A frequency-variable complex traveltime calculation method based on three-dimensional layer extrapolation

Abstract

The present application relates to the field of oil and gas exploration technology, and in particular to a method for calculating frequency-variant complex traveltimes based on a three-dimensional layer extrapolation method. In this technical solution, in view of the fact that conventional traveltime calculation methods cannot take into account the absorption attenuation effect caused by oil and gas and the high memory consumption of three-dimensional medium calculations, the three-dimensional space of seismic wave propagation is first divided into multiple layers, so that each layer has multiple points to be calculated for frequency-variant complex traveltimes, and then the layer is advanced outwards starting from the starting layer of the seismic wave, so that the frequency-variant complex traveltimes of each point in the three-dimensional space of seismic wave propagation are gradually obtained in the process of advancing outwards, and the computational memory consumption is reduced by gradually advancing outwards. This technical solution can use a three-dimensional velocity model and a quality factor model to calculate a three-dimensional frequency-variant complex traveltime field, and overcome the problem of large memory required for calculations.

Description

Technical Field

[0001] The present application relates to the technical field of oil and gas exploration, and in particular to a frequency-varying complex traveltime calculation method based on a three-dimensional layer extrapolation method. Background Art

[0002] Seismic forward modeling is one of the core technologies of seismic wave tomography and migration imaging, which provides methods and technologies for describing the propagation of seismic waves. Seismic forward modeling technology is divided into two categories: wave theory and ray theory. Wave theory mainly realizes seismic wave forward modeling by solving wave equations. Ray theory realizes seismic wave forward modeling through high-frequency approximation or finite-frequency approximation. Ray method is widely used in industrial applications due to its high efficiency. Seismic wave forward modeling based on ray theory mainly requires the calculation of travel time field, which provides the basis for tomography and depth migration imaging.

[0003] In oil and gas seismic exploration, the absorption attenuation effect caused by oil and gas-bearing media is an important feature of oil and gas resources. In ray theory, the description of the absorption attenuation effect relies on the frequency-variant complex traveltime field. The existing traveltime field calculation method is mainly aimed at the real traveltime field of non-absorbing attenuating media, and the frequency-variant complex traveltime field cannot be calculated. At the same time, since the propagation of seismic waves in the actual medium is three-dimensional, in order to better perform tomographic inversion and pre-stack depth imaging, it is necessary to calculate the three-dimensional frequency-variant complex traveltime field. However, the absorbing attenuation medium contains two medium parameters, which leads to a large amount of memory required to calculate the three-dimensional frequency-variant complex traveltime field and low computational efficiency. Summary of the invention

[0004] In order to at least to some extent overcome the problem in the related art that the three-dimensional frequency-variant complex traveltime field cannot be directly calculated and the large memory required for calculation is large, the present application provides a frequency-variant complex traveltime calculation method based on three-dimensional layer extrapolation method.

[0005] The scheme of this application is as follows:

[0006] A frequency-variant complex traveltime calculation method based on three-dimensional layer extrapolation method, comprising:

[0007] S1. Divide the three-dimensional space of seismic wave propagation into multiple layers, each layer having multiple points to be calculated for frequency-dependent complex travel times distributed in a grid shape;

[0008] S2, the starting layer of the seismic wave is the advanced layer, and the next layer along the propagation direction of the seismic wave along the advanced layer is the layer to be advanced;

[0009] S3, setting the travel time and dissipation travel time of the starting point of the seismic wave to 0, and taking the starting point of the seismic wave as the propulsion starting point, and setting the propulsion starting point to the first state;

[0010] S4, taking the adjacent points of the advancing starting point in the advanced layer, the corresponding points of the advancing starting point in the to-be-advanced layer, and the adjacent points of the corresponding points as the first-category adjacent points of the advancing starting point, setting the first-category adjacent points of the advancing starting point to the second state, and setting the remaining points in the advanced layer and the to-be-advanced layer to the third state;

[0011] S5, based on the preset three-dimensional seismic velocity model and quality factor model, as well as the travel time and dissipative travel time of the propulsion starting point, calculate the travel time and dissipative travel time of the first type of adjacent points of the propulsion starting point;

[0012] S6, updating the minimum point when traveling in the second state as the current propulsion point, and updating the current propulsion point to the first state;

