Method, device and terminal for determining offset velocity

Abstract

The embodiments of the present application disclose a method, device, and terminal for determining an offset velocity, which belongs to the field of seismic data processing. The method includes: for an imaging point in a first formation, performing pre-stack depth migration on the seismic data of the imaging point to obtain a plurality of first common imaging point trace sets; when the straightness of the event axis of each first common imaging point trace set is not less than a preset straightness, interpolating the plurality of first offset velocities to obtain a plurality of second offset velocities; for any second offset velocity, generating a second common imaging point trace set based on the first target common imaging point trace set; determining a target second offset velocity from the plurality of second offset velocities, and determining the target second offset velocity as the offset velocity of the first formation. The above scheme does not require pre-stack depth migration of the seismic data according to each second offset velocity, significantly reduces the amount of calculation for generating the second common imaging point trace set, and improves the efficiency of determining the offset velocity.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of seismic data processing, and in particular to a method, device, and terminal for determining an offset velocity. Background Art

[0002] Migration imaging is a key seismic data processing technique. Migration imaging involves migrating seismic data reflected from formations based on their migration velocities, generating seismic images that reflect the formation structure. Therefore, accurately determining the migration velocities required to generate seismic images remains a challenging technical challenge.

[0003] In related technologies, for any given formation, a velocity enumeration method is typically used to generate multiple migration velocities for that formation. Based on each migration velocity, deep prestack migration (a depth-domain migration imaging technique) is then performed on the seismic data to generate a seismic image corresponding to each migration velocity. Based on the straightness of the events displayed on the seismic image, the migration velocity corresponding to the seismic image with the straightest event is used as the migration velocity for that formation.

[0004] However, this method requires multiple deep prestack migrations for each formation. Furthermore, if no seismic images with relatively straight events exist, multiple new migration velocities must be recalculated. Deep prestack migration is then performed based on these new migration velocities, resulting in a high computational load and low efficiency in determining migration velocities. Summary of the Invention

[0005] The embodiments of the present application provide a method, device, and terminal for determining migration velocity, which eliminates the need to perform prestack depth migration on seismic data based on each migration velocity, significantly reduces the computational complexity of generating common imaging point gathers, and improves the efficiency of determining migration velocity. The technical solution is as follows:

[0006] In one aspect, a method for determining an offset velocity is provided, the method comprising:

[0007] For imaging points in the first stratum, prestack depth migration is performed on seismic data of the imaging points to obtain a plurality of first common imaging point gathers, where the first common imaging point gathers are used to represent amplitude values ​​of the seismic data at different depths underground;

[0008] When the straightness of the event axis of each first common imaging point gather is not less than a preset straightness, interpolating the plurality of first migration velocities to obtain a plurality of second migration velocities, wherein the first migration velocities are used to perform prestack depth migration on the seismic data of the imaging points;

[0009] For any second migration velocity, a second common imaging point gather is generated based on a first target common imaging point gather, where the first target common imaging point gather is a first common imaging point gather generated using a target first migration velocity, the target first migration velocity being a first migration velocity having a minimum difference with the second migration velocity among the plurality of first migration velocities, and the second common imaging point gather is used to reflect a result of prestack depth migration of seismic data of the imaging point using the second migration velocity;

[0010] A target second offset velocity is determined from the plurality of second offset velocities, the target second offset velocity is determined as the offset velocity of the first formation, and the straightness of the event axis of a second common imaging point gather generated by the target second offset velocity is less than the preset straightness.

[0011] In another aspect, a device for determining an offset velocity is provided, the device comprising:

[0012] a migration module configured to perform prestack depth migration on seismic data of imaging points in a first stratum to obtain a plurality of first common imaging point gathers, wherein the first common imaging point gathers are used to represent amplitude values ​​of the seismic data at different depths underground;

[0013] an interpolation module, configured to interpolate a plurality of first migration velocities respectively to obtain a plurality of second migration velocities when the straightness of the event axis of each first common imaging point gather is not less than a preset straightness, wherein the first migration velocities are used to perform prestack depth migration on the seismic data of the imaging points;

[0014] a first generating module configured to generate, for any second migration velocity, a second common imaging point gather based on a first target common imaging point gather, wherein the first target common imaging point gather is a first common imaging point gather generated using a target first migration velocity, the target first migration velocity being a first migration velocity having a minimum difference with the second migration velocity among the plurality of first migration velocities, and the second common imaging point gather reflecting a result of prestack depth migration of seismic data of the imaging point using the second migration velocity;

[0015] a first determining module configured to determine a target second offset velocity from the plurality of second offset velocities, determine the target second offset velocity as the offset velocity of the first formation, and wherein the straightness of an event axis of a second common imaging point gather generated using the target second offset velocity is less than a preset straightness.

[0016] In some embodiments, the second common imaging point gather is used to represent the amplitude value of the seismic data at a first depth, where the first depth is the depth of the location of the imaging point; and the first generating module includes:

[0017] an acquisition unit, configured to acquire a travel time and a target position of a first ray, wherein the first ray is a ray emitted toward the surface at a preset exit angle at the location of the imaging point, the travel time is the time taken for the first ray to exit the surface, and the target position is the position where the first ray exits the surface;

[0018] a first determining unit, configured to, in response to a successful emission of a second ray, count down based on the travel time and determine a depth reached by the second ray when the travel time expires as a second depth, wherein the second ray is a ray emitted underground at the target location;

[0019] a second determining unit, configured to determine an amplitude value of the seismic data at the second depth based on the first target common imaging point gather;

[0020] The third determining unit is configured to use the amplitude value of the seismic data at the second depth as the amplitude value of the seismic data at the first depth.

[0021] In some embodiments, the acquisition unit is used to obtain the initial offset velocity of each formation; based on the preset exit angle and the transmission velocity of the first ray in each formation, the incident angle and the exit angle of the first ray at each formation interface are determined by the law of refraction, and the transmission velocity of the first ray in each formation is the initial offset velocity of each formation; based on the transmission velocity of the first ray in each formation, the incident angle and the exit angle of the first ray at each formation interface and the first depth, the travel time of the first ray and the target position are determined.

[0022] In some embodiments, the second determination unit is used to, when there is a depth sampling point at the second depth in the first target common imaging point gather, use the amplitude value of the depth sampling point as the amplitude value of the seismic data at the second depth; and when there is or is not a depth sampling point at the second depth in the first target common imaging point gather, interpolate the amplitude value of at least one adjacent depth sampling point at the second depth to obtain the amplitude value of the seismic data at the second depth.

[0023] In some embodiments, the apparatus further comprises:

[0024] An acquisition module, configured to acquire an initial velocity model, wherein the initial velocity model is used to represent a relationship between a depth of a formation and an initial migration velocity of the formation;

[0025] a second determining module, configured to determine an initial migration velocity of the first formation based on the initial velocity model;

[0026] The second generating module is configured to generate the plurality of first offset velocities within a preset speed range based on the initial offset velocity and in accordance with a generating step length, wherein the generating step length is used to represent a difference between two adjacent first offset velocities.

[0027] In some embodiments, the apparatus further comprises:

[0028] An analysis module is configured to perform time-domain velocity analysis on the seismic data of the imaging point to obtain a time-domain velocity field, wherein the time-domain velocity field is configured to represent a relationship between a transmission time of the seismic data in each stratum and a migration velocity of the stratum;

[0029] The migration module is further used to perform pre-stack time migration on the seismic data of the imaging point to obtain a time domain migration profile, wherein the time domain migration profile is used to divide multiple underground strata and determine the depth of each stratum;

[0030] A construction module is used to construct the initial velocity model based on the time domain velocity field and the time domain migration profile.

[0031] In some embodiments, the interpolation module is configured to determine, when the straightness of the event of each of the first common imaging point gathers is not less than the preset straightness, a second target common imaging point gather, the second target common imaging point gather being the first common imaging point gather having the smallest difference between the straightness of the event and the preset straightness; determine, based on the second target common imaging point gather, a third migration velocity, the third migration velocity being the first migration velocity for generating the second target common imaging point gather; and interpolate the third migration velocity within a preset velocity range according to an interpolation interval to obtain the multiple second migration velocities.

[0032] In some embodiments, the apparatus further comprises:

[0033] The third determination module is configured to determine the offset velocity of the second formation based on a plurality of common imaging point gathers of imaging points in the second formation in response to obtaining the offset velocity of the first formation, where the second formation is a layer below the first formation.

[0034] On the other hand, a terminal is provided, comprising a processor and a memory, wherein the memory stores at least one computer program, and the at least one computer program is loaded and executed by the processor to implement the offset velocity determination method as described in the above aspect.

[0035] On the other hand, a computer-readable storage medium is provided, wherein at least one computer program is stored in the computer-readable storage medium, and the at least one computer program is loaded and executed by a processor to implement the offset velocity determination method according to the above aspect.

[0036] On the other hand, a computer program product is provided, comprising a computer program, wherein the computer program is loaded and executed by a processor to implement the offset velocity determination method according to the above aspect.

