OVT domain three-dimensional VSP multi-wave joint imaging method and device

Abstract

The invention provides an OVT domain three-dimensional VSP multi-wave combined imaging method. The method comprises the steps that an initial speed model is determined according to downlink longitudinal wave and downlink transverse wave first arrival of a zero offset shot gather; determining a shot point and an imaging point, dividing a plurality of azimuth sectors according to the azimuth of the shot point relative to the imaging point, and generating an OVT common imaging point gather of each azimuth sector; performing reaction correction on the OVT common imaging point gather until the event of the OVT common imaging point gather is horizontal, and generating a second longitudinal wave root-mean-square velocity of a second longitudinal wave-longitudinal wave gather and a second transverse wave root-mean-square velocity of a second longitudinal wave-transverse wave gather; eliminating the influence of anisotropy of the second longitudinal wave-longitudinal wave gather and the second longitudinal wave-transverse wave gather in each azimuth sector on travel time, and determining a third longitudinal wave root-mean-square velocity of a third longitudinal wave-longitudinal wave gather and a third transverse wave root-mean-square velocity of the third longitudinal wave-transverse wave gather; and determining a matching relationship between the third longitudinal wave-longitudinal wave gather and the third longitudinal wave-transverse wave gather at the same depth in the same time domain, and performing combined imaging.

Description

Technical Field

[0001] The present application relates to the technical field of VSP seismic exploration, and particularly to a three-dimensional VSP multi-wave joint imaging method and device in the OVT domain. Background Art

[0002] In the process of three-dimensional (3D) Vertical Seismic Profile (VSP) imaging, since most 3D VSP data are acquired with wide azimuths, Offset Vector Tile (OVT) migration is used in surface seismic exploration. Sectors are divided according to the azimuths of shot points and geophones to eliminate the influence of azimuthal anisotropy on travel times. However, in VSP data, the azimuth of the geophones is fixed, so the OVT migration used in surface seismic exploration is no longer applicable to VSP data. Summary of the Invention

[0003] In view of this, the purpose of the present application is to propose a three-dimensional VSP multi-wave joint imaging method and device in the OVT domain that overcomes or at least partially solves the above problems.

[0004] Based on the above purpose, in the first aspect of the present application, a three-dimensional VSP multi-wave joint imaging method in the OVT domain is provided, including:

[0005] Determine an initial velocity model according to the first arrivals of the downgoing P-wave and downgoing S-wave in the zero-offset gather;

[0006] Determine the shot points and imaging points, divide a plurality of azimuth sectors according to the azimuth of the shot points on the ground relative to the imaging points, and generate OVT common image point gathers for each of the azimuth sectors based on the initial velocity model;

[0007] Perform reverse moveout correction on the OVT common image point gathers and conduct velocity analysis until the in-phase axes of the OVT common image point gathers in each azimuth sector are horizontal, and determine the second P-wave root-mean-square velocity of the second P-wave - P-wave gather and the second S-wave root-mean-square velocity of the second P-wave - S-wave gather;

[0008] Determine the travel time reference, eliminate the influence of anisotropy on travel times in each azimuth sector of the second P-wave - P-wave gather and the second P-wave - S-wave gather, and determine the third P-wave root-mean-square velocity of the third P-wave - P-wave gather and the third S-wave root-mean-square velocity of the third P-wave - S-wave gather;

[0009] Based on the third P-wave root-mean-square velocity and the third S-wave root-mean-square velocity, determine the matching relationship between the third P-wave - P-wave gather and the third P-wave - S-wave gather in the same time domain at the same depth, and perform joint imaging;

[0010] Perform corridor superposition constraint on the joint imaging and determine the layer matching accuracy of the joint imaging.

[0011] Optionally, the determining the initial velocity model according to the first arrivals of the downgoing P-wave and the downgoing S-wave in the zero-offset gather includes:

[0012] Determine the P-wave layer velocity, the S-wave layer velocity, and the P-wave to S-wave velocity ratio according to the first arrivals of the downgoing P-wave and the downgoing S-wave in the zero-offset gather;

[0013] Determine the P-wave root-mean-square velocity, the S-wave root-mean-square velocity, and the P-wave to S-wave root-mean-square velocity ratio respectively according to the P-wave layer velocity, the S-wave layer velocity, and the P-wave to S-wave velocity ratio;

[0014] Determine the initial velocity model according to the P-wave root-mean-square velocity, the S-wave root-mean-square velocity, and the P-wave to S-wave root-mean-square velocity ratio.

[0015] Optionally, determining the shot points and the imaging points, and dividing a plurality of azimuth sectors according to the azimuth of the shot points relative to the imaging points on the ground includes:

[0016] Determine a plurality of shot points located on the ground;

[0017] Determine the imaging points;

[0018] Form the azimuth sectors by equally dividing according to the azimuths of the plurality of shot points relative to the imaging points.

[0019] Optionally, generating the OVT common image point gather for each of the range sectors based on the initial velocity model includes:

[0020] Determine a receiving well, and a plurality of geophones are evenly distributed along the wellhead to the bottom of the receiving well;

[0021] Determine the reflection points vertically extending underground from the imaging points;

[0022] In response to any one of the geophones detecting the S-wave and / or P-wave reflected from the reflection point, extend from the reflection point to the geophone towards the ground, and determine the virtual geophone points located on the ground;

[0023] Determine the offset according to the sum of the distances between the shot point and the imaging point and between the imaging point and the virtual geophone point;

[0024] Determine the OVT common image point gather for each of the azimuth sectors according to the offset and the P-wave root-mean-square velocity, the S-wave root-mean-square velocity, and the P-wave to S-wave root-mean-square velocity ratio.

[0025] Optionally, the OVT common image point gather includes a first P-wave - P-wave gather and a first P-wave - S-wave gather;

[0026] Perform reverse moveout correction on the OVT common image point gather and conduct velocity analysis until the in-phase axis of the OVT common image point gather in each azimuth sector is horizontal, and determine the second P-wave root-mean-square velocity of the second P-wave-P-wave gather and the second S-wave root-mean-square velocity of the second P-wave-S-wave gather, including:

[0027] Perform reverse moveout correction on the first P-wave-P-wave gather using the P-wave root-mean-square velocity and conduct iterative velocity analysis until the in-phase axis of the first P-wave-P-wave gather in each azimuth sector is horizontal, and determine the second P-wave root-mean-square velocity of the second P-wave-P-wave gather;

[0028] Calculate the average velocity of the P-wave root-mean-square velocity and the S-wave root-mean-square velocity;

[0029] Perform reverse moveout correction on the first P-wave-S-wave gather using the average velocity and conduct iterative velocity analysis until the in-phase axis of the first P-wave-S-wave gather in each azimuth sector is horizontal, and determine the second average velocity of the second P-wave-S-wave gather;

[0030] Determine the second S-wave root-mean-square velocity according to the second average velocity and the second P-wave root-mean-square velocity.

[0031] Optionally, determine the travel-time reference, eliminate the influence of anisotropy on travel time in each azimuth sector of the second P-wave-P-wave gather and the second P-wave-S-wave gather, and determine the third P-wave root-mean-square velocity of the third P-wave-P-wave gather and the third S-wave root-mean-square velocity of the third P-wave-S-wave gather, including:

[0032] Determine the travel times of the second P-wave-P-wave gather and the second P-wave-S-wave gather located on the same in-phase axis;

[0033] Determine the average value of the travel times, use the average value as the travel-time reference, and determine the third P-wave root-mean-square velocity of the third P-wave-P-wave gather and the third S-wave root-mean-square velocity of the third P-wave-S-wave gather.

[0034] Optionally, based on the third P-wave root-mean-square velocity and the third S-wave root-mean-square velocity, determine the matching relationship between the third P-wave-P-wave gather and the third P-wave-S-wave gather in the same time domain at the same depth and perform joint imaging, including:

[0035] Determine the third P-wave-S-wave velocity contrast according to the third P-wave root-mean-square velocity and the third S-wave root-mean-square velocity;

[0036] Determine the matching relationship between the third P-wave-P-wave gather and the third P-wave-S-wave gather in the same time domain according to the third P-wave root-mean-square velocity, the third S-wave root-mean-square velocity, and the third P-wave to S-wave velocity ratio;

[0037] Stack the third P-wave-P-wave gathers and the third P-wave-S-wave gathers in different azimuth sectors according to the matching relationship to form the joint imaging;

[0038] The matching relationship is expressed as:

[0039]

[0040] where, V P and γ respectively represent the third P-wave root-mean-square velocity and the third P-wave to S-wave root-mean-square velocity ratio, t 0(i) represents the third P-wave-P-wave gather in the i-th time series, where, t 0(i) is a vector representing time, i represents the i-th value in the vector, V C represents the third S-wave root-mean-square velocity, and t 0(j) represents the third P-wave-P-wave gather in the j-th time series.