[0013] S7, taking the adjacent points in the layer where the current advancing point is located, and the corresponding points of the current advancing point in the advanced layer / to-be-advanced layer as the second type of adjacent points of the current advancing point;

[0014] S8, based on the three-dimensional seismic velocity model and the quality factor model, as well as the travel time and dissipative travel time of the current propulsion point, calculate and update the travel time and dissipative travel time of the second type of neighboring points of the current propulsion point;

[0015] S9, repeating steps S6-S8 until the states of all points in the advanced layer and the layer to be advanced are updated to the first state;

[0016] S10, updating the current layer to be advanced as the advanced layer in the next cycle, updating the point with the minimum travel time in the advanced layer in the next cycle as the advancement starting point in the next cycle, and setting it to the first state, and repeating steps S4-S9 until all layers in the three-dimensional space are advanced;

[0017] S11. Obtain the frequency-variant complex traveltime of each point based on the traveltime and dissipative traveltime of each point in the three-dimensional space where seismic waves propagate. Determine the frequency-variant complex traveltime field of the three-dimensional space where seismic waves propagate based on the frequency-variant complex traveltime of each point.

[0018] Preferably, the calculation of the travel time of the current point includes:

[0019] Determine a calculation surface among the surfaces in various directions around the current point; the states of the four vertices of the calculation surface are the first state or the second state;

[0020] Assuming that the seismic wave propagates through the calculation surface to the current point, the coordinates of the corresponding position of the starting position of the seismic wave on the calculation surface are solved by the gradient descent method;

[0021] Calculate the travel time of the starting position of the seismic wave at the corresponding position of the calculation surface according to the coordinates and travel time of the four vertices of the calculation surface;

[0022] The travel time of the current point is calculated based on the coordinates and travel times of the four vertices of the calculation surface and the coordinates and travel times of the corresponding position of the starting position of the seismic wave on the calculation surface.

[0023] Preferably, calculating the dissipated travel time of the current point includes:

[0024] Calculate the dissipative travel time of the starting position of the seismic wave at the corresponding position of the calculation surface according to the coordinates of the four vertices of the calculation surface and the dissipative travel time;

[0025] The dissipative travel time of the current point is calculated based on the coordinates and dissipative travel time of the four vertices of the calculation surface, and the coordinates and dissipative travel time of the corresponding position of the starting position of the seismic wave on the calculation surface.

[0026] Preferably, if there are multiple calculation surfaces, the minimum value of the travel time of the current point obtained by each calculation surface is taken as the final travel time of the current point.

[0027] Preferably, the three-dimensional space in which seismic waves propagate is divided into multiple layers, including:

[0028] The three-dimensional space between the shallowest and deepest locations where seismic waves propagate is divided into multiple layers.

[0029] Preferably, the advancement of all layers in three-dimensional space includes:

[0030] Starting from the seismic wave initiation layer, advance downward to the layer where the seismic wave propagates the deepest;

[0031] Retracing back in the layer where the seismic waves propagate the deepest, and advancing upward to the layer where the seismic waves propagate the shallowest;

[0032] The shallowest layer where the seismic wave propagates is turned back and advanced downward to the layer where the seismic wave starts, completing the advancement of all layers in three-dimensional space.

[0033] Preferably, among the first type of adjacent points of the advancing starting point, the adjacent points of the advancing starting point in the advanced layer include: adjacent points in front, behind, left, right, left front, right front, left back and right back of the advancing starting point;

[0034] The corresponding point of the advancement starting point in the layer to be advanced is the corresponding point above and below the advancement starting point in the layer to be advanced;

[0035] The adjacent points of the corresponding point include: the adjacent points in front, behind, left, right, left front, right front, left back and right back of the corresponding point.

[0036] Preferably, among the second type of adjacent points of the current advancing point, the adjacent points in the layer where the current advancing point is located include: adjacent points in front, behind, left and right of the current advancing point;

[0037] The corresponding point of the current advancing point in the advanced layer / the layer to be advanced is the corresponding point above and below the current advancing point in the advanced layer / the layer to be advanced.

[0038] Preferably, the faces in various directions around the current point include: 4 faces in 6 directions of front, back, left, right, top and bottom of the current point.

