A method and related device for complex zone velocity modeling and gather correction imaging

Abstract

The application discloses a method for complex area velocity modeling and gather correction imaging, and belongs to the technical field of seismic data processing in geophysical exploration. The method comprises the following steps: acquiring full-offset initial time of seismic data, performing step-by-step constraint on seismic initial tomographic inversion based on the initial time, obtaining a near-surface velocity model and inversion ray density, determining a model fusion top interface and a model fusion bottom interface of the near-surface velocity model based on the inversion ray density, establishing a fluctuating ground small-circle smooth migration floating surface based on true ground geophone elevation height, obtaining a sliding time window weighted velocity fusion model, calculating a floating surface change equivalent time difference correction amount based on the fluctuating ground small-circle smooth migration floating surface, determining a near-surface high-speed layer top interface based on the sliding time window weighted velocity fusion model, and calculating a low-deceleration layer equivalent time difference correction amount. The method carries out prestack gather time difference correction under complex true ground conditions, and realizes gather and velocity model matching application.

Description

Technical Field

[0001] This invention belongs to the field of geophysical exploration seismic data processing technology, and relates to a method and related apparatus for velocity modeling and gather correction imaging in complex areas. Background Technology

[0002] With the advancement of seismic exploration in complex onshore areas, in regions such as deserts, thick loess areas, Gobi gravel areas, and steep mountains, the near-surface velocity modeling is less refined due to the complex near-surface structure, affecting the accuracy of seismic imaging. Existing modeling methods have revealed many problems, such as: ① While travel-time tomography can achieve iterative velocity updates in areas with high signal-to-noise ratios, it is difficult to effectively update data with low coverage times and extremely low signal-to-noise ratios. How can a relatively accurate velocity model be obtained in shallow to medium-depth regions? ② First-arrival tomography inversion can obtain a velocity model reflecting the longitudinal and lateral variations of the near-surface medium. Structural modeling and velocity filling can establish a relatively accurate mid-deep model. How can these two methods be integrated to establish a reliable velocity model across the entire depth range under true surface conditions? ③ CMP gathers are generated based on signal processing under horizontal assumptions. After velocity fusion modeling based on true surface conditions, how can the shot and receiver positions of the pre-stack CMP gathers be corrected to the true surface migration floating surface to achieve matching between the gathers and the velocity model during ray tracing? These three technical problems require new technical solutions. Summary of the Invention

[0003] The purpose of this invention is to solve the technical problem that the near-surface velocity modeling in the prior art is of low precision, which affects the accuracy of seismic imaging, and to provide a method and related apparatus for velocity modeling and gather correction imaging in complex areas.

[0004] To achieve the above objectives, the present invention employs the following technical solution:

[0005] In a first aspect, the present invention provides a method for velocity modeling and gather correction imaging in complex regions, comprising:

[0006] First arrival times of earthquake data at full offset are obtained, and the earthquake first arrival tomography inversion is constrained step by step based on the first arrival times to obtain the near-surface velocity model and the inverted ray density.

[0007] Based on the inverted ray density, the model fusion top interface and model fusion bottom interface of the near-surface velocity model are determined. Based on the actual elevation of the surface receiver points, a small smooth offset floating surface of undulating surface is established. Then, the sliding time window weighted velocity model is fused to obtain the sliding time window weighted velocity fusion model.

[0008] The equivalent time difference correction amount for the floating surface change is calculated based on the small smooth offset floating surface of the undulating surface; the equivalent time difference correction amount for the low velocity layer is calculated based on the sliding time window weighted velocity fusion model to determine the top interface of the near-surface high velocity layer;

[0009] Pre-stack gather equivalent time difference correction is performed based on the equivalent time difference correction amount of the floating surface change and the equivalent time difference correction amount of the low-deceleration layer.

[0010] A further improvement of the present invention is that:

[0011] The near-surface velocity model and inverted ray density are obtained through the following steps:

[0012] The first arrival time of the full offset of the seismic data was obtained, and the near-shot offset inversion constrained by micro-logging was used to obtain the very shallow velocity.

[0013] By performing a mid-range gun-detector distance constraint inversion, a stable high-speed top interface is obtained, and the static correction amount is calculated.