[0041] Optionally, performing corridor stack constraint on the joint imaging and determining the layer matching accuracy of the joint imaging includes:

[0042] Determine the geophone located at the wellhead of the receiving well and separate the fourth P-wave-P-wave gather and the fourth P-wave-S-wave gather in a short time window of the first arrival to this geophone;

[0043] Use the P-wave layer velocity and the P-wave to S-wave velocity ratio to correct the fourth P-wave-P-wave gather and the fourth P-wave-S-wave gather to the in-phase axis level respectively;

[0044] Convert the corrected fourth P-wave-P-wave gather and the corrected fourth P-wave-S-wave gather to the same time domain as the matching relationship, and stack them respectively to generate a corridor stack profile;

[0045] Insert the corridor stack profile into the joint imaging, and use the corresponding relationship of the same in-phase axis between the corridor stack profile and the joint imaging profile to constrain the joint imaging to determine the matching accuracy of the joint imaging.

[0046] Optionally, the average velocities of the P-wave root-mean-square velocity and the S-wave root-mean-square velocity are expressed as:

[0047]

[0048] where, represents the azimuth Root-mean-square velocity of the longitudinal wave, V S represents the root-mean-square velocity of the shear wave represents the azimuth root-mean-square velocity ratio of the longitudinal wave to the shear wave;

[0049] The reaction correction amount of the average velocity is expressed as:

[0050]

[0051] where z represents the depth of the reflection point represents the azimuth average velocity represents the azimuth offset of the shot point represents the azimuth distance between the shot point and the imaging point, x u represents the distance between the imaging point and the wellhead of the receiving well.

[0052] In the second aspect of the present application, an OVT domain three-dimensional VSP multi-wave joint imaging device is provided, including:

[0053] An initial velocity model module for determining an initial velocity model according to the first arrivals of the down-going longitudinal wave and the down-going shear wave in the zero-offset gather;

[0054] A common imaging point gather module for determining the shot point and the imaging point, dividing a plurality of azimuth sectors according to the azimuth of the shot point relative to the imaging point on the ground, and generating OVT common imaging point gathers of each of the azimuth sectors based on the initial velocity model;

[0055] A velocity update module for performing reaction correction on the OVT common imaging point gathers and performing velocity analysis until the in-phase axes of the OVT common imaging point gathers of each of the azimuth sectors are horizontal, and determining the root-mean-square velocity of the second longitudinal wave of the second longitudinal wave-longitudinal wave gather and the root-mean-square velocity of the second shear wave of the second longitudinal wave-shear wave gather;

[0056] A travel time reference module for determining a travel time reference, eliminating the influence of anisotropy on the travel time in each azimuth sector of the second longitudinal wave-longitudinal wave gather and the second longitudinal wave-shear wave gather, and determining the root-mean-square velocity of the third longitudinal wave of the third longitudinal wave-longitudinal wave gather and the root-mean-square velocity of the third shear wave of the third longitudinal wave-shear wave gather;

[0057] A joint imaging module for determining the matching relationship between the third longitudinal wave-longitudinal wave gather and the third longitudinal wave-shear wave gather at the same depth in the same time domain based on the root-mean-square velocity of the third longitudinal wave and the root-mean-square velocity of the third shear wave, and performing joint imaging;

[0058] A corridor superposition module is used to perform corridor superposition constraints on the joint imaging and determine the layer matching accuracy of the joint imaging.

[0059] As can be seen from the above, the OVT-domain 3D VSP multi-wave joint imaging method and device provided by the present application divide azimuth sectors based on the azimuth of the shot point relative to the imaging point, establish a division criterion for the virtual surface seismic offset of the VSP data for the azimuth sectors, and determine the OVT common image point gather for each azimuth sector; by performing anti-moveout correction on the first P-P wave and the first P-S wave in the OVT common image point gather until the in-phase axis of the OVT common image point gather in each azimuth sector is horizontal, an accurate velocity model of the second P-P wave gather and the second P-S wave gather in each azimuth sector is obtained, that is, the second P-wave root-mean-square velocity and the second S-wave root-mean-square velocity are obtained. Finally, the travel-time reference of the second P-P wave gather and the second P-S wave gather in each azimuth sector is corrected to eliminate the influence of anisotropy on the travel time in each azimuth sector, generate the third P-wave root-mean-square velocity of the third P-P wave gather and the third S-wave root-mean-square velocity of the third P-S wave gather, and establish a matching relationship between the accurate third P-P wave gather and the second P-S wave gather at the same depth in the same time domain, realizing multi-wave joint imaging in the same time domain.

[0060] Perform corridor superposition constraints on the joint imaging, and use the corridor superposition constraints to determine the layer matching accuracy of the joint imaging.

[0061] The above description is only an overview of the technical solution of the present invention. In order to be able to understand the technical means of the present invention more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features and advantages of the present invention more obvious and understandable, the following specifically illustrates the embodiments of the present invention. Description of the Drawings

[0062] In order to more clearly illustrate the technical solutions in the present application or related technologies, the following will briefly introduce the drawings required for use in the embodiments or related technology descriptions. Obviously, the drawings in the following description are only the embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0063] Figure 1 It is a flowchart of the OVT-domain 3D VSP multi-wave joint imaging method 100 according to an embodiment of the present application;

[0064] Figure 2 It is a schematic diagram of the initial velocity model according to an embodiment of the present application;

[0065] Figure 3 It is a schematic diagram of the 3D VSP propagation path according to an embodiment of the present application;

[0066] Figure 4 Schematic diagram of azimuth division of non-wellhead imaging points in the embodiment of the present application;

[0067] Figure 5 Schematic diagram of the longitudinal wave-longitudinal wave point gather in the OVT common imaging point gather before anti-reaction correction in the embodiment of the present application;

[0068] Figure 6 Schematic diagram of the second longitudinal wave-longitudinal wave point gather in the OVT common imaging point gather after anti-reaction correction in the embodiment of the present application;

[0069] Figure 7 Schematic diagram of the longitudinal wave-transverse wave point gather in the OVT common imaging point gather before anti-reaction correction in the embodiment of the present application;

[0070] Figure 8 Schematic diagram of the second longitudinal wave-transverse wave point gather in the OVT common imaging point gather after anti-reaction correction in the embodiment of the present application;

[0071] Figure 9 Schematic diagram of the spiral gather of the second longitudinal wave-longitudinal wave in the embodiment of the present application;

[0072] Figure 10 Schematic diagram of the spiral gather of the second longitudinal wave-transverse wave in the embodiment of the present application;

[0073] Figure 11 Schematic diagram of the joint imaging profile of the second longitudinal wave-longitudinal wave and the second longitudinal wave-transverse wave in the embodiment of the present application;

[0074] Figure 12 Schematic diagram of the corridor stack profile in the embodiment of the present application;

[0075] Figure 13 Schematic diagram of inserting the joint imaging of the second longitudinal wave-longitudinal wave into the corridor stack profile in the embodiment of the present application;

[0076] Figure 14 Schematic diagram of inserting the joint imaging of the second longitudinal wave-transverse wave into the corridor stack profile in the embodiment of the present application;

[0077] Figure 15 Schematic diagram of the OVT domain three-dimensional VSP multi-wave joint imaging device in the embodiment of the present application;

[0078] Figure 16 Schematic diagram of the electronic device in the embodiment of the present application. Detailed implementation manners

[0079] To make the objectives, technical solutions and advantages of the present application clearer and more understandable, the following further elaborates on the present application in detail with reference to specific embodiments and the accompanying drawings.

[0080] It should be noted that unless otherwise defined, the technical terms or scientific terms used in the embodiments of the present application should have the ordinary meanings understood by those with ordinary skills in the field to which the present application belongs. The "first", "second" and similar terms used in the embodiments of the present application do not denote any order, quantity or importance, but are only used to distinguish different components. Words such as "including" or "comprising" mean that the elements or objects appearing before this word cover the elements or objects listed after this word and their equivalents, without excluding other elements or objects. Words such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Upper", "lower", "left", "right", etc. are only used to represent relative position relationships. When the absolute position of the object being described changes, the relative position relationship may also change accordingly.

