A migration imaging method and device based on uplink ray tracing strategy

Abstract

The present invention discloses a migration imaging method and device based on an uplink ray tracing strategy, which relates to the field of geological exploration technology. The imaging steps are as follows: S1: obtaining input parameters, which include a P-wave velocity parameter field, anisotropy parameter field, and an observation shot record; S2: generating a shot point x according to the input parameters using the following imaging expression s The corresponding imaging results. The present invention can not only solve the illusion problem of the traditional frequency domain Gaussian beam migration imaging method, but also make the diffraction wave energy more convergent, thereby producing clearer imaging results. The time-space domain VTI medium Gaussian beam migration imaging technology based on the uplink ray tracing strategy is developed, which provides high-precision imaging guarantee for seismic data processing in complex structural areas and improves the quality and reliability of subsequent interpretation work.

Description

Technical Field

[0001] The invention relates to the technical field of geological exploration, and in particular to a migration imaging method based on an uplink ray tracing strategy. Background Art

[0002] The traditional frequency domain Gaussian beam migration method may produce weak illumination and strong artifacts in complex deep structures due to the inaccurate paraxial ray tracing of the reverse wave field. As for the traditional time-space domain acoustic medium Gaussian beam migration method, it does not take into account the complexity of the underground medium, resulting in non-convergence of diffraction wave energy and poor imaging results. Therefore, in order to obtain high-precision imaging results, it is necessary to further improve the diffraction wave energy.

[0003] Based on this, the present invention proposes a Gaussian beam migration imaging method for VTI media in the spatiotemporal domain based on an uplink ray tracing strategy. Summary of the invention

[0004] The object of the present invention is to provide a migration imaging method based on an uplink ray tracing strategy to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a migration imaging method based on an uplink ray tracing strategy, wherein the imaging steps are as follows:

[0006] S1: obtaining input parameters, wherein the input parameters include a P-wave velocity parameter field, an anisotropy parameter field, and observation shot records;

[0007] S2: Based on the input parameters, the following imaging expression is used to generate the shot point x s The corresponding imaging results:

[0008]

[0009] Among them, I(x 0 ) represents the migration imaging result, i is the imaginary unit, ω m is the dominant frequency of the observed data, x s represents the shot point, x r is the receiving point coordinate, is the spatial azimuth, P U is the observation shot record, ω is the circular frequency of the seismic wavelet, t is the propagation time of the seismic wavelet, τ is the travel time, P(s) and Q(s) are the basic solutions of the dynamic ray tracing equation, n is the normal direction of the ray coordinate system, and p z is the slowness in the Z direction, ε is the initial parameter of the Gaussian beam, v is the propagation velocity of the seismic wave, s is the tangential direction of the ray coordinate system, and s 0 is the tangential coordinate value of the initial position, () * denotes conjugation;

[0010] S3: Superimpose the imaging results corresponding to each shot point, generate and output the migration imaging result.

[0011] Preferably, in the technical solution, the imaging expression described in step S2 is pre-obtained based on the following steps:

[0012] N1: In the two-dimensional ray coordinate system (s,n), considering the acoustic wave medium, the seismic forward wave field represented by the Gaussian beam is expressed as:

[0013]

[0014] Among them, W (1) is the earthquake positive wave field;

[0015] N2: Use dynamic ray tracing in VTI medium to obtain Gaussian beam amplitude and travel time information;

[0016] N3: According to the observation shot record, the reverse propagation process from the receiving point to the underground imaging point can be realized by the upward ray tracing strategy, and the seismic reverse wave field can be expressed as:

[0017]

[0018] Among them, W (2) is the earthquake reverse wave field, T is the total time of earthquake wave propagation, G is the Green function, t 0 is the initial moment, x 0 is the underground imaging point,

[0019] Under high frequency approximation, the derivative expression of Green's function can be simplified to:

[0020]

[0021] N4: Use the superposition of a series of Gaussian beams to approximate the expression of Green's function:

[0022]

[0023] Then the seismic reverse wave field can be simplified as:

[0024]

[0025] The time domain part of this expression is transformed by Fourier:

[0026]

[0027] N5: In the time window, when the phases of the forward and reverse wave fields are the same, the cross-correlation output of the two reaches the maximum value, and the noise effect is reduced by superposition of multi-shot data. The formula of the VTI medium Gaussian beam migration method in the space-time domain based on the uplink ray tracing strategy can be obtained:

[0028]

[0029] Among them, t∈[t 1 ,t 2 ] represents the time window;

[0030] Substituting the forward and reverse wave field expressions, we can get the final imaging expression.

