A method, apparatus, device and readable medium for constraining first arrival tomographic inversion

Abstract

The application discloses a method for constraining first arrival tomographic inversion, comprising the following steps: converting a depth-time curve into a depth-grid velocity curve, and horizontally deploying a surface elevation to build a high-speed top interface; obtaining an initial tomographic model containing a surface elevation, and dividing the initial tomographic model into a plurality of grids based on a preset size; subtracting the elevation corresponding to each grid from the high-speed top interface respectively to obtain the depth corresponding to each grid, and obtaining the grid velocity corresponding to each grid based on the depth corresponding to each grid and the depth-grid velocity curve; marking the grid velocity corresponding to each grid in the corresponding grid respectively, and performing linear interpolation on the grids below the high-speed top interface based on a preset initial velocity and a preset maximum velocity to obtain a velocity model; and establishing a constraint model based on a weight function and the velocity model, performing tomographic inversion based on the constraint model, and updating the velocity model based on the weight function in the tomographic inversion process.

Description

Technical Field

[0001] This invention relates to the field of near-surface modeling and static correction technology in seismic exploration, and in particular to a method, apparatus, equipment and readable medium for constrained first-arrival tomographic inversion. Background Technology

[0002] First-arrival tomographic inversion is currently the most common method for establishing near-surface velocity models. This method yields a time-equivalent velocity model, providing a relatively accurate near-surface velocity model for true surface depth migration. To further improve the accuracy of the velocity model in tomographic inversion, surface survey results are typically used to constrain the tomographic inversion method. However, due to the limited number of data points and shallow depth of surface surveys, the constraint model required for tomographic inversion is usually established through numerical interpolation. This model has low accuracy and is not effective for constraining tomographic inversion.

[0003] In desert regions, the high-velocity top interface is relatively flat, and near-surface velocity exhibits a clear correlation with depth. A mature static correction method using time-depth curves (depth-time curves) exists. This method uses the time-depth curve and a known high-velocity top interface to obtain accurate velocity values ​​above the high-velocity top interface from the curve, thus calculating accurate static correction values. A near-surface velocity model directly established using time-depth curves represents the average velocity in the vertical direction, from the surface to the high-velocity top interface, and is also an equivalent velocity value. However, conventional tomography uses network tomography, which consists of multiple grids in the vertical direction. The velocity in each grid is a constant, and the velocity gradually changes from shallow to deep. Therefore, the velocity model established using time-depth curves cannot be directly used with the constrained model derived from tomography. Summary of the Invention

[0004] In view of this, the purpose of this invention is to propose a method, apparatus, device and readable medium for constrained first-arrival tomographic inversion. By establishing a constrained model with continuous medium characteristics through time-depth curves, a velocity model of the deep layer below the high-velocity top interface is obtained while ensuring that the overall accuracy of the low-velocity layer velocity and static correction remains unchanged, thus providing a high-precision near-surface velocity model for migration.

[0005] To achieve the above objectives, one aspect of this invention provides a method for constrained first-arrival tomographic inversion, comprising the following steps: converting a depth-time curve into a depth-grid velocity curve, and horizontally deploying the surface elevation to construct a high-velocity top interface; obtaining an initial tomographic model containing the surface elevation, and dividing the initial tomographic model into several grids based on a preset size; subtracting the elevation corresponding to each grid from the high-velocity top interface to obtain the depth corresponding to each grid, and obtaining the grid velocity corresponding to each grid based on the depth corresponding to each grid and the depth-grid velocity curve; marking the grid velocity corresponding to each grid in the corresponding grid, and performing linear interpolation on the grid below the high-velocity top interface based on a preset initial velocity and a preset maximum velocity to obtain a velocity model; establishing a weight function based on the depth direction, establishing a constraint model based on the weight function and the velocity model, performing tomographic inversion based on the constraint model, and updating the velocity model based on the weight function during the tomographic inversion process.

[0006] In some implementations, converting a depth-time curve into a depth-mesh velocity curve includes: acquiring a depth-time curve and converting the depth-time curve into a depth-mesh velocity curve based on the time difference at different depths and the mesh size.

[0007] In some implementations, converting the depth-time curve into a depth-mesh velocity curve based on the time difference at different depths and the mesh size includes calculating the mesh velocity based on the following formula:

[0008]

[0009] Among them, v i Let dz be the mesh velocity of the i-th mesh in the depth direction, dz be the mesh size in the depth direction, and t be the mesh velocity of the ith mesh in the depth direction. i+1 Let t be the time corresponding to the (i+1)th grid. i Let be the time corresponding to the i-th grid.

