Anisotropic VTI medium elastic wave Gaussian beam migration imaging method and device

Abstract

The invention relates to the technical field of seismic data processing, and particularly discloses an anisotropic VTI medium elastic wave Gaussian beam migration imaging method and device. Determining center ray travel time and path information of elastic waves of the anisotropic VTI medium and dynamic ray parameters; according to the center ray travel time, the path information, the dynamic ray parameters, the transverse wave speed information, the longitudinal wave speed information and the anisotropy parameter information, a seismic source displacement wave field is determined; according to the forward continuation wave field and the reverse continuation wave field of the seismic source displacement wave field and the cross-correlation result of the forward continuation wave field, the reverse continuation wave field and the reverse continuation wave field at the center of the Gaussian beam, determining a migration imaging value corresponding to the seismic record; and all migration imaging values are superposed, and anisotropic VTI medium elastic wave Gaussian beam migration imaging is determined, so that a new solution can be provided for complex anisotropic VTI medium elastic wave migration imaging.

Description

Technical Field

[0001] The present invention relates to the technical field of seismic data processing, and particularly to an elastic wave Gaussian beam migration imaging method and device for an anisotropic VTI medium. Background Art

[0002] Seismic migration imaging technology plays a crucial role in oil and gas field exploration. Elastic wave seismic exploration can effectively utilize the information of longitudinal and transverse waves, reduce the ambiguity of seismic exploration, and effectively improve the accuracy of seismic exploration. With the deepening of research, the current seismic migration imaging technology has gradually transitioned from conventional isotropic media to anisotropic media. Progress has been made in the forward modeling of seismic waves in anisotropic media and wave field separation. However, less progress has been made in elastic wave migration imaging in anisotropic media because the wave field propagation in anisotropic media is complex, and there are problems such as difficulty in wave field separation and large influence of imaging crosstalk. Summary of the Invention

[0003] In view of this, the purpose of the embodiments of the present invention is to propose an elastic wave Gaussian beam migration imaging method and device for an anisotropic VTI medium, which solves the problem of elastic wave migration imaging in anisotropic media.

[0004] One aspect of the embodiments of the present invention provides an elastic wave Gaussian beam migration imaging method for an anisotropic VTI medium, the method comprising:

[0005] Obtaining the shear wave velocity information, longitudinal wave velocity information, anisotropic parameter information required in the tracking of elastic waves in an anisotropic VTI medium, and the single-shot elastic wave seismic record of the anisotropic VTI medium;

[0006] Determining the kinematic ray tracing equation of elastic waves in an anisotropic VTI medium and the dynamic ray tracing equation of elastic waves in an anisotropic VTI medium according to the shear wave velocity information, the longitudinal wave velocity information, and the anisotropic parameter information;

[0007] Determining the central ray travel time and path information of elastic waves in the anisotropic VTI medium according to the kinematic ray tracing equation of elastic waves in the anisotropic VTI medium, the shear wave velocity information, the longitudinal wave velocity information, and the anisotropic parameter information;

[0008] Determining the dynamic ray tracing parameters according to the dynamic ray tracing equation of elastic waves in the anisotropic VTI medium, the shear wave velocity information, the longitudinal wave velocity information, and the anisotropic parameter information;

[0009] Determining the Gaussian beam source displacement wave field of elastic waves in an anisotropic VTI medium according to the central ray travel time, path information, dynamic ray parameters, shear wave velocity information, longitudinal wave velocity information, and anisotropic parameter information;

[0010] Based on the forward-propagating wave field and backward-propagating wave field of the elastic wave Gaussian beam source displacement wave field in anisotropic VTI media, and the cross-correlation results between the forward-propagating wave field and backward-propagating wave field and the backward-propagating wave field at the center of the Gaussian beam, determine the anisotropic VTI media elastic wave Gaussian beam migration imaging value corresponding to the single-shot elastic wave seismic record in anisotropic VTI media;

[0011] Superimpose the anisotropic VTI media elastic wave Gaussian beam migration imaging values corresponding to all single-shot seismic records to determine the anisotropic VTI media elastic wave Gaussian beam migration imaging.