[0031] Preferably, in the technical solution, the dynamic ray tracing equations under the VTI medium described in step N2 are:

[0032]

[0033] Among them, W, V, and H are:

[0034]

[0035] Among them, p n is the slowness in the normal direction, and G is the process function.

[0036] In combination with the above-mentioned offset imaging method based on the uplink ray tracing strategy, the technical solution of the present invention also proposes an electronic device, which includes a memory, a processor, and a computing program stored in the memory and executable on the processor, wherein the processor implements the above-mentioned offset imaging method based on the uplink ray tracing strategy when executing the computing program.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] This migration imaging method based on the uplink ray tracing strategy can not only solve the illusion problem of the traditional frequency domain Gaussian beam migration imaging method, but also make the diffraction wave energy more convergent, thereby producing clearer imaging results. The development of time-space domain VTI medium Gaussian beam migration imaging technology based on the uplink ray tracing strategy provides high-precision imaging guarantee for seismic data processing in complex structural areas, and improves the quality and reliability of subsequent interpretation work. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A schematic diagram of a flow chart provided in the embodiments of this specification;

[0040] Figure 2 is the true velocity field of the depression model;

[0041] Figure 3is the anisotropic parameter field ε of the depression model;

[0042] Figure 4 is the anisotropic parameter field δ of the depression model;

[0043] Figure 5 It is the first shot record of anisotropy observation of depression model;

[0044] Figure 6 This is the result of Gaussian beam migration imaging of VTI medium in the traditional frequency domain;

[0045] Figure 7 This is the imaging result of Gaussian beam migration of acoustic medium in time and space domain;

[0046] Figure 8 This is the imaging result provided by the embodiments of this specification. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solution and advantages of the present application clearer, the technical solution of the present application will be clearly and completely described below in combination with the specific embodiments of the present application and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in this specification, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0048] First, the uplink ray tracing strategy and the implementation method of the VTI medium used in the embodiments of this specification are explained in detail.

[0049] In the two-dimensional ray coordinate system (s,n), considering the acoustic wave medium, the seismic forward wave field represented by the Gaussian beam can be written as:

[0050]

[0051] Among them, W (1) is the earthquake positive wave field, i is an imaginary unit, is the spatial azimuth, ω is the circular frequency of the seismic wavelet, ε is the initial parameter of the Gaussian beam, v is the propagation velocity of the seismic wave, s is the tangential direction of the ray coordinate system, n is the normal direction of the ray coordinate system, and s 0 is the tangential coordinate value of the initial position, t is the propagation time of the seismic wavelet, τ is the travel time, and P(s) and Q(s) are the basic solutions of the dynamic ray tracing equation.

[0052] In isotropic media, the ray center coordinate systems are mutually orthogonal. However, when considering anisotropic media, the ray direction no longer maintains a perpendicular relationship with the wavefront. At this time, if the isotropic ray tracing theory is continued to be used, the travel time and amplitude information will be calculated inaccurately, which will eventually reduce the accuracy of the migration imaging results in this paper. Therefore, it is necessary to introduce a weight along the ray direction to deal with this non-orthogonality, so that the relevant parameter information of the ray tracing calculation is relatively accurate, and the central ray adjacent wave field of the VTI medium is further accurately constructed, which provides favorable conditions for the subsequent migration imaging results. Consider the dynamic ray tracing equations under VTI media:

[0053]

[0054] Among them, W, V, and H are:

[0055]

[0056] Among them, p n is the slowness in the normal direction, and G is the process function.