[0010] In some implementations, the method further includes smoothing the grid velocity based on the following formula:

[0011]

[0012] Among them, v is v is the smoothed mesh velocity of the i-th mesh in the depth direction. i Let r be the mesh velocity of the i-th mesh in the depth direction, r be the smoothing radius, and n be the total number of points involved in the calculation.

[0013] In some implementations, the method of horizontally displaying the surface elevation to construct a high-speed top interface includes: searching for the minimum surface elevation in each grid based on a preset grid size, and shifting the minimum elevation point in each grid down by a preset depth to obtain several discrete elevation values; and constructing the high-speed top interface based on the several discrete elevation values.

[0014] In some implementations, the method further includes: determining whether the horizontal distance between the minimum elevation points of adjacent grids is less than a preset distance; if the horizontal distance between the minimum elevation points of adjacent grids is less than the preset distance, then deleting the point with the larger surface elevation.

[0015] In some implementations, linear interpolation of the mesh below the high-speed top interface based on a preset initial velocity and a preset maximum velocity includes: setting the mesh velocity of the first mesh below the high-speed top interface based on the preset initial velocity, and setting the mesh velocity of the bottom mesh of the model based on the preset maximum velocity; calculating the mesh velocity corresponding to each mesh between the high-speed top interface and the bottom of the model based on the number of meshes between the high-speed top interface and the bottom of the model.

[0016] In some implementations, calculating the mesh velocity corresponding to each mesh between the high-speed top interface and the bottom of the model, based on the number of meshes between the high-speed top interface and the bottom of the model, includes: calculating the mesh velocity corresponding to each mesh between the high-speed top interface and the bottom of the model based on the following formula:

[0017] v i =v0+(v1-v0)*i / n

[0018] Where i is the i-th mesh below the high-speed top interface, n is the number of meshes between the high-speed top interface and the bottom of the model, v0 is the preset initial velocity, v1 is the preset maximum velocity, and v i Let be the mesh velocity of the i-th mesh below the high-speed top interface.

[0019] In some implementations, establishing a depth-oriented weighting function includes establishing the depth-oriented weighting function based on the following formula:

[0020]

[0021] Where w(x) is the weight function in the depth direction, h is the depth value from the ground surface to the high-speed interface, and f(x) is a preset function with a value between [0, 1].

[0022] In some implementations, updating the velocity model based on the weight function during the tomographic inversion process includes: updating the slowness based on the weight function during the tomographic inversion process, and updating the velocity based on the weight function after the tomographic inversion to perform a smoothing operation on the model.

[0023] In some implementations, updating the slowness based on the weight function during the tomographic inversion process includes updating the slowness based on the following formula during the tomographic inversion process:

[0024] s new =s old +ds*w(x)

[0025] Among them, s new For the updated slowness, s old ds is the reciprocal of the grid velocity, w(x) is the change in the reciprocal of the grid velocity obtained from the tomographic inversion, and w(x) is the weighting function.

[0026] In some implementations, updating the velocity based on the weight function after tomographic inversion to smooth the model includes updating the velocity based on the following formula after tomographic inversion:

[0027] v new =v old +dv*w(x)

[0028] Among them, v new v is the speed of the smoothed grid. old dv represents the mesh velocity before smoothing, w(x) represents the change in mesh velocity after the smoothing operation, and w(x) represents the weight function.

[0029] In another aspect of this invention, an apparatus for constrained first-arrival tomographic inversion is provided, comprising: a first module configured to convert a depth-time curve into a depth-grid velocity curve and to horizontally deploy the surface elevation to construct a high-velocity top interface; a second module configured to acquire an initial tomographic model including the surface elevation and to divide the initial tomographic model into several grids based on a preset size; a third module configured to subtract the elevation corresponding to each grid from the high-velocity top interface to obtain the depth corresponding to each grid, and to obtain the grid velocity corresponding to each grid based on the depth corresponding to each grid and the depth-grid velocity curve; a fourth module configured to mark the grid velocity corresponding to each grid in the corresponding grid, and to perform linear interpolation on the grid below the high-velocity top interface based on a preset initial velocity and a preset maximum velocity to obtain a velocity model; and a fifth module configured to establish a weight function based on the depth direction, establish a constraint model based on the weight function and the velocity model, perform tomographic inversion based on the constraint model, and update the velocity model based on the weight function during the tomographic inversion process.

[0030] In another aspect of the present invention, a computer device is provided, comprising: at least one processor; and a memory storing computer instructions executable on the processor, the instructions, when executed by the processor, implementing the steps of the above-described method.

[0031] In another aspect, the present invention provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described method steps.