[0037] An embodiment of the present application provides a migration velocity determination scheme. To determine the migration velocity of a first formation, prestack depth migration is first performed on seismic data of imaging points in the first formation based on multiple first migration velocities, resulting in multiple first common imaging point gathers. Since the straighter the events of a common imaging point gather, the better the imaging effect and the higher the reliability of the common imaging point gather. Therefore, the migration velocity corresponding to the first common imaging point gather whose event straightness is less than a preset straightness can be determined as the migration velocity of the first formation. If the straightness of the events of each first common imaging point gather is not less than the preset straightness, the multiple migration velocities are less reliable and cannot be used as the migration velocity of the first formation. Then, the multiple first migration velocities are interpolated to obtain multiple second migration velocities. For each second migration velocity, a second common imaging point gather is generated based on the first common imaging point gather corresponding to the first migration velocity with the smallest difference. The migration velocity corresponding to the second common imaging point gather with the straighter event is then used as the migration velocity of the first formation. By adopting the above method, it is no longer necessary to perform prestack depth migration on the seismic data according to each second migration velocity, which significantly reduces the computational complexity of generating the second common imaging point gathers and improves the efficiency of determining the migration velocity. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0039] Figure 1 This is a schematic diagram of an implementation environment provided by an embodiment of the present application;

[0040] Figure 2 is a flow chart of a method for determining an offset velocity provided by an embodiment of the present application;

[0041] Figure 3 is a flow chart of another method for determining offset velocity provided by an embodiment of the present application;

[0042] Figure 4 This is a flow chart for determining an offset speed provided by an embodiment of the present application;

[0043] Figure 5This is a schematic diagram of imaging shallow low signal-to-noise ratio seismic data provided by an embodiment of the present application;

[0044] Figure 6 is a schematic diagram of a horizontal layered model provided in an embodiment of the present application;

[0045] Figure 7 is a schematic diagram of an imaging effect provided by an embodiment of the present application;

[0046] Figure 8 is a schematic diagram of an actual underground model provided in an embodiment of the present application;

[0047] Figure 9 is a schematic diagram of another imaging effect provided by an embodiment of the present application;

[0048] Figure 10 is a schematic diagram of another imaging effect provided by an embodiment of the present application;

[0049] Figure 11 is a structural diagram of an offset velocity determination device provided in an embodiment of the present application;

[0050] Figure 12 is a structural diagram of another device for determining offset velocity provided in an embodiment of the present application;

[0051] Figure 13 This is a schematic diagram of the structure of a terminal provided in an embodiment of the present application. DETAILED DESCRIPTION

[0052] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the implementation methods of the present application will be further described in detail below with reference to the accompanying drawings.

[0053] It should be understood that the terms "first," "second," and so forth, used herein may be used to describe various concepts, but unless otherwise specified, these concepts are not limited by these terms. These terms are used solely to distinguish one concept from another. For example, a first common imaging point gather could be referred to as a second common imaging point gather, and similarly, a second common imaging point gather could be referred to as a first common imaging point gather, without departing from the scope of this application.

[0054] 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 this application are all authorized by the user or fully authorized by all parties, and the collection, use, and processing of relevant data must comply with the relevant laws, regulations, and standards of the relevant countries and regions. For example, the earthquake data involved in this application was obtained with full authorization.

[0055] The following introduces the implementation environment of the embodiments of the present application.

[0056] Figure 1 This is a schematic diagram of an implementation environment provided by an embodiment of the present application, see Figure 1 , the implementation environment includes: a terminal 101 and a server 102. The terminal 101 can be connected to the server 102 via a wireless network or a wired network.

[0057] Optionally, terminal 101 can be at least one of a smartphone, a desktop computer, a laptop computer, and a portable computer. An application can be installed and run on terminal 101, and the application is used to perform various migration imaging processes on the seismic data of imaging points in the formation, such as pre-stack depth migration, post-stack depth migration, pre-stack time migration, and post-stack time migration. A user can log in to the application through terminal 101 and use the application to perform pre-stack depth migration on the seismic data to obtain a common imaging point gather of the imaging points. The user can also use the application to view the straightness of the event axes of the common imaging point gather. The application is associated with server 102, and server 102 provides backend services.

[0058] Optionally, server 102 is an independent physical server, or a server cluster or distributed system composed of multiple physical servers. It can also be a cloud server that provides basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communications, middleware services, domain name services, security services, CDN (Content Delivery Network), and big data and artificial intelligence platforms. In some embodiments, server 102 performs the primary computing work and terminal 101 performs the secondary computing work; alternatively, server 102 performs the secondary computing work and terminal 101 performs the primary computing work; alternatively, server 102 and terminal 101 use a distributed computing architecture to perform collaborative computing.

[0059] Terminal 101 may generally refer to one of multiple terminals. This embodiment uses terminal 101 as an example. Those skilled in the art will appreciate that the number of terminals may be greater or lesser. For example, there may be a few terminals, or dozens, hundreds, or even more. This embodiment does not limit the number or device type of terminals.

[0060] Figure 2 This is a flow chart of a method for determining an offset speed provided by an embodiment of the present application. The embodiment of the present application is executed by a terminal as an example. Figure 2 , the method comprising:

[0061] 201. For imaging points in a first stratum, the terminal performs pre-stack depth migration on seismic data of the imaging points to obtain a plurality of first common imaging point gathers, where the first common imaging point gathers are used to represent amplitude values ​​of seismic data at different depths underground.

[0062] In the embodiment of the present application, the first stratum is any stratum to be detected underground. The imaging point is a point in the first stratum that can reflect seismic data. The first stratum includes at least one imaging point. The embodiment of the present application is described by taking an imaging point of the first stratum as an example. After the seismic wave is successfully excited from the blast point on the surface to any direction underground, the seismic wave propagates in multiple strata to be detected underground. During the propagation process, the seismic wave can be reflected to the surface by the imaging point in the stratum. Accordingly, the terminal can collect the seismic wave reflected by the imaging point through multiple detectors on the surface, that is, collect the seismic data reflected by the imaging point. Among them, the seismic data collected by a detector is called a seismic trace. The seismic trace records multiple seismic data collected by the corresponding detector.

[0063] The terminal performs prestack depth migration on the collected seismic data according to multiple first migration velocities, generating multiple first common imaging point gathers. A gather is a collection of multiple seismic traces. A first common imaging point gather is a gather obtained by sorting seismic data reflected from the same underground imaging point according to the shot offset (the distance between the shot point and the receiver point). Using this first common imaging point gather, the terminal can determine the amplitude of the seismic data at different depths underground.

[0064] 202. When the straightness of the event axis of each first common imaging point gather is not less than a preset straightness, the terminal interpolates the multiple first migration velocities to obtain multiple second migration velocities. The first migration velocities are used to perform prestack depth migration on the seismic data of the imaging points.

[0065] In this embodiment of the present application, the event of the first common imaging point gather refers to the line connecting the extreme values ​​(commonly known as peaks or troughs) of the seismic data vibration phase that are identical in each seismic trace. Therefore, in the first common imaging point gather, the terminal determines the maximum or minimum amplitude value of the seismic data recorded in each seismic trace. The terminal then connects the maximum or minimum amplitude values ​​recorded in each seismic trace to obtain the event of the first common imaging point gather and the straightness of the event. The terminal can use the straightness of the event to determine the imaging quality of the first common imaging point gather. The straighter the event, the better the imaging quality and the higher the reliability of the common imaging point gather. If the straightness of the event is not less than a preset straightness, it indicates that the event is relatively curved; if the straightness of the event is less than the preset straightness, it indicates that the event is relatively straight. The preset straightness can be a preset angle, such as 10°, 15°, or 20°, which is not limited in this embodiment of the present application. Therefore, the terminal can determine a first common imaging point gather whose event straightness is less than a preset straightness, and determine the migration velocity used to generate the first common imaging point gather as the migration velocity of the first formation. Based on this migration velocity, the terminal can generate a seismic image with better imaging quality and higher reliability.

[0066] If the straightness of the event axis of each first common imaging point gather is not less than a preset straightness, it indicates that none of the first migration velocities can be used as the migration velocity of the first formation. The terminal interpolates the multiple first migration velocities to obtain multiple second migration velocities. The terminal can determine whether there is a second migration velocity among the multiple second migration velocities that can be used as the migration velocity of the first formation.

[0067] 203. For any second migration velocity, the terminal generates a second common imaging point gather based on the first target common imaging point gather, where the first target common imaging point gather is a first common imaging point gather generated using the target first migration velocity, where the target first migration velocity is the first migration velocity having the smallest difference with the second migration velocity among multiple first migration velocities, and the second common imaging point gather is used to reflect the result of pre-stack depth migration of seismic data of the imaging point using the second migration velocity.

[0068] In an embodiment of the present application, during the generation of a common imaging point gather for any second migration velocity, the terminal determines the difference between the second migration velocity and each of the first migration velocities and identifies the first migration velocity with the smallest difference as the target first migration velocity. In step 201, the terminal performs prestack depth migration on the seismic data of the imaging point according to the target first migration velocity, thereby obtaining a first target common imaging point gather. The terminal generates a second common imaging point gather based on the amplitude values ​​of the seismic data represented by the first target common imaging point gather at different depths. The terminal generates a second common imaging point gather for each second migration velocity in the aforementioned manner. Based on the straightness of the event axis of the second common imaging point gather, the terminal determines whether the second migration velocity can be used as the migration velocity of the first formation. In this manner, the terminal can obtain a second common imaging point gather that reflects the results of prestack depth migration without performing prestack depth migration on the seismic data of the imaging point according to the second migration velocity, significantly improving the efficiency of generating the second common imaging point gather.