[0057] According to the observation shot record, the reverse propagation process from the receiving point to the underground imaging point can be realized by the upward ray tracing strategy, and the seismic reverse wave field can be expressed as:

[0058]

[0059] Among them, W (2) is the earthquake reverse wave field, T is the total time of earthquake wave propagation, x r is the receiving point coordinate, P U is the observation gun record, G is the Green function, t 0 is the initial moment, x 0 It is an underground imaging point.

[0060] Under high frequency approximation, the derivative expression of Green's function can be simplified to:

[0061]

[0062] Among them, ω m is the dominant frequency of the observed data, p z is the slowness in the Z direction.

[0063] The expression of Green's function is approximated by the superposition of a series of Gaussian beams:

[0064]

[0065] Then the seismic reverse wave field can be simplified as:

[0066]

[0067] The time domain part of this expression is transformed by Fourier:

[0068]

[0069] in,() * Indicates conjugation.

[0070] In the migration algorithm, the imaging condition is very critical and directly affects the final imaging quality. In the time window, when the phases of the forward and reverse wave fields are the same, the cross-correlation output of the two reaches the maximum value, and the noise effect is reduced by superposition of multi-shot data. The formula of the VTI medium Gaussian beam migration method in the space-time domain based on the uplink ray tracing strategy can be obtained:

[0071]

[0072] Among them, I(x 0 ) represents the migration imaging result, x s represents the shot point, t∈[t 1 ,t 2 ] represents the time window.

[0073] Substituting the forward and reverse wave field expressions, we can get the final I(x 0 ) is expressed as:

[0074]

[0075] The above section specifically describes the uplink ray tracing strategy and VTI medium implementation method used in the embodiments of this specification.

[0076] Based on the foregoing, the embodiments of this specification provide a method for Gaussian beam migration imaging of VTI media in the spatiotemporal domain based on an uplink ray tracing strategy, specifically including:

[0077] S1: obtaining input parameters, wherein the input parameters include a P-wave velocity parameter field, an anisotropy parameter field, and observation shot records;

[0078] S2: Based on the input parameters, the following imaging expression is used to generate the shot point x s The corresponding imaging results:

[0079]

[0080] Among them, I(x 0 ) represents the migration imaging result, i is the imaginary unit, ω m is the dominant frequency of the observed data, x s represents the shot point, x r is the receiving point coordinate, is the spatial azimuth, P Uis the observation shot record, ω is the circular frequency of the seismic wavelet, t is the propagation time of the seismic wavelet, τ is the travel time, P(s) and Q(s) are the basic solutions of the dynamic ray tracing equation, n is the normal direction of the ray coordinate system, and p z is the slowness in the Z direction, ε is the initial parameter of the Gaussian beam, v is the propagation velocity of the seismic wave, s is the tangential direction of the ray coordinate system, and s 0 is the tangential coordinate value of the initial position, () * denotes conjugation;

[0081] S3: Superimpose the imaging results corresponding to each shot point, generate and output the migration imaging result.

[0082] like Figure 1 As shown, the process specifically includes the following steps:

[0083] Obtain input parameters, including P-wave velocity parameter field, anisotropy parameter field and observation shot records;

[0084] The travel time and amplitude information of Gaussian beam in VTI medium are calculated by anisotropic ray tracing theory;

[0085] Using the above migration imaging formula, multiple shot data are superimposed to obtain the imaging result.

[0086] The following is an illustration of the actual effect of the embodiments of the present invention in the model.

[0087] The method provided by the present invention is applied to a depression model imaging, and a relatively ideal imaging effect is achieved. Figure 2 As shown, that is, the P-wave velocity parameter field), the anisotropy parameter field ε (such as Figure 3 As shown), anisotropic parameter field δ (as shown Figure 4 ); establish a mobile receiving observation system, input the real velocity field and the observation gun record obtained by anisotropic forward simulation (the first gun result is shown in Figure 5 The forward and reverse wave fields are cross-correlated using the cross-correlation imaging condition to obtain the traditional frequency domain VTI medium Gaussian beam migration imaging result (as shown in Figure 6 As shown in the figure), the results of Gaussian beam migration imaging of acoustic wave media in the time and space domain (as shown in the figure Figure 7 As shown), the imaging results provided in the embodiments of this specification (as shown Figure 8 shown).

