CN114942472A - Offset imaging method and equipment based on uplink ray tracing strategy - Google Patents
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Abstract
The invention discloses an offset imaging method and equipment based on an uplink ray tracing strategy, and relates to the technical field of geological exploration. The imaging steps are as follows: s1: acquiring input parameters, wherein the input parameters comprise a P-wave velocity parameter field, an anisotropy parameter field and an observation shot record; s2: generating a shot point x by adopting the following imaging expression according to the input parameters s Corresponding imaging results. The method can solve the false image problem of the traditional frequency domain Gaussian beam migration imaging method, can enable the diffracted wave energy to be more convergent, further generates a clearer imaging result, develops the time-space domain VTI medium Gaussian beam migration imaging technology based on the uplink ray tracing strategy, provides high-precision imaging guarantee for the seismic data processing of a complicated structural area, and improves the quality and reliability of subsequent interpretation work.
Description
Technical Field
The invention relates to the technical field of geological exploration, in particular to an offset imaging method based on an uplink ray tracing strategy.
Background
Conventional frequency domain gaussian beam migration methods may produce weak illumination and strong artifacts in complex deep structures due to inaccuracies in paraxial ray tracing of the backward wavefield. For the traditional time-space domain acoustic wave medium Gaussian beam migration method, the complexity of the underground medium is not considered, so that diffracted wave energy is not converged, and the imaging result is poor. Therefore, in order to obtain a high-precision imaging result, it is necessary to further increase the diffracted wave energy.
Based on the method, the invention provides a time-space domain VTI medium Gaussian beam offset imaging method based on an uplink ray tracing strategy.
Disclosure of Invention
The present invention is directed to provide an offset imaging method based on an up-ray tracing strategy, so as to solve the problems mentioned in the background art.
In order to achieve the purpose, the invention provides the following technical scheme: an offset imaging method based on an uplink ray tracing strategy comprises the following imaging steps:
s1: acquiring input parameters, wherein the input parameters comprise a P-wave velocity parameter field, an anisotropy parameter field and an observation shot record;
s2: generating a shot point x by adopting the following imaging expression according to the input parameters s The corresponding imaging results are:
wherein, I (x) 0 ) Representing the result of offset imaging, i being the unit of an imaginary number, ω m For observing dominant frequencies, x, of the data s Indicating shot point, x r In order to receive the coordinates of the point,
is the attitude, P U For observing the 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), Q(s) are the basic solutions of the dynamical ray tracing equation, n is the normal direction of the ray coordinate system, p is the normal direction of the ray coordinate system z For slowness in the Z direction,. epsilon.is the initial parameter of the Gaussian beam,. v is the propagation velocity of the seismic wave, and s isTangential direction of ray coordinate system, s 0 Is a tangential coordinate value of the initial position, () * Represents a conjugation;
s3: and (4) superposing the imaging results corresponding to the shot points, and generating and outputting an offset imaging result.
In the present embodiment, preferably, the imaging expression described in step S2 is obtained in advance based on the following steps:
n1: in a two-dimensional ray coordinate system (s, n), considering the acoustic medium, the seismic forward wavefield, represented by a Gaussian beam, is then represented as:
wherein, W (1) Is a seismic forward wavefield;
n2: kinetic ray tracing under a VTI medium is utilized to obtain Gaussian beam amplitude and travel time information;
n3: the backward propagation process from the receiving point to the underground imaging point according to the observation shot record can be realized by an uplink ray tracing strategy, and the seismic backward wave field can be expressed as:
wherein, W (2) Is the seismic backward wave field, T is the total time of seismic wave propagation, G is the Green function, T 0 Is an initial time, x 0 Is a point of imaging in the ground,
under high frequency approximation, the derivative expression of the green function can be simplified as:
n4: an expression that approximately characterizes the green's function is made using a superimposed form of a series of gaussian bundles:
the seismic backward wavefield can be simplified to:
the time domain part of the expression is transformed by fourier transform:
n5: in a time window, when the phase of the positive wave field and the phase of the negative wave field are the same, the cross-correlation output of the positive wave field and the negative wave field reaches the maximum value, and the noise influence is reduced by superposing multi-shot data, so that a time-space domain VTI medium Gaussian beam migration method formula based on an uplink ray tracing strategy can be obtained:
wherein t ∈ [ t ] 1 ,t 2 ]Represents a time window;
and substituting the positive and negative wave field expressions to obtain a final imaging expression.