[0069] 204. The terminal determines a target second offset velocity from the plurality of second offset velocities, and determines the target second offset velocity as the offset velocity of the first formation. The straightness of the event axis of the second common imaging point gather generated by the target second offset velocity is less than a preset straightness.

[0070] In an embodiment of the present application, when a second common imaging point gather exists whose event straightness is less than a preset straightness, the terminal determines the target second migration velocity for generating the second common imaging point gather as the migration velocity of the first stratum. Furthermore, the terminal can perform migration imaging processing on the seismic data reflected from the first stratum based on the migration velocity of the first stratum, obtaining a seismic image that reflects the stratum structure. The seismic image has a relatively straight event shape, high clarity, and good imaging quality, facilitating further analysis and exploration of the underground strata based on the seismic image.

[0071] It should be noted that the above embodiment is described using a single co-imaged point in the first stratum as an example. In some embodiments, the first stratum includes multiple co-imaged points. If there are multiple co-imaged points in the first stratum, the terminal can perform the above processing on at least one of the imaged points through steps 201-204, and use the resulting offset velocity as the offset velocity of the imaged point. The terminal can also interpolate the offset velocity of the imaged point to obtain the offset velocities of the remaining imaged points. The terminal uses the offset velocity field composed of the offset velocities of each imaged point in the first stratum as the offset velocity field of the first stratum.

[0072] An embodiment of the present application provides a method for determining migration velocities. To determine the migration velocity of a first formation, prestack depth migration is first performed on seismic data of imaging points in the first formation based on multiple first migration velocities, resulting in multiple first common imaging point gathers. Since the straighter the events of a common imaging point gather, the better the imaging effect and the higher the reliability of the common imaging point gather. Therefore, the migration velocity corresponding to the first common imaging point gather whose event straightness is less than a preset straightness can be determined as the migration velocity of the first formation. If the straightness of the events of each first common imaging point gather is not less than the preset straightness, the multiple migration velocities have low reliability and cannot be used as the migration velocity of the first formation. Then, the multiple first migration velocities are interpolated to obtain multiple second migration velocities. For each second migration velocity, a second common imaging point gather is generated based on the first common imaging point gather corresponding to the first migration velocity with the smallest difference. The migration velocity corresponding to the second common imaging point gather with the straighter event is then used as the migration velocity of the first formation. By adopting the above method, it is no longer necessary to perform prestack depth migration on the seismic data according to each second migration velocity, which significantly reduces the computational complexity of generating the second common imaging point gathers and improves the efficiency of determining the migration velocity.

[0073] above Figure 2 The main process of the offset speed determination method provided in the embodiment of the present application is exemplified. The offset speed determination method is described in detail below. Figure 3 This is a flow chart of another method for determining an offset velocity provided by an embodiment of the present application. The method is executed by a terminal. Figure 3 , the method comprising:

[0074] 301. The terminal obtains an initial velocity model, where the initial velocity model is used to represent the relationship between the depth of a formation and the initial migration velocity of the formation.

[0075] In an embodiment of the present application, there are multiple strata to be detected underground, and the depths of the multiple strata increase layer by layer. In the process of detecting the strata, the terminal usually performs offset imaging on the seismic data reflected by each stratum to obtain a seismic image that can reflect the stratum structure. Since the depths of different strata are different, the reflection angles of different strata for the seismic data emitted by the same shot point are also different. Therefore, in the offset imaging process, the offset velocity of each stratum is also different. The terminal usually determines the initial offset velocity of the stratum according to the depth of the stratum through an initial velocity model. The initial offset velocity of the stratum is used to perform pre-stack depth migration on the seismic data reflected by the imaging point in the stratum, and then the offset seismic data is sorted according to the shot offset to obtain a common imaging point gather. Among them, pre-stack depth migration is a depth domain migration imaging technology. The common imaging point gather can reflect the results after pre-stack depth migration of seismic data collected from different detection points.

[0076] In some embodiments, the terminal can directly perform prestack depth migration on seismic data reflected from imaging points in the formation based on the initial migration velocity of the formation, thereby obtaining a common imaging point gather of the formation. Technicians can determine the accuracy of the initial migration velocity of the formation based on the imaging quality or the straightness of the events of the common imaging point gather.

[0077] In some embodiments, the terminal can construct an initial velocity model based on the seismic data at the imaging point. The seismic data at the imaging point refers to the seismic data reflected from the imaging point, collected by the terminal through the receiver points, after a seismic wave is successfully excited in any direction underground from the shot point. The terminal performs time-domain velocity analysis on the seismic data at the imaging point to obtain a time-domain velocity field. The time-domain velocity field represents the relationship between the transmission time of the seismic data in each stratum and the migration velocity of each stratum. In other words, the time-domain velocity field expresses the migration velocity of the underground stratum based on time. The terminal performs pre-stack time migration on the seismic data at the imaging point to obtain a time-domain migration profile. Pre-stack time migration is a time-domain migration imaging technique. By performing stratigraphic interpretation on the time-domain migration profile, the terminal can delineate multiple underground strata and determine the depth of each stratum. Based on the time-domain velocity field and the time-domain migration profile, the terminal determines the relationship between the depth of the stratum and the migration velocity of the stratum, and uses this to construct an initial velocity model. The initial velocity model is a depth-domain velocity field that expresses the migration velocity of the underground stratum based on the depth of the stratum. Optionally, the terminal may also create a depth domain velocity field based on the collected well data, which is not limited in the embodiment of the present application.

[0078] In some embodiments, after acquiring seismic data from a reflection point, the terminal processes the data according to conventional seismic data processing procedures to produce a time-domain shot-gather seismic record. Conventional processing includes basic processing such as static correction, pre-stack denoising, amplitude compensation, deconvolution, and velocity analysis. The time-domain shot-gather seismic record represents seismic data acquired over time from individual seismic traces. The terminal performs time-domain velocity analysis and pre-stack time migration on the time-domain shot-gather record to produce a time-domain velocity field and a time-domain migration profile.

[0079] 302. The terminal determines an initial migration velocity of the first formation based on the initial velocity model.

[0080] In an embodiment of the present application, the first stratum is any stratum to be detected underground. The terminal determines the depth of the first stratum and determines the initial offset velocity of the first stratum based on the initial velocity model. Optionally, the terminal can directly perform prestack depth migration on the seismic data reflected by the imaging point in the first stratum based on the initial offset velocity to obtain a common imaging point gather of the first stratum. However, if the initial velocity model is not accurate and the initial offset velocity is low, the imaging quality of the obtained common imaging point gather is poor, it is difficult to identify valid phase axes, and the reliability is low.

[0081] 303. The terminal generates a plurality of first migration velocities within a preset velocity range based on the initial migration velocity and a generation step length, wherein the generation step length is used to represent a difference between two adjacent first migration velocities. The first migration velocities are used to perform prestack depth migration on the seismic data of the imaging point.

[0082] In an embodiment of the present application, to obtain a more accurate offset speed, the terminal enumerates the initial offset speed according to a generation step size, thereby generating multiple first offset speeds within a preset speed range. Furthermore, the terminal can determine whether a highly accurate offset speed exists among the multiple first offset speeds. The preset speed range can be a preset percentage range or a preset numerical range. Accordingly, the generation step size can be a preset percentage or a preset numerical value, and this embodiment of the present application does not limit this.

[0083] For example, when the initial offset speed is 2000 m / s (meters / second), the preset speed range is 80%-120%, and the generation step size is 2%, the terminal can determine a total of 21 first offset speeds of 1600 m / s, 1640 m / s, 1680 m / s...2360 m / s and 2400 m / s.

[0084] 304. For the imaging points in the first stratum, the terminal performs pre-stack depth migration on the seismic data of the imaging points according to the multiple first migration velocities, and obtains multiple first common imaging point gathers. The multiple common imaging point gathers correspond one-to-one to the multiple first migration velocities. The first common imaging point gathers are used to represent the amplitude values ​​of the seismic data at different depths underground.

[0085] In the embodiment of the present application, an imaging point is a point in the first stratum that can reflect seismic data. The first stratum includes at least one imaging point. The embodiment of the present application uses one imaging point in the first stratum as an example. After a seismic wave is successfully excited from a shot point on the surface in any direction underground, the seismic wave propagates through multiple strata to be explored underground. During this propagation process, the seismic wave can be reflected back to the surface by the imaging point in the stratum. Accordingly, the terminal can collect the seismic wave reflected by the imaging point using multiple surface detectors, that is, collect seismic data reflected by the imaging point. The seismic data collected by one detector is called a seismic trace. A seismic trace records multiple seismic data collected by the corresponding detector. The terminal then performs prestack depth migration on the collected seismic data according to multiple first migration velocities, obtaining multiple first common imaging point gathers. Using the first common imaging point gathers, the terminal can determine the amplitude values ​​of the seismic data at different depths underground.

[0086] In some embodiments, the terminal can perform pre-stack depth migration on the conventionally processed time-domain shot gather seismic records according to the first migration velocity to obtain a first common imaging point gather corresponding to the first migration velocity.