[0012] Furthermore, based on the shear wave velocity information, longitudinal wave velocity information, and anisotropic parameter information, determine the kinematic ray tracing equation for the elastic wave qP wave in anisotropic VTI media:

[0013]

[0014]

[0015]

[0016]

[0017] where x qP , z qP are the x-component and z-component of the qP wave ray tracing path respectively, and s qP represents the qP wave phase slowness scalar; are the x-component and z-component of the qP wave slowness vector p qP respectively; E qP , F qP , L qP , G qP , K qP are the longitudinal wave vertical velocity v P0 , the shear wave vertical velocity v S0 , the anisotropic parameter ε of the anisotropic VTI media, the anisotropic parameter δ of the anisotropic VTI media, and the parameter variables composed of the x-component qP and z-component of the qP wave slowness vector p respectively;

[0018] where,

[0019] Furthermore, based on the shear wave velocity information, longitudinal wave velocity information, and anisotropic parameter information, determine the kinematic ray tracing equation for the elastic wave qSV wave in anisotropic VTI media:

[0020]

[0021]

[0022]

[0023]

[0024] Among them, x qSV , z qSV are the x-component and z-component of the qSV-wave ray tracing path respectively, and s qSV represents the qSV-wave phase slowness scalar; are the x-component and z-component of the qSV-wave slowness vector p qSV respectively; E qSV , F qSV , L qSV , G qSV , K qSV are the longitudinal wave vertical velocity v P0 , the transverse wave vertical velocity v S0 , the anisotropic parameter ε of the anisotropic VTI medium, the anisotropic parameter δ of the anisotropic VTI medium, and the x-component qSV and z-component of the qSV-wave slowness vector p constitute the parameter variables;

[0025] Among them,

[0026] Furthermore, according to the shear wave velocity information, longitudinal wave velocity information, and anisotropic parameter information, the dynamic ray tracing equation of the elastic wave qP-wave in the anisotropic VTI medium is determined:

[0027]

[0028]

[0029] Among them, and represent the qP-wave dynamic ray parameters; M and N represent the coordinate variables in the ray center coordinate system. For a two-dimensional medium, M and N take the value of 1; i and j represent the coordinate variables in the Cartesian coordinate system. For a two-dimensional medium, i and j can take the values of 1 and 3; represents the qP-wave dynamic ray tracing calculation coefficient, which are respectively:

[0030] Furthermore, based on the shear wave velocity information, compressional wave velocity information, and anisotropic parameter information, the elastic wave qSV wave dynamic ray tracing equation for anisotropic VTI media is determined:

[0031]

[0032]

[0033] where, and represent the qSV wave dynamic ray parameters; M and N represent the coordinate variables in the ray center coordinate system. For two-dimensional media, M and N take the value of 1; i and j represent the coordinate variables in the Cartesian coordinate system. For two-dimensional media, i and j can take the values of 1 and 3; represent the qSV wave dynamic ray tracing calculation coefficients, respectively:

[0034] Furthermore, based on the central ray travel time, path information, dynamic ray parameters, shear wave velocity information, compressional wave velocity information, and anisotropic parameter information, the elastic wave Gaussian beam source displacement wave field for anisotropic VTI media is determined, and the expression is:

[0035]

[0036] where x s is the source point, x is the subsurface imaging point, and the superscript ν represents different types of waves, including qP waves and qSV waves. is a complex constant, v ν (s) is the phase velocity of different types of waves, ρ(s) is the density, τ ν (s) is the travel time of different types of waves, i represents the imaginary number, ω is the angular frequency, Q ν represents the dynamic tracking parameters of different types of waves (qP waves and qSV waves), e ν is the polarization vector of different types of waves at x, M ν (s) is the second-order partial derivative of the travel time corresponding to different types of waves with respect to the ray center coordinate system coordinates (s, n). s represents the coordinate in the tangent direction of ray propagation, and n represents the coordinate in the normal direction of ray propagation.

[0037] Furthermore, the anisotropic VTI media elastic wave Gaussian beam migration imaging values corresponding to the single-shot elastic wave seismic records of anisotropic VTI media are determined, including:

[0038] Using the elastic wave Gaussian beam to determine the elastic wave Gaussian beam displacement vector of anisotropic VTI media calculated at the subsurface imaging point excited by the source point;

[0039] According to the elastic wave Gaussian beam displacement vector in anisotropic VTI media, determine the forward-propagating wave field of elastic waves in anisotropic VTI media and the backward-propagating wave field of elastic waves in anisotropic VTI media using Gaussian beams;

[0040] Based on the cross-correlation imaging condition, determine the anisotropic VTI media elastic wave Gaussian beam migration imaging value corresponding to the single-shot elastic wave seismic record in anisotropic VTI media through the forward-propagating wave field of elastic waves in anisotropic VTI media and the backward-propagating wave field of elastic waves in anisotropic VTI media using Gaussian beams.