In this embodiment, preferably, the dynamic ray tracing equation under the VTI medium in step N2 is:
wherein W, V, H are respectively:
wherein p is n G is a path function for slowness in the normal direction.
In combination with the above offset imaging method based on the upward ray tracing policy, the technical solution of the present invention further provides an electronic device, which includes a memory, a processor, and a computing program stored in the memory and capable of being executed on the processor, wherein when the processor executes the computing program, the above offset imaging method based on the upward ray tracing policy is implemented.
Compared with the prior art, the invention has the beneficial effects that:
the migration imaging method based on the uplink ray tracing strategy can solve the false image problem of a traditional frequency domain Gaussian beam migration imaging method, enables diffracted wave energy to be more convergent, further generates a clearer imaging result, develops a 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 of a complex structure area, and improves quality and reliability of subsequent interpretation work.
Drawings
FIG. 1 is a schematic flow chart provided by an embodiment of the present disclosure;
FIG. 2 is a true velocity field of the dimple model;
FIG. 3 is an anisotropy parameter field ε of the dimple model;
FIG. 4 is an anisotropy parameter field δ of the dimple model;
FIG. 5 is an anisotropic observation initial shot record of the dimple model;
FIG. 6 shows the result of Gaussian beam shift imaging of a conventional frequency domain VTI medium;
FIG. 7 shows the time-space domain acoustic medium Gaussian beam shift imaging results;
fig. 8 shows the imaging results provided in the examples of the present specification.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be described in detail and completely with reference to the following specific embodiments of the present application and the accompanying drawings. It should be apparent that the described embodiments are only some of the embodiments of the present application, and not all of the embodiments. All other embodiments obtained by a person skilled in the art based on the embodiments in the present specification without any inventive step are within the scope of the present application.
First, the implementation of the upstream ray tracing policy and the VTI medium used in the embodiments of the present specification will be specifically explained.
In a two-dimensional ray coordinate system (s, n), considering the acoustic medium, the seismic forward wavefield, represented by a Gaussian beam, can be written as:
wherein, W (1) For the seismic forward wavefield, i is in imaginary units,
is the space azimuth angle, omega is the circular frequency of the seismic wavelet, epsilon 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, s 0 The tangential coordinate value of the initial position, t is the propagation time of the seismic wavelet, tau is the travel time, and P(s), Q(s) are the basic solutions of the dynamic ray tracing equation.
In an isotropic medium, ray center coordinate systems are mutually orthogonal, but when the anisotropic medium is considered, the ray direction is no longer perpendicular to a wave front surface, at this time, if the isotropic ray tracing theory is continuously adopted, travel time and amplitude information calculation are inaccurate, and finally the precision of the offset imaging result of the text is reduced, so that a weight along the ray direction needs to be introduced to process the non-orthogonality, the related parameter information of the ray tracing calculation is relatively accurate, the central ray wave field proximity of the VTI medium is further accurately constructed, favorable conditions are provided for the subsequent offset imaging result, and a dynamic ray tracing equation set under the VTI medium is considered:
wherein W, V, H is:
wherein p is n For slowness in the normal direction, G is a function of the degree.
The backward propagation process from the receiving point to the underground imaging point according to the observation shot record can be realized by an uplink ray tracing strategy, and the seismic backward wave field can be expressed as:
wherein, W (2) Is the seismic backward wavefield, T is the total time of seismic wave propagation, x r To receive point coordinates, P U For observing shot records, G is the Green function, t 0 Is an initial time, x 0 Is a subsurface imaging point.
