Method and device for establishing near-surface velocity model and computer equipment

Abstract

This application discloses a method, apparatus, and computer equipment for establishing a near-surface velocity model, belonging to the field of geophysical exploration technology. The method includes: determining the time delay and refraction velocity corresponding to multiple shot points and multiple receiver distances based on multiple first arrival times and multiple shot-receiver distances; determining the regolith thickness and regolith velocity corresponding to the multiple shot points based on the time delay and refraction velocity; determining the regolith thickness and regolith velocity corresponding to the multiple receiver points based on the time delay and refraction velocity; determining a constraint model based on the refraction velocity, regolith thickness, and regolith velocity corresponding to the multiple shot points and multiple receiver points; and performing tomographic inversion on the constraint model to obtain the near-surface velocity model. By utilizing various information corresponding to the multiple shot points and multiple receiver points, and combining the refraction wave method and travel-time tomography, the accuracy of the near-surface velocity model is improved.

Description

Technical Field

[0001] This application relates to the field of geophysical exploration technology, and in particular to a method, apparatus and computer equipment for establishing a near-surface velocity model. Background Technology

[0002] In geophysical exploration technology, near-surface velocity models are used to characterize seismic wave velocities at different strata depths. For layered media, these can be defined as refraction velocities or regolith velocities. Refraction velocities refer to the propagation speed of seismic waves through refraction layers, while regolith velocities refer to the propagation speed of seismic waves through weathered layers. The accuracy of the near-surface velocity model not only affects the excitation and reception of seismic waves in the exploration area but also the accuracy of other data determined based on the model. For example, a user sets up a shot point in the exploration area and excites seismic waves through it. Then, based on the regolith velocity and refraction velocities characterized by the near-surface velocity model, the user determines the first arrival time of the seismic wave at the detection point, thereby determining the location of the detection point. If the accuracy of the near-surface velocity model is low, the detection point determined by the user based on the model may not receive the seismic wave. In related technologies, methods such as interpolation, refraction wave analysis, and travel-time tomography are commonly used to establish near-surface velocity models. However, near-surface velocity models established using these methods have low accuracy and are not suitable for all near-surface types. For example, in regions with flat surfaces and stable refractive layers, the near-surface velocity model can be quickly established using the refraction wave method. However, for regions with unstable refractive layers, the near-surface velocity model established using the refraction wave method is not applicable. Therefore, how to establish a near-surface velocity model has become an urgent problem to be solved. Summary of the Invention

[0003] This application provides a method, apparatus, and computer equipment for establishing a near-surface velocity model, which can solve the problem of low accuracy in related technologies for near-surface velocity models. The technical solution is as follows:

[0004] On the one hand, a method for establishing a near-surface velocity model is provided, wherein the exploration area has multiple shot points and multiple detection points, and the method includes:

[0005] Based on multiple first arrival times and multiple shot-receiver distances, the delay time and refraction velocity corresponding to the multiple shot points and the multiple detection points are determined respectively. The first arrival time refers to the time it takes for a seismic wave excited by a shot point to first reach a detection point. The shot-receiver distance refers to the distance between a shot point and a detection point. The delay time corresponding to the shot point is the difference between the time it takes for the seismic wave to travel from the shot point to the refraction layer and a first reference time. The first reference time is the ratio of the horizontal projection length of the propagation distance of the seismic wave along the weathering layer to the refraction layer to the refraction velocity. The delay time of the detection point is the difference between the time it takes for the seismic wave to travel from the refraction layer to the detection point and a second reference time. The second reference time is the ratio of the horizontal projection length of the propagation distance of the seismic wave along the weathering layer to the detection point to the refraction velocity.

[0006] Based on the delay time and refraction velocity corresponding to the multiple shot points, the weathering layer thickness and weathering layer velocity corresponding to the multiple shot points are determined. Based on the delay time and refraction velocity corresponding to the multiple detection points, the weathering layer thickness and weathering layer velocity corresponding to the multiple detection points are determined.

[0007] Based on the refraction velocity, weathering layer thickness, and weathering layer velocity corresponding to the multiple shot points and multiple detection points, a constraint model is determined. The constraint model includes M*N*Z three-dimensional grids. The M*N*Z three-dimensional grids are obtained by meshing the weathering layer and refraction layer of the exploration area. Each three-dimensional grid located in the weathering layer has a weathering layer velocity, and each three-dimensional grid located in the refraction layer has a refraction velocity.

[0008] The constrained model is subjected to tomographic inversion to obtain a near-surface velocity model, which represents the seismic wave velocity corresponding to different strata depths in the exploration area.

[0009] On the other hand, an apparatus for establishing a near-surface velocity model is provided, wherein the exploration area has multiple shot points and multiple detection points, and the apparatus includes:

[0010] The first determining module is used to determine the delay time and refraction velocity corresponding to the multiple shot points and the multiple detection points based on multiple first arrival times and multiple shot-receiver distances. The first arrival time refers to the time it takes for a seismic wave excited by a shot point to first reach a detection point. The shot-receiver distance refers to the distance between a shot point and a detection point. The delay time corresponding to the shot point is the difference between the time it takes for the seismic wave to reach the refraction layer from the shot point and a first reference time. The first reference time is the ratio of the horizontal projection length of the propagation distance of the seismic wave along the weathering layer to the refraction layer to the refraction velocity. The delay time of the detection point is the difference between the time it takes for the seismic wave to reach the detection point from the refraction layer and a second reference time. The second reference time is the ratio of the horizontal projection length of the propagation distance of the seismic wave along the weathering layer to the detection point to the refraction velocity.

[0011] The second determining module is used to determine the weathering layer thickness and weathering layer velocity corresponding to the multiple shot points based on the delay time and refraction velocity corresponding to the multiple shot points, and to determine the weathering layer thickness and weathering layer velocity corresponding to the multiple detection points based on the delay time and refraction velocity corresponding to the multiple detection points.

[0012] The third determining module is used to determine a constraint model based on the refraction velocity, weathering layer thickness, and weathering layer velocity corresponding to the multiple shot points and the multiple detection points, respectively. The constraint model includes M*N*Z three-dimensional grids, which are obtained by meshing the weathering layer and refraction layer of the exploration area. Each three-dimensional grid located in the weathering layer has a weathering layer velocity, and each three-dimensional grid located in the refraction layer has a refraction velocity.

[0013] The tomographic inversion module is used to perform tomographic inversion on the constrained model to obtain a near-surface velocity model, which represents the seismic wave velocity corresponding to different strata depths in the exploration area.

[0014] On the other hand, a computer device is provided, the computer device including a memory and a processor, the memory for storing computer programs, and the processor for executing the computer programs stored in the memory to implement the steps of the method for establishing the near-surface velocity model described above.

[0015] On the other hand, a computer-readable storage medium is provided, wherein a computer program is stored therein, and when the computer program is executed by a processor, it implements the steps of the method for establishing the near-surface velocity model described above.

[0016] On the other hand, a computer program product containing instructions is provided, which, when run on a computer, cause the computer to perform the steps of the method for establishing the near-surface velocity model described above.

[0017] The technical solutions provided in this application can bring at least the following beneficial effects:

[0018] Because the constraint model is determined based on the refraction velocity, regolith thickness, and regolith velocity corresponding to multiple shot points and multiple detection points, and the near-surface velocity model is obtained by tomographic inversion of the constraint model, the accuracy of the near-surface velocity model is improved by using various information corresponding to multiple shot points and multiple detection points, combined with the refraction wave method and travel-time tomography. Furthermore, since the near-surface velocity model is established by combining the refraction wave method and travel-time tomography, it can solve the problem that near-surface velocity models established by a single method cannot be applied to all near-surface types. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a flowchart of a method for establishing a near-surface velocity model provided in an embodiment of this application;

[0021] Figure 2 This is a schematic diagram illustrating the excitation and reception of seismic waves according to an embodiment of this application;

[0022] Figure 3 This is a schematic diagram of a planar gridded exploration area provided in an embodiment of this application;

[0023] Figure 4 This is a schematic diagram of a constraint model provided in an embodiment of this application;

[0024] Figure 5 This is a schematic diagram of a near-surface velocity model provided in an embodiment of this application;

[0025] Figure 6 This is a schematic diagram of a device for establishing a near-surface velocity model provided in an embodiment of this application;

[0026] Figure 7 This is a schematic diagram of the structure of a computer device provided in an embodiment of this application. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the implementation methods of this application will be further described in detail below with reference to the accompanying drawings.

[0028] Before providing a detailed explanation of the method for establishing the near-surface velocity model provided in the embodiments of this application, the business scenarios provided in the embodiments of this application will be introduced first.

[0029] The near-surface velocity model establishment method provided in this application can be applied to various scenarios. For example, in the field of geophysical exploration technology, methods such as interpolation, refraction wave method, and travel-time tomography can be used to establish a near-surface velocity model to characterize the refraction velocity or weathering layer velocity corresponding to different strata depths. However, if the established near-surface velocity model has low accuracy, it will affect the excitation and reception of seismic waves in the exploration area. Therefore, the near-surface velocity model establishment method provided in this application can determine a high-accuracy constraint model based on the refraction velocity, weathering layer thickness, and weathering layer velocity corresponding to multiple shot points and multiple detection points, and then perform tomographic inversion on the constraint model to obtain a high-accuracy near-surface velocity model.