[0039] The technical solution provided by the present application may include the following beneficial effects: In the present technical solution, in view of the problem that conventional travel time calculation methods cannot consider the absorption attenuation effect caused by oil and gas and the high memory consumption of three-dimensional medium calculation, the three-dimensional space of seismic wave propagation is first divided into multiple layers, so that each layer has multiple points of frequency-variant complex travel time to be calculated, and then the frequency-variant complex travel time of each point in the three-dimensional space of seismic wave propagation is gradually obtained in the process of advancing outward, and the memory consumption of calculation is reduced by gradually advancing outward. The present technical solution can use the three-dimensional velocity model and the quality factor model to calculate the three-dimensional frequency-variant complex travel time field, and overcome the problem of large memory required for calculation.

[0040] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0042] Figure 1 It is a flow chart of a method for calculating frequency-variant complex traveltime based on three-dimensional layer extrapolation provided by an embodiment of the present application;

[0043] Figure 2 It is a schematic diagram of contour line slices during a three-dimensional travel provided by an embodiment of the present application;

[0044] Figure 3 It is a schematic diagram of contour slices of a three-dimensional dissipative travel time provided by an embodiment of the present application. DETAILED DESCRIPTION

[0045] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0046] A frequency-variant complex traveltime calculation method based on three-dimensional layer extrapolation method, comprising:

[0047] S1. Divide the three-dimensional space of seismic wave propagation into multiple layers, each layer having multiple points to be calculated for frequency-dependent complex travel times distributed in a grid shape;

[0048] It should be noted that the frequency-dependent complex traveltime consists of traveltime and dissipative traveltime. Traveltime is the time it takes for a seismic wave to propagate from a shot point to any point in the underground space. Dissipative traveltime is used to describe the frequency variation and attenuation of a seismic wave propagating from a shot point to any point in the underground space. The shot point is the starting point of the seismic wave.

[0049] The three-dimensional space where seismic waves propagate is divided into multiple layers, including:

[0050] The three-dimensional space between the shallowest and deepest locations where seismic waves propagate is divided into multiple layers.

[0051] It should be noted that the points to be calculated for the frequency-dependent complex traveltimes in each layer are distributed in a grid shape.

[0052] S2, the starting layer of the seismic wave is the advanced layer, and the next layer along the propagation direction of the seismic wave along the advanced layer is the layer to be advanced;

[0053] It should be noted that, in this embodiment, the method starts from the seismic wave initiation layer and advances outward along the seismic wave propagation direction.

[0054] Specifically, starting from the seismic wave initiation layer, the method advances downward to the layer where the deepest position of seismic wave propagation is located;

[0055] Retracing back from the layer where the seismic waves propagate the deepest, and advancing upward to the layer where the seismic waves propagate the shallowest;

[0056] The shallowest layer where the seismic wave propagates is turned back and advanced downward to the layer where the seismic wave starts, completing the advancement of all layers in three-dimensional space.

[0057] S3, setting the travel time and dissipation travel time of the starting point of the seismic wave to 0, and taking the starting point of the seismic wave as the propulsion starting point, and setting the propulsion starting point to the first state;

[0058] S4, taking the adjacent points of the advancing starting point in the advanced layer, the corresponding points of the advancing starting point in the to-be-advanced layer, and the adjacent points of the corresponding points as the first-category adjacent points of the advancing starting point, setting the first-category adjacent points of the advancing starting point to the second state, and setting the remaining points in the advanced layer and the to-be-advanced layer to the third state;

[0059] S5, based on the preset three-dimensional seismic velocity model and quality factor model, as well as the travel time and dissipative travel time of the propulsion starting point, calculate the travel time and dissipative travel time of the first type of adjacent points of the propulsion starting point;

[0060] S6, updating the minimum point when traveling in the second state as the current propulsion point, and updating the current propulsion point to the first state;

[0061] S7, taking the adjacent points in the layer where the current advancing point is located, and the corresponding points of the current advancing point in the advanced layer / to-be-advanced layer as the second type of adjacent points of the current advancing point;

[0062] S8, based on the three-dimensional seismic velocity model and the quality factor model, as well as the travel time and dissipative travel time of the current advancing point, calculate and update the travel time and dissipative travel time of the second type of adjacent points of the current advancing point;

