Anisotropic medium reverse time migration imaging method and equipment for undulating surface

Abstract

The embodiment of the invention discloses an anisotropic medium reverse time migration imaging method and equipment for an undulating surface. The method comprises the following steps: determining body-fitted grid coordinates; inputting the body-fitted grid coordinates, the migration velocity field, the anisotropy parameter field and the seismic shot record, and adjusting related imaging parameters; carrying out continuation along a time forward propagation direction by adopting a wave equation to obtain a forward propagation wave field of a shot point; performing reverse continuation along the time reverse propagation direction by adopting the wave equation to obtain a reverse propagation wave field of the detection point; and cross-correlation imaging is carried out on the forward propagation wave field and the backward propagation wave field at the same moment to obtain a reverse time migration imaging result, so that the influence of the undulating surface is eliminated, and a more accurate imaging result with higher resolution is obtained.

Description

Technical Field

[0001] The present invention relates to the field of Internet technology, and in particular to a method and device for reverse time migration imaging of anisotropic media on undulating surfaces. Background Art

[0002] In seismic exploration and seismology, the properties and occurrence of underground media can be obtained through seismic wave forward modeling, migration imaging and velocity inversion technology. Usually, these methods are based on the assumption of horizontal surface and are not very adaptable to undulating surfaces. The undulating surface will have a great impact on the seismic wave field and seismic cannon records. If these effects are ignored during the imaging process, accurate imaging results will not be obtained.

[0003] The body-fitting grid is a curved grid that has good adaptability to undulating surfaces. Using this grid to deal with undulating surface problems can eliminate false scattered waves caused by step discretization, correct the impact of terrain undulations, and accurately simulate the propagation process of seismic waves underground.

[0004] Based on this, a more accurate migration imaging solution suitable for undulating terrain is needed. Summary of the invention

[0005] The embodiments of this specification provide a reverse time migration imaging method for anisotropic media on an undulating surface, which is used to solve the following technical problem: a more accurate migration imaging solution suitable for undulating terrain is needed.

[0006] To solve the above technical problems, one or more embodiments of this specification are implemented as follows:

[0007] In a first aspect, an embodiment of the present specification provides a more accurate migration imaging method suitable for undulating terrain, comprising:

[0008] Determine body-fitting grid coordinates;

[0009] Input the body-fitting grid coordinates, migration velocity field, anisotropic parameter field, seismic shot records and adjust relevant imaging parameters;

[0010] The following wave equation is used to extend along the time forward propagation direction to obtain the forward propagation wave field of the shot point:

[0011]

[0012] Among them, u, w are the vibration velocities of the particle, p, q are the horizontal and vertical components of stress, ρ is the medium density, ε, δ are the anisotropy parameters, V p is the medium velocity;

[0013] in, J is the Jacobian determinant and its value is non-zero;

[0014] The wave equation is used to perform reverse extension along the time reverse propagation direction to obtain the reverse propagation wave field of the detection point;

[0015] The forward wave field and the reverse wave field at the same time are cross-correlated and imaged to obtain the reverse time migration imaging result.

[0016] In a second aspect, one or more embodiments of this specification provide an electronic device, including:

[0017] at least one processor; and,

[0018] a memory communicatively connected to the at least one processor; wherein,

[0019] The memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to perform the method according to the first aspect.

[0020] At least one of the above-mentioned technical solutions adopted in one or more embodiments of the present specification can achieve the following beneficial effects: by determining the body-fitting grid coordinates; inputting the body-fitting grid coordinates, the migration velocity field, the anisotropic parameter field, the seismic shot record and adjusting the relevant imaging parameters; using the wave equation to extend along the forward propagation direction of time to obtain the forward wave field of the shot point; using the wave equation to reversely extend along the reverse propagation direction of time to obtain the reverse wave field of the detection point; cross-correlating the forward wave field and the reverse wave field at the same time to obtain the reverse time migration imaging result, thereby eliminating the influence of the undulating surface and obtaining a higher resolution and more accurate imaging result. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of this specification or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0022] Figure 1 A schematic flow chart of a method for reverse time migration imaging of anisotropic media on an undulating surface provided in an embodiment of this specification;

[0023] Figure 2 A schematic diagram of a body-fitting grid provided in an embodiment of this specification;

[0024] Figure 3 A schematic diagram of a velocity field provided in an embodiment of this specification;

[0025] Figure 4 A schematic diagram of the anisotropy parameter ε provided in the embodiments of this specification;

[0026] Figure 5 A schematic diagram of anisotropy parameter δ provided in an embodiment of this specification;

[0027] Figure 6 A snapshot of the seismic wave field provided in the embodiments of this specification;

[0028] Figure 7 Single shot record provided for the embodiment of this specification;

[0029] Figure 8 This is the result of acoustic isotropic reverse time migration imaging using conventional technology;

[0030] Fig. 9 This is the reverse time migration imaging result of anisotropic media with undulating surface adopted in the embodiments of this specification. DETAILED DESCRIPTION

[0031] The embodiments of the present specification provide a method and device for reverse time migration imaging of anisotropic media on an undulating surface.