[0030] Because near-surface velocity models can characterize the refraction velocity or weathering velocity at different strata depths in an exploration area, and these velocities can characterize the structure and porosity of each rock layer at different depths, establishing a near-surface velocity model helps users understand the structure and porosity of each rock layer in the exploration area.

[0031] The near-surface velocity model establishment method provided in this application is executed by a computer device. This computer device can be any electronic product capable of human-computer interaction with the user via voice, such as a PC (Personal Computer), mobile phone, smartphone, PDA (Personal Digital Assistant), PPC (Pocket PC), tablet computer, etc. Furthermore, the computer device can also interact with the user through one or more methods such as a keyboard, touchpad, touchscreen, remote control, or handwriting device.

[0032] Those skilled in the art should understand that the above application scenarios and computer devices are merely examples. Other existing or future application scenarios and computer devices that are applicable to the embodiments of this application should also be included within the scope of protection of the embodiments of this application, and are hereby incorporated by reference.

[0033] It should be noted that the business scenarios described in the embodiments of this application are for the purpose of more clearly illustrating the technical solutions of the embodiments of this application, and do not constitute a limitation on the technical solutions provided in the embodiments of this application. As those skilled in the art will know, with the emergence of new business scenarios, the technical solutions provided in the embodiments of this application are also applicable to similar technical problems.

[0034] The method for establishing the near-surface velocity model provided in the embodiments of this application will be explained in detail below.

[0035] Figure 1 This is a flowchart illustrating a method for establishing a near-surface velocity model according to an embodiment of this application. Please refer to it. Figure 1 The method includes the following steps.

[0036] Step 101: Based on multiple first arrival times and multiple shot-receiver distances, determine the delay time and refraction velocity corresponding to the multiple shot points and the multiple detection points, respectively. The first arrival time refers to the time it takes for a seismic wave excited by a shot point to first reach a detection point. The shot-receiver distance refers to the distance between a shot point and a detection point. The delay time corresponding to a shot point is the difference between the time it takes for a seismic wave to travel from the shot point to the refraction layer and the first reference time. The first reference time is the ratio of the horizontal projection length of the propagation distance of the seismic wave along the weathering layer to the refraction layer to the refraction velocity. The delay time of a detection point is the difference between the time it takes for a seismic wave to travel from the refraction layer to the detection point and the second reference time. The second reference time is the ratio of the horizontal projection length of the propagation distance of the seismic wave along the weathering layer to the detection point to the refraction velocity.

[0037] The exploration area has multiple shot points and multiple detection points, which together form multiple shot-detector pairs. Each shot-detector pair includes one shot point and one detection point. Each shot-detector pair corresponds to one first arrival time and one shot-detector distance.

[0038] For example, please refer to Figure 2 , Figure 2 This is a schematic diagram illustrating the excitation and reception of seismic waves according to an embodiment of this application. Figure 2 In the middle, the shot detection pair A includes a shot point S. A and a detection point R A The initial arrival time t corresponding to shot-receiver pair A. A For gun point S A The triggered seismic waves first reached the detection point R. A The elapsed time. The shot-receiver distance x corresponding to shot-receiver pair A. A For gun point S A With detection point R A The distance between them. The initial arrival time t corresponding to shot-receiver pair A. AEach is designated as a firing point S. A and detection point R A The corresponding first arrival time, and the corresponding shot-receiver distance x for shot-receiver pair A. A Each is designated as a firing point S. A and detection point R A Corresponding shot-receiver distance. Shot point S A The corresponding delay time is the time from the seismic wave at the shot point S. A The time t taken to reach the top surface of the refractive layer AS Subtract the ratio of the horizontal projection length x1 of the seismic wave's propagation distance along the weathered layer to the refraction layer to the refraction velocity, and the detection point R... A The corresponding time delay is when the seismic wave reaches the detection point R from the top surface of the refraction layer. A The elapsed time t AR Subtract the seismic wave propagating along the weathered layer to the detection point R A The ratio of the horizontal projection length x2 of the corresponding propagation distance to the refraction speed.

[0039] Select one of the multiple shot points as the first shot point, and determine the delay time and refraction velocity corresponding to the first shot point according to the following operations (11)-(14) until the delay time and refraction velocity corresponding to the multiple shot points are determined respectively.

[0040] (11) Obtain multiple first arrival times and multiple first shot-detector distances corresponding to the first shot point. The multiple first arrival times refer to the time elapsed after the seismic wave triggered by the first shot point first arrives at multiple first detection points. The multiple first shot-detector distances refer to the distance between the first shot point and the multiple first detection points. The multiple first detection points are the detection points corresponding to the first shot point.

[0041] The first shot point corresponds to multiple first detection points, meaning that multiple detection points can receive seismic waves generated by the same shot point. The first shot point and these multiple first detection points form multiple shot-detector pairs. Each shot-detector pair includes a first shot point, and each detection point within a shot-detector pair is a separate first detection point. Based on the above description, one shot-detector pair corresponds to one first arrival time and one shot-detector distance. Thus, the multiple shot-detector pairs consisting of the first shot point and these multiple first detection points correspond to multiple first arrival times and multiple first shot-detector distances. In other words, the first shot point corresponds to multiple first arrival times and multiple first shot-detector distances.

[0042] In some embodiments, the database stores the correspondence between shot point identifiers, first arrival times, and shot-receiver distances. Therefore, after selecting a shot point from the plurality of shot points as the first shot point, multiple first arrival times and multiple first shot-receiver distances corresponding to the first shot point can be obtained from the stored correspondence between shot point identifiers, first arrival times, and shot-receiver distances based on the identifier of the first shot point.

[0043] The identifier of the firing point is used to uniquely identify the firing point. The firing point identifier can be the firing point number, plane rectangular coordinates, etc., or a combination of these information.

[0044] Suppose that the first shot point S1 corresponds to four first detection points, namely R1, R2, R3, and R4. Then, the four first arrival times corresponding to the first shot point S1 are t1, R2, R3, and R4, respectively. 11 t 12 t 13 and t 14 The four first shot receiver distances corresponding to the first shot point S1 are x. 11 x 12 x 13 and x 14 .

[0045] (12) Based on the multiple first arrival times and the multiple first shot-receiver distances, multiple first delay times and multiple first refraction velocities are determined.

[0046] Based on the above description, the first arrival time is the time elapsed after the seismic wave generated by the shot point first reaches the detection point. Furthermore, the seismic wave generated by the shot point first reaches the refraction layer, then slides along the shot-receiver distance at the top surface of the refraction layer according to the refraction velocity, and finally reaches the detection point from the refraction layer. Therefore, the first arrival time is related to the shot-receiver distance, the delay time corresponding to the shot point, the delay time corresponding to the detection point, and the refraction velocity.

[0047] For the first shot point, the delay time corresponding to the first shot point is the same among the multiple first arrival times. Therefore, by substituting the multiple first arrival times and the multiple first shot-receiver distances into the following formula (1), multiple expressions can be obtained. In these multiple expressions, the first arrival time is known, the delay time corresponding to the shot point is the same and unknown, the delay time corresponding to the detection point is known, the first shot-receiver distance is known, and the first refraction velocity is unknown. Thus, by solving these multiple expressions together, multiple first delay times and multiple first refraction velocities can be obtained.

[0048]

[0049] In the above formula (1), t represents the first arrival time, t S When t represents the delay corresponding to the shot point, R When representing the delay corresponding to the detection point, x represents the first shot-detector distance, and v represents the first refraction velocity.

[0050] (13) Take the average of the multiple first delay times to obtain the delay time corresponding to the first shot point.

[0051] Since these multiple first delay times are determined based on multiple first arrival times and multiple first shot-receiver distances corresponding to the first shot point, averaging these multiple first delay times directly yields the delay time corresponding to the first shot point.

[0052] (14) Take the average of the multiple first refraction velocities to obtain the refraction velocity corresponding to the first shot point.

[0053] Since these multiple first refraction velocities are determined based on multiple first arrival times and multiple first shot-receiver distances corresponding to the first shot point, averaging these multiple first refraction velocities directly yields the refraction velocity corresponding to the first shot point.

[0054] Similarly, select one of the multiple detection points as the second detection point, and determine the delay time and refraction velocity corresponding to the second detection point according to the following operations (21)-(24) until the delay time and refraction velocity corresponding to the multiple detection points are determined respectively.

[0055] (21) Obtain multiple second arrival times and multiple second shot-receiver distances corresponding to the second detection point. The multiple second arrival times refer to the time elapsed after the second detection point first detects the seismic waves generated by the multiple second shot points. The multiple second shot-receiver distances refer to the distance between the second detection point and the multiple second shot points. The multiple second shot points are the shot points corresponding to the second detection point.

[0056] The second detection point corresponds to multiple second shot points, meaning that the same detection point can receive seismic waves generated by multiple shot points. The second detection point and these multiple second shot points form multiple shot-detector pairs. Each shot-detector pair includes shot points that are the multiple second shot points, and each detection point included in each shot-detector pair is a second detection point. Based on the above description, one shot-detector pair corresponds to one first arrival time and one shot-detector distance. Thus, the multiple shot-detector pairs formed by the second detection point and these multiple second shot points correspond to multiple second first arrival times and multiple second shot-detector distances. In other words, the second detection point corresponds to multiple second first arrival times and multiple second shot-detector distances.