[0081] The zero-offset gather, also known as the zero-offset shot gather, is a special type of shot gather data in VSP data. Its core feature is that the projection positions of the shot point and the geophones in the receiving well coincide or are nearly coincident on the horizontal plane, that is, the offset approaches zero.

[0082] P-wave to P-wave (PP wave): The seismic wave is triggered from the seismic source in the form of a longitudinal (Primary, P) wave and returns to the geophone in the form of a longitudinal wave after being reflected by the subsurface interface.

[0083] P-wave to S-wave (PS wave): The seismic wave is triggered from the seismic source in the form of a longitudinal (Primary, P) wave and is converted to a transverse (Secondary, S) wave and returns to the geophone after being reflected by the subsurface interface.

[0084] A coherent event is a continuous waveform sequence composed of reflected waves or refracted waves with similar phase characteristics on multiple adjacent traces in a seismic record. It is manifested as a linear or curved form in which wave crests or wave troughs are continuously arranged in the time-space domain.

[0085] Common Image Gathers (CIGs) is a data set formed by gathering seismic data from different shot points or azimuth angles around the same subsurface imaging point according to specific rules in seismic imaging processing.

[0086] According to Figure 1 As shown, the embodiments of the present application provide a 3D VSP multi-wave joint imaging method 100 in the OVT domain. The method includes:

[0087] S100. Determine an initial velocity model according to the first arrivals of the downgoing P-wave and the downgoing S-wave in the zero-offset gather;

[0088] Specifically, according to the first arrivals of the downgoing P-wave and downgoing S-wave in the zero-offset gather, the P-wave interval velocity, S-wave interval velocity, and P / S velocity ratio are determined; according to the P-wave interval velocity, S-wave interval velocity, and P / S velocity ratio, the P-wave root-mean-square (RMS) velocity, S-wave RMS velocity, and P / S RMS velocity ratio are respectively determined; and an initial velocity model is determined based on the P-wave RMS velocity, S-wave RMS velocity, and P / S RMS velocity ratio.

[0089] It should be noted that the above root-mean-square values (P-wave RMS velocity, S-wave RMS velocity, and P / S RMS velocity ratio) are types of velocity models. That is to say, the initial velocity model can be one or more of the P-wave RMS velocity, S-wave RMS velocity, and P / S RMS velocity ratio.

[0090] Reference Figure 2 As shown, it is a schematic diagram of the initial velocity model in an embodiment of the present application, where a respectively shows the P-wave interval velocity V P , S-wave interval velocity V S , as well as the P-wave RMS velocity RMSV P and S-wave RMS velocity RMSV S . b shows the P / S velocity ratio V P / V S ratio, and the P / S RMS velocity ratio RMSV P / V S ratio.

[0091] Seismic waves (simulated by shot points) are usually a P-wave, but when impacting downward, an S-wave will also be formed. Generally, the S-wave cannot be received in surface seismic surveys. For geophones, they are evenly distributed from the wellhead to the bottom of the receiving well. For example, a geophone is buried every 20 m. The geophones are arranged in layers, so the velocities of the downgoing P-wave and downgoing S-wave excited from the zero-offset gather can be detected for each layer, which are the P-wave interval velocity and S-wave interval velocity. By detecting the S-wave interval velocity and the S-wave interval velocity, it is convenient to calculate the P / S velocity ratio and the P / S RMS velocity ratio. Further, the P-wave interval velocity V P , S-wave interval velocity V S , as well as the P-wave RMS velocity RMSV P , S-wave RMS velocity RMSV S , P / S velocity ratio V P / V S ratio, and the P / S RMS velocity ratio RMSV P / V S ratio obtained from the initial velocity model provide basic velocity parameters for the generation of subsequent OVT common image point gathers.

[0092] In step S102, a shot point and an imaging point are determined. Multiple azimuth sectors are divided according to the azimuth of the shot point relative to the imaging point on the ground. Based on the initial velocity model, OVT common imaging point gathers of each azimuth sector are generated.

[0093] In ground seismic data processing, azimuth sectors are divided according to the offset and azimuth angle of the shot point and the geophone. Different from ground seismic, in a vertical seismic profile (VSP), the geophone is fixed in the receiving well, and the method of dividing azimuth sectors in ground seismic cannot be directly used. In the embodiments of the present application, after seismic waves (including P-waves and S-waves) excited by shot points in different directions propagate to the same reflection point, they propagate along the same reflection path to the geophone in the receiving well, that is, waves in different directions propagate along the same reflection path to the geophone after reaching the reflection point. Therefore, the influence of azimuth anisotropy on the travel time of seismic waves is mainly in the propagation stage when the seismic waves travel downward to the reflection point. In order to flip the division of each azimuth sector, the method of pseudo-ground seismic offset is adopted, and azimuth sectors are divided according to the relative azimuth between the shot point and the imaging point of the reflection point on the ground, which is convenient for subsequent elimination of the influence of anisotropy on travel time.

[0094] In some embodiments, determining a shot point and an imaging point, and dividing multiple azimuth sectors according to the azimuth of the shot point relative to the imaging point on the ground includes:

[0095] Determining multiple shot points located on the ground;

[0096] Determining the imaging point;

[0097] Dividing azimuth sectors at equal angles according to the azimuths of multiple shot points relative to the imaging point.

[0098] In some exemplary embodiments, the number of shot points is not less than 2.

[0099] The purpose of the embodiments of the present application is for a vertical seismic profile. When the traditional ground seismic method of dividing azimuth sectors using the offset and azimuth angle between the shot point and the geophone is not applicable, azimuth sectors are further divided by the relative azimuth between the shot point and the imaging point, which is convenient for subsequent elimination of the influence of azimuth anisotropy. Further, for a vertical seismic profile, since the reflection point is located underground, directly using the reflection point to divide azimuth sectors with the shot point may cause deviation in the division of azimuth sectors. Using the imaging point of the reflection point on the ground in the vertically upward direction to divide azimuth sectors can reflect the anisotropy of shot points from different azimuths relative to the reflection point, and is convenient for the division of azimuth sectors and more accurate.

[0100] It should be noted that the reflection point is used to reflect the seismic waves excited by the shot point. In formations at different depths relative to the ground, each formation has an imaging point. Similarly, in the same formation, there may not necessarily be only one reflection point. In the embodiments of the present application, any reflection point can be used to divide the azimuth sector.

[0101] As Figure 3 shown, according to the Kirchhoff prestack time migration theory, after the seismic waves excited by shot points S1, S2, and S3 from different ranges propagate to the same reflection point C, they propagate along the same reflection path CR to the ground. Further, the imaging point of the reflection point C on the ground is determined as C0. Multiple sectors are formed by equally dividing the azimuths of shot points S1, S2, and S3 relative to the imaging point C0. Further, in combination with Figure 4 , taking the azimuth of the Inline line as 0°, and taking 45° as the division angle, the shot points are divided into four azimuth sectors at each imaging point (reflection point): Azimuth I: -22.5° - 22.5°, Azimuth II: 22.5° - 67.5°, Azimuth III: 67.5° - 112.5°, and Azimuth IV: 112.5° - 157.5°. At the same time, the distances from shot points S1, S2, and S3 to the imaging point C0 are x d1 , x d2 and x d3 .

[0102] In some embodiments, based on the initial velocity model, OVT common imaging point gathers for each azimuth sector are generated, including:

[0103] Determine the receiving well, and a plurality of geophones are evenly distributed along the receiving well from the wellhead to the bottom of the well; determine the reflection point where the imaging point extends vertically underground; in response to any geophone detecting the shear wave and / or longitudinal wave reflected from the reflection point, extend from the imaging point to the geophone towards the ground to determine the virtual geophone located on the ground; determine the offset according to the sum of the distances between the shot point and the imaging point and between the imaging point and the virtual geophone; determine the OVT common imaging point gathers in each azimuth sector according to the offset and the root-mean-square velocity of the longitudinal wave, the root-mean-square velocity of the shear wave, and the ratio of the root-mean-square velocities of the longitudinal and shear waves.