[0088] exist Figure 6 In the frequency domain Gaussian beam migration method, some migration artifacts are produced (indicated by arrows). Figure 7 and Figure 8In the figure, it can be seen that since the time-reverse wave field adopts the upward ray tracing strategy, all reflection interfaces can be clearly imaged. Compared with the Gaussian beam migration imaging results of acoustic wave media in the time-space domain, the energy of the anisotropic diffraction layer of the present invention is more convergent ( Figure 8 box).

[0089] Correspondingly, an embodiment of the present application also provides an electronic device, which includes a memory, a processor, and a computing program stored in the memory and executable on the processor, wherein when the processor executes the computing program, the offset imaging method based on the uplink ray tracing strategy as described above is implemented.

[0090] 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 migration imaging method based on an uplink ray tracing strategy, characterized in that: The imaging steps are as follows: S1: obtaining input parameters, wherein the input parameters include a P-wave velocity parameter field, an anisotropy parameter field, and observation shot records; S2: Based on the input parameters, the following imaging expression is used to generate the shot point x s The corresponding imaging results: Where I(x0) represents the migration imaging result, i is the imaginary unit, ω m is the dominant frequency of the observed data, x s represents the shot point, x r is the receiving point coordinate, is the spatial azimuth, P U is the observed shot record, ω is the circular frequency of the seismic wavelet, t is the propagation time of the seismic wavelet, τ is the travel time, P(s) and Q(s) are the basic solutions of the dynamic ray tracing equation, n is the normal direction of the ray coordinate system, and p z is the slowness in the Z direction, ε is the initial parameter of the Gaussian beam, v is the propagation velocity of the seismic wave, s is the tangential direction of the ray coordinate system, s0 is the tangential coordinate value of the initial position, () * denotes conjugation; S3: Superimpose the imaging results corresponding to each shot point, generate and output the migration imaging result.

2. The migration imaging method based on the uplink ray tracing strategy according to claim 1, characterized in that: The imaging expression described in step S2 is obtained in advance based on the following steps: N1: In the two-dimensional ray coordinate system (s,n), considering the acoustic wave medium, the seismic forward wave field represented by the Gaussian beam is expressed as: Among them, W (1) is the earthquake positive wave field; N2: Use dynamic ray tracing in VTI medium to obtain Gaussian beam amplitude and travel time information; N3: According to the observation shot record, the reverse propagation process from the receiving point to the underground imaging point can be realized by the upward ray tracing strategy, and the seismic reverse wave field can be expressed as: Among them, W (2) is the seismic reverse wave field, T is the total time of seismic wave propagation, G is the Green function, t0 is the initial time, x0 is the underground imaging point, Under high frequency approximation, the derivative expression of Green's function can be simplified to: N4: Use the superposition of a series of Gaussian beams to approximate the expression of Green's function: Then the seismic reverse wave field can be simplified as: The time domain part of this expression is transformed by Fourier: N5: In the time window, when the phases of the forward and reverse wave fields are the same, the cross-correlation output of the two reaches the maximum value, and the noise effect is reduced by superposition of multi-shot data. The formula of the VTI medium Gaussian beam migration method in the space-time domain based on the uplink ray tracing strategy can be obtained: Among them, t∈[t1,t2] represents the time window; Substituting the forward and reverse wave field expressions, we can get the final imaging expression.

3. The migration imaging method based on the uplink ray tracing strategy according to claim 2, characterized in that: The dynamic ray tracing equations in the VTI medium described in step N2 are: Among them, W, V, and H are: Among them, p n is the slowness in the normal direction, and G is the process function.

4. An electronic device, characterized in that: The method comprises a memory, a processor and a computing program stored in the memory and executable on the processor, wherein the processor implements the method according to any one of claims 1 to 3 when executing the computing program.

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