[0057] In some embodiments, the database stores the correspondence between detection point identifiers, first arrival times, and shot-receiver distances. Therefore, after selecting one detection point from the plurality of detection points as the second detection point, multiple second first arrival times and multiple second shot-receiver distances corresponding to the second detection point can be obtained from the stored correspondence between detection point identifiers, first arrival times, and shot-receiver distances based on the identifier of the second detection point.

[0058] The identifier of the detection point is used to uniquely identify the detection point. The identifier can be the detection point number, plane rectangular coordinates, etc., or a combination of these information.

[0059] (22) Based on the multiple second arrival times and the multiple second gun-receiver distances, determine multiple second delay times and multiple second refraction velocities.

[0060] The process of determining multiple second delay times and multiple second refraction velocities based on multiple second first arrival times and multiple second gun-receiver distances is similar to the process of determining multiple first delay times and multiple first refraction velocities based on multiple first first arrival times and multiple first gun-receiver distances in step (12) above. Therefore, you can refer to the relevant content of step (12) above, which will not be repeated here.

[0061] (23) Take the average of the multiple second delay times to obtain the delay time corresponding to the second detection point.

[0062] The process of averaging the multiple second delay times to obtain the delay time corresponding to the second detection point is similar to the process of averaging the multiple first delay times to obtain the delay time corresponding to the first shot point in step (13) above. Therefore, you can refer to the relevant content of step (13) above, which will not be repeated here.

[0063] (24) Take the average of the multiple second refraction velocities to obtain the refraction velocity corresponding to the second detection point.

[0064] The process of averaging the multiple second refraction velocities to obtain the refraction velocity corresponding to the second detection point is similar to the process of averaging the multiple first refraction velocities to obtain the refraction velocity corresponding to the first shot point in step (14) above. Therefore, you can refer to the relevant content of step (14) above, which will not be repeated here.

[0065] In some embodiments, to accurately determine the delay time and refraction velocity corresponding to the plurality of shot points and the plurality of detection points, before determining the delay time and refraction velocity corresponding to the plurality of shot points and the plurality of detection points based on the plurality of first arrival times and the plurality of shot-receiver distances, it is necessary to filter the first arrival times corresponding to the target shot-receiver distance from the plurality of first arrival times. That is, the coordinates of the common center point corresponding to each of the plurality of first arrival times are obtained to obtain a plurality of common center point coordinates. The common center point coordinates refer to the coordinates of the midpoint of the line connecting the shot point and the detection point corresponding to the corresponding first arrival time. From the plurality of common center point coordinates, the common center point coordinates that meet the preset conditions are selected to obtain candidate common center point coordinates. The shot-receiver distances corresponding to the candidate common center point coordinates are obtained to obtain candidate shot-receiver distances. From the candidate shot-receiver distances, the target shot-receiver distance that is within the shot-receiver distance threshold range is selected. From the plurality of first arrival times, the first arrival time corresponding to the target shot-receiver distance is selected.

[0066] Based on the above description, one first arrival time corresponds to one shot-detector pair, and one shot-detector pair includes one shot point and one detector point. Therefore, one first arrival time corresponds to one shot point and one detector point. Thus, for any one of these multiple first arrival times, the midpoint of the line connecting the shot point and the detector point corresponding to that first arrival time can be determined as the common center point corresponding to that first arrival time, and the coordinates of this common center point can be determined as the coordinates of the common center point corresponding to that first arrival time. In this way, for each of these multiple first arrival times, the coordinates of the common center point corresponding to each first arrival time can be determined according to the above method, thereby obtaining multiple common center point coordinates.

[0067] Next, the computer device maps the coordinates of these multiple common center points to the same Cartesian coordinate system to obtain a scatter plot of the common center point coordinates. The computer device displays a user interface that includes the scatter plot of the common center point coordinates and a region selection box. The user can drag the region selection box to place a densely packed area of ​​scatter points from the common center point coordinate scatter plot within the region selection box. When the computer device detects the user's confirmation operation, it determines the coordinates of each common center point located within the dense area as candidate common center point coordinates. Since the common center point coordinates are the coordinates of the midpoint of the line connecting the shot point and the detection point, one common center point coordinate corresponds to one shot point and one detection point, that is, one common center point coordinate corresponds to one shot-receiver distance. In this way, after determining the candidate common center point coordinates, the candidate shot-receiver distances corresponding to the candidate common center point coordinates can be obtained. Then, the target shot-receiver distance within the shot-receiver distance threshold range is selected from the candidate shot-receiver distances, and the first arrival time corresponding to the target shot-receiver distance is selected from the multiple first arrival times.

[0068] The shot-receiver distance threshold range is preset. Moreover, the shot-receiver distance threshold range can be adjusted according to different needs.

[0069] The distance traveled by the refracted wave, which travels through the regolith and refraction layers to reach the detection point, is typically different from the distance traveled by the direct wave, which travels from the shot point along the surface to the detection point. By using the shot-receiver offset threshold range, it can be determined whether the seismic wave received at the detection point is a refracted wave or a direct wave. Therefore, identifying candidate shot-receiver offsets within the threshold range as the target offset, and then selecting the first arrival time corresponding to the target offset, helps to eliminate direct waves from the seismic waves received at the detection point. This ensures a more accurate constraint model based on refracted waves determined according to the following steps, further improving the accuracy of the near-surface velocity model.

[0070] Optionally, before determining the delay time and refraction velocity corresponding to the multiple shot points and multiple detection points based on the multiple first arrival times and multiple shot-receiver distances, abnormal first arrival times can be eliminated from the multiple first arrival times to ensure the quality of the first arrival times and facilitate a more accurate determination of the constraint model. For example, there is a specific correlation between the first arrival time and the shot-receiver distance, which can be linear or nonlinear. Therefore, after obtaining the multiple first arrival times and multiple shot-receiver distances, abnormal first arrival times that do not satisfy the correlation can be eliminated. As another example, for the same shot point, there is a specific correlation between the first arrival times corresponding to the multiple detection points. Therefore, after obtaining the multiple first arrival times, abnormal first arrival times that do not satisfy the correlation can be eliminated.

[0071] Step 102: Based on the delay time and refraction velocity corresponding to the multiple shot points, determine the weathering layer thickness and weathering layer velocity corresponding to the multiple shot points. Based on the delay time and refraction velocity corresponding to the multiple detection points, determine the weathering layer thickness and weathering layer velocity corresponding to the multiple detection points.

[0072] Since the weathering layer thickness and weathering layer velocity corresponding to the multiple shot points are determined in the same way, one shot point is selected from the multiple shot points as the first shot point, and the weathering layer thickness and weathering layer velocity corresponding to the first shot point are determined according to the following operations (31)-(33) until the weathering layer thickness and weathering layer velocity corresponding to the multiple shot points are determined.

[0073] (31) Obtain the weathering layer information corresponding to the first shot point, which includes the weathering layer thickness or the weathering layer velocity corresponding to the first shot point.

[0074] In some embodiments, the database stores a correspondence between shot point identifiers and weathering layer information. Therefore, after selecting one shot point from the plurality of shot points as the first shot point, the weathering layer information corresponding to the first shot point can be obtained from the stored correspondence between shot point identifiers and weathering layer information based on the identifier of the first shot point. Due to certain special reasons, the weathering layer information corresponding to the first shot point can only include one of weathering layer thickness and weathering layer velocity. That is, the weathering layer information includes the weathering layer thickness corresponding to the first shot point. Or, the weathering layer information includes the weathering layer velocity corresponding to the first shot point.

[0075] (32) If the weathering layer information includes the weathering layer thickness corresponding to the first shot point, the weathering layer velocity corresponding to the first shot point is determined based on the delay time, refraction velocity and weathering layer thickness corresponding to the first shot point.

[0076] For example, based on the delay time, refraction velocity and weathering layer thickness corresponding to the first shot point, the weathering layer velocity corresponding to the first shot point is determined according to the following formula (2);

[0077]

[0078] In formula (2) above, t S1 When h represents the delay corresponding to the first shot, S1 v represents the thickness of the weathered layer corresponding to the first shot point. S1 v represents the refraction velocity corresponding to the first shot point. wS1 This represents the velocity of the weathering layer corresponding to the first shot point.

[0079] (33) If the weathering layer information includes the weathering layer velocity corresponding to the first shot point, the weathering layer thickness corresponding to the first shot point is determined based on the delay time, refraction velocity and weathering layer velocity corresponding to the first shot point.

[0080] The process of determining the thickness of the weathered layer corresponding to the first shot point based on the delay time, refraction velocity and weathering layer velocity corresponding to the first shot point is similar to the process of determining the velocity of the weathered layer corresponding to the first shot point based on the delay time, refraction velocity and weathering layer thickness corresponding to the first shot point in step (32) above. Therefore, you can refer to the relevant content of step (32) above, which will not be repeated here.

[0081] Of course, in practical applications, the weathering layer information corresponding to the first shot point may be 0. That is, the database does not store the weathering layer information corresponding to the first shot point. In this case, the weathering layer information corresponding to the first shot point can be determined according to relevant algorithms based on the weathering layer information corresponding to other shot points adjacent to the first shot point, and the surface undulation state between the first shot point and other shot points. For example, if the weathering layer information corresponding to other shot points includes the weathering layer thickness corresponding to other shot points, then the weathering layer thickness corresponding to the first shot point can be determined based on the weathering layer thickness corresponding to other shot points and the surface undulation state between the first shot point and other shot points. As another example, if the weathering layer information corresponding to other shot points includes the weathering layer velocity corresponding to other shot points, then the weathering layer velocity corresponding to the first shot point can be determined based on the weathering layer velocity corresponding to other shot points and the surface undulation state between the first shot point and other shot points.