Under high frequency approximation, the derivative expression of the green function can be simplified as:
wherein, ω is m For observing the dominant frequency, p, of the data z Is the slowness in the Z direction.
An expression that approximately characterizes the green's function is made using a superimposed form of a series of gaussian bundles:
the seismic backward wavefield can be simplified to:
the time domain part of the expression is transformed by fourier transform:
wherein (C) * Representing conjugation.
In the offset algorithm, the imaging conditions are very critical, and the final imaging quality is directly influenced. In a time window, when the phase of the positive wave field and the phase of the negative wave field are the same, the cross-correlation output of the positive wave field and the negative wave field reaches the maximum value, and the noise influence is reduced by superposing multi-shot data, so that a time-space domain VTI medium Gaussian beam migration method formula based on an uplink ray tracing strategy can be obtained:
wherein, I (x) 0 ) Representing offset imaging results, x s Denotes the shot point, t ∈ [ t [ ] 1 ,t 2 ]Representing a time window.
Substituting the positive and negative wave field expression to obtain the final I (x) 0 ) The expression is as follows:
the above sections specifically describe the implementation of the VTI medium and the upstream ray tracing strategy used in the embodiments of the present specification.
Based on the foregoing, an embodiment of the present specification provides a time-space domain VTI medium gaussian beam offset imaging method based on an uplink ray tracing strategy, which specifically includes:
s1: acquiring input parameters, wherein the input parameters comprise a P-wave velocity parameter field, an anisotropy parameter field and an observation shot record;
s2: generating a shot point x by adopting the following imaging expression according to the input parameters s The corresponding imaging results are:
wherein, I (x) 0 ) Representing the result of offset imaging, i being the unit of an imaginary number, ω m For observing dominant frequencies, x, of the data s Indicating shot point, x r In order to receive the coordinates of the point,
is the attitude, P U For observing the 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), Q(s) are the basic solutions of the dynamical ray tracing equation, n is the normal direction of the ray coordinate system, p is the normal direction of the ray coordinate system z For slowness in the Z direction,. epsilon.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,. s 0 Is a tangential coordinate value of the initial position, () * Represents a conjugation;
s3: and superposing the imaging results corresponding to the shot points, and generating and outputting an offset imaging result.
As shown in fig. 1, the process specifically includes the following steps:
acquiring input parameters, wherein the input parameters comprise a P-wave velocity parameter field, an anisotropy parameter field and an observation shot record;
calculating travel time and amplitude information of a Gaussian beam under a VTI medium by an anisotropic ray tracing theory;
and superposing the multi-shot data by using the offset imaging formula to obtain an imaging result.
A description of the practical effects of the embodiments of the present invention in the model is given below.
The method provided by the invention is applied to imaging of a hollow model, and a relatively ideal imaging effect is achieved. The real velocity model (shown in fig. 2, namely, the P-wave velocity parameter field), the anisotropy parameter field epsilon (shown in fig. 3), and the anisotropy parameter field delta (shown in fig. 4); establishing a mobile receiving observation system, and inputting a real velocity field and an observation shot record obtained by anisotropic forward modeling (a first shot result is shown in figure 5); and cross-correlating the forward-transmission wave field and the backward-transmission wave field by adopting a cross-correlation imaging condition to obtain a traditional frequency domain VTI medium Gaussian beam migration imaging result (shown in figure 6), a time-space domain acoustic wave medium Gaussian beam migration imaging result (shown in figure 7) and an imaging result provided by the embodiment of the specification (shown in figure 8).
In fig. 6, the frequency domain gaussian beam shifting method produces some shifting artifacts (shown by the arrows). In fig. 7 and 8, it can be seen that all reflection interfaces can be clearly imaged due to the upward ray tracing strategy adopted by the temporal backward wave field. Compared with the Gaussian beam shift imaging result of the time-space domain acoustic wave medium, the energy of the anisotropic diffraction layer is more converged (shown in a box of FIG. 8).