[0104] Refer to Figure 3 shown, after the seismic waves excited by shot points S1, S2, and S3 propagate downward to the same imaging point C, they propagate along the same reflection path CR to the geophone R in the receiving well. In order to form the OVT common imaging point gathers, by determining the receiving well, a reflection path is formed when any geophone in the plurality of geophones evenly distributed along the receiving well from the wellhead to the bottom of the well detects the wave (upward longitudinal wave and / or upward shear wave) reflected from the reflection point.

[0105] After determining the reflection path, it is further necessary to determine the offset of the common image point gather. In the embodiments of the present application, the virtual surface seismic offset is used as the offset in the common image point gather. That is, the up-going shear wave and / or up-going P-wave reflected from the reflection point to the geophone are extended towards the ground to determine the virtual geophone points located on the ground. That is to say, along the reflection path extending towards the ground, the virtual geophone points located on the ground are determined. The sum of the distances between the shot point and the imaging point and between the imaging point and the virtual geophone point is used as the offset of the common image point gather, and the OVT common image point gather in each azimuth sector is determined according to the offset, the root-mean-square velocity of the P-wave, the root-mean-square velocity of the S-wave, and the ratio of the root-mean-square velocities of the P-wave and S-wave to determine the common image point gather.

[0106] Reference Figure 3 As shown, the distances of the shot points S1, S2, and S3 from the imaging point are x d1 , x d2 and x d3 , respectively. According to the Kirchhoff prestack time migration theory, taking the shot point S2 as an example, the propagation time of the seismic wave with the propagation path S2CR' is:

[0107]

[0108] Among them, represents the azimuth angle, and respectively represent the propagation time and propagation speed of the down-going wave from the shot point to the reflection point at the azimuth angle T u and V u respectively represent the propagation time and propagation speed of the up-going wave from the reflection point to the virtual geophone point, z represents the depth of the reflection point, x u represents the distance from the imaging point to the wellhead of the receiving well, z r represents the distance between the geophone and the wellhead of the receiving well, that is, the depth of the geophone that detects the shear wave and / or P-wave reflected from the reflection point, represents the azimuth angle the distance between the shot point and the imaging point at the azimuth angle.

[0109] It should be noted that the down-going wave refers to the down-going shear wave and / or down-going P-wave propagating from the shot point to the imaging point, and the up-going wave is the up-going shear wave and / or up-going P-wave reflected from the imaging point.

[0110] The distance from the shot point to the virtual geophone point R' is used as the offset of the common image point gather, which is expressed as:

[0111]

[0112] Among them, x' u = x u + z r tanθu , (3)

[0113] Among them, represents the offset of the azimuth angle of, represents the azimuth angle the distance between the lower shot point and the imaging point, x' u represents the distance between the imaging point and the virtual geophone, x u represents the distance between the imaging point and the wellhead of the receiving well, z r represents the distance between the geophone and the wellhead of the receiving well, θ u represents the angle between the reflected shear wave and / or compressional wave and the receiving well.

[0114] In step S104, inverse moveout correction is performed on the OVT common image gather, and velocity analysis iteration is carried out until the in-phase axis of the OVT common image gather in each azimuth sector is horizontal, and the second compressional wave root-mean-square velocity of the second compressional wave-compressional wave gather and the second shear wave root-mean-square velocity of the second compressional wave-shear wave gather are determined.

[0115] If there is a time difference in the in-phase axis of different azimuth sectors, it indicates that azimuthal anisotropy causes travel-time anomalies, that is, the travel times of seismic waves (mainly compressional waves) excited from shot points at different azimuths to the reflection point are inconsistent. In the OVT common image gather, the horizontal degree of the in-phase axis directly reflects the accuracy of the velocity model. If the in-phase axis is tilted or bent, the velocity model needs to be iteratively updated until it is horizontal.

[0116] In some embodiments, the OVT common image gather includes a first compressional wave-compressional wave gather and a first compressional wave-shear wave gather. Among them, the first compressional wave-compressional wave gather represents the set of down-going compressional waves propagating from the shot point to the reflection point and up-going compressional waves propagating from the reflection point to the virtual imaging point; the first compressional wave-shear wave gather represents the set of down-going compressional waves propagating from the shot point to the reflection point and up-going shear waves propagating from the reflection point to the virtual imaging point.

[0117] In some embodiments, performing inverse moveout correction on the OVT common image gather and carrying out velocity analysis iteration until the in-phase axis of the OVT common image gather in each azimuth sector is horizontal, and determining the second compressional wave root-mean-square velocity of the second compressional wave-compressional wave gather and the second shear wave root-mean-square velocity of the second compressional wave-shear wave gather includes:

[0118] Using the compressional wave root-mean-square velocity to perform inverse moveout correction on the first compressional wave-compressional wave gather, and carrying out velocity analysis iteration until the in-phase axis of the first compressional wave-compressional wave gather in each azimuth sector is horizontal, and determining the second compressional wave root-mean-square velocity of the second compressional wave-compressional wave gather.

[0119] In this step, after performing reverse normal moveout correction on the first P-P wave gather using the root-mean-square velocity of the P-wave, velocity analysis is carried out using the surface seismic reverse normal moveout correction method until the in-phase axis of the first P-P wave gather is horizontal in each azimuth sector. Mainly, the root-mean-square velocity of the P-wave is updated until the in-phase axis of the first P-P wave gather is horizontal in each range sector, and at this time, the root-mean-square velocity of the P-wave is updated to the second root-mean-square velocity of the P-wave. Similarly, the first P-P wave gather is updated to the second P-P wave gather.

[0120] Calculate the average velocity of the root-mean-square velocity of the P-wave and the root-mean-square velocity of the S-wave;

[0121] Perform reverse normal moveout correction on the P-S wave gather using the average velocity and carry out velocity analysis iteration until the in-phase axis of the first P-S wave gather is horizontal in each azimuth sector, and determine the second average velocity for generating the second P-S wave gather;

[0122] Determine the second root-mean-square velocity of the S-wave according to the second average velocity and the second root-mean-square velocity of the P-wave.

[0123] Specifically, for the first P-S wave gather, a time-depth relationship is established using the equivalent C-wave velocity, that is, the down-going P-wave is equivalent to the up-going S-wave, and the root-mean-square velocity of the down-going P-wave can be equivalent to the root-mean-square velocity of the up-going S-wave. In other words, calculate the average velocity of the root-mean-square velocity of the P-wave and the root-mean-square velocity of the S-wave, and use this average velocity as the equivalent C-wave velocity. With this average velocity, the first P-S wave gather can be equivalently treated as an S-wave gather for reverse normal moveout correction. The updated average velocity obtained by performing reverse normal moveout correction on the first P-S wave gather using the average velocity is the second average velocity. Similarly, after reverse normal moveout correction of the first P-S wave gather to the horizontal in-phase axis, the second P-S wave gather is obtained. Reverse derivation is carried out in the same way as obtaining the average velocity using the root-mean-square velocity of the P-wave and the root-mean-square velocity of the S-wave, that is, the second root-mean-square velocity of the S-wave is derived in the reverse direction using the second average velocity and the second root-mean-square velocity of the P-wave.

[0124] For the first P-P wave gather and the first P-S wave gather, the horizontal degree of the event directly reflects the accuracy of the velocity model. If the event is inclined or curved, the velocity model needs to be iteratively updated until it is horizontal. Therefore, normal moveout corrections are performed using the P-wave root-mean-square velocity and the average velocity respectively. During the correction process, velocity analysis iterations are carried out. For example, the velocity analysis iteration can be expressed as making the event in the first P-P wave gather and the first P-S wave gather change from curved to horizontal. During the correction process, mainly the P-wave root-mean-square velocity and the S-wave root-mean-square velocity are updated. After the correction, the events in the first P-P wave gather and the first P-S wave gather in each azimuth sector are horizontal, obtaining the second P-wave root-mean-square velocity and the second S-wave root-mean-square velocity. At the same time, the corrected first P-P wave gather and the corrected first P-S wave gather are obtained, that is, the second P-P wave gather and the second P-S wave gather.