[0082] In other words, if the absolute value of the difference in surface undulation between the first firing point and other firing points is less than the undulation threshold, the weathering layer information corresponding to the other firing points is directly determined as the weathering layer information corresponding to the first firing point. If the absolute value of the difference in surface undulation between the first firing point and other firing points is not less than the undulation threshold, the ratio between the surface of the first firing point and the surface of the other firing points is determined to obtain the surface ratio. Then, the weathering layer information corresponding to the other firing points is multiplied by this surface ratio to obtain the weathering layer information corresponding to the first firing point.

[0083] The fluctuation threshold is preset. Moreover, the fluctuation threshold can be adjusted according to different needs.

[0084] Similarly, select one of the multiple detection points as the second detection point, and determine the weathering layer thickness and weathering layer velocity corresponding to the second detection point according to the following operations (41)-(43) until the weathering layer thickness and weathering layer velocity corresponding to the multiple detection points are determined respectively.

[0085] (41) Obtain the weathering layer information corresponding to the second detection point, which includes the weathering layer thickness or the weathering layer velocity corresponding to the second detection point.

[0086] In some embodiments, the database stores a correspondence between detection point identifiers and weathering layer information. Therefore, after selecting one detection point from the plurality of detection points as the second detection point, the weathering layer information corresponding to the second detection point can be obtained from the stored correspondence between detection point identifiers and weathering layer information based on the identifier of the second detection point.

[0087] (42) If the weathering layer information includes the weathering layer thickness corresponding to the second detection point, the weathering layer velocity corresponding to the second detection point is determined based on the delay time, refraction velocity and weathering layer thickness corresponding to the second detection point.

[0088] The process of determining the weathering velocity corresponding to the second detection point based on the delay time, refraction velocity and weathering layer thickness of the second detection point is similar to the process of determining the weathering velocity corresponding to the first shot point based on the delay time, refraction velocity and weathering layer thickness of the first shot point in step (32) above. Therefore, you can refer to the relevant content of step (32) above, which will not be repeated here.

[0089] (43) If the weathering layer information includes the weathering layer velocity corresponding to the second detection point, the weathering layer thickness corresponding to the second detection point is determined based on the delay time, refraction velocity and weathering layer velocity corresponding to the second detection point.

[0090] The process of determining the thickness of the weathered layer corresponding to the second detection point based on the delay time, refraction velocity and weathering layer velocity corresponding to the second detection point is similar to the process of determining the thickness of the weathered layer corresponding to the first shot point based on the delay time, refraction velocity and weathering layer velocity corresponding to the first shot point in step (33) above. Therefore, you can refer to the relevant content of step (33) above, which will not be repeated here.

[0091] Of course, in practical applications, the weathering layer information corresponding to the second detection point may be 0. That is, the database does not store the weathering layer information corresponding to the second detection point. In this case, the weathering layer information corresponding to the second detection point can be determined based on the weathering layer information corresponding to other detection points adjacent to the second detection point, as well as the surface undulation state between the second detection point and other detection points, according to relevant algorithms. For detailed implementation process, please refer to the relevant content of the above steps, which will not be repeated here.

[0092] Step 103: Based on the refraction velocity, weathering layer thickness, and weathering layer velocity corresponding to the multiple shot points and multiple detection points, determine the constraint model. The constraint model includes M*N*Z three-dimensional grids. The M*N*Z three-dimensional grids are obtained by meshing the weathering layer and refraction layer of the exploration area. Each three-dimensional grid located in the weathering layer has the weathering layer velocity, and each three-dimensional grid located in the refraction layer has the refraction velocity.

[0093] In some embodiments, the constraint model is determined according to the following steps (51)-(55).

[0094] (51) The exploration area is divided into planar grids to obtain M*N planar grids, each of which corresponds to a range of Cartesian coordinates.

[0095] The exploration area is divided into M intervals in the horizontal direction and N intervals in the vertical direction to obtain M*N planar grids. The area of ​​each of the M*N planar grids is the same.

[0096] Suppose that the exploration area is divided into 4 intervals in the horizontal direction and 3 intervals in the vertical direction to obtain 4*3 planar grids, and the area of ​​each planar grid in the 4*3 planar grids is the same.

[0097] (52) Match the plane rectangular coordinates corresponding to the multiple shot points and the multiple detection points with the plane rectangular coordinate ranges corresponding to the M*N plane grids, so as to determine the plane grid matched for each shot point and the plane grid matched for each detection point from the M*N plane grids.

[0098] The database stores the Cartesian coordinates corresponding to the multiple shot points and the multiple detection points. For any shot point, its Cartesian coordinates are matched with the range of Cartesian coordinates corresponding to the M*N planar grids to determine the matching planar grid for that shot point. In other words, if the Cartesian coordinates of the shot point fall within the range of Cartesian coordinates of a certain planar grid among the M*N planar grids, then that planar grid is determined to be the matching planar grid for that shot point.

[0099] Similarly, for any one of the multiple detection points, the Cartesian coordinates corresponding to that detection point are matched with the Cartesian coordinate ranges corresponding to the M*N planar grids to determine the matching planar grid for that detection point. That is, if the Cartesian coordinates corresponding to that detection point fall within the Cartesian coordinate range of a certain planar grid among the M*N planar grids, then that planar grid is determined to be the matching planar grid for that detection point.

[0100] Assume that the planar meshes matched by shot points S1, S2, and S3, and the planar meshes matched by detection points R1, R2, R3, R4, and R5 are as follows: Figure 3 As shown. In Figure 3 In the process, the planar mesh matched by the shot point S1 is the same as the planar mesh matched by the detection point R3.

[0101] (53) Map the refraction velocity, weathering layer thickness and weathering layer velocity corresponding to the multiple shot points and the multiple detection points to their respective matched planar grids.

[0102] Based on the above description, following steps 101 and 102, the refraction velocity, weathering layer thickness, and weathering layer velocity corresponding to the plurality of shot points and the plurality of detection points can be determined. Therefore, after determining the planar meshes that match the plurality of shot points and the plurality of detection points, the refraction velocity, weathering layer thickness, and weathering layer velocity corresponding to the plurality of shot points and the plurality of detection points can be mapped to their respective matching planar meshes, so that the planar meshes matching the plurality of shot points and the plurality of detection points have matching refraction velocities, weathering layer thicknesses, and weathering layer velocities.

[0103] (54) In the case that there are a effective planar grids in the M planar grids located in the same row, the refraction velocity, weathering layer thickness and weathering layer velocity corresponding to the a effective planar grids are interpolated to obtain the refraction velocity, weathering layer thickness and weathering layer velocity corresponding to each blank planar grid in the M planar grids. a is greater than 1 and less than M. The effective planar grid refers to the planar grid that matches the multiple shot points and the multiple detection points. The blank planar grid refers to the planar grid other than the effective planar grid.

[0104] In some embodiments, the multiple shot points and multiple detection points may not cover the entire exploration area. That is, among the M*N planar grids obtained by planarizing the exploration area, there are planar grids that match the multiple shot points and multiple detection points respectively, and there are also planar grids that do not match the multiple shot points and multiple detection points. The planar grids that match the multiple shot points and multiple detection points are valid planar grids, and valid planar grids have matching refraction velocities, weathering layer thicknesses, and weathering layer velocities. The planar grids that do not match the multiple shot points and multiple detection points are blank planar grids, and blank planar grids do not have matching refraction velocities, weathering layer thicknesses, and weathering layer velocities.

[0105] Given that *a* effective planar grids exist among M planar grids in the same row, the refraction velocities corresponding to these *a* effective planar grids are interpolated using relevant techniques to obtain the refraction velocities corresponding to the blank planar grids in the M planar grids. Similarly, the weathering layer thicknesses corresponding to these *a* effective planar grids are interpolated using relevant techniques to obtain the weathering layer thicknesses corresponding to the blank planar grids in the M planar grids. Finally, the weathering layer velocities corresponding to these *a* effective planar grids are interpolated using relevant techniques to obtain the weathering layer velocities corresponding to the blank planar grids in the M planar grids. In this way, each planar grid in the M planar grids in the same row has a matching refraction velocity, weathering layer thickness, and weathering layer velocity.

[0106] For example, please refer to Figure 3 ,exist Figure 3 In the first row of four planar grids, there are two valid planar grids and two blank planar grids. The first valid planar grid is the one matched to shot point S3, and the second valid planar grid is the one matched to detection point R4. The refraction velocities corresponding to the first and second valid planar grids are interpolated to obtain the refraction velocities corresponding to the two blank planar grids in the first row. Similarly, the weathering layer thicknesses corresponding to the first and second valid planar grids are interpolated to obtain the weathering layer thicknesses corresponding to the two blank planar grids in the first row. Finally, the weathering layer velocities corresponding to the first and second valid planar grids are interpolated to obtain the weathering layer velocities corresponding to the two blank planar grids in the first row.