[0087] 305. When the straightness of the event axis of each first common imaging point gather is not less than the preset straightness, the terminal determines a second target common imaging point gather, where the second target common imaging point gather is the first common imaging point gather having the smallest difference between the straightness of the event axis and the preset straightness.

[0088] In this embodiment of the present application, the event of the first common imaging point gather refers to the line connecting the extreme values ​​(commonly known as peaks or troughs) of the seismic data vibration phase that are identical in each seismic trace. Therefore, in the first common imaging point gather, the terminal determines the maximum or minimum amplitude value of the seismic data recorded in each seismic trace. The terminal then connects the maximum or minimum amplitude values ​​recorded in each seismic trace to obtain the event of the first common imaging point gather and the straightness of the event. The terminal can use the straightness of the event to determine the imaging quality of the first common imaging point gather. The straighter the event, the better the imaging quality and the higher the reliability of the common imaging point gather. If the straightness of the event is not less than a preset straightness, it indicates that the event is relatively curved; if the straightness of the event is less than the preset straightness, it indicates that the event is relatively straight. The preset straightness can be a preset angle, such as 10°, 15°, or 20°, which is not limited in this embodiment of the present application. Therefore, the terminal can determine a first common imaging point gather whose event straightness is less than a preset straightness, and determine the first migration velocity generated from the first common imaging point gather as the migration velocity of the first formation. Based on this migration velocity, the terminal can generate a seismic image with better imaging quality and higher reliability.

[0089] In some embodiments, the terminal stacks data from each seismic trace in the first common imaging point gather to obtain a stacked section. The terminal determines the offset velocity of the first formation based on at least one of the straightness of the events in the first common imaging point gather and the imaging quality of the stacked section. For example, the terminal determines a first common imaging point gather from multiple first common imaging point gathers that has relatively straight events, good event continuity in the stacked section, a high signal-to-noise ratio, and clear faults, and determines the first offset velocity generated from the first common imaging point gather as the offset velocity of the first formation.

[0090] If the straightness of the events in each first common imaging point gather is not less than a preset straightness, this indicates that the events in all first common imaging point gathers at the first formation depth have not been flattened, and none of the aforementioned multiple first migration velocities can be used as the migration velocity of the first formation. Therefore, the terminal generates a new batch of migration velocities and common imaging point gathers corresponding to the new migration velocities, and determines whether there is a new migration velocity that can be used as the migration velocity of the first formation based on the straightness of the events in the newly generated common imaging point gathers.

[0091] During the process of generating new migration velocities, the terminal can generate new migration velocities based on a first common imaging point gather with relatively straight events. The terminal determines the difference between the straightness of the events in each first common imaging point gather and a preset straightness, and generates new migration velocities based on the first common imaging point gather with the smallest difference. The following steps describe the specific process by which the terminal generates new migration velocities based on a second target common imaging point gather (a first common imaging point gather with relatively straight events).

[0092] 306. The terminal determines a third migration velocity based on the second target common imaging point gather, where the third migration velocity is the first migration velocity used to generate the second target common imaging point gather.

[0093] In this embodiment of the present application, after determining a second target common imaging point gather with relatively straight events, the terminal determines a first migration velocity for generating the second target common imaging point gather, referred to as a third migration velocity for ease of description. Because the events of the second target common imaging point gather are relatively straight, the difference between the third migration velocity and the more accurate migration velocity is relatively small. Therefore, the terminal can generate multiple new migration velocities based on the third migration velocity.

[0094] 307. The terminal interpolates the third offset speed according to the interpolation interval within a preset speed range to obtain multiple second offset speeds.

[0095] In this embodiment of the present application, to obtain a more accurate offset speed, the terminal interpolates the third offset speed according to an interpolation interval within a preset speed range to obtain multiple second offset speeds. The terminal can then determine whether a highly accurate offset speed exists among the multiple second offset speeds. The preset speed range can be a preset percentage range or a preset numerical range. Correspondingly, the interpolation interval can be a preset percentage or a preset numerical value, and this embodiment of the present application does not limit this.

[0096] In some embodiments, the terminal may also generate the second migration velocity using other methods. For example, after generating multiple first migration velocities based on the initial migration velocity, the terminal may use some of the first migration velocities as second migration velocities. Furthermore, the terminal performs prestack depth migration on the seismic data of the imaging points based solely on the first migration velocities, generating a first common imaging point gather. If the straightness of the event axes of each first common imaging point gather is no less than a preset straightness, the terminal then generates a second common imaging point gather corresponding to the second migration velocity. For example, if the initial migration velocity is 2000 m / s, the preset velocity range is 80%-120%, and the generation step size is 1%, the terminal may determine a total of 41 migration velocities: 1600 m / s, 1620 m / s, 1640 m / s…2380 m / s, and 2400 m / s, corresponding to 80%, 81%, 82%,…119%, and 120%, respectively. The terminal uses the offset speeds corresponding to 80%, 82%, 84% ... 118% and 120% as the first offset speeds, and uses the offset speeds corresponding to 81%, 83%, 85% ... 117% and 119% as the second offset speeds.

[0097] 308. For any second offset velocity, the terminal generates a second common imaging point gather based on the first target common imaging point gather, where the first target common imaging point gather is a first common imaging point gather generated using the target first offset velocity, where the target first offset velocity is the first offset velocity having the smallest difference with the second offset velocity among multiple first offset velocities, and the second common imaging point gather is used to reflect the result of pre-stack depth migration of seismic data of the imaging point using the second offset velocity.

[0098] In an embodiment of the present application, during the generation of a common imaging point gather for any second migration velocity, the terminal determines the difference between the second migration velocity and each of the first migration velocities and identifies the first migration velocity with the smallest difference as the target first migration velocity. If two first migration velocities with the smallest difference exist, the terminal selects one of them as the target first migration velocity. Because the terminal performs prestack depth migration on the seismic data of the imaging point according to the target first migration velocity in step 304, a first target common imaging point gather is obtained. The terminal generates a second common imaging point gather based on the amplitude values ​​of the seismic data represented by the first target common imaging point gather at different depths. The terminal can generate a second common imaging point gather for each second migration velocity in the above manner. The terminal determines whether the second migration velocity can be used as the migration velocity of the first formation based on the straightness of the event axis of the second common imaging point gather. In this manner, the terminal can obtain a second common imaging point gather that reflects the results of prestack depth migration without performing prestack depth migration on the seismic data of the imaging point according to the second migration velocity, thereby improving the efficiency of generating the second common imaging point gather.

[0099] In some embodiments, the terminal generates a second common imaging point gather based on the amplitude values ​​of the seismic data represented by the first target common imaging point gather. The second common imaging point gather represents the amplitude values ​​of the seismic data at a first depth, where the first depth is the depth of the imaging point. Therefore, by determining the amplitude values ​​of the seismic data at the first depth, the terminal can generate the second common imaging point gather. To determine the amplitude values ​​of the seismic data at the first depth, a technician first transmits a first ray toward the surface at the depth of the imaging point. After the first ray successfully exits the surface, the terminal can determine the travel time and target position of the first ray. The first ray is transmitted toward the surface at the depth of the imaging point at a preset exit angle. The preset exit angle can be in the range of 0° to 90°, and is not limited in this embodiment of the present application. The travel time is the time it takes for the first ray to exit the surface from the time it is transmitted. The target position is the position where the first ray exits the surface. The technician can then transmit a second ray underground at the depth of the target position. In response to the successful emission of the second ray, the terminal counts down based on the travel time and determines the depth reached by the second ray when the travel time expires as the second depth. The terminal determines the amplitude value of the seismic data at the second depth based on the first target common imaging point gather and uses the amplitude value of the seismic data at the second depth as the amplitude value of the seismic data at the first depth.

[0100] In some embodiments, the terminal is capable of determining the travel time and target position of the first ray based on the transmission speed of the first ray and a preset exit angle. The terminal obtains the initial offset velocity of each stratum based on the initial velocity model. The transmission speed of the first ray in each stratum is the initial offset velocity of each stratum. Based on the preset exit angle and the transmission speed of the first ray in each stratum, the terminal determines the incident angle and exit angle of the first ray at each stratum interface using the law of refraction. The terminal determines the travel time and target position of the first ray based on the transmission speed of the first ray in each stratum, the incident angle and exit angle of the first ray at each stratum interface, and the first depth.

[0101] Optionally, the terminal can obtain the velocity curve {z′} corresponding to the first target common imaging point gather according to the depth of the stratum represented by the initial velocity model and the initial offset velocity of the stratum. i ,v′ i} i＝1,n and the velocity curve {z i ,v i} i＝1,n The velocity curve can represent the relationship between the depth of the underground depth sampling point and the migration velocity. n is the maximum number of depth sampling points. i ,v i are the depth and initial migration velocity of the i-th depth sampling point in the velocity curve corresponding to the second common imaging point gather to be generated, z i ′,v i ′ are the depth and initial migration velocity of the i-th depth sampling point in the velocity curve corresponding to the first target common imaging point gather.

[0102] For example, the first depth of the imaging point of the first formation is z i ; The depth of the previous layer of the first layer is z i-1 ; The depth of the ground is z0; the preset emission angle is α i,j , j is the exit angle index, which is used to identify different preset exit angles. The first ray starts from the first depth z i After being emitted, when the ray reaches the depth z i-1 When , the terminal can determine the lateral offset of the first ray by the following formula (1).