[0125] Based on the second P-wave root-mean-square velocity and the second S-wave root-mean-square velocity, determine the second P-S root-mean-square velocity ratio;

[0126] In some embodiments, the average velocities of the P-wave root-mean-square velocity and the S-wave root-mean-square velocity are expressed as:

[0127]

[0128] where, represents the P-wave root-mean-square velocity at azimuth , V S represents the S-wave root-mean-square velocity, represents the P-S root-mean-square velocity ratio at azimuth ;

[0129] The normal moveout correction amount of the average velocity is expressed as:

[0130]

[0131] where z represents the depth of the reflection point, represents the average velocity at azimuth , represents the offset of the shot point at azimuth , represents the distance between the shot point and the imaging point at azimuth , x u represents the distance between the imaging point and the wellhead of the receiving well.

[0132] Refer to Figure 5 , Figure 6 , Figure 7 and Figure 8As shown, the first P-wave to P-wave gather in the OVT common image point gather before anti-aliasing correction, the second P-wave to P-wave gather in the OVT common image point gather after anti-aliasing correction, the first P-wave to S-wave gather in the OVT common image point gather before anti-aliasing correction, and the second P-wave to S-wave gather in the OVT common image point gather after anti-aliasing correction are respectively shown. Among them, (a), (b), (c), and (d) respectively show Figure 4 the gathers in azimuths I, II, III, and IV of the mid azimuth. (e), (f), (g), and (h) respectively represent the enlarged display in the red frames in (a), (b), (c), and (d). By comparison, whether it is the first P-wave to P-wave gather or the first P-wave to S-wave gather, the same event axis is more horizontal after anti-aliasing correction, and the more horizontal event axis indicates that the velocity model obtained after anti-aliasing correction is more accurate.

[0133] In step S106, a travel time reference is determined to eliminate the influence of anisotropy in each azimuth sector of the second P-wave to P-wave gather and the second P-wave to S-wave gather on the travel time, and the third P-wave root mean square velocity of the third P-wave to P-wave gather and the third S-wave root mean square velocity of the third P-wave to S-wave gather are determined.

[0134] After obtaining the accurate velocity models of the second P-wave to P-wave gather and the second P-wave to S-wave gather in each azimuth sector, at this time, among the OVT common image point gathers in each azimuth sector located at the same imaging point, there is an obvious time difference between the event axes of the same horizon or the same depth. For example, taking Figure 3 the formation where the reflection point C is located as the same horizon, but the arrival times at the reflection point C are different, which is reflected on the event axis as not being in the same time domain. This time difference is the travel time anomaly caused by azimuthal anisotropy. If this anomaly is not corrected during the imaging process, the resolution of the joint imaging profile obtained will be reduced. In order to eliminate the influence of the travel time anomaly on the joint imaging, it is necessary to correct the travel times of the same event axis in each azimuth. According to statistical principles, it is corrected to the average time of the travel times in all azimuths.

[0135] In some embodiments, determining a travel time reference to eliminate the influence of anisotropy in each azimuth sector of the second P-wave to P-wave gather and the second P-wave to S-wave gather on the travel time, and determining the third P-wave root mean square velocity of the third P-wave to P-wave gather and the third S-wave root mean square velocity of the third P-wave to S-wave gather includes:

[0136] Determining the travel times of the second P-wave to P-wave gather and the second P-wave to S-wave gather located on the same event axis; determining the average value of the travel times, using the average value as the travel time reference, and determining the third P-wave root mean square velocity of the third P-wave to P-wave gather and the third S-wave root mean square velocity of the third P-wave to S-wave gather.

[0137] In this embodiment, through the statistical averaging method, the travel times of the in-phase axes in different directions are corrected to the average time, eliminating the travel time anomalies of the same in-phase axis caused by azimuthal anisotropy, and using this travel time to correct the above-mentioned precise velocity model to obtain a velocity model with horizon matching. That is, at different azimuths, the time to reach the same in-phase axis is the same.

[0138] It can be understood that when using the travel time reference to correct the second P-P wave gather and the second P-S wave gather to eliminate anisotropy, essentially, it is the update of the velocities in each azimuth sector, that is, the update of the second P-wave root-mean-square velocity and the second S-wave root-mean-square velocity to obtain the third P-wave root-mean-square velocity and the third S-wave root-mean-square velocity. Correspondingly, after the update of the second P-P wave gather and the second P-S wave gather, the third P-P wave gather and the third P-S wave gather are generated.

[0139] Refer to Figure 6 In (e), (f), (g), and (h) of Figure 8 There are obvious time differences in the point gathers of the same in-phase axis at different azimuths in (e), (f), (g), and (h) of Figure 9 and Figure 10 respectively show that the second P-P wave gather and the second P-S wave gather arrange the OVT common image point gather at the same imaging point into a spiral gather according to the offset and azimuth angle, where Figure 9 In (a) of Figure 9 shows the spiral gather of the second P-P wave gather before correcting the travel time reference, that is, the spiral gather of the second P-P wave gather before correcting anisotropy; Figure 9 In (b) of Figure 9 shows the spiral gather of the second P-P wave gather after correcting the travel time reference, that is, the spiral gather of the third P-P wave gather; Figure 9 In (c) of Figure 9 the red frame in (a) of Figure 10 is enlarged and shown; Figure 10 In (d) of Figure 10 the red frame in (a) of Figure 10 is enlarged and shown. Figure 10 In (a) of Figure 10 shows the spiral gather of the second P-S wave gather before correcting the travel time reference, that is, the spiral gather of the second P-S wave gather before correcting anisotropy; Figure 9 In (c) and (d) ofFigure 10 Comparing (c) and (d) shows that after the travel-time reference is corrected, that is, after anisotropy correction, the travel-time errors of the in-phase axes in different azimuth sectors are eliminated, and the in-phase axes are straighter and more focused.

[0140] After that, in step S108, based on the third P-wave root-mean-square velocity and the third S-wave root-mean-square velocity, the matching relationship between the third P-wave - P-wave gather and the third P-wave - S-wave gather at the same depth in the same time domain is determined, and joint imaging is performed.

[0141] After correcting the migration velocity of the travel-time anomaly in each azimuth, it is necessary to establish the horizon matching relationship between the third P-wave - P-wave gather and the third P-wave - S-wave gather, that is, the matching relationship at PPt0 in the same time domain.

[0142] In some embodiments, step S108 includes:

[0143] Determine the third P-wave to S-wave velocity contrast according to the third P-wave root-mean-square velocity and the third S-wave root-mean-square velocity; determine the matching relationship between the third P-wave - P-wave gather and the third P-wave - S-wave gather in the same time domain according to the third P-wave root-mean-square velocity, the third S-wave root-mean-square velocity, and the third P-wave to S-wave velocity contrast; stack the third P-wave - P-wave gather and the third P-wave - S-wave gather in different azimuth sectors respectively according to the matching relationship to form joint imaging.

[0144] The matching relationship is expressed as:

[0145]

[0146] where V P and γ represent the third P-wave root-mean-square velocity and the ratio of the third P-wave to S-wave root-mean-square velocity respectively, t 0(i) represents the third P-wave - P-wave gather in the i-th time series, where t 0(i) is a vector representing time, i represents the i-th value in the vector, V C represents the third S-wave root-mean-square velocity, and t 0(j) represents the third P-wave - P-wave gather in the j-th time series.

[0147] It can be understood that for the third P-wave - P-wave gather and the third P-wave - S-wave gather, they each have their own joint imaging.

[0148] It can be understood that and both reflect the matching relationship between the third P-wave - S-wave gather and the reflector depth z in the time domain t 0(i) reflects the matching relationship between the third P-wave - S-wave gather and the reflector depth z in the time domain t 0(j) ​​

[0149] For the third P - P wave gather, at time t 0(j) in the time domain, the imaging depth z is determined by the root - mean - square velocity V of the third P - wave after correcting the travel - time reference anomaly caused by azimuthal anisotropy P .

[0150] For the third P - S wave gather, at the same depth z, t 0(i) in the time domain is jointly determined by the root - mean - square velocity V of the third P - wave after correcting the travel - time reference anomaly caused by azimuthal anisotropy P and the root - mean - square velocity ratio γ of the third P - S wave. Thus, the influence of azimuthal anisotropy on the third P - P wave gather and the third P - S wave gather is eliminated. According to formula (1), the imaging results of the third P - P wave gather and the third P - S wave gather in the OVT domain can be obtained, and the same event is matched in the time - space domain.

[0151] Since the polarities of the third P - P wave gather and the third P - S wave gather are opposite, if the result of horizon matching is accurate, that is, in the time - space domain for the same event, at the same event axis in the same time domain for the third P - P wave gather and the third P - S wave gather, the wave peak of the third P - P wave gather profile corresponds to the wave trough of the third P - S wave gather profile, and the wave trough of the third P - P wave gather profile corresponds to the wave peak of the third P - S wave gather profile.