[0014] A full gun-receiver distance constraint inversion was performed to obtain a velocity model at large detection depth;

[0015] Based on the extremely shallow velocity, static correction, and deep-penetration velocity model, the near-surface velocity model and the inverted ray density are obtained.

[0016] The model fusion top interface and model fusion bottom interface for determining the near-surface velocity model based on the inverted ray density specifically include:

[0017] The interface with uniform inverted ray density and gentle lateral trend transformation in the near-surface velocity model was selected as the top interface for model fusion.

[0018] By comparing the tomographic inversion velocity with VSP and ultra-deep micrologging, the bottom interface of confidence of the near-surface velocity model was determined by selecting the well-seismic velocity comparison error with the range of reference inversion ray penetration, and serving as the bottom interface for velocity model fusion.

[0019] The establishment of a small-circular offset floating surface for undulating terrain based on the actual elevation of surface receiver points specifically includes:

[0020] By using the actual elevation of the geostationary points on the ground, a smooth interpolation is performed to obtain a small circular offset floating surface.

[0021] The sliding window weighted velocity fusion model is obtained through the following steps:

[0022] Based on the model fusion top interface and model fusion bottom interface, velocity is fused vertically. Above the model fusion top interface, the floating surface is completely filled with the tomographic inversion velocity from the small circular offset. Below the model fusion bottom interface, the filling depth is offset from the initial model. The two velocity volumes between the model fusion top interface and model fusion bottom interface are fused by sliding time window weighted fusion for a smooth transition.

[0023] The calculation of the equivalent time difference correction for floating surface changes based on the small smooth offset floating surface of the undulating surface; and the calculation of the equivalent time difference correction for the low-velocity layer based on the sliding time window weighted velocity fusion model to determine the near-surface high-velocity layer top interface, specifically include:

[0024] Calculate the elevation depth and time elevation of the small smooth offset floating surface;

[0025] By superimposing the small smooth offset floating surface and the time elevation using CMP, the time correction between the small smooth offset floating surface and the CMP superimposed floating surface is calculated, and corresponding scale smoothing is performed to eliminate high-frequency components and retain only the relatively low- and mid-frequency components, thus obtaining the equivalent time difference correction for the floating surface change.

[0026] Based on the sliding time window weighted velocity fusion model, the velocity interface of the work area filling velocity definition value is taken as the top interface of the near-surface high-speed layer.

[0027] Based on the sliding window weighted velocity fusion model, the pre-stack gather time correction amount caused by low velocity in the low-decline zone is calculated. The pre-stack gather time correction amount is then scaled smoothly to retain only the relatively low-to-medium frequency components, thus obtaining the equivalent time difference correction amount for the low-decline layer.

[0028] The pre-stack gather equivalent time difference correction based on the equivalent time difference correction amount of the floating surface change and the equivalent time difference correction amount of the low-decline layer specifically includes:

[0029] By superimposing the equivalent time difference correction amount of the floating surface change and the equivalent time difference correction amount of the low velocity layer, the CMP gather shot point and receiver point are corrected from the original CMP superimposed floating surface to the small smooth offset floating surface.

[0030] Secondly, the present invention provides a system for velocity modeling and gather correction imaging in complex regions, comprising:

[0031] The near-surface velocity model building module is used to obtain the first arrival time of the full offset of the seismic data, and to perform stepwise constraints on the first arrival tomographic inversion of the seismic data based on the first arrival time, so as to obtain the near-surface velocity model and the inverted ray density.

[0032] The sliding time window weighted velocity fusion model establishment module is used to determine the model fusion top interface and model fusion bottom interface of the near-surface velocity model based on the inverted ray density, establish a small smooth offset floating surface of undulating surface based on the elevation of the real surface receiver point, and then perform sliding time window weighted velocity model fusion to obtain the sliding time window weighted velocity fusion model.

[0033] The equivalent time difference calculation module is used to calculate the equivalent time difference correction amount of the floating surface change based on the small smooth offset floating surface of the undulating surface; and to determine the top interface of the near-surface high-velocity layer based on the sliding time window weighted velocity fusion model, and to calculate the equivalent time difference correction amount of the low-velocity layer.

[0034] The gather correction module is used to perform pre-stack gather equivalent time difference correction based on the floating surface change equivalent time difference correction amount and the low-deceleration layer equivalent time difference correction amount.