[0103] dx i,j =(z i -z i-1 )·tan(α i,j ) (1)

[0104] Among them, dx i,j For the first ray from the first depth z i Reach depth z i-1The lateral offset during the process. α i,j is the preset emission angle.

[0105] Then, the terminal can determine the angle of exit of the first ray from the first interface by the following formula (2), which is also the formula of the refraction law. The first interface is the interface between the first layer and the layer above the first layer.

[0106] sinα i,j / v1=sin α i-1,j / v2 (2)

[0107] Among them, α i, is the preset exit angle, that is, the angle between the first ray in the first stratum and the normal of the first interface, which can also be called the incident angle of the first ray at the first interface. i-1, is the angle between the first ray and the normal of the first interface in the previous stratum, which can also be called the exit angle of the first ray at the first interface. v1 is the transmission speed of the first ray in the first stratum. v2 is the transmission speed of the first ray in the previous stratum. Furthermore, the terminal can sequentially determine the incident angle and exit angle of the first ray at each stratum interface using the following formula (3) until the first ray exits the surface.

[0108]

[0109] Where k is the index of the ray unit at different depths of the first ray. k,j For the first ray at depth z k The stratum and depth are z k-1 The incident angle at the interface of the strata, α k-1, is the angle of incidence of the first ray at the interface. k For the first ray at depth z k The transmission velocity in the formation. k-1 For the first ray at depth z k-1 The transmission speed in the formation.

[0110] Then, the terminal can recursively calculate the travel time of the first ray using the following formula (4), and recursively calculate the position where the first ray exits the ground using the following formula (5).

[0111]

[0112]

[0113] Among them, T i,j For the first ray from the first depth z i The time it takes from launch to exiting the Earth's surface. i,jis the position where the first ray exits the surface, that is, the first ray from the first depth z i The sum of the lateral displacements during the process of reaching the surface. k,j and v k Compared with α in the above formula (3) k,j and v k The meaning of is the same, so I will not elaborate on it here. When k=1, z k-1 is 0, which means the surface depth z0 is 0.

[0114] In some embodiments, the terminal determines the depth reached by the second ray when the travel time is exhausted as the second depth. However, the first target common imaging point gather may or may not have a depth sampling point at the second depth. In the case that the first target common imaging point gather has a depth sampling point at the second depth, the terminal uses the amplitude value of the depth sampling point as the amplitude value of the seismic data at the second depth. In the case that the first target common imaging point gather has or does not have a depth sampling point at the second depth, the terminal interpolates the amplitude value of at least one depth sampling point adjacent to the second depth to obtain the amplitude value of the seismic data at the second depth.

[0115] The terminal can perform the above processing on each second migration velocity in the above manner to generate multiple second common imaging point gathers. The terminal can obtain second common imaging point gathers that reflect the results of prestack depth migration without performing prestack depth migration on the seismic data of the imaging points based on the second migration velocities, thereby improving the efficiency of generating the second common imaging point gathers.

[0116] 309. The terminal determines a target second offset velocity from the multiple second offset velocities, determines the target second offset velocity as the offset velocity of the first formation, and the straightness of the event axis of the second common imaging point gather generated by the target second offset velocity is less than a preset straightness.

[0117] In an embodiment of the present application, when there is a second common imaging point gather whose event straightness is less than a preset straightness, the terminal determines the target second offset velocity for generating the second common imaging point gather as the offset velocity of the first stratum. Furthermore, the terminal can perform prestack depth migration on the seismic data reflected by the first stratum based on the offset velocity of the first stratum to obtain a seismic image that can reflect the stratum structure. Among them, the event shape of the seismic image is relatively straight, the clarity is high, and the imaging effect is good, which facilitates technicians to further analyze and detect the underground strata based on the seismic image. In addition, if there is still no second common imaging point gather with a relatively straight event, the terminal repeats the above steps 302-308 to regenerate multiple new offset velocities and common imaging point gathers until a common imaging point gather with a relatively straight event exists.

[0118] It should be noted that the above embodiment is described using a single co-imaged point in the first stratum as an example. In some embodiments, the first stratum includes multiple co-imaged points. If there are multiple co-imaged points in the first stratum, the terminal can perform the above processing on at least one of the imaged points through steps 301-309, and use the resulting offset velocity as the offset velocity of the imaged point. The terminal can also interpolate the offset velocity of the imaged point to obtain the offset velocities of the remaining imaged points. The terminal uses the offset velocity field composed of the offset velocities of each imaged point in the first stratum as the offset velocity field of the first stratum.

[0119] 310. In response to obtaining the offset velocity of the first stratum, the terminal determines the offset velocity of the second stratum based on a plurality of common imaging point gathers of imaging points in the second stratum, where the second stratum is a stratum below the first stratum.

[0120] In this embodiment of the present application, the terminal determines the offset velocity of each stratum layer by layer, from top to bottom. In response to obtaining the offset velocity of the first stratum, the terminal processes the seismic data of the imaging points in the second stratum by executing steps 301-309 to generate multiple common imaging point gathers. The terminal then determines the offset velocity of the second stratum based on the straightness of the event axis of each common imaging point gather. The process of generating the common imaging point gathers and determining the offset velocity is similar to the above-described steps and will not be further described here.

[0121] In order to more clearly explain the process of determining the displacement velocity of the formation by the terminal, Figure 4 The flowchart shown in FIG. 1 illustrates the process of determining the offset velocity of any formation by the terminal. Figure 4 As shown, the terminal first generates N migration velocities based on the initial migration velocity of the formation. Then, the terminal performs prestack depth migration on the seismic data of the formation based only on the N / 2 migration velocities, obtaining N / 2 first common imaging point gathers. If the events of each first common imaging point gather are not straight, the terminal generates second common imaging point gathers corresponding to the remaining migration velocities based on the first common imaging point gathers. The terminal then determines a second common imaging point gather with a straighter event and uses the migration velocity generated from this second common imaging point gather as the migration velocity of the formation. The terminal then performs prestack depth migration on the seismic data of the formation based on the migration velocity of the formation, obtaining common imaging point gathers. The terminal verifies the accuracy of the migration velocity based on the straightness of the events of the common imaging point gathers. If the events are relatively straight, the migration velocity is highly accurate. The terminal determines the migration velocity as the migration velocity of the aforementioned formation and proceeds to determine the migration velocity of the next formation.

[0122] Compared with pre-stack depth migration directly based on the initial migration velocity of the formation, the above method can determine a more accurate migration velocity and obtain seismic images with better imaging effects. Figure 5 A schematic diagram of imaging shallow, low-signal-to-noise ratio seismic data. Figure 5 The left side is a stacked section obtained by performing pre-stack depth migration on the above seismic data according to the initial migration velocity of the formation and then stacking it. Figure 5 The right side shows the stacked section obtained by determining the migration velocity of the formation using the above method, performing prestack depth migration on the seismic data based on the migration velocity, and then stacking the data. As can be seen, the event continuity of the stacked section on the right side is good, and the faults are relatively clear. Therefore, the migration velocity determination method provided in the embodiments of the present application can more accurately determine the migration velocity of the formation, and is an effective method for accurately imaging seismic data with low signal-to-noise ratios.

[0123] In addition, in order to compare the method of generating the second common imaging point gather proposed in the embodiment of the present application (a method of generating a new common imaging point gather based on an existing common imaging point gather, hereinafter referred to as the method provided by the present application) with the traditional method of generating a common imaging point gather using deep prestack migration, the following method is used. Figure 6 The 7-layer horizontal layered model shown in the figure is used to conduct a comparative test on the above two methods. Figure 6 In the horizontal layered model shown, the initial migration velocities of each layer from top to bottom are 2000m / s, 2500m / s, 3000m / s, 3500m / s, 4000m / s, 4500m / s, and 5000m / s, respectively. Taking the first layer as an example, the terminal generates 41 first migration velocities based on the initial migration velocity of the first layer, according to the preset velocity range of 80% to 120% and the generation step size of 1%. If the traditional method is used, it is necessary to perform pre-stack depth migration on the seismic data according to each first migration velocity, calculate 41 pre-stack depth migrations, and obtain 41 common imaging point gathers, which is computationally intensive. If the method provided in this application is used, a thinned range can be used for pre-stack depth migration, that is, pre-stack depth migration is performed within the preset velocity range of 80% to 120% with a step size of 2%, requiring only 21 pre-stack depth migrations to obtain 21 common imaging point gathers. The remaining 20 common imaging point gathers are then generated using the method provided in this application. The following takes 91% of the migration speed as an example to demonstrate the imaging effects of the above two methods. Figure 7As shown, on the left is a common imaging point gather obtained by performing prestack depth migration on seismic data at a 91% migration velocity. On the right is a common imaging point gather generated by the terminal at a 92% migration velocity. This common imaging point gather, generated using the method provided in this application, corresponds to a 91% migration velocity. A comparison shows that there is virtually no difference between the two. In other words, the imaging quality of seismic images obtained using the method provided in this application is guaranteed.