[0107] When there are *a* valid planar grids among M planar grids in the same row, before interpolating the refraction velocity, weathering layer thickness, and weathering layer velocity corresponding to each of the *a* valid planar grids, it is necessary to determine the refraction velocity, weathering layer thickness, and weathering layer velocity corresponding to any one of the M planar grids. That is, if any one of the M planar grids has multiple refraction velocities, multiple weathering layer thicknesses, and multiple weathering layer velocities, then each of these multiple refraction velocities, multiple weathering layer thicknesses, and multiple weathering layer velocities is averaged to obtain the refraction velocity, weathering layer thickness, and weathering layer velocity corresponding to any one planar grid.

[0108] Based on the above description, the planar mesh matched by the multiple shot points and multiple detection points is determined based on the Cartesian coordinates corresponding to the shot points and multiple detection points, and the range of Cartesian coordinates corresponding to the M*N planar meshes. Therefore, when multiple Cartesian coordinates corresponding to the multiple shot points and multiple detection points are within the same Cartesian coordinate range, and this Cartesian coordinate range corresponds to the Cartesian coordinate range of a certain Cartesian mesh among the M*N planar meshes, then this planar mesh is the planar mesh matched by the multiple points corresponding to the multiple Cartesian coordinates. In this case, the planar mesh matches multiple refraction velocities, multiple weathering layer thicknesses, and multiple weathering layer velocities.

[0109] For example, please refer to Figure 3 ,exist Figure 3 In the third row, among the four planar grids, there are three valid planar grids and one blank planar grid. The first valid planar grid is the grid matched between the shot point S1 and the detection point R3. Therefore, the first valid planar grid has two refraction velocities, two weathering layer thicknesses, and two weathering layer velocities. The two refraction velocities are the refraction velocities corresponding to the shot point S1 and the detection point R3, respectively. The two weathering layer thicknesses are the weathering layer thicknesses corresponding to the shot point S1 and the detection point R3, respectively. Then, the two refraction velocities are averaged to obtain the refraction velocity corresponding to the first valid planar grid; the two weathering layer thicknesses are averaged to obtain the weathering layer thickness corresponding to the first valid planar grid; and the two weathering layer velocities are averaged to obtain the weathering layer velocity corresponding to the first valid planar grid.

[0110] (55) Discretize the M*N planar meshes mapped with refraction velocity, weathering layer thickness and weathering layer velocity to obtain the constraint model.

[0111] Select one planar grid from the M*N planar grids as the first planar grid, and discretize the first planar grid according to the following operation until each planar grid has been discretized:

[0112] The surface velocity is obtained, and the first planar grid is extended multiple times along the depth direction of the stratum according to the reference thickness until the bottom surface of the refractive layer is reached to obtain Z three-dimensional grids. Based on the weathering layer thickness and weathering layer velocity corresponding to the first planar grid, the velocity factor is determined. The velocity factor is used to indicate the correspondence between the weathering layer velocity and the stratum depth. Based on the surface velocity and the velocity factor, the weathering layer velocity corresponding to each three-dimensional grid located in the weathering layer in the Z three-dimensional grids is determined. The refractive velocity corresponding to the first planar grid is determined as the refractive velocity corresponding to each three-dimensional grid located in the refractive layer in the Z three-dimensional grids.

[0113] Based on the reference thickness, the first planar grid is extended multiple times along the depth direction of the strata, with each extension resulting in a 3D grid, until it reaches the bottom of the refractive layer, resulting in Z 3D grids. The length and width of each of the Z 3D grids are the same as those of the first planar grid. Some of the Z 3D grids are located in the weathering layer, and some are located in the refractive layer. The height of each 3D grid located in the weathering layer is the same as the reference thickness, and the sum of the heights of the Z 3D grids is the same as the weathering layer thickness corresponding to the first planar grid.

[0114] Assuming a reference thickness of 10 meters, the first planar grid is the planar grid matched to shot point S3, and the weathering layer thickness corresponding to the first planar grid is 25 meters. Then, extending the first planar grid three times along the depth direction according to the reference thickness will reach the bottom of the refractive layer, resulting in three 3D grids. The first and second 3D grids are located in the weathering layer, while the third 3D grid is located in the refractive layer.

[0115] For example, based on the weathering layer thickness and weathering layer velocity corresponding to the first planar grid, the velocity factor is determined according to the following formula (3);

[0116]

[0117] In the above formula (3), η represents the velocity factor, v w represents the weathering velocity corresponding to the first planar grid, and h represents the weathering thickness corresponding to the first planar grid.

[0118] Then, based on the surface velocity and velocity factor, the weathering velocity corresponding to each three-dimensional grid located in the weathering layer is determined according to the following formula (4);

[0119] v w1 =v0+ηΔh1 (4)

[0120] In formula (4) above, v w1 Δh1 represents the weathering velocity corresponding to any three-dimensional grid in the various three-dimensional grids located in the weathering layer; v0 represents the surface velocity, η represents the velocity factor, and Δh1 represents the distance between the bottom surface of the three-dimensional grid and the surface.

[0121] Based on the above description, the first planar grid is the planar grid matched with the shot point S3. Therefore, the refraction velocity corresponding to the first planar grid is the refraction velocity corresponding to the shot point S3. Thus, the refraction velocity corresponding to the first planar grid is determined to be the refraction velocity corresponding to the third solid grid among the three solid grids.

[0122] The reference thickness is preset. Moreover, the reference thickness can be adjusted according to different needs.

[0123] For example, please refer to Figure 4 , Figure 4 This is a schematic diagram of a constraint model provided in an embodiment of this application. Figure 4 In this model, different gray levels are used to represent the weathering velocity or refraction velocity of each of the M*N*Z 3D grids in the constraint model.

[0124] Step 104: Perform tomographic inversion on the constrained model to obtain the near-surface velocity model, which represents the seismic wave velocity corresponding to different strata depths in the exploration area.

[0125] The constraint model is extended to the effective model depth to obtain the near-surface velocity model. The effective model depth is the difference between the minimum ordinate of the multiple shot points and the multiple detection points and the reference value.

[0126] Based on the above description, each of the M*N planar grids is discretized according to step 103 to obtain a constraint model. This constraint model includes M*N*Z three-dimensional grids, which include grids located in the weathering layer and grids located in the refractive layer. The grids located in the refractive layer are then extended to the effective model depth using relevant techniques to obtain the near-surface velocity model.

[0127] Optionally, the top surface of the refractive layer is taken as the high-velocity top, and the constraint model is extended to the effective model depth, that is, each 3D mesh located below the high-velocity top is extended to the effective model depth. For example, the 3D mesh located below the high-velocity top is extended to the effective model depth using a small gradient extrapolation method. Of course, in practical applications, other methods can also be used to extend the 3D mesh located below the high-velocity top to the effective model depth, and this application embodiment does not limit this.

[0128] The reference value is preset. Furthermore, the reference value can be adjusted according to different needs. For example, the reference value is 500.

[0129] In some embodiments, before performing tomographic inversion on the constrained model to obtain the near-surface velocity model, constraint factors can be set for each of the M*N*Z three-dimensional grids included in the constrained model according to relevant technologies. Then, the weathering velocity or refraction velocity corresponding to each three-dimensional grid can be optimized by using the constraint factors corresponding to each three-dimensional grid, thereby improving the accuracy of the constrained model and further improving the accuracy of the near-surface velocity model.

[0130] For example, please refer to Figure 5 , Figure 5 This is a schematic diagram of a near-surface velocity model provided in an embodiment of this application. Figure 5 The top figure shows the near-surface velocity model obtained by directly performing tomographic inversion on the constrained model, without optimizing the weathering or refraction velocities corresponding to each 3D grid within the constrained model using constraint factors. The bottom figure shows the near-surface velocity model obtained by optimizing the weathering or refraction velocities corresponding to each 3D grid within the constrained model using constraint factors, and then performing tomographic inversion on the constrained model. Figure 5 It can be seen that after optimizing the weathering layer velocity or refraction velocity corresponding to each three-dimensional grid by constraint factors, the boundary between the weathering layer and the refraction layer in the near-surface velocity model obtained by performing tomographic inversion on the constraint model is clearer, and the refraction velocity or weathering layer velocity corresponding to different strata depths is more accurate.

[0131] In some embodiments, after determining the near-surface velocity model according to the above steps, the near-surface velocity model can be analyzed and evaluated from aspects such as model accuracy, model rationality, and model application effect. If the user is not satisfied with the near-surface velocity model, the first arrival time and shot-receiver distance are reacquired, and a new near-surface velocity model is determined according to the above steps until the user is satisfied with the near-surface velocity model.

[0132] In this embodiment, the constraint model is determined based on the refraction velocity, regolith thickness, and regolith velocity corresponding to the multiple shot points and multiple detection points, respectively, and the near-surface velocity model is obtained by tomographic inversion of the constraint model. That is, the accuracy of the near-surface velocity model is improved by combining various information corresponding to the multiple shot points and multiple detection points with the refraction wave method and travel-time tomography. Furthermore, since the near-surface velocity model is established by combining the refraction wave method and travel-time tomography, it can solve the problem that near-surface velocity models established using a single method cannot be applied to all near-surface types.

[0133] Figure 6 This is a schematic diagram of a near-surface velocity model building device provided in an embodiment of this application. This near-surface velocity model building device can be implemented as part or all of a computer device, using software, hardware, or a combination of both. Please refer to... Figure 6 The device includes: a first determining module 601, a second determining module 602, a third determining module 603, and a tomographic inversion module 604.