[0152] Figure 11 The joint imaging profiles of the third P - P wave gather and the third P - S wave gather are respectively shown, where Figure 11 (a) in shows the cross - well profile of the third P - P wave gather along Figure 4 the Inline line in, Figure 11 (b) in shows the cross - well profile of the third P - S wave gather Figure 4 along the Inline line in, Figure 11 (c) in shows the cross - well profile of the third P - P wave gather along the Xline line, Figure 11 (d) in shows the cross - well profile of the third P - S wave gather along the Xline. From Figure 11 the imaging profiles in (a) and (b), it can be seen that the polarities of the third P - P wave gather and the third P - S wave gather profiles are opposite, and the resolution of the third P - P wave gather profile is slightly higher than that of the third P - S wave gather profile. For the target horizon at the top of the anticline between 2.0 s and 2.2 s, both the third P - P wave gather and the third P - S wave gather profiles can clearly depict the structure of the horizon. Figure 11 (a) in and Figure 11In (b), the peak of the third P - P gather indicated by the red arrow corresponds to the trough of the third P - S gather, and the trough of the third P - P gather corresponds to the peak of the third P - S gather, with the same - phase axis having the same dip direction. Figure 11 In (c) and Figure 11 In (d), it is the same as the Inline profile, and the arrow position shows a clear polarity reversal feature. In the Inline profile, the same - phase axis of the third P - P gather profile shows discontinuity at the wellhead position, but the orientation of the fault is difficult to determine. The third P - S gather profile clearly shows the development of inclination at the same position, providing more abundant information for subsequent interpretation and inversion.

[0153] In step S110, corridor stack constraint is performed on the joint imaging and the layer - matching accuracy of the joint imaging is determined.

[0154] In order to constrain the 3D VSP data OVT and multi - wave joint imaging, multi - wave corridor stack in the same time domain as the above - mentioned embodiment is used for constraint.

[0155] Specifically, step S110 includes:

[0156] Determine the geophones located at the wellhead of the receiving well and separate the fourth P - P gather and the fourth P - S gather of a short - time window whose first arrivals reach these geophones; use the P - wave layer velocity and the P - to - S wave velocity ratio to correct the fourth P - P gather and the fourth P - S gather to the same - phase axis level respectively; convert the corrected fourth P - P gather and the corrected fourth P - S gather into the same time domain as the matching relationship and generate corridor stack profiles by stacking respectively; insert the corridor stack profiles into the joint imaging, and use the corresponding relationship of the same - phase axis between the corridor stack profiles and the joint imaging profiles to constrain the joint imaging to determine the matching accuracy of the joint imaging.

[0157] The corridor refers to a short - time window near the wellhead of the receiving well (such as 0.5 seconds after the first arrival), and the seismic wave signals in this window are less affected by noise.

[0158] According to the initial velocity model, the signal received by the detector within a short time window starting from the first arrival is the reflected wave signal of the formation at the depth of the detector. Since most VSP sources are P-wave sources and the reflection of the seismic wave occurs at the detector position, which is close to the wellhead of the receiving well, the propagation time of the upgoing wave can be ignored. Therefore, when performing corridor stacking, it is first necessary to separate the upgoing fourth P-wave-P-wave gather and the fourth P-wave-S-wave gather. The upgoing fourth P-wave-P-wave gather and the upgoing fourth P-wave-S-wave gather are directly reflected from the detector at the wellhead to avoid the influence of azimuthal anisotropy. The OVT common imaging gathers are then cropped using a short time window (e.g., 0.5 seconds) after the first arrival of the fourth P-wave and the fourth S-wave from the shot point directly to the geophone. The upgoing fourth P-wave gather and the fourth P-wave gather are then horizontally corrected based on the layer velocity (P-wave layer velocity and P-S wave velocity ratio) obtained from the initial velocity model. At this point, the upgoing fourth P-wave and fourth S-wave fields from the geophone are both one-way trips in the vertical direction. These waves are converted to the same time domain as the matching relationship and superimposed to obtain an accurate corridor stack profile within this time domain at the wellhead. Using the corridor stack profile, which is less affected by noise at the wellhead, the stacked corridor profile can accurately reflect the horizon matching results of the strata at the wellhead within this time domain. Corridor stacking constrains the horizon matching of the joint imaging. By using the corridor stacking sections to compare joint imaging, the events of the corridor stacking sections at the wellhead constrain the joint imaging to be on the same event. That is, the corridor stacking sections are used to constrain the joint imaging to be at the same stratum as the wellhead. This allows for matching of the strata far from the wellhead in the joint imaging.

[0159] If the peaks and troughs of the fourth P-wave gather match the peaks and troughs of the third P-wave gather at the wellhead, and the peaks and troughs of the fourth P-wave gather match the peaks and troughs of the third P-wave gather at the wellhead, the matching is successful. If the peaks and troughs of the fourth P-wave gather do not match the peaks and troughs of the third P-wave gather at the wellhead and / or the peaks and troughs of the fourth P-wave gather do not match the peaks and troughs of the third P-wave gather at the wellhead, the matching fails, and the precise velocity models of the third P-wave gather and the third P-wave gather, that is, the third P-wave root mean square velocity and the third S-wave root mean square velocity, are readjusted until they match.

[0160] It can be understood that, similar to the joint imaging, the fourth P-wave-P-wave gather and the fourth P-wave-S-wave gather each have their own corridor stacking imaging.

[0161] In order to further constrain the results of the joint imaging, the embodiment of the present application uses the corridor superposition imaging results for constraint. Figure 12Schematic diagram of corridor superposition in the embodiments of the present application; wherein, Figure 12 (a) in Figure 12 and (c) in Figure 12 are respectively the wave fields of the zero-offset upgoing fourth P-P wave channel set and the fourth P-S wave channel set, where the red line is the wave field clipping position; after correcting the clipped wave field to the horizontal with the accurate layer velocity at the import position, the corrected fourth P-P wave channel set and the corrected wave field of the fourth P-S wave channel set as shown in Figure 12 (b) in Figure 13 and (d) in Figure 13 can be obtained. After converting them to the same time domain as the matching relationship, that is, the PP t0 time domain, the corridor superposition profile in this time domain is obtained, as shown in Figure 13 (c) in Figure 13 (a) in Figure 13 and (b) in Figure 14 respectively show the results of embedding the corridor superposition profile of the fourth P-P wave channel set into the Inline and Xline profiles of the joint imaging of the third P-P wave channel set. The corresponding relationship of the in-phase axes is good at the target horizon. Figure 14 (a) in and (b) in

[0162] respectively show the results of embedding the corridor superposition profile of the fourth P-S wave channel set into the Inline and Xline profiles of the joint imaging of the third P-S wave channel set. The in-phase axes of its target horizon still correspond consistently, indicating that the joint imaging results of the third P-P wave channel set and the third P-S wave channel set in the OVT domain are relatively accurate. It should be noted that the method in the embodiments of the present application can be executed by a single device, such as a computer or a server, etc. The method in this embodiment can also be applied to a distributed scenario and completed by multiple devices cooperating with each other. In this case of the distributed scenario, one of these multiple devices can only execute one or more steps in the method in the embodiments of the present application, and these multiple devices will interact with each other to complete the described method.

[0163] It should be noted that some embodiments of the present application have been described above. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims can be executed in a different order from those in the above embodiments and still achieve the desired results. Additionally, the processes depicted in the drawings do not necessarily require the specific order or sequential order shown to achieve the desired results. In certain embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0164] Based on the same inventive concept, corresponding to the method of any of the above embodiments, the present application further provides an OVT domain three-dimensional VSP multi-wave joint imaging device.