[0035] Thirdly, the present invention provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the above-described method for velocity modeling and gather correction imaging in complex regions.

[0036] Fourthly, the present invention provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the above-described method for velocity modeling and gather correction imaging in complex regions.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] This invention discloses a method for velocity modeling and gather correction imaging in complex areas. It utilizes stepwise constrained first-arrival travel time tomography inversion to obtain a near-surface velocity model and inverted ray density distribution. The method then tracks and picks the model fusion interface to perform vertical fusion of the velocity model. Finally, the fused velocity model is used to characterize the high-velocity top interface, and pre-stack gather equivalent time difference calculation and correction are performed to achieve matching between the pre-stack gathers and the velocity model under true surface conditions. First, this invention uses a velocity model established by fusing near-surface first-arrival tomography velocities with mid-to-deep velocities for fusion modeling, achieving fine velocity modeling across the entire depth range in complex areas. Second, under conditions of drastic lateral variations in near-surface velocity in complex exploration areas, it achieves matching between the pre-stack CMP gathers and the velocity model, laying a solid foundation for pre-stack depth migration based on small smooth floating migration surfaces. This invention can be widely applied in seismic exploration of complex onshore areas and is of great significance for improving the accuracy of depth migration imaging. Attached Figure Description

[0039] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a flowchart of a method for velocity modeling and gather correction imaging in complex regions according to the present invention;

[0041] Figure 2 This diagram illustrates the specific operational steps of a method for velocity modeling and gather correction imaging in complex regions according to the present invention.

[0042] Figure 3 This is a flowchart of the stepwise constrained first arrival tomography inversion process for complex regions in the method of velocity modeling and gather correction imaging in complex regions of the present invention.

[0043] Figure 4 This invention provides a method for velocity modeling and gather correction imaging in complex mountainous loess areas, including an initial arrival tomographic inversion velocity model and ray density profile. Figure 4 (a) is the tomographic inversion velocity model. Figure 4 (b) shows the inverted ray density distribution;

[0044] Figure 5 This is a comparison of the cross-sections of the fused depth migration velocity models in a method for velocity modeling and gather correction imaging in complex regions according to the present invention. Figure 5 (a) is a cross-sectional view of the depth migration velocity model before fusion. Figure 5 (b) is a cross-sectional view of the depth migration velocity model after fusion.

[0045] Figure 6 This is a schematic diagram of a small circular floating offset surface in a method for velocity modeling and gather correction imaging in complex areas according to the present invention; continuous lines represent the elevation of receiver points; dotted lines represent small circular floating offset surfaces.

[0046] Figure 7 This is a schematic diagram of the equivalent time difference correction process for gathers in a method for velocity modeling and gather-corrected imaging in complex regions according to the present invention; line ① represents the equivalent time difference correction caused by changes in the floating surface; line ② represents the equivalent time difference correction caused by the low-velocity zone;

[0047] Figure 8 A comparison of pre-stack and post-stack depth migration profiles for a method of velocity modeling and gather correction imaging in complex regions in this invention. Figure 8 (a) indicates velocity fusion modeling NG and gather time difference correction NG; Figure 8(b) indicates that velocity fusion modeling is OK, but gather time difference correction is NG; Figure 8 (c) indicates that velocity fusion modeling is OK and gather time difference correction is OK;

[0048] Figure 9 This is a system diagram of a complex region velocity modeling and gather correction imaging method in this invention;

[0049] Figure 10 This is a block diagram of the electronic device in this invention. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0051] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0052] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0053] The present invention will now be described in further detail with reference to the accompanying drawings:

[0054] See Figure 1 This invention discloses a method for velocity modeling and gather correction imaging in complex regions, comprising:

[0055] S1, Obtain the first arrival time of the full offset of the seismic data, and apply stepwise constraints to the first arrival tomographic inversion of the seismic data based on the first arrival time to obtain the near-surface velocity model and the inverted ray density;

[0056] S2, based on the inverted ray density, determine the model fusion top interface and model fusion bottom interface of the near-surface velocity model, establish a small smooth offset floating surface of undulating surface based on the actual surface receiver elevation, and then perform sliding time window weighted velocity model fusion to obtain the sliding time window weighted velocity fusion model.