[0124] In addition, you can also Figure 8 The actual underground model shown in the figure verifies the above two methods. Figure 8 As shown, the strata in the selected actual underground model are mainly flat layers, and the medium-deep layers (approximately 3000m-4000m) have reverse fault structures. The following takes the processing of seismic data from the medium-deep layers as an example. Based on the initial migration velocity of the medium-deep layers, the terminal generates 11 first migration velocities according to a preset velocity range of 90% to 110% and a generation step size of 2%. If the above-mentioned traditional generation method is adopted, it is necessary to perform pre-stack depth migration on the seismic data according to each first migration velocity, calculate 11 pre-stack depth migrations, and obtain 11 common imaging point gathers. Taking the example of the terminal performing pre-stack depth migration through the pre-stack depth migration module with 5 computing nodes in GeoEast (an application for seismic data processing), it takes 4.5 minutes for the terminal to generate a common imaging point gather, and it takes about 11*4.5=49.5 minutes to complete the generation of all the gathers. If the method provided in this application is used, the terminal only needs to perform prestack depth migration for five migration velocity ratios: 92%, 96%, 100%, 104%, and 108%. Common imaging point gathers for other migration velocity ratios (90%, 94%, 98%, 102%, 106%, and 110%) can be obtained using the method provided in this application. Since generating a common imaging point gather using the method provided in this application only takes 21 seconds, the total time required for the above calculation is: 4.5 minutes * 5 + 21 seconds * 6 = 24.5 minutes, which significantly improves the calculation efficiency compared to the previous 49.5 minutes.

[0125] The following takes 90% of the migration speed as an example to demonstrate the imaging effects of the above two methods. Figure 9 As shown, on the left is the common imaging point gather obtained by performing prestack depth migration on the seismic data according to the 90% migration velocity. On the right is the common imaging point gather generated by the terminal according to the 92% migration velocity. The common imaging point gather generated by the method provided in the present application corresponds to the 90% migration velocity. As can be seen from the figure, the straightness of the event axes of the two is consistent. Therefore, for some migration velocities, the common imaging point gather generated by the method provided in the present application can be used instead of the common imaging point gather obtained by performing prestack depth migration according to the migration velocity, which can improve the calculation efficiency.

[0126] In addition, due to Figure 8 The lateral velocity of the actual underground model shown does not change much, so the terminal can only perform a pre-stack depth migration for the 100% offset velocity to generate a common imaging point gather. The common imaging point gathers corresponding to the other ten offset velocities are all generated using the method provided in this application. The following also takes the 90% offset velocity as an example to demonstrate the imaging effects of the above two methods. Figure 10 As shown, the left side is the common imaging point gather obtained by the terminal according to the 90% migration velocity, by performing prestack depth migration on the seismic data. The right side is the common imaging point gather generated by the terminal according to the 100% migration velocity using the method provided by this application, and the common imaging point gather corresponds to the 90% migration velocity. Figure 10 It can be seen that the straightness of the two phase axes is still consistent. Moreover, using the method provided by the present application, the total time required is 4.5 minutes + 21 seconds * 10 = 8 minutes, while using the above-mentioned traditional generation method requires 49.5 minutes. Therefore, the offset velocity determination method provided by the present application can not only accurately determine the offset velocity of the underground strata, but also significantly save calculation time and greatly improve the calculation efficiency. Furthermore, the terminal can perform offset imaging processing on the seismic data reflected by each stratum according to the offset velocity of each underground stratum, and obtain a seismic image that can reflect the stratum structure. Among them, the shape of the phase axis of the seismic image is relatively straight, the clarity is high, and the imaging effect is good, so that technicians can further analyze and detect the underground strata based on the seismic image.

[0127] An embodiment of the present application provides a method for determining migration velocities. To determine the migration velocity of a first formation, prestack depth migration is first performed on seismic data of imaging points in the first formation based on multiple first migration velocities, resulting in multiple first common imaging point gathers. Since the straighter the events of a common imaging point gather, the better the imaging effect and the higher the reliability of the common imaging point gather. Therefore, the migration velocity corresponding to the first common imaging point gather whose event straightness is less than a preset straightness can be determined as the migration velocity of the first formation. If the straightness of the events of each first common imaging point gather is not less than the preset straightness, the multiple migration velocities have low reliability and cannot be used as the migration velocity of the first formation. Then, the multiple first migration velocities are interpolated to obtain multiple second migration velocities. For each second migration velocity, a second common imaging point gather is generated based on the first common imaging point gather corresponding to the first migration velocity with the smallest difference. The migration velocity corresponding to the second common imaging point gather with the straighter event is then used as the migration velocity of the first formation. By adopting the above method, it is no longer necessary to perform prestack depth migration on the seismic data according to each second migration velocity, which significantly reduces the computational complexity of generating the second common imaging point gathers and improves the efficiency of determining the migration velocity.

[0128] Figure 11 Schematic diagram of a device for determining an offset velocity according to an embodiment of the present application. Figure 11 The device includes: an offset module 1101, an interpolation module 1102, a first generation module 1103 and a first determination module 1104.

[0129] A migration module 1101 is configured to perform prestack depth migration on seismic data of imaging points in a first stratum to obtain a plurality of first common imaging point gathers, wherein the first common imaging point gathers are used to represent amplitude values ​​of seismic data at different depths underground.

[0130] An interpolation module 1102 is configured to interpolate a plurality of first migration velocities to obtain a plurality of second migration velocities when the straightness of the event axis of each first common imaging point gather is less than a preset straightness. The first migration velocities are used to perform prestack depth migration on the seismic data of the imaging points.

[0131] A first generating module 1103 is configured to generate, for any second migration velocity, a second common imaging point gather based on the first target common imaging point gather, wherein the first target common imaging point gather is a first common imaging point gather generated using a target first migration velocity, the target first migration velocity being a first migration velocity having a minimum difference with the second migration velocity among a plurality of first migration velocities, and the second common imaging point gather is configured to reflect a result of prestack depth migration of seismic data of the imaging point using the second migration velocity;

[0132] The first determining module 1104 is configured to determine a target second offset velocity from the plurality of second offset velocities, determine the target second offset velocity as the offset velocity of the first formation, and ensure that the straightness of the event axis of the second common imaging point gather generated using the target second offset velocity is not less than a preset straightness.

[0133] In some embodiments, the second common imaging point gather is used to represent the amplitude value of the seismic data at a first depth, where the first depth is the depth of the location of the imaging point; Figure 12 This is a schematic diagram of the structure of another offset velocity determination device provided in an embodiment of the present application, see Figure 12 The first generation module 1103 includes:

[0134] Acquisition unit 11031 is used to obtain the travel time and target position of the first ray, where the first ray is emitted toward the surface at a preset angle at the imaging point. The travel time is the time it takes for the first ray to exit the surface. The target position is the position where the first ray exits the surface.

[0135] A first determining unit 11032 is configured to, in response to the successful emission of the second ray, count down based on the travel time and determine the depth reached by the second ray when the travel time expires as a second depth, where the second ray is emitted underground at the target location;

[0136] A second determining unit 11033 is configured to determine an amplitude value of the seismic data at a second depth based on the first target common imaging point gather;

[0137] The third determining unit 11034 is configured to use the amplitude value of the seismic data at the second depth as the amplitude value of the seismic data at the first depth.

[0138] In some embodiments, the acquisition unit 11031 is used to obtain the initial offset velocity of each formation; based on the preset exit angle and the transmission velocity of the first ray in each formation, the incident angle and the exit angle of the first ray at each formation interface are determined by the law of refraction, and the transmission velocity of the first ray in each formation is the initial offset velocity of each formation; based on the transmission velocity of the first ray in each formation, the incident angle and the exit angle of the first ray at each formation interface and the first depth, the travel time and target position of the first ray are determined.

[0139] In some embodiments, the second determination unit 11033 is used to, when there is a depth sampling point at the second depth in the first target common imaging point gather, use the amplitude value of the depth sampling point as the amplitude value of the seismic data at the second depth; and when there is or is not a depth sampling point at the second depth in the first target common imaging point gather, interpolate the amplitude value of at least one adjacent depth sampling point at the second depth to obtain the amplitude value of the seismic data at the second depth.

[0140] In some embodiments, the apparatus further comprises:

[0141] An acquisition module 1105 is used to acquire an initial velocity model, where the initial velocity model is used to represent the relationship between the depth of a formation and the initial migration velocity of the formation;

[0142] A second determining module 1106 is configured to determine an initial migration velocity of the first formation based on the initial velocity model;

[0143] The second generating module 1107 is configured to generate a plurality of first offset velocities within a preset speed range based on the initial offset velocity and in accordance with a generation step length, wherein the generation step length is used to represent a difference between two adjacent first offset velocities.

[0144] In some embodiments, the apparatus further comprises:

[0145] An analysis module 1108 is configured to perform time domain velocity analysis on the seismic data of the imaging point to obtain a time domain velocity field, which is used to represent the relationship between the transmission time of the seismic data in each stratum and the offset velocity of each stratum;

[0146] The migration module 1101 is further used to perform pre-stack time migration on the seismic data of the imaging point to obtain a time domain migration profile. The time domain migration profile is used to divide multiple underground strata and determine the depth of each stratum.

[0147] The construction module 1109 is used to construct an initial velocity model based on the time domain velocity field and the time domain migration profile.