[0134] The first determining module 601 is used to determine the delay time and refraction velocity corresponding to the multiple shot points and multiple detection points based on multiple first arrival times and multiple shot-receiver distances. The first arrival time refers to the time it takes for a seismic wave excited by a shot point to first reach a detection point. The shot-receiver distance is the distance between a shot point and a detection point. The delay time corresponding to a shot point is the difference between the time it takes for the seismic wave to travel from that shot point to the refraction layer and a first reference time. The first reference time is the ratio of the horizontal projection length of the propagation distance of the seismic wave along the weathering layer to the refraction layer to the refraction velocity. The delay time of a detection point is the difference between the time it takes for the seismic wave to travel from the refraction layer to that detection point and a second reference time. The second reference time is the ratio of the horizontal projection length of the propagation distance of the seismic wave along the weathering layer to the detection point to the refraction velocity. Detailed implementation processes are described in the corresponding contents of the above embodiments and will not be repeated here.

[0135] The second determining module 602 is used to determine the weathering layer thickness and weathering layer velocity corresponding to the plurality of shot points based on the delay time and refraction velocity corresponding to the plurality of shot points, and to determine the weathering layer thickness and weathering layer velocity corresponding to the plurality of detection points based on the delay time and refraction velocity corresponding to the plurality of detection points. Detailed implementation processes are described in the corresponding contents of the above embodiments and will not be repeated here.

[0136] The third determining module 603 is used to determine a constraint model based on the refraction velocity, weathering layer thickness, and weathering layer velocity corresponding to the multiple shot points and multiple detection points, respectively. The constraint model includes M*N*Z three-dimensional grids, which are obtained by meshing the weathering layer and refraction layer of the exploration area. Each three-dimensional grid located in the weathering layer has a weathering layer velocity, and each three-dimensional grid located in the refraction layer has a refraction velocity. For detailed implementation process, please refer to the corresponding content in the above embodiments, which will not be repeated here.

[0137] The tomographic inversion module 604 is used to perform tomographic inversion on the constrained model to obtain the near-surface velocity model, which represents the seismic wave velocity corresponding to different strata depths in the exploration area. Detailed implementation processes are described in the corresponding contents of the above embodiments and will not be repeated here.

[0138] Optionally, the first determining module 601 is specifically used for:

[0139] Select one shot point from the multiple shot points as the first shot point, and determine the time delay and refraction velocity corresponding to the first shot point according to the following operation, until the time delay and refraction velocity corresponding to each of the multiple shot points are determined:

[0140] Obtain multiple first arrival times and multiple first shot-detector distances corresponding to the first shot point. The multiple first arrival times refer to the time elapsed after the seismic wave triggered by the first shot point first arrives at the multiple first detection points. The multiple first shot-detector distances refer to the distance between the first shot point and the multiple first detection points. The multiple first detection points are the detection points corresponding to the first shot point.

[0141] Based on the multiple first arrival times and the multiple first shot-receiver distances, multiple first delay times and multiple first refraction velocities are determined;

[0142] The average of these multiple first delay times is taken to obtain the delay time corresponding to the first shot point;

[0143] The average of these multiple first refraction velocities is taken to obtain the refraction velocity corresponding to the first shot point.

[0144] Optionally, the device further includes:

[0145] The first acquisition module is used to acquire the coordinates of the common center point corresponding to each of the multiple arrival times, so as to obtain multiple common center point coordinates. The common center point coordinates refer to the coordinates of the midpoint of the line connecting the shot point and the detection point corresponding to the corresponding arrival time.

[0146] The first selection module is used to select the coordinates of the common center point that meet the preset conditions from the multiple common center point coordinates to obtain the candidate common center point coordinates;

[0147] The second acquisition module is used to acquire the shot-receiver distance corresponding to the coordinates of the candidate common center point, so as to obtain the candidate shot-receiver distance;

[0148] The second selection module is used to select the target gun-receiver distance from the candidate gun-receiver distances that is within the gun-receiver distance threshold range.

[0149] The third selection module is used to select the first arrival time corresponding to the target shot-receiver distance from the multiple first arrival times.

[0150] Optionally, the second determining module 602 is specifically used for:

[0151] Select one of the multiple firing points as the first firing point, and determine the weathering layer thickness and weathering layer velocity corresponding to the first firing point according to the following operations, until the weathering layer thickness and weathering layer velocity corresponding to each of the multiple firing points are determined:

[0152] Obtain the weathering layer information corresponding to the first shot point. The weathering layer information includes the weathering layer thickness or the weathering layer velocity corresponding to the first shot point.

[0153] Given that the weathering layer information includes the weathering layer thickness corresponding to the first shot point, the weathering layer velocity corresponding to the first shot point is determined based on the delay time, refraction velocity, and weathering layer thickness corresponding to the first shot point.

[0154] Given that the weathering layer information includes the weathering layer velocity corresponding to the first shot point, the weathering layer thickness corresponding to the first shot point is determined based on the delay time, refraction velocity, and weathering layer velocity corresponding to the first shot point.

[0155] Optionally, the third determining module 603 includes:

[0156] Planar gridding unit is used to divide the exploration area into planar grids to obtain M*N planar grids, each planar grid corresponding to a range of Cartesian coordinates;

[0157] The matching unit is used to match the Cartesian coordinates corresponding to the multiple shot points and the multiple detection points with the Cartesian coordinate ranges corresponding to the M*N planar grids, so as to determine the planar grid matched by each shot point and the planar grid matched by each detection point from the M*N planar grids.

[0158] The mapping unit is used to map the refraction velocity, weathering layer thickness, and weathering layer velocity corresponding to the multiple shot points and the multiple detection points to their respective matched planar meshes.

[0159] The interpolation processing unit is used to interpolate the refraction velocity, weathering layer thickness, and weathering layer velocity corresponding to the a effective planar grids in the M planar grids located in the same row, so as to obtain the refraction velocity, weathering layer thickness, and weathering layer velocity corresponding to each blank planar grid in the M planar grids. a is greater than 1 and less than M. The effective planar grids refer to the planar grids that match the multiple shot points and the multiple detection points, and the blank planar grids refer to the planar grids other than the effective planar grids.

[0160] Discrete processing unit is used to discretize the M*N planar meshes mapped with refraction velocity, weathering layer thickness and weathering layer velocity to obtain the constraint model.

[0161] Optionally, the discrete processing unit is specifically used for:

[0162] Select one planar grid from the M*N planar grids as the first planar grid, and discretize the first planar grid according to the following operation until each planar grid has been discretized:

[0163] Obtain surface velocity;

[0164] Based on the reference thickness, the first planar grid is extended multiple times along the depth direction of the stratum until the bottom surface of the refractive layer is reached to obtain Z three-dimensional grids.

[0165] Based on the weathering layer thickness and weathering layer velocity corresponding to the first planar grid, a velocity factor is determined. The velocity factor is used to indicate the correspondence between the weathering layer velocity and the formation depth.

[0166] Based on the surface velocity and velocity factor, the weathering layer velocity corresponding to each three-dimensional grid located in the weathering layer in the Z three-dimensional grids is determined;

[0167] The refraction velocity corresponding to the first planar grid is determined as the refraction velocity corresponding to each of the Z three-dimensional grids located in the refraction layer.

[0168] Optionally, the third determining module 603 further includes:

[0169] An average element is used to average the multiple refraction velocities, multiple weathering layer thicknesses, and multiple weathering layer velocities of any one of the M planar grids, so as to obtain the refraction velocity, weathering layer thickness, and weathering layer velocity corresponding to any one planar grid.

[0170] Optionally, the tomographic inversion module 604 is specifically used for:

[0171] The constraint model is extended to the effective model depth to obtain the near-surface velocity model. The effective model depth is the difference between the minimum ordinate of the multiple shot points and the multiple detection points and the reference value.

[0172] In this embodiment, the constraint model is determined based on the refraction velocity, regolith thickness, and regolith velocity corresponding to the multiple shot points and multiple detection points, respectively, and the near-surface velocity model is obtained by tomographic inversion of the constraint model. That is, the accuracy of the near-surface velocity model is improved by combining various information corresponding to the multiple shot points and multiple detection points with the refraction wave method and travel-time tomography. Furthermore, since the near-surface velocity model is established by combining the refraction wave method and travel-time tomography, it can solve the problem that near-surface velocity models established using a single method cannot be applied to all near-surface types.

[0173] It should be noted that the near-surface velocity model building device provided in the above embodiments is only illustrated by the division of the above functional modules. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above. In addition, the near-surface velocity model building device and the near-surface velocity model building method embodiments provided in the above embodiments belong to the same concept, and the specific implementation process is detailed in the method embodiments, which will not be repeated here.

[0174] Figure 7 This is a structural block diagram of a computer device 700 provided in an embodiment of this application. The computer device 700 can be a portable mobile terminal, such as a smartphone, tablet computer, laptop computer, or desktop computer. The computer device 700 may also be referred to as user equipment, portable terminal, laptop terminal, desktop terminal, or other names.

[0175] Typically, computer device 700 includes a processor 701 and a memory 702.

[0176] Processor 701 may include one or more processing cores, such as a quad-core processor, an octa-core processor, etc. Processor 701 may be implemented using at least one hardware form selected from DSP (Digital Signal Processing), FPGA (Field-Programmable Gate Array), and PLA (Programmable Logic Array). Processor 701 may also include a main processor and a coprocessor. The main processor, also known as a CPU (Central Processing Unit), is used to process data in the wake-up state; the coprocessor is a low-power processor used to process data in the standby state. In some embodiments, processor 701 may integrate a GPU (Graphics Processing Unit), which is responsible for rendering and drawing the content to be displayed on the screen. In some embodiments, processor 701 may also include an AI (Artificial Intelligence) processor, which is used to handle computational operations related to machine learning.