[0032] The present invention has at least the following beneficial technical effects: by using the time-depth curve in combination with the given high-velocity layer top interface, the velocity model of the low-velocity layer is determined, and this model is used to constrain the tomographic inversion. While ensuring that the overall accuracy of the low-velocity layer velocity and static correction remains unchanged, the velocity model of the deeper layers below the high-velocity layer top interface is obtained, providing a high-precision near-surface velocity model for migration.

[0033] For the Dasha area, the top interface of the high-speed road is flat and stable, and the near-surface velocity sometimes has deep curve characteristics. The near-surface model required for the first-arrival tomographic constraint established by the method of this invention not only ensures the accuracy of the near-surface velocity and static correction, but also inverses the velocity model of deeper layers through tomographic methods, providing a reasonable near-surface velocity model and static correction for processing. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0035] Figure 1 A schematic diagram of an embodiment of the constrained first-arrival tomographic inversion method provided by the present invention;

[0036] Figure 2 (a) is a schematic diagram of the depth-time curve;

[0037] Figure 2 (b) is a schematic diagram of the depth-mesh velocity curve;

[0038] Figure 3 (a) is a plane distribution map of the ground elevation;

[0039] Figure 3 (b) is a planar distribution diagram of the high-speed top interface;

[0040] Figure 4 A velocity model for an embodiment of the constrained first-arrival tomographic inversion method provided by the present invention;

[0041] Figure 5 This is a schematic diagram of the weighting function;

[0042] Figure 6 A schematic diagram of an embodiment of the constrained first-arrival tomography inversion apparatus provided by the present invention;

[0043] Figure 7 A schematic diagram of an embodiment of the computer device provided by the present invention;

[0044] Figure 8 A schematic diagram illustrating an embodiment of the computer-readable storage medium provided by the present invention. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0046] It should be noted that all uses of "first" and "second" in the embodiments of the present invention are for the purpose of distinguishing two entities or parameters with the same name but different names. It is clear that "first" and "second" are only for the convenience of expression and should not be construed as limiting the embodiments of the present invention. Subsequent embodiments will not explain this in detail.

[0047] Based on the above objectives, a first aspect of the present invention provides an embodiment of a method for constrained first-arrival tomographic inversion. Figure 1 The diagram shown is a schematic representation of an embodiment of the constrained first-arrival tomography inversion method provided by the present invention. Figure 1 As shown, the constrained first-arrival tomography inversion method of this invention includes the following steps:

[0048] 001. Convert the depth-time curve into a depth-grid velocity curve, and horizontally deploy the surface elevation to construct a high-speed top interface;

[0049] 002. Obtain the initial tomographic model containing the surface elevation, and divide the initial tomographic model into several grids based on the preset size;

[0050] 003. Subtract the elevation of each grid from the top interface of the high-speed network to obtain the depth of each grid, and obtain the grid velocity of each grid based on the depth of each grid and the depth-grid velocity curve;

[0051] 004. Mark the mesh velocity corresponding to each mesh in the corresponding mesh, and perform linear interpolation on the mesh below the high-speed top interface based on the preset initial velocity and preset maximum velocity to obtain the velocity model; and

[0052] 005. Establish a weight function based on the depth direction, and establish a constraint model based on the weight function and the velocity model. Perform tomographic inversion based on the constraint model, and update the velocity model based on the weight function during the tomographic inversion process.

[0053] In this embodiment, a regular grid model with continuous surface velocity characteristics is established based on the known time-depth curve and the high-velocity top interface, serving as the near-surface constraint model for first-arrival tomography inversion. For the Dasha area, the high-velocity top interface is flat and stable, and the near-surface velocity exhibits time-depth curve characteristics. The near-surface model established using the method of this invention, required for first-arrival tomography constraints, ensures the accuracy of near-surface velocity and static corrections, and also inverts deeper velocity models through tomography, providing a reasonable near-surface velocity model and static corrections for processing. The main steps include:

[0054] (1) Use time-depth curves to establish a grid model of single-point continuous medium characteristics: the time-depth curve is a depth-time curve, and the tomographic inversion requires a depth-grid velocity curve. Based on the time difference and grid size in different depths, the depth-time curve is converted into a depth-grid velocity curve.

[0055] (2) Establish the high-speed top interface of the work area using the ground surface: For the ground surface grid elevation of the model, take the lowest point of elevation within a certain range, and then subtract a fixed depth to obtain the discrete value of the lowest elevation point within the model range. Then use these discrete points to linearly interpolate to obtain the high-speed top interface.