[0165] Referring to Figure 15 , the OVT domain three-dimensional VSP multi-wave joint imaging device includes:

[0166] An initial velocity model module 1501, configured to determine an initial velocity model according to the first arrivals of the downgoing longitudinal wave and the downgoing shear wave in the zero-offset gather;

[0167] A common image point gather module 1502, configured to determine shot points and image points, divide a plurality of azimuth sectors according to the azimuth of the shot points on the ground relative to the image points, and generate OVT common image point gathers of each of the azimuth sectors based on the initial velocity model;

[0168] A velocity update module 1503, configured to perform reverse movement correction on the OVT common image point gathers and perform velocity analysis until the in-phase axes of the OVT common image point gathers of each of the azimuth sectors are horizontal, and determine the second root-mean-square velocity of the second longitudinal wave of the second longitudinal wave-longitudinal wave gather and the second root-mean-square velocity of the second shear wave of the second longitudinal wave-shear wave gather;

[0169] A travel time reference module 1504, configured to determine a travel time reference, eliminate the influence of anisotropy on travel time in each azimuth sector of the second longitudinal wave-longitudinal wave gather and the second longitudinal wave-shear wave gather, and determine the third root-mean-square velocity of the third longitudinal wave of the third longitudinal wave-longitudinal wave gather and the third root-mean-square velocity of the third shear wave of the third longitudinal wave-shear wave gather;

[0170] A joint imaging module 1505, configured to determine the matching relationship in the same time domain between the third longitudinal wave-longitudinal wave gather and the third longitudinal wave-shear wave gather at the same depth based on the third root-mean-square velocity of the third longitudinal wave and the third root-mean-square velocity of the third shear wave, and perform joint imaging;

[0171] A corridor stacking module 1506, configured to perform corridor stacking constraint on the joint imaging and determine the layer matching accuracy of the joint imaging.

[0172] For the convenience of description, when describing the above device, it is divided into various modules according to functions and described separately. Of course, when implementing the present application, the functions of each module can be implemented in one or more software and / or hardware.

[0173] The device of the above embodiment is used to implement the corresponding OVT domain three-dimensional VSP multi-wave joint imaging method in any of the foregoing embodiments, and has the beneficial effects of the corresponding method embodiments, which will not be elaborated herein.

[0174] Based on the same inventive concept, corresponding to the method of any of the above embodiments, the present application further provides an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, it implements the OVT domain three-dimensional VSP multi-wave joint imaging method described in any one of the above embodiments.

[0175] Figure 16 FIG. shows a more specific schematic diagram of the hardware structure of the electronic device provided in this embodiment. The device may include: a processor 1010, a memory 1020, an input / output interface 1030, a communication interface 1040, and a bus 1050. Among them, the processor 1010, the memory 1020, the input / output interface 1030, and the communication interface 1040 are communicatively connected to each other inside the device through the bus 1050.

[0176] The processor 1010 may be implemented in a general-purpose CPU (Central Processing Unit), a microprocessor, an application-specific integrated circuit (ASIC), or one or more integrated circuits, etc., and is used to execute relevant programs to implement the technical solutions provided in the embodiments of the present specification.

[0177] The memory 1020 may be implemented in the form of a ROM (Read Only Memory), a RAM (Random Access Memory), a static storage device, a dynamic storage device, etc. The memory 1020 may store an operating system and other application programs. When implementing the technical solutions provided in the embodiments of the present specification through software or firmware, the relevant program codes are stored in the memory 1020 and are called and executed by the processor 1010.

[0178] The input / output interface 1030 is used to connect to an input / output module to implement information input and output. The input / output module may be configured as a component in the device (not shown in the figure) or externally connected to the device to provide corresponding functions. Among them, the input device may include a keyboard, a mouse, a touch screen, a microphone, various sensors, etc., and the output device may include a display, a speaker, a vibrator, an indicator light, etc.

[0179] The communication interface 1040 is used to connect to a communication module (not shown in the figure) to implement communication interaction between this device and other devices. Among them, the communication module may communicate through a wired method (such as USB, network cable, etc.) or through a wireless method (such as a mobile network, WIFI, Bluetooth, etc.).

[0180] The bus 1050 comprises a path for transmitting information between the various components of the device (eg, the processor 1010 , the memory 1020 , the input / output interface 1030 , and the communication interface 1040 ).

[0181] It should be noted that although the above device only shows the processor 1010, the memory 1020, the input / output interface 1030, the communication interface 1040, and the bus 1050, in a specific implementation, the device may also include other components necessary for normal operation. In addition, it will be understood by those skilled in the art that the above device may only include the components necessary to implement the embodiments of this specification, and does not necessarily include all the components shown in the figure.

[0182] The electronic device of the above embodiment is used to implement the corresponding OVT domain three-dimensional VSP multi-wave joint imaging method in any of the above embodiments, and has the beneficial effects of the corresponding method embodiment, which will not be repeated here.

[0183] Based on the same technical concept, corresponding to any of the above-mentioned embodiments and methods, the present application also provides a non-transitory computer-readable storage medium, wherein the non-transitory computer-readable storage medium stores computer instructions, and the computer instructions are used to enable the computer to execute the OVT domain three-dimensional VSP multi-wave joint imaging method as described in any of the above embodiments.

[0184] The computer-readable media of this embodiment include permanent and non-permanent, removable and non-removable media that can be used to store information by any method or technology. The information can be computer-readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, read-only compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device.

[0185] The computer instructions stored in the storage medium of the above embodiment are used to enable the computer to execute the OVT domain three-dimensional VSP multi-wave joint imaging method as described in any of the above embodiments, and have the beneficial effects of the corresponding method embodiments, which will not be repeated here.

[0186] Based on the same inventive concept, corresponding to the OVT-domain 3D VSP multi-wave joint imaging method described in any of the above embodiments, the present disclosure further provides a computer program product comprising computer program instructions. In some embodiments, the computer program instructions can be executed by one or more processors of a computer to cause the computer and / or the processors to perform the OVT-domain 3D VSP multi-wave joint imaging method. For each step in each embodiment of the OVT-domain 3D VSP multi-wave joint imaging method, the processor executing the step can be a member of the corresponding execution entity.

[0187] The computer program product of the above embodiment is used to enable the computer and / or the processor to execute the OVT domain three-dimensional VSP multi-wave joint imaging method as described in any of the above embodiments, and has the beneficial effects of the corresponding method embodiments, which will not be repeated here.

[0188] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present application (including the claims) is limited to these examples. Within the scope of the present application, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the embodiments of the present application as described above, which are not provided in detail for the sake of simplicity.

[0189] In addition, for simplicity of description and discussion, and in order not to make the embodiment of the application difficult to understand, the known power supply / ground connection with integrated circuit (IC) chip and other components may or may not be shown in the accompanying drawings provided. In addition, the device can be shown in the form of a block diagram to avoid making the embodiment of the application difficult to understand, and this also takes into account the following fact, that is, the details of the embodiment of these block diagram devices are highly dependent on the platform to be implemented in the embodiment of the application (that is, these details should be fully within the scope of understanding of those skilled in the art). When specific details (for example, circuit) are set forth to describe exemplary embodiments of the application, it will be apparent to those skilled in the art that the embodiment of the application can be implemented without these specific details or when these specific details are changed. Therefore, these descriptions should be considered to be illustrative rather than restrictive.

[0190] Although the present invention has been described in conjunction with specific embodiments thereof, many alternatives, modifications, and variations of these embodiments will be apparent to those skilled in the art based on the foregoing description. For example, other memory architectures (e.g., dynamic RAM (DRAM)) may utilize the embodiments discussed.

[0191] Embodiments of the present application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present application shall be included within the protection scope of the present application.

Claims

1. A three-dimensional VSP multi-wave joint imaging method in the OVT domain, characterized in that, Including: Determine an initial velocity model based on the first arrivals of the downgoing P-wave and downgoing S-wave in the zero-offset gather; Determine the shot points and imaging points, divide multiple azimuth sectors according to the azimuth of the shot points on the ground relative to the imaging points, and generate OVT common image point gathers for each of the azimuth sectors based on the initial velocity model; Perform reverse movement correction on the OVT common image point gathers, and perform velocity analysis iteration until the event axes of the OVT common image point gathers in each azimuth sector are horizontal, and determine the second P-wave root-mean-square velocity of the second P-wave-P-wave gather and the second S-wave root-mean-square velocity of the second P-wave-S-wave gather; Determine the travel time reference, eliminate the influence of anisotropy on travel time in each azimuth sector of the second P-wave-P-wave gather and the second P-wave-S-wave gather, and determine the third P-wave root-mean-square velocity of the third P-wave-P-wave gather and the third S-wave root-mean-square velocity of the third P-wave-S-wave gather; Based on the third P-wave root-mean-square velocity and the third S-wave root-mean-square velocity, determine the matching relationship between the third P-wave-P-wave gather and the third P-wave-S-wave gather at the same depth in the same time domain, and perform joint imaging; Perform corridor stack constraint on the joint imaging and determine the layer matching accuracy of the joint imaging.