[0177] The memory 702 may include one or more computer-readable storage media, which may be non-transitory. The memory 702 may also include high-speed random access memory and non-volatile memory, such as one or more disk storage devices or flash memory devices. In some embodiments, the non-transitory computer-readable storage media in the memory 702 is used to store at least one instruction, which is executed by the processor 701 to implement the method for establishing a near-surface velocity model provided in the method embodiments of this application.

[0178] In some embodiments, the computer device 700 may also optionally include a peripheral device interface 703 and at least one peripheral device. The processor 701, memory 702, and peripheral device interface 703 can be connected via a bus or signal line. Each peripheral device can be connected to the peripheral device interface 703 via a bus, signal line, or circuit board. Specifically, the peripheral device includes at least one of the following: a radio frequency circuit 704, a touch display screen 705, a camera 706, an audio circuit 707, a positioning component 708, and a power supply 709.

[0179] Peripheral device interface 703 can be used to connect at least one I / O (Input / Output) related peripheral device to processor 701 and memory 702. In some embodiments, processor 701, memory 702 and peripheral device interface 703 are integrated on the same chip or circuit board; in some other embodiments, any one or two of processor 701, memory 702 and peripheral device interface 703 can be implemented on separate chips or circuit boards, which is not limited in this embodiment.

[0180] The radio frequency (RF) circuit 704 is used to receive and transmit RF (Radio Frequency) signals, also known as electromagnetic signals. The RF circuit 704 communicates with communication networks and other communication devices via electromagnetic signals. The RF circuit 704 converts electrical signals into electromagnetic signals for transmission, or converts received electromagnetic signals back into electrical signals. Optionally, the RF circuit 704 includes: an antenna system, an RF transceiver, one or more amplifiers, a tuner, an oscillator, a digital signal processor, a codec chipset, a user identity module card, etc. The RF circuit 704 can communicate with other computer devices through at least one wireless communication protocol. This wireless communication protocol includes, but is not limited to: the World Wide Web, metropolitan area networks, intranets, various generations of mobile communication networks (2G, 3G, 4G, and 5G), wireless local area networks, and / or WiFi (Wireless Fidelity) networks. In some embodiments, the RF circuit 704 may also include circuitry related to NFC (Near Field Communication), which is not limited in this application embodiment.

[0181] Display screen 705 is used to display a UI (User Interface). This UI may include graphics, text, icons, videos, and any combination thereof. When display screen 705 is a touch display screen, it also has the ability to collect touch signals on or above its surface. These touch signals can be input as control signals to processor 701 for processing. In this case, display screen 705 can also be used to provide virtual buttons and / or a virtual keyboard, also known as soft buttons and / or a soft keyboard. In some embodiments, there may be one display screen 705, positioned as the front panel of the computer device 700; in other embodiments, there may be at least two display screens 705, respectively positioned on different surfaces of the computer device 700 or in a folded design; in still other embodiments, display screen 705 may be a flexible display screen, positioned on a curved or folded surface of the computer device 700. Furthermore, display screen 705 may be configured as a non-rectangular, irregular shape, i.e., a non-rectangular screen. Display screen 705 may be made of materials such as LCD (Liquid Crystal Display) or OLED (Organic Light-Emitting Diode).

[0182] The camera assembly 706 is used to acquire images or videos. Optionally, the camera assembly 706 includes a front-facing camera and a rear-facing camera. Typically, the front-facing camera is located on the front panel of the computer device, and the rear-facing camera is located on the back of the computer device. In some embodiments, there are at least two rear-facing cameras, which are any one of a main camera, a depth-sensing camera, a wide-angle camera, and a telephoto camera, to achieve background blurring by fusion of the main camera and the depth-sensing camera, panoramic shooting by fusion of the main camera and the wide-angle camera, VR (Virtual Reality) shooting, or other fusion shooting functions. In some embodiments, the camera assembly 706 may also include a flash. The flash can be a single-color temperature flash or a dual-color temperature flash. A dual-color temperature flash refers to a combination of a warm-light flash and a cool-light flash, which can be used for light compensation at different color temperatures.

[0183] The audio circuit 707 may include a microphone and a speaker. The microphone is used to collect sound waves from the user and the environment, converting the sound waves into electrical signals that are input to the processor 701 for processing, or input to the radio frequency circuit 704 for voice communication. For stereo sound acquisition or noise reduction purposes, multiple microphones may be used, each located in a different part of the computer device 700. The microphone may also be an array microphone or an omnidirectional microphone. The speaker is used to convert electrical signals from the processor 701 or the radio frequency circuit 704 into sound waves. The speaker may be a conventional diaphragm speaker or a piezoelectric ceramic speaker. When the speaker is a piezoelectric ceramic speaker, it can convert electrical signals not only into audible sound waves but also into inaudible sound waves for purposes such as distance measurement. In some embodiments, the audio circuit 707 may also include a headphone jack.

[0184] The positioning component 708 is used to locate the current geographical location of the computer device 700 in order to enable navigation or LBS (Location Based Service). The positioning component 708 can be a positioning component based on the US GPS (Global Positioning System), China's BeiDou system, or Russia's Galileo system.

[0185] Power supply 709 is used to supply power to the various components in computer device 700. Power supply 709 can be AC ​​power, DC power, a disposable battery, or a rechargeable battery. When power supply 709 includes a rechargeable battery, the rechargeable battery can be a wired rechargeable battery or a wireless rechargeable battery. A wired rechargeable battery is a battery that is charged via a wired line, while a wireless rechargeable battery is a battery that is charged via a wireless coil. The rechargeable battery can also be used to support fast charging technology.

[0186] Those skilled in the art will understand that Figure 7 The structure shown does not constitute a limitation on the computer device 700, and may include more or fewer components than shown, or combine certain components, or use different component arrangements.

[0187] In some embodiments, a computer-readable storage medium is also provided, which stores a computer program that, when executed by a processor, implements the steps of the method for establishing the near-surface velocity model in the above embodiments. For example, the computer-readable storage medium may be a ROM, RAM, CD-ROM, magnetic tape, floppy disk, or optical data storage device, etc.

[0188] It is worth noting that the computer-readable storage medium mentioned in the embodiments of this application can be a non-volatile storage medium, in other words, it can be a non-transient storage medium.

[0189] It should be understood that all or part of the steps of the above embodiments can be implemented by software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented wholly or partially in the form of a computer program product. The computer program product includes one or more computer instructions. The computer instructions can be stored in the above-described computer-readable storage medium.

[0190] That is, in some embodiments, a computer program product containing instructions is also provided, which, when run on a computer, causes the computer to perform the steps of the method for establishing the near-surface velocity model described above.

[0191] It should be understood that "at least one" as mentioned herein refers to one or more, and "multiple" refers to two or more. In the description of the embodiments of this application, unless otherwise stated, " / " means "or," for example, A / B can mean A or B; "and / or" in this document is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. In addition, in order to clearly describe the technical solutions of the embodiments of this application, the terms "first," "second," etc., are used in the embodiments of this application to distinguish identical or similar items with substantially the same function and effect. Those skilled in the art will understand that the terms "first," "second," etc., do not limit the quantity or execution order, and the terms "first," "second," etc., are not necessarily different.

[0192] It should be noted that the information (including but not limited to user device information, user personal information, etc.), data (including but not limited to data used for analysis, stored data, displayed data, etc.), and signals involved in the embodiments of this application are all authorized by the user or fully authorized by all parties, and the collection, use, and processing of related data must comply with the relevant laws, regulations, and standards of the relevant countries and regions. For example, the first arrival time and shot-receiver distance involved in the embodiments of this application were obtained under full authorization.