[0063] S9, repeating steps S6-S8 until the states of all points in the advanced layer and the layer to be advanced are updated to the first state;

[0064] S10, updating the current layer to be advanced as the advanced layer in the next cycle, updating the point with the minimum travel time in the advanced layer in the next cycle as the advancement starting point in the next cycle, and setting it to the first state, and repeating steps S4-S9 until all layers in the three-dimensional space are advanced;

[0065] S11. Obtain the frequency-variant complex traveltime of each point based on the traveltime and dissipative traveltime of each point in the three-dimensional space where seismic waves propagate. Determine the frequency-variant complex traveltime field of the three-dimensional space where seismic waves propagate based on the frequency-variant complex traveltime of each point.

[0066] In this technical solution, three states of points are proposed. As above, the point in the first state is the point with the minimum travel time. It is considered to have a frequency-variable complex travel time and no calculation update is required. Although the point in the second state has a frequency-variable complex travel time, it has not yet become the point with the minimum travel time, so it needs to be calculated and updated until it becomes the point with the minimum travel time. The point in the second state has not yet calculated the frequency-variable complex travel time, so it needs to be calculated and updated.

[0067] In practice, the travel time t(x s ,y s ,z s ) and dissipative travel time t * (x s ,y s ,z s ) are all set to 0, and their states are set to the first state, where x s ,y s ,z sare the coordinates of the starting point of the seismic wave on the x, y and z axes respectively. The starting point of the seismic wave is taken as the starting point of advancement, the adjacent points of the starting point of advancement in the advanced layer, the corresponding points of the starting point of advancement in the layer to be advanced, and the adjacent points of the corresponding points are taken as the first-class adjacent points of the starting point of advancement, the first-class adjacent points of the starting point of advancement are set to the second state, and the remaining points in the advanced layer and the layer to be advanced are set to the third state.

[0068] Specifically, among the first type of adjacent points of the advancing starting point, the adjacent points of the advancing starting point in the advanced layer include: adjacent points in front, behind, left, right, left front, right front, left back and right back of the advancing starting point;

[0069] The corresponding point of the advancement starting point in the layer to be advanced is the corresponding point above and below the advancement starting point in the layer to be advanced;

[0070] The adjacent points of the corresponding point include: the adjacent points in front, behind, left, right, left front, right front, left back and right back of the corresponding point.

[0071] The following formulas are used to calculate the travel time and dissipated travel time of the first-class neighboring points of the advancement starting point:

[0072]

[0073] Wherein, v represents the three-dimensional seismic velocity model, q represents the quality factor model, and x, y, and z are the coordinates of the first type of adjacent points currently calculated on the x, y, and z axes, respectively.

[0074] Find the point with the smallest travel time among all the points in the second state, update it as the current advancing point, and update it as the first state.

[0075] The adjacent points in the layer where the current advancing point is located, and the corresponding points of the current advancing point in the advanced layer / to-be-advanced layer are taken as the second type of adjacent points of the current advancing point.

[0076] Among the second type of adjacent points of the current advancing point, the adjacent points in the layer where the current advancing point is located include: adjacent points in front, behind, left and right of the current advancing point;

[0077] The corresponding point of the current advancing point in the advanced layer / the layer to be advanced is the corresponding point above and below the current advancing point in the advanced layer / the layer to be advanced.

[0078] In specific practice, the calculation and updating of the travel time and dissipated travel time of the second type of neighboring points of the current propulsion point in step S8 specifically include:

[0079] If the second-type adjacent point of the current advancing point is in the first state, there is no need to calculate its travel time and dissipated travel time.

[0080] If the second type of adjacent point of the current advancing point is in the second state, after calculating the travel time and dissipated travel time, the lower value between the current calculated value and the historical calculated value is used as the update value. For example, if the travel time calculated by the current calculation point is 2 and its previous travel time is 3, the currently calculated travel time is used as the update value; if its currently calculated travel time is 3 and its previous travel time is 2, the previous travel time can be kept unchanged.

[0081] If the second type of adjacent points of the current propulsion point are in the third state, then after calculating the travel time and dissipated travel time, they can be directly assigned values.