[0057] S3, calculate the equivalent time difference correction amount for the floating surface change based on the small smooth offset floating surface of the undulating surface; determine the top interface of the near-surface high-velocity layer based on the sliding time window weighted velocity fusion model, and calculate the equivalent time difference correction amount for the low-velocity layer;

[0058] S4, perform pre-stack gather equivalent time difference correction based on the floating surface change equivalent time difference correction amount and the low-deceleration layer equivalent time difference correction amount.

[0059] This invention discloses a method for velocity modeling and gather correction imaging in complex areas. It utilizes stepwise constrained first-arrival travel time tomography inversion to obtain a near-surface velocity model and inverted ray density distribution. The method then tracks and picks the model fusion interface to perform vertical fusion of the velocity model. Finally, the fused velocity model is used to characterize the high-velocity top interface, and pre-stack gather equivalent time difference calculation and correction are performed to achieve matching between the pre-stack gathers and the velocity model under true surface conditions. First, this invention uses a velocity model established by fusing near-surface first-arrival tomography velocities with mid-to-deep velocities for fusion modeling, achieving fine velocity modeling across the entire depth range in complex areas. Second, under conditions of drastic lateral variations in near-surface velocity in complex exploration areas, it achieves matching between the pre-stack CMP gathers and the velocity model, laying a solid foundation for pre-stack depth migration based on small smooth floating migration surfaces. This invention can be widely applied in seismic exploration of complex onshore areas and is of great significance for improving the accuracy of depth migration imaging.

[0060] See Figure 2 This invention discloses a method for velocity modeling and gather correction imaging in complex regions. The following detailed description of the invention is provided in conjunction with specific embodiments:

[0061] The method includes the following steps: (1) obtaining the near-surface velocity model and inverted ray density based on the hierarchical constrained first arrival tomography inversion; (2) carrying out sliding time window weighted velocity model fusion based on the top and bottom interfaces of the picking model fusion; (3) calculating the equivalent time difference correction of the pre-stack gather; (4) carrying out the equivalent time difference correction of the pre-stack gather to obtain the velocity model data volume and the pre-stack gather data volume for true surface depth migration, and carrying out pre-stack depth migration imaging.

[0062] Step 1: Obtain the first arrival time of the full offset of the seismic data. Based on the first arrival time, apply stepwise constraints to the seismic first arrival tomography inversion to obtain the near-surface velocity model and the inverted ray density.

[0063] Pick the first arrival time of the full-offset seismic data and perform stepwise constrained first arrival tomography inversion:

[0064] 1) The first step is to use micro-logging constrained near-shot distance inversion to obtain accurate very shallow layer velocities;

[0065] 2) The second step is to perform a constrained inversion at the mid-range gun-receiver distance (within 3000m) to obtain a stable high-speed top interface and calculate the static correction amount;

[0066] 3) Finally, a constrained inversion of the entire gun-receiver distance (0-8000m) is performed to obtain a velocity model with a larger detection depth.

[0067] Stepwise constraint inversion can guarantee the maximum depth range of the final inversion result while not losing low-velocity information in the very shallow layers, maintaining velocity accuracy, and ultimately obtaining a near-surface velocity model and inverted ray density. For example... Figure 3 As shown.

[0068] Step 2: Based on the inverted ray density, determine the top and bottom interfaces of the near-surface velocity model fusion. Based on the actual elevation of the surface receiver points, establish a small smooth offset floating surface of the undulating surface. Then, perform sliding time window weighted velocity model fusion to obtain the sliding time window weighted velocity fusion model.

[0069] 1) Select a location with a relatively uniform and reliable ray density distribution for layer tracking. This interface should have a gentle lateral trend change as much as possible, and be able to pick up layers throughout the entire area, serving as the top interface for model fusion.

[0070] 2) Comparing the tomographic inversion velocity with VSP and ultra-deep micro-logging, the error in the well-seismic velocity comparison is relatively small. Referring to the penetration range of the inversion rays, the confidence level of the near-surface velocity model is determined as the bottom interface for model fusion; for example... Figure 4 As shown.