[0056] (3) Establish the initial velocity model for tomographic inversion using the depth-velocity curve: The depth is obtained by subtracting the high-velocity top interface from the surface elevation of the model (established in step 2). The grid velocity is extracted from the depth-grid velocity curve (established in step 1) to establish the velocity model above the high-velocity top interface. Based on the initial velocity and maximum velocity given by the user under the high-velocity top interface, the velocity between the high-velocity top interface and the bottom of the model is linearly interpolated to obtain the initial model for tomographic inversion.

[0057] (4) Determine the weight function of the constraint mesh between the surface and the top interface of the high-speed: Set the model constraint weight between the surface elevation and the top interface of the high-speed according to the accuracy of the time-depth curve. The value is between [0, 1]. The weight value can be a constant or it can vary with the depth. Set a weight gradient zone within a certain depth below the top interface of the high-speed.

[0058] (5) Tomographic inversion velocity update strategy: When updating the model during tomographic inversion, the slowness (reciprocal of velocity) value is updated according to the weight (established in step 4); when the model is smoothed, the velocity value is also updated according to the weight value.

[0059] In some embodiments of the present invention, converting a depth-time curve into a depth-mesh velocity curve includes: obtaining a depth-time curve and converting the depth-time curve into a depth-mesh velocity curve based on the time difference and mesh size at different depths.

[0060] In this embodiment, reference Figure 2 (a) and Figure 2 (b), Figure 2 (a) shows the depth-time curve. Figure 2 (b) shows the depth-mesh velocity curve.

[0061] In some embodiments of the present invention, converting the depth-time curve into a depth-mesh velocity curve based on the time difference at different depths and the mesh size includes: calculating the mesh velocity based on the following formula:

[0062]

[0063] Among them, v i Let dz be the mesh velocity of the i-th mesh in the depth direction, dz be the mesh size in the depth direction, and t be the mesh velocity of the ith mesh in the depth direction. i+1 Let t be the time corresponding to the (i+1)th grid. i Let be the time corresponding to the i-th grid.

[0064] In this embodiment, the known depth-time curve is composed of a set of discrete depth-time sampling points, and the time in the curve is the cumulative time value from the surface to a certain depth. Therefore, the depth-time curve is converted into a depth-grid velocity curve according to the following formula.

[0065]

[0066] Among them, v i Let d be the mesh velocity of the i-th mesh in the depth direction, dz be the mesh size in the depth direction (usually a constant), and t be the mesh velocity of the ith mesh in the depth direction. i+1 Let t be the time corresponding to the (i+1)th grid. i Let be the time corresponding to the i-th grid.

[0067] In some embodiments of the present invention, the method further includes: smoothing the grid velocity based on the following formula:

[0068]

[0069] Among them, v is v is the smoothed mesh velocity of the i-th mesh in the depth direction. i Let r be the mesh velocity of the i-th mesh in the depth direction, r be the smoothing radius, and n be the total number of points involved in the calculation.

[0070] In this embodiment, due to errors in sampling accuracy and curve data, the calculated grid velocity is not smooth and continuous, and the grid velocity needs to be smoothed using the following formula.

[0071]

[0072] Among them, v is v is the smoothed mesh velocity of the i-th mesh in the depth direction. i Let r be the mesh velocity of the i-th mesh in the depth direction, r be the smoothing radius (r is the number of meshes), and n be the total number of data points involved in the velocity smoothing calculation.

[0073] In some embodiments of the present invention, the method of horizontally displaying the surface elevation to construct a high-speed top interface includes: searching for the minimum surface elevation in each grid based on a preset grid size, and shifting the minimum elevation point in each grid down by a preset depth to obtain several discrete elevation values; and constructing a high-speed top interface based on several discrete elevation values.

[0074] In this embodiment, based on the grid origin coordinates and rotation angle information used in establishing the initial model using tomography, the coordinates of the receiver and excitation points measured in the field are rotated. An elevation distribution map of the receiver and excitation points is then generated based on the rotated coordinates. The approximate distance d between sand dunes is measured on the elevation distribution map. The coordinates of the rotated receiver and excitation points are then divided into square grids with d as the horizontal dimension. The minimum elevation value e falling within each grid is then searched. xy Record the coordinates and elevation values ​​of the minimum elevation to obtain discrete point information of the minimum elevation in each grid; and convert the collected discrete point elevation values ​​e xy Simultaneously, a depth constant value is subtracted, and these are used as discrete values ​​for the high-speed top interface. These discrete values ​​are used to construct a high-speed top interface with the same origin coordinates, rotation angle, horizontal mesh direction, size, and number as the initial tomography model.

[0075] In some embodiments of the present invention, the method further includes: determining whether the horizontal distance between the minimum elevation points of adjacent grids is less than a preset distance; if the horizontal distance between the minimum elevation points of adjacent grids is less than the preset distance, then deleting the point with the larger ground elevation.