[0193] The above descriptions are embodiments provided in this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method of building a near-surface velocity model, characterized in that, The exploration area has multiple shot points and multiple detection points, and the method includes: Based on multiple first arrival times and multiple shot-receiver distances, the delay time and refraction velocity corresponding to the multiple shot points and the multiple detection points are determined respectively. The first arrival time refers to the time it takes for a seismic wave excited by a shot point to first reach a detection point. The shot-receiver distance refers to the distance between a shot point and a detection point. The delay time corresponding to the shot point is the difference between the time it takes for the seismic wave to travel from the shot point to the refraction layer and a first reference time. The first reference time is the ratio of the horizontal projection length of the propagation distance of the seismic wave along the weathering layer to the refraction layer to the refraction velocity. The delay time of the detection point is the difference between the time it takes for the seismic wave to travel from the refraction layer to the detection point and a second reference time. The second reference time is the ratio of the horizontal projection length of the propagation distance of the seismic wave along the weathering layer to the detection point to the refraction velocity. Based on the delay time and refraction velocity corresponding to the multiple shot points, the weathering layer thickness and weathering layer velocity corresponding to the multiple shot points are determined respectively. Based on the delay time and refraction velocity corresponding to the multiple detection points, the weathering layer thickness and weathering layer velocity corresponding to the multiple detection points are determined respectively. plane-meshing the exploration area to obtain M N plane meshes, each plane mesh corresponding to a plane rectangular coordinate range; The plane rectangular coordinates corresponding to the plurality of shot points and the plurality of detection points are matched with the plane rectangular coordinates corresponding to the M N plane grids respectively, so as to determine the plane grid matched with each shot point and the plane grid matched with each detection point from the M N plane grids respectively, so as to determine the plane grid matched with each shot point and the plane grid matched with each detection point from the M The refraction velocity, weathering layer thickness, and weathering layer velocity corresponding to the plurality of shot points and the plurality of detection points are mapped to their respective matched planar grids; If there are a valid planar grids among M planar grids in the same row, the refraction velocity, weathering layer thickness, and weathering layer velocity corresponding to the a valid planar grids are interpolated to obtain the refraction velocity, weathering layer thickness, and weathering layer velocity corresponding to each blank planar grid in the M planar grids. Here, a is greater than 1 and less than M. The valid planar grids refer to the planar grids that match the multiple shot points and the multiple detection points. The blank planar grids refer to the planar grids other than the valid planar grids. For the M that is mapped to have refraction velocity, regolith thickness, and regolith velocity N planar grids are discretized to obtain a constraint model, wherein the constraint model includes M N Z three-dimensional grids, the M N Z three-dimensional grids are obtained by gridding the weathered layer and the refractive layer of the exploration area, and each three-dimensional grid located in the weathered layer has a weathering layer velocity, and each three-dimensional grid located in the refractive layer has a refractive velocity; The constrained model is subjected to tomographic inversion to obtain a near-surface velocity model, which represents the seismic wave velocity at different strata depths in the exploration area.

2. The method as described in claim 1, characterized in that, The step of determining the time delay and refraction velocity corresponding to the multiple shot points and the multiple detection points based on multiple first arrival times and multiple shot-receiver distances includes: Select one shot point from the plurality of shot points as the first shot point, and determine the delay time and refraction velocity corresponding to the first shot point according to the following operation, until the delay time and refraction velocity corresponding to each of the plurality of shot points are determined respectively: The first first arrival time and the first shot-detector distance are obtained corresponding to the first shot point. The first first arrival time refers to the time elapsed after the seismic wave excited by the first shot point first arrives at the first detection point. The first shot-detector distance refers to the distance between the first shot point and the first detection point. The first detection point is the detection point corresponding to the first shot point. Based on the plurality of first arrival times and the plurality of first shot-receiver distances, a plurality of first delay times and a plurality of first refraction velocities are determined; The average of the multiple first delay times is taken to obtain the delay time corresponding to the first shot point; The average of the multiple first refraction velocities is used to obtain the refraction velocity corresponding to the first shot point.

3. The method as described in claim 1 or 2, characterized in that, Before determining the delay time and refraction velocity corresponding to the multiple shot points and the multiple detection points based on multiple first arrival times and multiple shot-receiver distances, the method further includes: Obtain the coordinates of the common center point corresponding to each of the multiple arrival times to obtain multiple common center point coordinates. The common center point coordinates refer to the coordinates of the midpoint of the line connecting the shot point and the detection point corresponding to the corresponding arrival time. From the multiple common center point coordinates, select the common center point coordinates that meet the preset conditions to obtain the candidate common center point coordinates; Obtain the shot-receiver distance corresponding to the coordinates of the candidate common center point to obtain the candidate shot-receiver distance; Select the target gun-receiver distance that is within the gun-receiver distance threshold range from the candidate gun-receiver distances; Select the first arrival time corresponding to the target gun-receiver distance from the plurality of first arrival times.

4. The method as described in claim 1, characterized in that, The step of determining the weathering layer thickness and weathering layer velocity corresponding to the plurality of shot points based on the delay time and refraction velocity corresponding to the plurality of shot points includes: Select one shot from the plurality of shot points as the first shot point, and determine the weathering layer thickness and weathering layer velocity corresponding to the first shot point according to the following operation, until the weathering layer thickness and weathering layer velocity corresponding to each of the plurality of shot points are determined: Obtain weathering layer information corresponding to the first shot point, wherein the weathering layer information includes the weathering layer thickness or the weathering layer velocity corresponding to the first shot point. When the weathering layer information includes the weathering layer thickness corresponding to the first shot point, the weathering layer velocity corresponding to the first shot point is determined based on the delay time, refraction velocity and weathering layer thickness corresponding to the first shot point. When the weathering layer information includes the weathering layer velocity corresponding to the first shot point, the weathering layer thickness corresponding to the first shot point is determined based on the delay time, refraction velocity, and weathering layer velocity corresponding to the first shot point.

5. The method as described in claim 1, characterized in that, The M that is mapped with refraction velocity, regolith thickness, and regolith velocity The constraint model is obtained by discretizing N planar meshes, including: From the M From N planar grids, select one planar grid as the first planar grid, and discretize the first planar grid according to the following operation until each planar grid has been discretized: Obtain surface velocity; According to the reference thickness, the first planar grid is extended multiple times along the depth direction of the stratum until the bottom surface of the refractive layer is reached to obtain Z three-dimensional grids; Based on the weathering layer thickness and weathering layer velocity corresponding to the first planar grid, a velocity factor is determined, which is used to indicate the correspondence between the weathering layer velocity and the stratum depth. Based on the surface velocity and the velocity factor, determine the weathering layer velocity corresponding to each of the Z three-dimensional grids located in the weathering layer; The refraction velocity corresponding to the first planar grid is determined as the refraction velocity corresponding to each of the Z three-dimensional grids located in the refraction layer.

6. The method as described in claim 1, characterized in that, When there are a effective planar grids among the M planar grids located in the same row, before interpolating the refraction velocity, weathering layer thickness, and weathering layer velocity corresponding to the a effective planar grids respectively, the method further includes: When any one of the M planar grids is matched with multiple refraction velocities, multiple weathering layer thicknesses, and multiple weathering layer velocities, the average of each of the multiple refraction velocities, the multiple weathering layer thicknesses, and the multiple weathering layer velocities is taken to obtain the refraction velocity, weathering layer thickness, and weathering layer velocity corresponding to any one planar grid.

7. The method as described in claim 1, characterized in that, The step of performing tomographic inversion on the constrained model to obtain the near-surface velocity model includes: The constraint model is extended to the effective model depth to obtain the near-surface velocity model, where the effective model depth is the difference between the minimum ordinate of the plurality of shot points and the plurality of detection points and the reference value.

8. A device for establishing a near-surface velocity model, characterized in that, The exploration area has multiple blast points and multiple detection points, and the device includes: The first determining module is used to determine the delay time and refraction velocity corresponding to the multiple shot points and the multiple detection points based on multiple first arrival times and multiple shot-receiver distances. The first arrival time refers to the time it takes for a seismic wave excited by a shot point to first reach a detection point. The shot-receiver distance refers to the distance between a shot point and a detection point. The delay time corresponding to the shot point is the difference between the time it takes for the seismic wave to reach the refraction layer from the shot point and a first reference time. The first reference time is the ratio of the horizontal projection length of the propagation distance of the seismic wave along the weathering layer to the refraction layer to the refraction velocity. The delay time of the detection point is the difference between the time it takes for the seismic wave to reach the detection point from the refraction layer and a second reference time. The second reference time is the ratio of the horizontal projection length of the propagation distance of the seismic wave along the weathering layer to the detection point to the refraction velocity. The second determining module is used to determine the weathering layer thickness and weathering layer velocity corresponding to the multiple shot points based on the delay time and refraction velocity corresponding to the multiple shot points, and to determine the weathering layer thickness and weathering layer velocity corresponding to the multiple detection points based on the delay time and refraction velocity corresponding to the multiple detection points. The third determining module is used to perform planar gridding of the exploration area to obtain M. N planar grids, each corresponding to a Cartesian coordinate range; the Cartesian coordinates corresponding to the plurality of shot points and the plurality of detection points are respectively compared with the M... Matching is performed on the range of Cartesian coordinates corresponding to N planar grids, in order to obtain the coordinates from the M grid. In N planar grids, determine the planar grid matching each shot point and the planar grid matching each detection point; map the refraction velocity, weathering layer thickness, and weathering layer velocity corresponding to the multiple shot points and the multiple detection points to their respective matching planar grids; if there are a valid planar grids in M ​​planar grids in the same row, interpolate the refraction velocity, weathering layer thickness, and weathering layer velocity corresponding to the a valid planar grids to obtain the refraction velocity, weathering layer thickness, and weathering layer velocity corresponding to each blank planar grid in the M planar grids, where a is greater than 1 and less than M, the valid planar grids refer to the planar grids matching the multiple shot points and the multiple detection points, and the blank planar grids refer to the planar grids other than the valid planar grids; for the M planar grids mapped with refraction velocity, weathering layer thickness, and weathering layer velocity... N planar grids are discretized to obtain a constraint model, wherein the constraint model includes M N Z three-dimensional grids, the M N Z three-dimensional grids are obtained by gridding the weathered layer and the refractive layer of the exploration area, and each three-dimensional grid located in the weathered layer has a weathering layer velocity, and each three-dimensional grid located in the refractive layer has a refractive velocity; The tomographic inversion module is used to perform tomographic inversion on the constrained model to obtain a near-surface velocity model, which represents the seismic wave velocity corresponding to different strata depths in the exploration area.

9. A computer device, characterized in that, The computer device includes a memory and a processor. The memory is used to store computer programs, and the processor is used to execute the computer programs stored in the memory to implement the steps of the method according to any one of claims 1-7.

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