[0071] 3) Velocity fusion is performed using the top and bottom interfaces of the model fusion. The velocity from the top interface to the offset floating surface is completely filled with tomographic inversion velocities. Below the bottom interface, the initial model is offset by the filling depth. A sliding time-window weighted fusion is performed between the two velocity volumes at the top and bottom interfaces for a smooth transition. After fusion, the velocity model requires quality control to ensure no vertical velocity anomalies and consistency with VSP and sonic velocity patterns at well points. Figure 5 As shown.

[0072] Step 3: Calculate the equivalent time difference correction amount for the floating surface change based on the small smooth offset floating surface of the undulating surface; determine the top interface of the near-surface high-velocity layer based on the sliding time window weighted velocity fusion model, and calculate the equivalent time difference correction amount for the low-velocity layer.

[0073] 1) Utilize the actual elevation of the surface receiver points for smooth interpolation to calculate the elevation depth and temporal elevation of the small-circular offset floating surface. This ensures the small-circular offset floating surface accurately reflects the undulating trend of the actual surface elevation while eliminating high-frequency elevation variations. This step needs to be completed before velocity modeling. Figure 6 As shown;

[0074] 2) Using the time elevation of the CMP-overlay floating surface and the small-rounded offset floating surface, calculate the time correction between the small-rounded offset floating surface and the CMP-overlay floating surface, and perform corresponding scale smoothing to eliminate high-frequency components, retaining only the relatively low-to-medium frequency components. This is the equivalent time difference correction caused by the floating surface change. Figure 7 As shown;

[0075] 3) Based on the sliding time window weighted velocity fusion model after fusion in step two, the velocity interface is picked as the top interface of the near-surface high-velocity layer according to the defined value of the filling velocity of the work area;

[0076] 4) Calculate the pre-stack gather time correction caused by low velocity in the low-velocity zone using the sliding window weighted velocity fusion model obtained in step two. This correction is also scaled smoothly, retaining only the relatively low-to-mid-frequency components; this is the equivalent time difference correction caused by the low-velocity zone. Figure 7 As shown.

[0077] Step 4: Perform pre-stack gather equivalent time difference correction based on the floating surface change equivalent time difference correction amount and the low-deceleration layer equivalent time difference correction amount.

[0078] The CMP gather response obtained from pre-stack signal processing uses two parts of correction: equivalent time difference correction caused by floating surface change (equivalent time difference correction caused by floating surface change) and equivalent time difference correction caused by low velocity band (equivalent time difference correction caused by low velocity layer). This corrects the CMP gather shot point and receiver point from the original CMP superimposed floating surface to the current small smooth offset floating surface.

[0079] Step four corrects the CMP gather to contain only relatively high-frequency near-surface components, while the fused depth migration velocity model obtained in step two describes the low-frequency near-surface components. This achieves matching between the corrected gather and the velocity model, enabling pre-stack depth migration based on a small, smooth floating migration surface. Figure 8 As shown.

[0080] See Figure 9 This invention discloses a system for velocity modeling and gather correction imaging in complex regions, comprising:

[0081] The near-surface velocity model building module is used to obtain the first arrival time of the full offset of the seismic data, and to perform stepwise constraints on the first arrival tomographic inversion of the seismic data based on the first arrival time, so as to obtain the near-surface velocity model and the inverted ray density.

[0082] The sliding time window weighted velocity fusion model establishment module is used to determine the model fusion top interface and model fusion bottom interface of the near-surface velocity model based on the inverted ray density, establish a small smooth offset floating surface of undulating surface based on the elevation of the real surface receiver point, and then perform sliding time window weighted velocity model fusion to obtain the sliding time window weighted velocity fusion model.

[0083] The equivalent time difference calculation module is used to calculate the equivalent time difference correction amount of the floating surface change based on the small smooth offset floating surface of the undulating surface; and to determine the top interface of the near-surface high-velocity layer based on the sliding time window weighted velocity fusion model, and to calculate the equivalent time difference correction amount of the low-velocity layer.

[0084] The gather correction module is used to perform pre-stack gather equivalent time difference correction based on the floating surface change equivalent time difference correction amount and the low-deceleration layer equivalent time difference correction amount.