[0076] In this embodiment, if the horizontal distance between the searched discrete points in adjacent grids is less than d / 2, the discrete point information of the point with the larger elevation value is deleted.

[0077] In some embodiments of the present invention, linear interpolation of the mesh below the high-speed top interface based on a preset initial speed and a preset maximum speed includes: setting the mesh speed of the first mesh below the high-speed top interface based on the preset initial speed, and setting the mesh speed of the bottom mesh of the model based on the preset maximum speed; calculating the mesh speed corresponding to each mesh between the high-speed top interface and the bottom of the model based on the number of meshes between the high-speed top interface and the bottom of the model.

[0078] In this embodiment, the same processing is performed on each grid of the initial model of the tomography in the horizontal direction to obtain the corresponding velocity value; the vertical range is determined based on the known elevation and high-velocity top interface, and the corresponding depth value Depth of each grid is obtained in the vertical grid size dz within the range. Then, the velocity value at the corresponding Depth position is obtained from the depth-grid velocity curve and filled back into the corresponding grid of the tomography model.

[0079] In some embodiments of the present invention, calculating the mesh velocity corresponding to each mesh between the high-speed top interface and the bottom of the model based on the number of meshes between the high-speed top interface and the bottom of the model includes: calculating the mesh velocity corresponding to each mesh between the high-speed top interface and the bottom of the model based on the following formula:

[0080] v i=v0+(v1-v0)*i / n

[0081] Where i is the i-th mesh below the high-speed top interface, n is the number of meshes between the high-speed top interface and the bottom of the model, v0 is the preset initial velocity, v1 is the preset maximum velocity, and v i Let be the mesh velocity of the i-th mesh below the high-speed top interface.

[0082] In this embodiment, the velocity values ​​of the intermediate meshes between the high-speed top interface and the bottom of the tomographic model are interpolated using the following formula:

[0083] v i =v0+(v1-v0)*i / n

[0084] Where i is the i-th mesh below the high-speed top interface, n is the number of meshes between the high-speed top interface and the bottom of the model, v0 is the preset initial velocity, v1 is the preset maximum velocity, and v i Let be the mesh velocity of the i-th mesh below the high-speed top interface.

[0085] In some embodiments of the present invention, establishing a depth-oriented weighting function includes establishing the depth-oriented weighting function based on the following formula:

[0086]

[0087] Where w(x) is the weight function in the depth direction, h is the depth value from the ground surface to the high-speed interface, and f(x) is a preset function with a value between [0, 1].

[0088] In this embodiment, the constraint weight function for the entire model is constructed, and the function satisfies the following conditions:

[0089]

[0090] Where w(x) is the weighting function in the depth direction, h is the depth value from the surface to the high-velocity interface, and f(x) is a preset function with a value between [0, 1]. At the surface, the weight is zero, indicating that the velocity value at the surface remains unchanged during inversion; between the high-velocity top interface and the model bottom, the weight is 1, indicating that it can be 100% changed during tomographic inversion; the weight w between the surface and the high-velocity top interface increases with h, with a value between 0 and 1, indicating that it can be slightly changed during tomographic inversion.

[0091] Using a weighting function, an initial model, and a high-velocity top interface, constraint weights are established for each grid in the entire tomographic network model based on the surface elevation and the depth value of the high-velocity top interface, which are then used for constrained tomographic inversion.

[0092] In some embodiments of the present invention, updating the velocity model based on a weight function during the tomographic inversion process includes: updating the slowness based on a weight function during the tomographic inversion process, and updating the velocity based on a weight function after the tomographic inversion to perform a smoothing operation on the model.

[0093] In some embodiments of the present invention, updating the slowness based on a weight function during the tomographic inversion process includes updating the slowness based on the following formula during the tomographic inversion process:

[0094] s new =s old +ds*w(x)

[0095] Among them, s new For the updated slowness, s old ds is the reciprocal of the grid velocity, w(x) is the change in the reciprocal of the grid velocity obtained from the tomographic inversion, and w(x) is the weighting function.

[0096] In some embodiments of the present invention, updating the velocity based on a weight function after tomographic inversion to smooth the model includes updating the velocity based on the following formula after tomographic inversion:

[0097] v new =v old +dv*w(x)

[0098] Among them, v new v is the speed of the smoothed grid. old dv represents the mesh velocity before smoothing, w(x) represents the change in mesh velocity after the smoothing operation, and w(x) represents the weight function.

[0099] The specific embodiments of the present invention are further described below with reference to specific examples.

[0100] refer to Figure 2 (a) and Figure 2 (b) Convert the depth-time curve into a depth-mesh velocity curve. Figure 2 (a) shows the depth-time curve. Figure 2 (b) shows the depth-mesh velocity curve.