Correspondingly, an embodiment of the present application further provides an electronic device, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the above-mentioned offset imaging method based on the upward ray tracing policy when executing the computer program.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (4)
1. An offset imaging method based on an uplink ray tracing strategy is characterized in that: the imaging steps are as follows:
s1: acquiring input parameters, wherein the input parameters comprise a P-wave velocity parameter field, an anisotropy parameter field and an observation shot record;
s2: generating a shot point x by adopting the following imaging expression according to the input parameters s The corresponding imaging results are:
wherein, I (x) 0 ) Representing the result of offset imaging, i being the unit of an imaginary number, ω m For observing dominant frequencies, x, of the data s Indicating shot point, x r In order to receive the coordinates of the point,
is attitude angle, P U For observing the 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), Q(s) are the basic solutions of the dynamical ray tracing equation, n is the normal direction of the ray coordinate system, p is the normal direction of the ray coordinate system z For slowness in the Z direction,. epsilon.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, s 0 Is a tangential coordinate value of the initial position, () * Represents a conjugation;
s3: and superposing the imaging results corresponding to the shot points, and generating and outputting an offset imaging result.
2. The offset imaging method based on the up-ray tracing strategy according to claim 1, wherein: the imaging expression described in step S2 is obtained in advance based on the following steps:
n1: in a two-dimensional ray coordinate system (s, n), considering the acoustic medium, the seismic forward wavefield, represented by a Gaussian beam, is then represented as:
wherein, W (1) Is a seismic forward wavefield;
n2: the amplitude and travel time information of the Gaussian beam is obtained by using dynamic ray tracing under a VTI medium;
n3: the backward propagation process from the receiving point to the underground imaging point according to the observation shot record can be realized by an uplink ray tracing strategy, and the seismic backward wave field can be expressed as:
wherein the content of the first and second substances,W (2) is the seismic backward wave field, T is the total time of seismic wave propagation, G is the Green function, T 0 Is an initial time, x 0 Is a point of imaging in the subsurface,
under high frequency approximation, the derivative expression of the green function can be simplified as:
n4: an expression that approximately characterizes the green's function is made using a superimposed form of a series of gaussian bundles:
the seismic backward wavefield can be simplified to:
the time domain part of the expression is transformed by fourier transform:
n5: in a time window, when the phase of the positive wave field and the phase of the negative wave field are the same, the cross-correlation output of the positive wave field and the negative wave field reaches the maximum value, and the noise influence is reduced by superposing multi-shot data, so that a time-space domain VTI medium Gaussian beam migration method formula based on an uplink ray tracing strategy can be obtained:
wherein t ∈ [ t ] 1 ,t 2 ]Represents a time window;
and substituting the positive and negative wave field expressions to obtain a final imaging expression.
3. The offset imaging method based on the up-ray tracing strategy according to claim 2, wherein: the system of the dynamic ray tracing equation under the VTI medium described in the step N2 is as follows:
wherein W, V, H are respectively:
wherein p is n For slowness in the normal direction, G is a function of the degree.
4. An electronic device, characterized in that: comprising a memory, a processor and a computing program stored on the memory and executable on the processor, wherein the processor implements the method according to any of claims 1-3 when executing the computing program.
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| CN115993650A (en) * | 2023-03-22 | 2023-04-21 | 中国石油大学(华东) | Earthquake interference imaging method based on prismatic waves |
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| CN115993650A (en) * | 2023-03-22 | 2023-04-21 | 中国石油大学(华东) | Earthquake interference imaging method based on prismatic waves |
| CN115993650B (en) * | 2023-03-22 | 2023-06-06 | 中国石油大学(华东) | Earthquake interference imaging method based on prismatic waves |
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