[0085] The second objective of this invention is to provide a system for velocity modeling and gather correction imaging in complex areas. It utilizes stepwise constrained seismic first-arrival travel time tomography inversion to obtain a near-surface velocity model and inverted ray density distribution. The system tracks and picks up the model fusion interface, thereby performing vertical fusion of the velocity model. Finally, it uses the fused velocity model to characterize the high-velocity top interface, performing pre-stack gather equivalent time difference calculation and correction, achieving matching between the pre-stack gathers and the velocity model under true surface conditions. Firstly, this invention uses a velocity model established by fusing near-surface first-arrival tomography velocities with mid-to-deep velocities for fusion modeling, achieving fine velocity modeling across the entire depth range in complex areas. Secondly, under conditions of drastic lateral variations in near-surface velocity in complex exploration areas, it achieves matching between the pre-stack CMP gathers and the velocity model, laying a solid foundation for conducting pre-stack depth migration based on small smooth floating migration surfaces. This invention can be widely applied in seismic exploration of complex onshore areas and is of great significance for improving the accuracy of depth migration imaging.

[0086] See Figure 10 A third objective of this invention is to provide an electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the method for velocity modeling and gather correction imaging in complex regions.

[0087] The method for velocity modeling and gather-corrected imaging in complex regions includes the following steps:

[0088] First arrival times of earthquake data at full offset are obtained, and the earthquake first arrival tomography inversion is constrained step by step based on the first arrival times to obtain the near-surface velocity model and the inverted ray density.

[0089] Based on the inverted ray density, the model fusion top interface and model fusion bottom interface of the near-surface velocity model are determined. Based on the actual elevation of the surface receiver points, a small smooth offset floating surface of undulating surface is established. Then, the sliding time window weighted velocity model is fused to obtain the sliding time window weighted velocity fusion model.

[0090] The equivalent time difference correction amount for the floating surface change is calculated based on the small smooth offset floating surface of the undulating surface; the equivalent time difference correction amount for the low velocity layer is calculated based on the sliding time window weighted velocity fusion model to determine the top interface of the near-surface high velocity layer;

[0091] Pre-stack gather equivalent time difference correction is performed based on the equivalent time difference correction amount of the floating surface change and the equivalent time difference correction amount of the low-deceleration layer.

[0092] A fourth objective of this invention is to provide a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the method for velocity modeling and gather correction imaging in complex regions.

[0093] The method for velocity modeling and gather-corrected imaging in complex regions includes the following steps:

[0094] First arrival times of earthquake data at full offset are obtained, and the earthquake first arrival tomography inversion is constrained step by step based on the first arrival times to obtain the near-surface velocity model and the inverted ray density.

[0095] Based on the inverted ray density, the model fusion top interface and model fusion bottom interface of the near-surface velocity model are determined. Based on the actual elevation of the surface receiver points, a small smooth offset floating surface of undulating surface is established. Then, the sliding time window weighted velocity model is fused to obtain the sliding time window weighted velocity fusion model.

[0096] The equivalent time difference correction amount for the floating surface change is calculated based on the small smooth offset floating surface of the undulating surface; the equivalent time difference correction amount for the low velocity layer is calculated based on the sliding time window weighted velocity fusion model to determine the top interface of the near-surface high velocity layer;

[0097] Pre-stack gather equivalent time difference correction is performed based on the equivalent time difference correction amount of the floating surface change and the equivalent time difference correction amount of the low-deceleration layer.

[0098] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0099] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0100] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0101] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes, such as Figure 8 As shown.