[0101] refer to Figure 3 (a) and Figure 3 (b), Figure 3 (a) shows a horizontal distribution map of the ground elevation. The ground elevation is horizontally distributed, and a minimum value is searched in each grid with a size of 4000m. The point with the minimum elevation in the grid is taken and moved down 20m to obtain discrete values. These discrete values ​​are then used to construct the grid-based high-speed top interface within the work area. The grid orientation, size, origin coordinates, and rotation angle of this interface are completely consistent with the tomographic model. The results are as follows: Figure 3 As shown in (b).

[0102] refer to Figure 4 , Figure 4 The diagram illustrates the velocity model of an embodiment of the constrained first-arrival tomographic inversion method provided by the invention. Based on the elevation, high-velocity top interface, and depth-grid velocity curves, a grid velocity model is established above the high-velocity top interface. Below the high-velocity top interface, the velocity is filled to the bottom of the model using a linear increment of 1600 m / s. The results are as follows: Figure 4 As shown.

[0103] refer to Figure 5 , Figure 5 The diagram shows a weighting function, establishing weight constraints for the depth-direction model, as shown below. Figure 5 As shown.

[0104] When performing conventional tomographic inversion, constraint weights are used to constrain the rate change during rate updates.

[0105] It should be particularly noted that the steps in each embodiment of the above-described constrained first-arrival tomography inversion method can be interleaved, substituted, added, or deleted. Therefore, these reasonable permutations and combinations of the constrained first-arrival tomography inversion method should also fall within the protection scope of this invention, and the protection scope of this invention should not be limited to the embodiments.

[0106] Based on the above objectives, a second aspect of the present invention provides an apparatus for constrained first-arrival tomography inversion. Figure 2 The diagram shown is a schematic representation of an embodiment of the constrained first-arrival tomography inversion apparatus provided by the present invention. Figure 2 As shown, the constrained first-arrival tomographic inversion apparatus of this invention includes the following modules: a first module 011, configured to convert the depth-time curve into a depth-grid velocity curve and horizontally expand the surface elevation to construct a high-velocity top interface; a second module 012, configured to acquire an initial tomographic model containing the surface elevation and divide the initial tomographic model into several grids based on a preset size; a third module 013, configured to subtract the elevation corresponding to each grid from the high-velocity top interface to obtain the depth corresponding to each grid, and acquire the grid velocity corresponding to each grid based on the depth corresponding to each grid and the depth-grid velocity curve; a fourth module 014, configured to mark the grid velocity corresponding to each grid in the corresponding grid, and perform linear interpolation on the grid below the high-velocity top interface based on a preset initial velocity and a preset maximum velocity to obtain a velocity model; and a fifth module 015, configured to establish a weight function based on the depth direction, establish a constraint model based on the weight function and the velocity model, perform tomographic inversion based on the constraint model, and update the velocity model based on the weight function during the tomographic inversion process.

[0107] In view of the above objectives, a third aspect of the present invention provides a computer device. Figure 3 The diagram shown is a schematic representation of an embodiment of the computer device provided by the present invention. Figure 3 As shown, the computer device of this embodiment includes the following means: at least one processor 021; and a memory 022, the memory 022 storing computer instructions 023 that can be executed on the processor, the instructions implementing the steps of the above method when executed by the processor.

[0108] The present invention also provides a computer-readable storage medium. Figure 4 The diagram shown is a schematic representation of an embodiment of the computer-readable storage medium provided by the present invention. Figure 4 As shown, computer-readable storage medium 031 stores a computer program 032 that, when executed by a processor, performs the methods described above.

[0109] Finally, it should be noted that those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The program for constrained first-arrival tomography inversion can be stored in a computer-readable storage medium. When executed, the program can include the processes of the embodiments of the above methods. The storage medium for the program can be a magnetic disk, optical disk, read-only memory (ROM), or random access memory (RAM), etc. The above computer program embodiments can achieve the same or similar effects as any of the corresponding foregoing method embodiments.

[0110] Furthermore, the method disclosed in the embodiments of the present invention can also be implemented as a computer program executed by a processor, which may be stored in a computer-readable storage medium. When the computer program is executed by the processor, it performs the functions defined in the method disclosed in the embodiments of the present invention.

[0111] Furthermore, the above-described method steps and system units can also be implemented using a controller and a computer-readable storage medium for storing a computer program that enables the controller to perform the functions of the above-described steps or units.

