscoacoustic reverse time migration method in an inclined transversely isotropic medium according to claim 4, characterized in that: The specific process of implementing Q-compensated reverse time migration by using the pure viscoacoustic TTI wave equation with decoupled amplitude attenuation and phase dispersion operators in step S4 is: The source wave field is forward propagated according to the set pure viscoacoustic TTI wave equation, and the receiving wave field is reversely propagated according to its conjugate equation, and then the migration imaging result is obtained through the cross-correlation imaging condition.

6. The viscoacoustic reverse time migration method in an inclined transversely isotropic medium according to claim 5, characterized in that: The anisotropic parameter field contains ε, δ, The parameters are obtained by conducting multi-dimensional physical property testing and analysis on geological samples in the actual seismic exploration area, and are determined by combining the anisotropic feature extraction algorithm of seismic wave field data.

7. The viscoacoustic reverse time migration method in an inclined transversely isotropic medium according to claim 5, characterized in that: The quality factor Q is obtained by performing multi-scale and multi-angle inversion calculations on the attenuation data of seismic waves in the medium, and optimizing and adjusting the data in combination with prior information on the geological structure to ensure that the Q value can accurately reflect the attenuation characteristics of the medium.

8. The viscoacoustic reverse time migration method in an inclined transversely isotropic medium according to claim 1, characterized in that: In the process of constructing a high-precision wave field propagation operator in step S3, the pure viscoacoustic TTI wave equation is discretized using a finite difference method, and the difference format of the finite difference method is a high-order precision format and has an adaptive stability adjustment mechanism.

9. A computer device according to claim 1, comprising a memory, a processor and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the program, the method according to any one of claims 1 to 8 is implemented.

10. A computer-readable storage medium according to claim 1, wherein a computer program is stored thereon, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 8 is implemented.

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