[0082] After repeating this process, the states of all points in the layer that has been advanced and the layer that is to be advanced will be updated to the first state. In this technical solution, the travel time of all points in the layer that has been advanced and the layer that is to be advanced will be filtered to the lowest state, so that the frequency-variable complex travel time of all points in the layer that has been advanced and the layer that is to be advanced will also be filtered to the lowest state.

[0083] At this time, the next layer can be advanced by updating the current layer to be advanced to the advanced layer in the next cycle, updating the minimum point in the advanced layer in the next cycle as the starting point for advancement in the next cycle, and setting it to the first state. Repeating steps S4-S9 can complete the advancement of all layers in the three-dimensional space.

[0084] After completing the advancement of all layers in the three-dimensional space, the frequency-variant complex traveltime of each point can be obtained based on the traveltime and dissipative traveltime of each point in the three-dimensional space where the seismic wave propagates, and the frequency-variant complex traveltime field in the three-dimensional space where the seismic wave propagates can be determined based on the frequency-variant complex traveltime of each point.

[0085] It should be noted that during the advancement process, it is necessary to calculate the travel time and dissipative travel time of each point, that is, to calculate the frequency-variable complex travel time of each point.

[0086] Specifically, the calculation of the travel time of the current point includes:

[0087] Determine a calculation surface among the surfaces in all directions around the current point; the states of the four vertices of the calculation surface are the first state or the second state;

[0088] Assume that the seismic wave propagates through the calculation surface to the current point, and use the gradient descent method to solve the coordinates of the corresponding position of the starting position of the seismic wave on the calculation surface;

[0089] According to the coordinates and travel time of the four vertices of the calculation surface, the travel time of the starting position of the seismic wave at the corresponding position of the calculation surface is calculated;

[0090] The travel time of the current point is calculated based on the coordinates and travel time of the four vertices of the calculation surface and the coordinates and travel time of the corresponding position of the starting position of the seismic wave on the calculation surface.

[0091] It should be noted that the faces in all directions around the current point include: 4 faces in each direction of the 6 directions of the current point, namely, the 6 large faces in the 6 directions of the current point, namely, each face is divided into 4 small faces, for a total of 24 faces.

[0092] Assume the coordinates of the current point are (α, β, ξ), and the coordinates of the four vertices of the calculated surface are (α1, β1, ξ1).

[0093] (α1,β2,ξ1), (α2,β1,ξ1), (α2,β2,ξ1), their frequency-variant complex traveltimes are t1, t2, t3, t4 respectively. Since the computational surface may appear in the three planes xy, yz, and xz, there is an invariant in each of the three planes, which is represented by ξ; the other two quantities are variables, represented by α and β. When in the xy plane, ξ represents z, and α and β represent x and y. When in the yz plane, ξ represents x, and α and β represent y and z. When in the xz plane, ξ represents y, and α and β represent x and z.

[0094] Assume that the seismic wave propagates through the calculation surface to the current point, the coordinates of the corresponding position of the starting position of the seismic wave on the calculation surface are set to (α0, β0, ξ1), and the travel time is set to t0(α0, β0).

[0095] Then the travel time of the starting position of the seismic wave at the corresponding position of the calculation surface is calculated as:

[0096]

[0097] The travel time at the current point is:

[0098]

[0099] Among them, a1, a2, a3, and a4 represent the four vertices of the calculation surface, and a5 represents the current point;

[0100]

[0101] Since the four vertices of the calculation surface and the current point are all on the calculation grid, their coordinates are known. What is unknown is the α0 and β0 in the coordinates of the corresponding position of the starting position of the seismic wave on the calculation surface. Therefore, in this embodiment, the following optimization problem is solved by the gradient descent method to obtain α0 and β0:

[0102]

[0103] st:α1<α0<α2,β1<β0<β2 (5)

[0104] Substituting α0 and β0 into formulas (3) and (4) can calculate the travel time of the current point.

[0105] Calculate the dissipated travel time of the current point, including:

[0106] According to the coordinates of the four vertices of the calculation surface and the dissipation travel time, the dissipation travel time of the starting position of the seismic wave at the corresponding position of the calculation surface is calculated;

[0107] The dissipative travel time of the current point is calculated based on the coordinates and dissipative travel time of the four vertices of the calculation surface, as well as the coordinates and dissipative travel time of the corresponding position of the starting position of the seismic wave on the calculation surface.