[0102] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for velocity modeling and gather correction imaging in complex regions, characterized in that, include: First arrival times of the full-offset seismic data are obtained. Based on these first arrival times, stepwise constraints are applied to the seismic first arrival tomography inversion to obtain the near-surface velocity model and the inverted ray density; including: The first arrival time of the full offset of the seismic data was obtained, and the near-shot offset inversion constrained by micro-logging was used to obtain the very shallow velocity. By performing a mid-range gun-detector distance constraint inversion, a stable high-speed top interface is obtained, and the static correction amount is calculated. A full gun-receiver distance constraint inversion was performed to obtain a velocity model at large detection depth; Based on the extremely shallow velocity, static correction, and deep-penetration velocity model, the near-surface velocity model and the inverted ray density are obtained. Based on the inverted ray density, the top and bottom interfaces of the near-surface velocity model are determined. A small, smooth, offset floating surface with varying undulating surfaces is established using smooth interpolation based on the actual elevation of the surface receiver points. Then, a sliding window weighted velocity model fusion is performed to obtain the sliding window weighted velocity fusion model. This includes: vertical velocity fusion based on the top and bottom interfaces; complete filling of the tomographic inversion velocity above the top interface to the small, smooth, offset floating surface; filling of the initial model with depth offset below the bottom interface; and sliding window weighted fusion of the two velocity volumes between the top and bottom interfaces for a smooth transition. The equivalent time difference correction for floating surface changes is calculated based on the small-circular offset floating surface of the undulating surface; the equivalent time difference correction for low-velocity layers is calculated based on the sliding time window weighted velocity fusion model to determine the near-surface high-velocity layer top interface; including: Calculate the elevation depth and time elevation of the small smooth offset floating surface; By superimposing the small smooth offset floating surface and the time elevation using CMP, the time correction between the small smooth offset floating surface and the CMP superimposed floating surface is calculated, and corresponding scale smoothing is performed to eliminate high-frequency components and retain only the relatively low- and mid-frequency components, thus obtaining the equivalent time difference correction for the floating surface change. Based on the sliding time window weighted velocity fusion model, the velocity interface of the work area filling velocity definition value is taken as the top interface of the near-surface high-speed layer. Based on the sliding window weighted velocity fusion model, the pre-stack gather time correction amount caused by low velocity in the low-decline zone is calculated. The pre-stack gather time correction amount is then scaled smoothly to retain only the relatively low-to-medium frequency components, thus obtaining the equivalent time difference correction amount for the low-decline layer. Pre-stack gather equivalent time difference correction is performed based on the equivalent time difference correction amount of the floating surface change and the equivalent time difference correction amount of the low-deceleration layer.

2. The method for velocity modeling and gather correction imaging in complex regions according to claim 1, characterized in that, The model fusion top interface and model fusion bottom interface for determining the near-surface velocity model based on the inverted ray density specifically include: The interface with uniform inverted ray density and gentle lateral trend transformation in the near-surface velocity model was selected as the top interface for model fusion. By comparing the tomographic inversion velocity with VSP and ultra-deep micrologging, the bottom interface of confidence of the near-surface velocity model was determined by selecting the well-seismic velocity comparison error with the range of reference inversion ray penetration, and serving as the bottom interface for velocity model fusion.

3. The method for velocity modeling and gather correction imaging in complex regions according to claim 1, characterized in that, The pre-stack gather equivalent time difference correction based on the equivalent time difference correction amount of the floating surface change and the equivalent time difference correction amount of the low-decline layer specifically includes: By superimposing the equivalent time difference correction amount of the floating surface change and the equivalent time difference correction amount of the low velocity layer, the CMP gather shot point and receiver point are corrected from the original CMP superimposed floating surface to the small smooth offset floating surface.

4. A system for implementing the method of velocity modeling and gather correction imaging in complex regions as described in claim 1, characterized in that, include: The near-surface velocity model building module is used to obtain the first arrival time of the full offset of the seismic data, and to perform stepwise constraints on the first arrival tomographic inversion of the seismic data based on the first arrival time, so as to obtain the near-surface velocity model and the inverted ray density. The sliding time window weighted velocity fusion model establishment module is used to determine the model fusion top interface and model fusion bottom interface of the near-surface velocity model based on the inverted ray density, establish a small smooth offset floating surface of undulating surface based on the elevation of the real surface receiver point, and then perform sliding time window weighted velocity model fusion to obtain the sliding time window weighted velocity fusion model. The equivalent time difference calculation module is used to calculate the equivalent time difference correction amount of the floating surface change based on the small smooth offset floating surface of the undulating surface; and to determine the top interface of the near-surface high-velocity layer based on the sliding time window weighted velocity fusion model, and to calculate the equivalent time difference correction amount of the low-velocity layer. The gather correction module is used to perform pre-stack gather equivalent time difference correction based on the floating surface change equivalent time difference correction amount and the low-deceleration layer equivalent time difference correction amount.

5. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the method for velocity modeling and gather correction imaging in complex regions as described in any one of claims 1-3.

6. A computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the method for velocity modeling and gather correction imaging in complex regions as described in any one of claims 1-3.

Images