[0041] Furthermore, the single-shot elastic wave seismic record in anisotropic VTI media is used to obtain the wave field information from the source point to the detector point, and the wave field information includes the total travel time from the source point to the detector point.

[0042] Furthermore, the shear wave velocity information includes the vertical shear wave velocity; the compressional wave velocity information includes the vertical compressional wave velocity.

[0043] Furthermore, the anisotropic parameter information includes the anisotropic parameters of the anisotropic VTI media.

[0044] Another aspect of the embodiments of the present invention provides an anisotropic VTI media elastic wave Gaussian beam migration imaging device, which includes: an acquisition module and a determination module, where

[0045] The acquisition module is used to acquire the shear wave velocity information, compressional wave velocity information, anisotropic parameter information, and the single-shot elastic wave seismic record in anisotropic VTI media required for tracking elastic waves in anisotropic VTI media;

[0046] The determination module is used for:

[0047] Determine the kinematic ray tracing equation of elastic waves in anisotropic VTI media and the dynamic ray tracing equation of elastic waves in anisotropic VTI media according to the shear wave velocity information, compressional wave velocity information, and anisotropic parameter information;

[0048] Determine the central ray travel time and path information of the elastic waves in anisotropic VTI media according to the kinematic ray tracing equation of elastic waves in anisotropic VTI media, the shear wave velocity information, the compressional wave velocity information, and the anisotropic parameter information;

[0049] Determine the dynamic ray tracing parameters according to the dynamic ray tracing equation of elastic waves in anisotropic VTI media, the shear wave velocity information, the compressional wave velocity information, and the anisotropic parameter information;

[0050] Determine the elastic wave Gaussian beam source displacement wave field in an anisotropic VTI medium based on the travel time of the central ray, path information, dynamic ray parameters, shear wave velocity information, compressional wave velocity information, and anisotropic parameter information;

[0051] Based on the forward-propagating wave field and backward-propagating wave field of the elastic wave Gaussian beam source displacement wave field in the anisotropic VTI medium, and the cross-correlation results between the forward-propagating wave field and backward-propagating wave field and the backward-propagating wave field at the center of the Gaussian beam, determine the elastic wave Gaussian beam migration imaging value in the anisotropic VTI medium corresponding to the single-shot elastic wave seismic record in the anisotropic VTI medium;

[0052] Superimpose the elastic wave Gaussian beam migration imaging values in the anisotropic VTI medium corresponding to all single-shot seismic records to determine the elastic wave Gaussian beam migration imaging in the anisotropic VTI medium.

[0053] Furthermore, based on the shear wave velocity information, compressional wave velocity information, and anisotropic parameter information, determine the kinematic ray tracing equation of the elastic wave qP wave in the anisotropic VTI medium:

[0054]

[0055]

[0056]

[0057]

[0058] where x qP , z qP are the x-component and z-component of the qP wave ray tracing path respectively, and s qP represents the qP wave phase slowness scalar; are the x-component and z-component of the qP wave slowness vector p qP respectively; E qP , F qP , L qP , G qP , K qP are the compressional wave vertical velocity v P0 , the shear wave vertical velocity v S0 , the anisotropic parameter ε of the anisotropic VTI medium, the anisotropic parameter δ of the anisotropic VTI medium, and the parameters formed by the x-component qP and z-component of the qP wave slowness vector p ;

[0059] where,

[0060] Furthermore, based on the shear wave velocity information, the compressional wave velocity information, and the anisotropy parameter information, determine the kinematic ray tracing equation of the elastic wave qSV wave in the anisotropic VTI medium:

[0061]

[0062]

[0063]

[0064]