[0112] Those skilled in the art will also understand that the various exemplary logic blocks, modules, circuits, and algorithm steps described in conjunction with the disclosure herein can be implemented as electronic hardware, computer software, or a combination of both. To clearly illustrate this interchangeability between hardware and software, the functionality of various illustrative components, blocks, modules, circuits, and steps has been generally described. Whether this functionality is implemented as software or as hardware depends on the specific application and the design constraints imposed on the system as a whole. Those skilled in the art can implement the functionality in various ways for each specific application, but such implementation decisions should not be construed as departing from the scope of the embodiments disclosed herein.

[0113] In one or more exemplary designs, functionality may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functionality may be stored as one or more instructions or code on or transmitted via a computer-readable medium. Computer-readable media include computer storage media and communication media, including any medium that facilitates the transfer of a computer program from one location to another. Storage media may be any available medium accessible to a general-purpose or special-purpose computer. By way of example, and not limitation, computer-readable media may include RAM, ROM, EEPROM, CD-ROM or other optical disc storage devices, disk storage devices or other magnetic storage devices, or any other medium that may be used to carry or store the required program code in the form of instructions or data structures and is accessible to a general-purpose or special-purpose computer or a general-purpose or special-purpose processor. Furthermore, any connection may be appropriately referred to as computer-readable media. For example, if software is transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DOL), or wireless technologies such as infrared, radio, and microwave, then the aforementioned coaxial cable, fiber optic cable, twisted pair, DOL, or wireless technologies such as infrared, radio, and microwave are all included in the definition of media. As used herein, disks and optical discs include compact discs (CDs), laser discs, optical discs, digital versatile discs (DVDs), floppy disks, and Blu-ray discs, where disks typically reproduce data magnetically, while optical discs reproduce data optically using lasers. Combinations of the above should also be included within the scope of computer-readable media.

[0114] The above are exemplary embodiments disclosed in this invention. However, it should be noted that various changes and modifications can be made without departing from the scope of the embodiments of this invention as defined by the claims. The functions, steps, and / or actions of the methods according to the disclosed embodiments described herein do not need to be performed in any particular order. Furthermore, although the elements disclosed in the embodiments of this invention may be described or claimed individually, they may be understood as multiple unless explicitly limited to a singular number.

[0115] It should be understood that, as used herein, the singular form “a” is intended to include the plural form as well, unless the context clearly supports an exception. It should also be understood that, as used herein, “and / or” refers to any and all possible combinations of one or more of the associated listed items.

[0116] The embodiment numbers disclosed in the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0117] Those skilled in the art will understand that all or part of the steps of the above embodiments can be implemented by hardware or by a program instructing related hardware. The program can be stored in a computer-readable storage medium, such as a read-only memory, a disk, or an optical disk.

[0118] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of different aspects of the invention exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for constrained first-arrival tomographic inversion, characterized in that, Includes the following steps: The depth-time curve is converted into a depth-grid velocity curve, and the surface elevation is horizontally laid out to construct a high-speed top interface; Obtain an initial tomographic model containing the ground elevation, and divide the initial tomographic model into several grids based on a preset size; The elevation corresponding to each grid is subtracted from the high-speed top interface to obtain the depth corresponding to each grid, and the grid velocity corresponding to each grid is obtained based on the depth corresponding to each grid and the depth-grid velocity curve; The mesh velocity corresponding to each mesh is marked in the corresponding mesh, and linear interpolation is performed on the mesh below the high-speed top interface based on the preset initial velocity and the preset maximum velocity to obtain the velocity model; as well as A depth-based weighting function is established, and a constraint model is established based on the weighting function and the velocity model. A tomographic inversion is performed based on the constraint model, and the velocity model is updated based on the weighting function during the tomographic inversion process.

2. The method for constrained first-arrival tomography inversion according to claim 1, characterized in that, Converting the depth-time curve into a depth-mesh velocity curve includes: Obtain the depth-time curve and convert it into a depth-mesh velocity curve based on the time difference and mesh size at different depths.

3. The method for constrained first-arrival tomography inversion according to claim 2, characterized in that, The conversion of the depth-time curve into a depth-mesh velocity curve based on time differences and mesh sizes at different depths includes: Calculate the grid velocity using the following formula: Among them, v i Let dz be the mesh velocity of the i-th mesh in the depth direction, dz be the mesh size in the depth direction, and t be the mesh velocity of the ith mesh in the depth direction. i+1 Let t be the time corresponding to the (i+1)th grid. i Let be the time corresponding to the i-th grid.

4. The method for constrained first-arrival tomography inversion according to claim 3, characterized in that, Also includes: The grid velocity is smoothed based on the following formula: Among them, v is v is the smoothed mesh velocity of the i-th mesh in the depth direction. i Let r be the mesh velocity of the i-th mesh in the depth direction, r be the smoothing radius, and n be the total number of points involved in the calculation.