[0108] like Figure 2 As shown, Figure 2 This is a schematic diagram of the contour slices of the three-dimensional travel time of the current point, taking the x-coordinate of the starting position of the seismic wave as 3750m, the y-coordinate as 8750m, and the z-coordinate as 0m.

[0109] The dissipated travel time of the frequency-variable complex travel time of the four vertices in the design calculation surface is Then the dissipated travel time of the starting position of the seismic wave at the corresponding position of the calculation surface is calculated as:

[0110]

[0111] Calculate the dissipated travel time of the current point as:

[0112]

[0113] like Figure 3 As shown, Figure 3 This is a schematic diagram of the contour slices of the three-dimensional dissipative travel time of the current point, taking the x-coordinate of the starting position of the seismic wave as 3750m, the y-coordinate as 8750m, and the z-coordinate as 0m.

[0114] Finally, the frequency-variable complex travel time t of the current point can be obtained by using the travel time of the current point and the dissipated travel time c :

[0115]

[0116] Among them, ω is the circular frequency, ω0 is the reference circular frequency, and π is the circumference of a circle.

[0117] It should be noted that if there are multiple calculation surfaces, the minimum value of the travel time of the current point obtained by each calculation surface is taken as the final travel time of the current point;

[0118] It can be understood that in this technical solution, in order to solve the problem that conventional travel time calculation methods cannot take into account the absorption attenuation effect caused by oil and gas and the high memory consumption of three-dimensional medium calculation, the three-dimensional space of seismic wave propagation is first divided into multiple layers, so that each layer has multiple points of frequency-variant complex travel time to be calculated, and then the frequency-variant complex travel time of each point in the three-dimensional space of seismic wave propagation is gradually obtained in the process of advancing outward, and the memory consumption of calculation is reduced by gradually advancing outward. This technical solution can use the three-dimensional velocity model and the quality factor model to calculate the three-dimensional frequency-variant complex travel time field, and overcome the problem of large memory required for calculation.

[0119] It can be understood that the same or similar parts of the above embodiments can be referenced to each other, and the contents not described in detail in some embodiments can refer to the same or similar contents in other embodiments.

[0120] It should be noted that, in the description of this application, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In addition, in the description of this application, unless otherwise specified, the meaning of "plurality" refers to at least two.

[0121] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present application belong.

[0122] It should be understood that the various parts of the present application can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0123] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0124] In addition, each functional unit in each embodiment of the present application may be integrated into a processing module, or each unit may exist physically separately, or two or more units may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0125] The storage medium mentioned above can be a read-only memory, a magnetic disk or an optical disk, etc.