[0148] In some embodiments, the interpolation module 1102 is configured to determine a second target common imaging point gather when the straightness of the event of each first common imaging point gather is less than a preset straightness, where the second target common imaging point gather is the first common imaging point gather having the smallest difference between the straightness of the event and the preset straightness; determine a third migration velocity based on the second target common imaging point gather, where the third migration velocity is the first migration velocity for generating the second target common imaging point gather; and interpolate the third migration velocity within a preset velocity range according to an interpolation interval to obtain a plurality of second migration velocities.

[0149] In some embodiments, the apparatus further comprises:

[0150] The third determination module 1110 is configured to determine the migration velocity of the second formation based on a plurality of common imaging point gathers of imaging points in the second formation in response to obtaining the migration velocity of the first formation, where the second formation is a layer below the first formation.

[0151] An embodiment of the present application provides a migration velocity determination device. In determining the migration velocity of a first formation, prestack depth migration is first performed on seismic data of imaging points in the first formation based on a plurality of first migration velocities, resulting in a plurality of first common imaging point gathers. Since the straighter the events of the common imaging point gathers, the better the imaging effect and the higher the reliability of the common imaging point gathers. Therefore, the migration velocity corresponding to the first common imaging point gather whose event straightness is less than a preset straightness can be determined as the migration velocity of the first formation. If the straightness of the events of each first common imaging point gather is not less than the preset straightness, the reliability of the plurality of migration velocities is low and none of them can be used as the migration velocity of the first formation. Then, the plurality of first migration velocities are interpolated to obtain a plurality of second migration velocities. For each second migration velocity, a second common imaging point gather is generated based on the first common imaging point gather corresponding to the first migration velocity with the smallest difference therebetween. The migration velocity corresponding to the second common imaging point gather with the straighter event is then used as the migration velocity of the first formation. By adopting the above method, it is no longer necessary to perform prestack depth migration on the seismic data according to each second migration velocity, which significantly reduces the computational complexity of generating the second common imaging point gathers and improves the efficiency of determining the migration velocity.

[0152] It should be noted that the offset velocity determination apparatus provided in the above embodiment is merely illustrated by the division of the aforementioned functional modules. In actual applications, the aforementioned functions can be assigned to different functional modules as needed, i.e., the internal structure of the terminal can be divided into different functional modules to perform all or part of the functions described above. Furthermore, the offset velocity determination apparatus provided in the above embodiment and the offset velocity determination method embodiment are based on the same concept. The specific implementation process is detailed in the method embodiment and will not be further described here.

[0153] An embodiment of the present application further provides a terminal, which includes a processor and a memory. The memory stores at least one computer program, which is loaded and executed by the processor to implement the offset velocity determination method of the above embodiment.

[0154] Figure 13 This is a schematic diagram of the structure of a terminal provided in an embodiment of the present application.

[0155] The terminal 1300 includes a processor 1301 and a memory 1302 .

[0156] The processor 1301 may include one or more processing cores, such as a 4-core processor, an 8-core processor, etc. The processor 1301 may be implemented in at least one hardware form of DSP (Digital Signal Processing), FPGA (Field Programmable Gate Array), or PLA (Programmable Logic Array). The processor 1301 may also include a main processor and a coprocessor. The main processor is a processor for processing data in the awake state, also known as a CPU (Central Processing Unit); the coprocessor is a low-power processor for processing data in the standby state. In some embodiments, the processor 1301 may be integrated with a GPU (Graphics Processing Unit), which is responsible for rendering and drawing the content to be displayed on the display screen. In some embodiments, the processor 1301 may also include an AI (Artificial Intelligence) processor, which is used to process computing operations related to machine learning.

[0157] Memory 1302 may include one or more computer-readable storage media, which may be non-transitory. Memory 1302 may also include high-speed random access memory and non-volatile memory, such as one or more magnetic disk storage devices or flash memory storage devices. In some embodiments, the non-transitory computer-readable storage medium in memory 1302 is used to store at least one computer program, which is used by processor 1301 to implement the offset velocity determination method provided in the method embodiments of this application.

[0158] In some embodiments, terminal 1300 may optionally include a peripheral device interface 1303 and at least one peripheral device. Processor 1301, memory 1302, and peripheral device interface 1303 may be connected via a bus or signal lines. Each peripheral device may be connected to peripheral device interface 1303 via a bus, signal lines, or circuit boards. Optionally, the peripheral device includes at least one of a radio frequency circuit 1304, a display screen 1305, a camera assembly 1306, an audio circuit 1307, and a power supply 1308.

[0159] The peripheral device interface 1303 can be used to connect at least one I / O (Input / Output)-related peripheral device to the processor 1301 and the memory 1302. In some embodiments, the processor 1301, the memory 1302, and the peripheral device interface 1303 are integrated on the same chip or circuit board; in some other embodiments, any one or two of the processor 1301, the memory 1302, and the peripheral device interface 1303 can be implemented on separate chips or circuit boards, which is not limited in this embodiment.

[0160] The RF circuit 1304 is used to receive and transmit RF (Radio Frequency) signals, also known as electromagnetic signals. The RF circuit 1304 communicates with communication networks and other communication devices via electromagnetic signals. The RF circuit 1304 converts electrical signals into electromagnetic signals for transmission, or converts received electromagnetic signals into electrical signals. Optionally, the RF circuit 1304 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, and the like. The RF circuit 1304 can communicate with other devices via at least one wireless communication protocol. Such wireless communication protocols include, but are not limited to, metropolitan area networks, 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 1304 may also include circuits related to NFC (Near Field Communication), which is not limited in this application.

[0161] The display screen 1305 is used to display a UI (User Interface). The UI may include graphics, text, icons, videos, and any combination thereof. When the display screen 1305 is a touch screen display, the display screen 1305 also has the ability to collect touch signals on the surface or above the surface of the display screen 1305. The touch signal can be input as a control signal to the processor 1301 for processing. At this time, the display screen 1305 can also be used to provide virtual buttons and / or virtual keyboards, also known as soft buttons and / or soft keyboards. In some embodiments, there can be one display screen 1305, which is set on the front panel of the terminal 1300; in other embodiments, there can be at least two display screens 1305, which are respectively set on different surfaces of the terminal 1300 or in a folding design; in other embodiments, the display screen 1305 can be a flexible display screen, which is set on the curved surface or folding surface of the terminal 1300. Even more, the display screen 1305 can be set to a non-rectangular irregular shape, that is, a special-shaped screen. The display screen 1305 can be made of materials such as LCD (Liquid Crystal Display) and OLED (Organic Light-Emitting Diode).

[0162] The camera assembly 1306 is used to capture images or videos. Optionally, the camera assembly 1306 includes a front camera and a rear camera. The front camera is arranged on the front panel of the terminal 1300, and the rear camera is arranged on the back of the terminal 1300. In some embodiments, there are at least two rear cameras, which are any one of a main camera, a depth of field camera, a wide-angle camera, and a telephoto camera, so as to realize the fusion of the main camera and the depth of field camera to realize the background blur function, the fusion of the main camera and the wide-angle camera to realize panoramic shooting and VR (Virtual Reality) shooting function or other fusion shooting functions. In some embodiments, the camera assembly 1306 may also include a flash. The flash can be a single-color temperature flash or a dual-color temperature flash. The dual-color temperature flash refers to a combination of a warm light flash and a cold light flash, which can be used for light compensation at different color temperatures.

[0163] The audio circuit 1307 may include a microphone and a speaker. The microphone is used to collect sound waves from the user and the environment, and convert the sound waves into electrical signals that are input into the processor 1301 for processing, or input into the radio frequency circuit 1304 to achieve voice communication. For the purpose of stereo sound collection or noise reduction, there may be multiple microphones, each located in different parts of the terminal 1300. The microphone may also be an array microphone or an omnidirectional collection microphone. The speaker is used to convert electrical signals from the processor 1301 or the radio frequency circuit 1304 into sound waves. The speaker may be a traditional thin film speaker or a piezoelectric ceramic speaker. When the speaker is a piezoelectric ceramic speaker, it can not only convert electrical signals into sound waves audible to humans, but also convert electrical signals into sound waves inaudible to humans for purposes such as ranging. In some embodiments, the audio circuit 1307 may also include a headphone jack.

[0164] Power supply 1308 is used to power various components in terminal 1300. Power supply 1308 can be AC ​​power, DC power, a disposable battery, or a rechargeable battery. When power supply 1308 includes a rechargeable battery, the rechargeable battery can support wired charging or wireless charging. The rechargeable battery can also be used to support fast charging technology.

[0165] In some embodiments, the terminal 1300 further includes one or more sensors 1309 , including but not limited to: an acceleration sensor 1130 , a gyroscope sensor 1311 , a pressure sensor 1312 , an optical sensor 1313 , and a proximity sensor 1314 .

[0166] The accelerometer 1130 can detect the magnitude of acceleration along the three coordinate axes of the coordinate system established by the terminal 1300. For example, the accelerometer 1130 can be used to detect the components of gravity acceleration along the three coordinate axes. The processor 1301 can control the display screen 1305 to display the user interface in either a landscape or portrait view based on the gravity acceleration signal collected by the accelerometer 1130. The accelerometer 1130 can also be used to collect game or user motion data.