2. The method according to claim 1, wherein The determining an initial velocity model based on the first arrivals of the downgoing P-wave and downgoing S-wave in the zero-offset gather includes: Determine the P-wave layer velocity, S-wave layer velocity, and P-wave to S-wave velocity ratio based on the first arrivals of the downgoing P-wave and downgoing S-wave in the zero-offset gather; Respectively determine the P-wave root-mean-square velocity, S-wave root-mean-square velocity, and P-wave to S-wave root-mean-square velocity ratio based on the P-wave layer velocity, S-wave layer velocity, and P-wave to S-wave velocity ratio; Determine the initial velocity model based on the P-wave root-mean-square velocity, the S-wave root-mean-square velocity, and the P-wave to S-wave root-mean-square velocity ratio.

3. The method according to claim 1, characterized in that Determine the shot points and imaging points, and divide multiple azimuth sectors according to the azimuth of the shot points on the ground relative to the imaging points, including: Determine multiple shot points located on the ground; Determine the imaging points; Form the azimuth sectors by equally dividing according to the azimuth of the multiple shot points relative to the imaging points at equal angles.

4. The method according to claim 3, wherein Generating OVT common image point gathers for each of the range sectors based on the initial velocity model includes: Determine the receiving well, and a plurality of geophones are evenly distributed along the wellhead to the bottom of the receiving well; Determine the reflection points vertically extending underground from the imaging points; In response to any one of the geophones detecting the S-wave and / or P-wave reflected from the reflection point, extend from the reflection point to the geophone towards the ground, and determine the virtual geophone points located on the ground; Determine the offset based on the sum of the distances between the shot point and the imaging point and between the imaging point and the virtual geophone point; Determine the OVT common image point gathers in each azimuth sector according to the offset and the P-wave root-mean-square velocity, the S-wave root-mean-square velocity, and the P-wave to S-wave root-mean-square velocity ratio.

5. The method according to claim 4, wherein The OVT common image point gathers include a first P-wave-P-wave gather and a first P-wave-S-wave gather; Perform reverse moveout correction on the OVT common image point gather and conduct velocity analysis until the event axes of the OVT common image point gathers in each azimuth sector are horizontal, and determine the second P-wave root-mean-square velocity of the second P-wave-P-wave gather and the second S-wave root-mean-square velocity of the second P-wave-S-wave gather, including: Perform reverse moveout correction on the first P-wave-P-wave gather using the P-wave root-mean-square velocity and conduct iterative velocity analysis until the event axes of the first P-wave-P-wave gathers in each azimuth sector are horizontal, and determine the second P-wave root-mean-square velocity for generating the second P-wave-P-wave gather; Calculate the average velocity of the P-wave root-mean-square velocity and the S-wave root-mean-square velocity; Perform reverse moveout correction on the first P-wave-S-wave gather using the average velocity and conduct iterative velocity analysis until the event axes of the first P-wave-S-wave gathers in each azimuth sector are horizontal, and determine the second average velocity for generating the second P-wave-S-wave gather; Determine the second S-wave root-mean-square velocity according to the second average velocity and the second P-wave root-mean-square velocity.

6. The method according to claim 5, wherein Determine the travel-time reference, eliminate the influence of anisotropy on travel time in each azimuth sector of the second P-wave-P-wave gather and the second P-wave-S-wave gather, and determine the third P-wave root-mean-square velocity of the third P-wave-P-wave gather and the third S-wave root-mean-square velocity of the third P-wave-S-wave gather, including: Determine the travel times of the second P-wave-P-wave gather and the second P-wave-S-wave gather located on the same event axis; Determine the average value of the travel times, use the average value as the travel-time reference, and determine the third P-wave root-mean-square velocity of the third P-wave-P-wave gather and the third S-wave root-mean-square velocity of the third P-wave-S-wave gather.

7. The method according to claim 6, wherein Based on the third P-wave root-mean-square velocity and the third S-wave root-mean-square velocity, determine the matching relationship between the third P-wave-P-wave gather and the third P-wave-S-wave gather in the same time domain at the same depth, and perform joint imaging, including: Determine the third P-wave-S-wave velocity contrast according to the third P-wave root-mean-square velocity and the third S-wave root-mean-square velocity; Determine the matching relationship between the third P-wave-P-wave gather and the third P-wave-S-wave gather in the same time domain according to the third P-wave root-mean-square velocity, the third S-wave root-mean-square velocity, and the third P-wave-S-wave velocity contrast; Superimpose the third P-wave-P-wave gathers and the third P-wave-S-wave gathers in different azimuth sectors respectively according to the matching relationship to form the joint imaging; The matching relationship is expressed as: Among them, V P and γ respectively represent the root-mean-square velocity of the third longitudinal wave and the root-mean-square velocity ratio of the third longitudinal wave to the third transverse wave. t 0(i) represents the third longitudinal wave-longitudinal wave gather at the i-th time series. Among them, t 0(i) is a vector representing time, i represents the i-th value in the vector, and V C represents the root-mean-square velocity of the third transverse wave, and t 0(j) represents the third longitudinal wave-longitudinal wave gather at the j-th time series.

8. The method according to claim 4, characterized in that, Perform corridor stack constraint on the joint imaging and determine the layer matching accuracy of the joint imaging, including: Determine the geophone located at the wellhead of the receiving well and separate the fourth P-wave-P-wave gather and the fourth P-wave-S-wave gather in a short time window where the first arrival reaches this geophone; Correct the fourth P-wave-P-wave gather and the fourth P-wave-S-wave gather to the horizontal event axis level using the P-wave layer velocity and the P-wave-S-wave velocity ratio respectively; Convert the corrected fourth P-wave - P-wave gather and the corrected fourth P-wave - S-wave gather to the same time domain as the matching relationship, and stack them respectively to generate a corridor stack section; Insert the corridor stack section into the joint imaging, and use the corresponding relationship of the same in-phase axis between the corridor stack section and the joint imaging section to constrain the joint imaging to determine the matching accuracy of the joint imaging.

9. The method according to claim 5, characterized in that, The average velocities of the P-wave root-mean-square velocity and the S-wave root-mean-square velocity are expressed as: Among them, represents the root-mean-square velocity of the longitudinal wave of the azimuth, and V S represents the root-mean-square velocity of the shear wave, represents the azimuth of the root-mean-square velocity ratio of the longitudinal and shear waves; The anti-correction amount of the average velocity is expressed as: where z represents the depth of the reflection point, represents the azimuth angle of the average velocity, represents the azimuth angle of the offset of the shot point, represents the azimuth angle of the distance between the shot point and the imaging point, x u represents the distance between the imaging point and the wellhead of the receiving well.

10. An OVT domain three-dimensional VSP multi-wave joint imaging device, characterized in that, Including: An initial velocity model module, configured to determine an initial velocity model according to the first arrivals of the downgoing P-wave and the downgoing S-wave of the zero-offset gather; A common image point gather module, which determines the shot point and the imaging point, divides a plurality of azimuth sectors according to the azimuth of the shot point relative to the imaging point on the ground, and generates OVT common image point gathers for each of the azimuth sectors based on the initial velocity model; A velocity update module, configured to perform anti-correction on the OVT common image point gathers and perform velocity analysis until the in-phase axes of the OVT common image point gathers in each azimuth sector are horizontal, and determine the second P-wave root-mean-square velocity of the second P-wave - P-wave gather and the second S-wave root-mean-square velocity of the second P-wave - S-wave gather; A travel-time reference module, configured to determine a travel-time reference, eliminate the influence of anisotropy on the travel time in each azimuth sector of the second P-wave - P-wave gather and the second P-wave - S-wave gather, and determine the third P-wave root-mean-square velocity of the third P-wave - P-wave gather and the third S-wave root-mean-square velocity of the third P-wave - S-wave gather; A joint imaging module, configured to determine the matching relationship between the third P-wave - P-wave gather and the third P-wave - S-wave gather at the same depth in the same time domain based on the third P-wave root-mean-square velocity and the third S-wave root-mean-square velocity, and perform joint imaging; A corridor stack module, configured to perform corridor stack constraint on the joint imaging and determine the layer matching accuracy of the joint imaging.

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