[0126] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0127] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A frequency-dependent complex traveltime calculation method based on three-dimensional layer extrapolation method, characterized in that: include: S1. Divide the three-dimensional space of seismic wave propagation into multiple layers, each layer having multiple points to be calculated for frequency-dependent complex travel times distributed in a grid shape; S2, the starting layer of the seismic wave is the advanced layer, and the next layer along the propagation direction of the seismic wave along the advanced layer is the layer to be advanced; S3, setting the travel time and dissipation travel time of the starting point of the seismic wave to 0, and taking the starting point of the seismic wave as the propulsion starting point, and setting the propulsion starting point to the first state; S4, taking the adjacent points of the advancing starting point in the advanced layer, the corresponding points of the advancing starting point in the to-be-advanced layer, and the adjacent points of the corresponding points as the first-category adjacent points of the advancing starting point, setting the first-category adjacent points of the advancing starting point to the second state, and setting the remaining points in the advanced layer and the to-be-advanced layer to the third state; S5, based on the preset three-dimensional seismic velocity model and quality factor model, as well as the travel time and dissipative travel time of the advancement starting point, calculate the travel time and dissipative travel time of the first type of adjacent points of the advancement starting point; S6, updating the minimum point when traveling in the second state as the current propulsion point, and updating the current propulsion point to the first state; S7, taking the adjacent points in the layer where the current advancing point is located, and the corresponding points of the current advancing point in the advanced layer / to-be-advanced layer as the second type of adjacent points of the current advancing point; S8, based on the three-dimensional seismic velocity model and the quality factor model, as well as the travel time and dissipative travel time of the current propulsion point, calculate and update the travel time and dissipative travel time of the second type of neighboring points of the current propulsion point; S9, repeating steps S6-S8 until the states of all points in the advanced layer and the layer to be advanced are updated to the first state; S10, updating the current layer to be advanced as the advanced layer in the next cycle, updating the point with the minimum travel time in the advanced layer in the next cycle as the advancement starting point in the next cycle, and setting it to the first state, and repeating steps S4-S9 until all layers in the three-dimensional space are advanced; S11, obtaining the frequency-varying complex traveltime of each point according to the traveltime and dissipative traveltime of each point in the three-dimensional space of seismic wave propagation, and determining the frequency-varying complex traveltime field of the three-dimensional space of seismic wave propagation according to the frequency-varying complex traveltime of each point; Calculate the travel time of the current point to be calculated, including: Determine a calculation surface among the surfaces in various directions around the current point to be calculated; the states of the four vertices of the calculation surface are the first state or the second state; Assuming that the seismic wave propagates through the calculation surface to the current point to be calculated, the coordinates of the corresponding position of the starting position of the seismic wave on the calculation surface are solved by the gradient descent method; Calculate the travel time of the starting position of the seismic wave at the corresponding position of the calculation surface according to the coordinates and travel time of the four vertices of the calculation surface; Calculate the travel time of the current point to be calculated according to the coordinates and travel times of the four vertices of the calculation surface and the coordinates and travel times of the corresponding position of the starting position of the seismic wave on the calculation surface; Calculate the dissipative travel time of the current point to be calculated, including: Calculate the dissipative travel time of the starting position of the seismic wave at the corresponding position of the calculation surface according to the coordinates of the four vertices of the calculation surface and the dissipative travel time; Calculate the dissipative travel time of the current point to be calculated according to the coordinates and dissipative travel time of the four vertices of the calculation surface, and the coordinates and dissipative travel time of the corresponding position of the starting position of the seismic wave on the calculation surface; According to the travel time and dissipative travel time of each point in the three-dimensional space of seismic wave propagation, the frequency-dependent complex travel time of each point is obtained, including: Among them, t c is the frequency-variable complex travel time, t is the travel time, t * is the dissipative travel time, ω is the circular frequency, ω0 is the reference circular frequency, and π is the circumference of a circle.

2. The method according to claim 1, characterized in that If there are multiple calculation surfaces, the minimum value of the travel time of the current point to be calculated obtained by each calculation surface is taken as the final travel time of the current point to be calculated.

3. The method according to claim 1, characterized in that The three-dimensional space where seismic waves propagate is divided into multiple layers, including: The three-dimensional space between the shallowest and deepest locations where seismic waves propagate is divided into multiple layers.

4. The method according to claim 3, characterized in that: Advancement of all layers in three-dimensional space, including: Starting from the seismic wave initiation layer, advance downward to the layer where the seismic wave propagates the deepest; Retracing back in the layer where the seismic waves propagate the deepest, and advancing upward to the layer where the seismic waves propagate the shallowest; The shallowest layer where the seismic wave propagates is turned back and advanced downward to the layer where the seismic wave starts, completing the advancement of all layers in three-dimensional space.

5. The method according to claim 1, characterized in that Among the first type of adjacent points of the advancing starting point, the adjacent points of the advancing starting point in the advanced layer include: adjacent points in front, behind, left, right, left front, right front, left back and right back of the advancing starting point; The corresponding point of the advancement starting point in the layer to be advanced is the corresponding point above and below the advancement starting point in the layer to be advanced; The adjacent points of the corresponding point include: the adjacent points in front, behind, left, right, left front, right front, left back and right back of the corresponding point.

6. The method according to claim 1, characterized in that Among the second type of adjacent points of the current advancing point, the adjacent points in the layer where the current advancing point is located include: adjacent points in front, behind, left and right of the current advancing point; The corresponding point of the current advancing point in the advanced layer / the layer to be advanced is the corresponding point above and below the current advancing point in the advanced layer / the layer to be advanced.

7. The method according to claim 1, characterized in that The faces in various directions around the current point to be calculated include: 4 faces in each direction, namely, front, back, left, right, top and bottom of the current point to be calculated.

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