[0167] The gyroscope sensor 1311 can detect the orientation and rotation angle of the terminal 1300. It can also work with the accelerometer 1130 to collect the user's 3D movements on the terminal 1300. Based on the data collected by the gyroscope sensor 1311, the processor 1301 can implement the following functions: motion sensing (for example, changing the UI based on the user's tilt operation), image stabilization during shooting, game control, and inertial navigation.

[0168] The pressure sensor 1312 can be provided on the side frame of the terminal 1300 and / or below the display screen 1305. When the pressure sensor 1312 is provided on the side frame of the terminal 1300, it can detect the user's gripping signal of the terminal 1300. The processor 1301 then performs left-hand or right-hand recognition or shortcut operations based on the gripping signal collected by the pressure sensor 1312. When the pressure sensor 1312 is provided below the display screen 1305, the processor 1301 controls the operable controls on the UI interface based on the user's pressure operation on the display screen 1305. Operable controls include at least one of a button control, a scroll bar control, an icon control, and a menu control.

[0169] Optical sensor 1313 is used to detect ambient light intensity. In one embodiment, processor 1301 can control the display brightness of display screen 1305 based on the ambient light intensity detected by optical sensor 1313. Optionally, when the ambient light intensity is high, the display brightness of display screen 1305 is increased; when the ambient light intensity is low, the display brightness of display screen 1305 is decreased. In another embodiment, processor 1301 can also dynamically adjust the shooting parameters of camera assembly 1306 based on the ambient light intensity detected by optical sensor 1313.

[0170] Proximity sensor 1314, also known as a distance sensor, is provided on the front panel of terminal 1300. Proximity sensor 1314 is used to detect the distance between the user and the front of terminal 1300. In one embodiment, when proximity sensor 1314 detects that the distance between the user and the front of terminal 1300 is gradually decreasing, processor 1301 controls display screen 1305 to switch from the screen-on state to the screen-off state. When proximity sensor 1314 detects that the distance between the user and the front of terminal 1300 is gradually increasing, processor 1301 controls display screen 1305 to switch from the screen-off state to the screen-on state.

[0171] Those skilled in the art will understand that Figure 13 The structure shown in the figure does not constitute a limitation on the terminal 1300, and the terminal 1300 may include more or fewer components than shown in the figure, or combine certain components, or adopt a different component arrangement.

[0172] An embodiment of the present application further provides a computer-readable storage medium, in which at least one computer program is stored. The at least one computer program is loaded and executed by a processor to implement the offset velocity determination method of the above embodiment.

[0173] An embodiment of the present application further provides a computer program product, including a computer program, which is loaded and executed by a processor to implement the offset velocity determination method as described in the above embodiment.

[0174] Those skilled in the art will understand that all or part of the steps for implementing the above embodiments may be accomplished by hardware, or may be accomplished by instructing the relevant hardware through a program, and the above program may be stored in a computer-readable storage medium, which may be a read-only memory, a disk, or an optical disk, etc.

[0175] The above are only optional embodiments of the embodiments of the present application and are not intended to limit the embodiments of the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the embodiments of the present application should be included in the scope of protection of this application.

Claims

1. A method for determining an offset velocity, characterized in that: The method comprises: For imaging points in the first stratum, prestack depth migration is performed on seismic data of the imaging points to obtain a plurality of first common imaging point gathers, where the first common imaging point gathers are used to represent amplitude values ​​of the seismic data at different depths underground; When the straightness of the event axis of each first common imaging point gather is not less than a preset straightness, interpolating the plurality of first migration velocities to obtain a plurality of second migration velocities, wherein the first migration velocities are used to perform prestack depth migration on the seismic data of the imaging points; For any second migration velocity, a second common imaging point gather is generated based on a first target common imaging point gather, where the first target common imaging point gather is a first common imaging point gather generated using a target first migration velocity, the target first migration velocity being a first migration velocity having a minimum difference with the second migration velocity among the plurality of first migration velocities, and the second common imaging point gather is used to reflect a result of prestack depth migration of seismic data of the imaging point using the second migration velocity; A target second offset velocity is determined from the plurality of second offset velocities, the target second offset velocity is determined as the offset velocity of the first formation, and the straightness of the event axis of a second common imaging point gather generated by the target second offset velocity is less than the preset straightness.

2. The method according to claim 1, characterized in that The second common imaging point gather is used to represent the amplitude value of the seismic data at a first depth, where the first depth is the depth of the location of the imaging point; The step of generating a second common imaging point gather based on the first target common imaging point gather for any second migration velocity includes: Obtaining the travel time and target position of a first ray, where the first ray is emitted toward the surface at a preset angle from the location of the imaging point, the travel time is the time taken for the first ray to exit the surface, and the target position is the position where the first ray exits the surface; In response to the successful emission of the second ray, a countdown is performed based on the travel time, and a depth reached by the second ray when the travel time expires is determined as a second depth, wherein the second ray is a ray emitted underground at the target location; determining an amplitude value of the seismic data at the second depth based on the first target common imaging point gather; The amplitude value of the seismic data at the second depth is used as the amplitude value of the seismic data at the first depth.

3. The method according to claim 2, characterized in that The obtaining of the travel time and target position of the first ray includes: Obtain the initial migration velocity of each formation; Based on the preset exit angle and the transmission speed of the first ray in each stratum, determining the incident angle and the exit angle of the first ray at each stratum interface by the law of refraction, wherein the transmission speed of the first ray in each stratum is the initial migration speed of each stratum; The travel time of the first ray and the target position are determined based on the transmission speed of the first ray in each stratum, the incident angle and the exit angle of the first ray at each stratum interface, and the first depth.

4. The method according to claim 2, characterized in that Determining the amplitude value of the seismic data at the second depth based on the first target common imaging point gather includes: In a case where the first target common imaging point gather has a depth sampling point at the second depth, using the amplitude value of the depth sampling point as the amplitude value of the seismic data at the second depth; In the case where there is or is not a depth sampling point in the first target common imaging point gather at the second depth, the amplitude value of at least one adjacent depth sampling point at the second depth is interpolated to obtain the amplitude value of the seismic data at the second depth.

5. The method according to claim 1, wherein The method further comprises: Acquire an initial velocity model, wherein the initial velocity model is used to represent the relationship between the depth of the formation and the initial migration velocity of the formation; determining an initial migration velocity of the first formation based on the initial velocity model; Based on the initial offset speed, the plurality of first offset speeds are generated within a preset speed range according to a generation step length, where the generation step length is used to represent a difference between two adjacent first offset speeds.

6. The method according to claim 5, characterized in that The method further comprises: Performing time domain velocity analysis on the seismic data of the imaging point to obtain a time domain velocity field, wherein the time domain velocity field is used to represent the relationship between the transmission time of the seismic data in each stratum and the offset velocity of each stratum; Performing prestack time migration on the seismic data of the imaging point to obtain a time domain migration profile, wherein the time domain migration profile is used to divide multiple underground strata and determine the depth of each stratum; The initial velocity model is constructed based on the time-domain velocity field and the time-domain migration profile.

7. The method according to claim 1, characterized in that The method of interpolating the plurality of first migration velocities to obtain the plurality of second migration velocities when the straightness of the event axis of each first common imaging point gather is not less than a preset straightness comprises: determining a second target common imaging point gather when the straightness of the event of each first common imaging point gather is not less than the preset straightness, the second target common imaging point gather being the first common imaging point gather having the smallest difference between the straightness of the event and the preset straightness; determining a third migration velocity based on the second target common imaging point gather, where the third migration velocity is the first migration velocity for generating the second target common imaging point gather; The third offset speed is interpolated according to an interpolation interval within a preset speed range to obtain the plurality of second offset speeds.

8. The method according to claim 1, characterized in that The method further comprises: In response to obtaining the migration velocity of the first formation, the migration velocity of the second formation is determined based on multiple common imaging point gathers of imaging points in the second formation, where the second formation is a layer below the first formation.

9. A device for determining an offset velocity, characterized in that: The device comprises: a migration module configured to perform prestack depth migration on seismic data of imaging points in a first stratum to obtain a plurality of first common imaging point gathers, wherein the first common imaging point gathers are used to represent amplitude values ​​of the seismic data at different depths underground; an interpolation module, configured to interpolate a plurality of first migration velocities respectively to obtain a plurality of second migration velocities when the straightness of the event axis of each first common imaging point gather is not less than a preset straightness, wherein the first migration velocities are used to perform prestack depth migration on the seismic data of the imaging points; a first generating module configured to generate, for any second migration velocity, a second common imaging point gather based on a first target common imaging point gather, wherein the first target common imaging point gather is a first common imaging point gather generated using a target first migration velocity, the target first migration velocity being a first migration velocity having a minimum difference with the second migration velocity among the plurality of first migration velocities, and the second common imaging point gather reflecting a result of prestack depth migration of seismic data of the imaging point using the second migration velocity; a first determining module configured to determine a target second offset velocity from the plurality of second offset velocities, determine the target second offset velocity as the offset velocity of the first formation, and wherein the straightness of an event axis of a second common imaging point gather generated using the target second offset velocity is less than a preset straightness.

10. A terminal, characterized in that: The terminal includes a processor and a memory, wherein the memory stores at least one computer program, and the at least one computer program is loaded and executed by the processor to implement the offset velocity determination method according to any one of claims 1 to 8.

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