5. The method for constrained first-arrival tomography inversion according to claim 1, characterized in that, The horizontal layout of the ground elevation to construct the high-speed top interface includes: The minimum elevation of the ground surface in each grid is searched based on a preset grid size, and the minimum elevation point in each grid is moved down by a preset depth to obtain several discrete elevation values. A high-speed top interface is constructed based on the aforementioned discrete elevation values.

6. The method for constrained first-arrival tomography inversion according to claim 5, characterized in that, Also includes: Determine whether the horizontal distance between the minimum elevation points of adjacent grids is less than a preset distance; If the horizontal distance between the minimum elevation points of adjacent grids is less than the preset distance, then the point with the larger surface elevation will be deleted.

7. The method for constrained first-arrival tomography inversion according to claim 1, characterized in that, Linear interpolation of the mesh below the high-speed top interface based on a preset initial velocity and a preset maximum velocity includes: The mesh velocity of the first mesh below the high-speed top interface is set based on a preset initial velocity, and the mesh velocity of the bottom mesh of the model is set based on a preset maximum velocity. The grid velocity corresponding to each grid between the high-speed top interface and the bottom of the model is calculated based on the number of grids between the high-speed top interface and the bottom of the model.

8. The method for constrained first-arrival tomography inversion according to claim 7, characterized in that, The calculation of the mesh velocity corresponding to each mesh between the high-speed top interface and the bottom of the model, based on the number of meshes between the high-speed top interface and the bottom of the model, includes: The mesh velocity for each mesh between the high-speed top interface and the bottom of the model is calculated using the following formula: v i =v0+(v1-v0)*i / n Where i is the i-th mesh below the high-speed top interface, n is the number of meshes between the high-speed top interface and the bottom of the model, v0 is the preset initial velocity, v1 is the preset maximum velocity, and v i Let be the mesh velocity of the i-th mesh below the high-speed top interface.

9. The method for constrained first-arrival tomography inversion according to claim 1, characterized in that, Establishing a depth-based weighting function includes: The depth-based weighting function is established based on the following formula: Where w(x) is the weight function in the depth direction, h is the depth value from the ground surface to the high-speed interface, and f(x) is a preset function with a value between [0, 1].

10. The method for constrained first-arrival tomographic inversion according to claim 1, characterized in that, Updating the velocity model based on the weighting function during the tomographic inversion process includes: During the tomographic inversion process, the slowness is updated based on the weight function, and after the tomographic inversion, the velocity is updated based on the weight function to perform a smoothing operation on the model.

11. The method for constrained first-arrival tomographic inversion according to claim 10, characterized in that, The slowness update based on the weight function during the tomographic inversion process includes: The slowness is updated based on the following formula during the tomographic inversion process: s new =s old +ds*w(x) Among them, s new For the updated slowness, s old ds is the reciprocal of the grid velocity, w(x) is the change in the reciprocal of the grid velocity obtained from the tomographic inversion, and w(x) is the weighting function.

12. The method for constrained first-arrival tomographic inversion according to claim 10, characterized in that, The process of updating the velocity based on the weight function after tomographic inversion to perform a smoothing operation on the model includes: The velocity is updated based on the following formula after tomographic inversion: v new =v old +dv*w(x) Among them, v new v represents the speed of the smoothed grid. old dv represents the mesh velocity before smoothing, w(x) represents the change in mesh velocity after the smoothing operation, and w(x) represents the weight function.

13. An apparatus for constrained first-arrival tomographic inversion, characterized in that, include: The first module is configured to convert the depth-time curve into a depth-grid velocity curve and to horizontally deploy the surface elevation to construct a high-speed top interface. The second module is configured to acquire an initial tomographic model containing the ground surface elevation, and to divide the initial tomographic model into several grids based on a preset size; The third module is configured to subtract the elevation corresponding to each grid from the high-speed top interface to obtain the depth corresponding to each grid, and to obtain the grid velocity corresponding to each grid based on the depth corresponding to each grid and the depth-grid velocity curve; The fourth module is configured to mark the grid velocity corresponding to each grid in the corresponding grid, and to perform linear interpolation on the grid below the high-speed top interface based on the preset initial velocity and the preset maximum velocity to obtain the velocity model; as well as The fifth module is configured to establish a weight function based on the depth direction, establish a constraint model based on the weight function and the velocity model, perform tomographic inversion based on the constraint model, and update the velocity model based on the weight function during the tomographic inversion process.

14. A computer device, characterized in that, include: At least one processor; as well as A memory storing computer instructions executable on the processor, which, when executed by the processor, implement the steps of the method according to any one of claims 1-12.

15. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1-12.

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