[0032] In order to enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below in conjunction with the drawings in the embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this application, not all of them. Based on the embodiments of this specification, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this application.

[0033] like Figure 1 As shown, Figure 1 A schematic flow chart of a method for reverse time migration imaging of anisotropic media on an undulating surface provided in an embodiment of the present specification.

[0034] Figure 1 The process in may include the following steps:

[0035] S102: Determine body-fitting grid coordinates.

[0036] Specifically, the body-fitting grid coordinates can be calculated using the following equations.

[0037]

[0038] Where (x, y) is the grid coordinate value of the physical domain, (ξ, η) is the grid coordinate value of the computational domain, and ξ xx ,ξ yy ,ηxx ,η yy It represents the second-order partial derivatives of ξ and η with respect to x and y. P and Q are source terms. By obtaining the source terms, the trend of the grid can be controlled, thereby directly controlling the quality of grid generation.

[0039] S104, inputting the body-fitting grid coordinates, migration velocity field, anisotropic parameter field, seismic shot records and adjusting relevant imaging parameters.

[0040] The relevant imaging parameters include the number of grid points nx, nz of the model, the spatial sampling interval dx, dz of the model, the time sampling interval dt, the maximum recording time tmax, the number of excitation shots ns, the shot spacing ds, the number of receiving channels ng, the channel spacing dg, and the main frequency f of the source wavelet.

[0041] S106, using the following wave equation to extend along the time forward propagation direction to obtain the forward propagation wave field of the shot point.

[0042]

[0043] Among them, u, w are the vibration velocities of the particle, p, q are the horizontal and vertical components of stress, ρ is the medium density, ε, δ are the anisotropy parameters, V p is the medium velocity. When extended in different directions, the q component can characterize the forward wave field and the reverse wave field of the image respectively;

[0044] The vertical component q of stress is used as the forward wave field and the reverse wave field in the imaging process. The coordinate conversion coefficient in the above equation is It can be solved by the following equation.

[0045]

[0046] where J is the Jacobian determinant and its value cannot be zero.

[0047] S108, using the wave equation to extend along the time reverse propagation direction to obtain the reverse propagation wave field of the detection point.

[0048] The wave equations used to calculate the forward and reverse wave fields are the same, except that the time propagation directions are opposite.

[0049] S110, performing cross-correlation imaging on the forward wave field and the reverse wave field at the same time to obtain a reverse time migration imaging result.

[0050] By introducing a normalization processing method, the amplitude of the imaging result obtained under the cross-correlation imaging condition is improved, and the influence of the source or the detection point is eliminated, so as to obtain an imaging result closer to the actual formation reflection coefficient. The source normalized cross-correlation imaging condition proposed by Kaelin and Guitton is adopted, and the specific expression is as follows:

[0051]

[0052] Among them, Image(x,z) is the imaging result, Indicates the superposition of the cross-correlation results of all guns. Indicates the superposition of the cross-correlation results at all times, S s (x,z,t) represents the forward wave field at time t, R s (x,z,t) The back propagation wave field at time t.

[0053] The method comprises the following steps: determining body-fitting grid coordinates; inputting the body-fitting grid coordinates, migration velocity field, anisotropic parameter field, seismic shot records and adjusting relevant imaging parameters; using the wave equation to extend along the forward propagation direction of time to obtain the forward wave field of the shot point; using the wave equation to extend in the reverse propagation direction of time to obtain the reverse wave field of the detection point; performing cross-correlation imaging on the forward wave field and the reverse wave field at the same time to obtain the reverse time migration imaging result, thereby eliminating the influence of the undulating surface and obtaining a higher resolution and more accurate imaging result.

[0054] In order to explain the method of the present invention in more detail, the applicant also conducted the following specific experiments to provide the actual application effect of the present invention in the modified Hess model.

[0055] Figure 2 This is the generated body-fitting mesh. It can be seen that the generated body-fitting mesh adapts well to the undulating surface, has good orthogonality near the surface, and has good smoothness inside the mesh.

[0056] The model has an undulating surface and strong anisotropy. Input migration velocity field (such as Figure 3 As shown), anisotropy parameter ε (as shown Figure 4 As shown in), anisotropy parameter δ (as shown in Figure 5 and establish a corresponding observation system.

[0057] Based on the above parameters, the acoustic wave equation of anisotropic medium with undulating surface is simulated forward, and the seismic wave field snapshot is obtained (such as Figure 6 as shown) and single shot records (as shown Figure 7 As shown in the figure). It can be seen from the wave field snapshot that there are no false scattered waves near the undulating surface and there is no dispersion phenomenon in the wave field, which shows that the forward simulation method of the present invention can eliminate the influence of the undulating surface and obtain correct numerical simulation results, which is a prerequisite for subsequent accurate imaging. It can be found from the single shot record that the reflected wave event axis is distorted to varying degrees due to the influence of the undulating surface. If this influence is ignored in the subsequent imaging process, accurate results cannot be obtained.

[0058] The forward wave field at each moment is obtained by forward modeling the acoustic wave equation of anisotropic media on the undulating surface, and then the reverse wave field at each moment is obtained by reverse time propagation. Finally, imaging is performed using the cross-correlation imaging condition to obtain the reverse time migration imaging section. Figure 8 It is a conventional technique of acoustic isotropic reverse time migration imaging. Fig. 9 It is the reverse time migration imaging result of the anisotropic medium on the undulating surface of the present invention.

[0059] Compared with the acoustic isotropic reverse time migration results of conventional technology, the reflection wave event axis near the salt dome boundary in the imaging section of this application can be correctly reset, such as Figure 8 and Fig. 9 As shown in the box. In addition, the diffraction waves at the fault position in the imaging section of the present application converge, the fault section is clear, and the resolution is higher, such as Figure 8 and Fig. 9 Shown in the oval box.

[0060] In summary, the reverse time migration imaging method for anisotropic media with undulating surfaces proposed in the present invention can eliminate the influence of undulating surfaces, accurately simulate the propagation law of seismic waves in underground media, achieve high-precision and high-resolution imaging of underground structures, and provide a basic guarantee for the subsequent accurate interpretation of complex geological structures.

[0061] 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 anisotropic medium reverse time migration imaging method for an undulating surface is implemented.

[0062] 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.

[0063] The above is a description of a specific embodiment of the specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps or modules recorded in the claims can be performed in an order different from that in the embodiments and still achieve the desired results. In addition, the processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0064] The above description is only one or more embodiments of this specification and is not intended to limit this specification. For those skilled in the art, one or more embodiments of this specification may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of one or more embodiments of this specification shall be included in the scope of the claims of this specification.

Claims

1. A method for reverse time migration imaging of anisotropic media on an undulating surface, comprising: Determine body-fitting grid coordinates; Input the body-fitting grid coordinates, migration velocity field, anisotropic parameter field, seismic shot records and adjust relevant imaging parameters; The following wave equation is used to extend along the time forward propagation direction to obtain the forward propagation wave field of the shot point: Among them, u, w are the vibration velocities of the particle, p, q are the horizontal and vertical components of stress, ρ is the medium density, ε, δ are the anisotropy parameters, V p is the medium velocity; in, J is the Jacobian determinant and its value is non-zero; The wave equation is used to perform reverse extension along the time reverse propagation direction to obtain the reverse propagation wave field of the detection point; The forward wave field and the reverse wave field at the same time are cross-correlated and imaged to obtain the reverse time migration imaging result.

2. The method of claim 1, wherein: Determine the body-fitting grid coordinates, including: The body-fitting grid coordinates are determined as follows: Where (x, y) is the grid coordinate value of the physical domain, (ξ, η) is the grid coordinate value of the computational domain, and ξ xx ,ξ yy ,η xx ,η yy They represent the second-order partial derivatives of ξ and η with respect to x and y respectively, and P and Q are source terms.

3. The method of claim 1, wherein: The forward wave field and the reverse wave field at the same time are cross-correlated and imaged to obtain the reverse time migration imaging results, including: Cross-correlation imaging is performed in the following manner: Among them, Image(x,z) is the reverse time migration imaging result, Indicates the superposition of the cross-correlation results of all guns. Indicates the superposition of the cross-correlation results at all times, S s (x,z,t) represents the forward wave field at time t, R s (x,z,t) The back propagation wave field at time t.

4. An electronic device comprising: at least one processor; as well as, a memory communicatively connected to the at least one processor; wherein, The memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to perform the method according to any one of claims 1 to 3.

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