[0065] where x qSV , z qSV are the x-component and z-component of the qSV wave ray tracing path respectively, and s qSV represents the qSV wave phase slowness scalar; are the x-component and z-component of the qSV wave slowness vector p qSV respectively; E qSV , F qSV , L qSV , G qSV , K qSV are the compressional wave vertical velocity v P0 , the shear wave vertical velocity v S0 , the anisotropy parameter ε of the anisotropic VTI medium, the anisotropy parameter δ of the anisotropic VTI medium, and the parameter variables composed of the x-component qSV and z-component of the qSV wave slowness vector p respectively;

[0066] where

[0067] Furthermore, based on the shear wave velocity information, the compressional wave velocity information, and the anisotropy parameter information, determine the dynamic ray tracing equation of the elastic wave qP wave in the anisotropic VTI medium:

[0068]

[0069]

[0070] where and represent the qP wave dynamic ray parameters; M and N represent the coordinate variables in the ray center coordinate system. For a two-dimensional medium, the values of M and N are 1; i and j represent the coordinate variables in the Cartesian coordinate system. For a two-dimensional medium, i and j can take the values of 1 and 3; represents the qP wave dynamic ray tracing calculation coefficient, which are respectively:

[0071] Further, based on the shear wave velocity information, the P-wave velocity information, the anisotropy parameter information, and the seismic record, determine the elastic wave qSV wave dynamic ray tracing equation for the anisotropic VTI medium:

[0072]

[0073]

[0074] where, and represent the qSV wave dynamic ray parameters; M and N represent the coordinate variables in the ray center coordinate system. For a two-dimensional medium, M and N take the value of 1; i and j represent the coordinate variables in the Cartesian coordinate system. For a two-dimensional medium, i and j can take the values of 1 and 3; represent the qSV wave dynamic ray tracing calculation coefficients, respectively:

[0075] Further, based on the central ray travel time, the path information, the dynamic ray parameters, the shear wave velocity information, the P-wave velocity information, and the anisotropy parameter information, determine the elastic wave Gaussian beam source displacement wave field for the anisotropic VTI medium, and the expression is:

[0076]

[0077] where, x s is the source point, x is the subsurface imaging point, and the superscript ν represents different types of waves, including qP waves and qSV waves. is a complex constant, v ν (s) is the phase velocity of different types of waves, ρ(s) is the density, τ ν (s) is the travel time of different types of waves, i represents the imaginary number, ω is the angular frequency, Q ν represents the dynamic tracking parameter of different types of waves, e ν is the polarization vector of different types of waves at x, M ν (s) is the second-order partial derivative of the travel time corresponding to different types of waves (qP waves and qSV waves) with respect to the ray center coordinate system coordinates (s, n). s represents the coordinate in the tangent direction of ray propagation, and n represents the coordinate in the normal direction of ray propagation.

[0078] Further, the determination module is used for:

[0079] Using elastic wave Gaussian beams to determine the displacement vectors of elastic wave Gaussian beams at the imaging points underground excited at the source point in an anisotropic VTI medium;

[0080] According to the displacement vectors of elastic wave Gaussian beams in an anisotropic VTI medium, determine the forward-propagating wave field of elastic wave Gaussian beams in an anisotropic VTI medium and the backward-propagating wave field of elastic wave Gaussian beams in an anisotropic VTI medium;

[0081] Based on the cross-correlation imaging condition, through the forward-propagating wave field of elastic wave Gaussian beams in an anisotropic VTI medium and the backward-propagating wave field of elastic wave Gaussian beams in an anisotropic VTI medium, determine the migration imaging values of elastic wave Gaussian beams corresponding to the single-shot elastic wave seismic records in an anisotropic VTI medium.

[0082] Furthermore, the single-shot elastic wave seismic records in an anisotropic VTI medium are used to obtain the wave field information from the source point to the geophone, and the wave field information includes the total travel time from the source point to the geophone.

[0083] Furthermore, the shear wave velocity information includes the vertical shear wave velocity; the P-wave velocity information includes the vertical P-wave velocity.

[0084] Furthermore, the anisotropic parameter information includes the anisotropic parameters of the anisotropic VTI medium.

[0085] The present invention has at least the following beneficial technical effects:

[0086] The present invention can achieve accurate elastic wave ray tracing in an anisotropic VTI medium, and then achieve elastic wave migration imaging in an anisotropic VTI medium. The present invention can be applied to strongly anisotropic media, solve the problem of elastic wave imaging in an anisotropic VTI medium, and improve the quality of elastic wave migration imaging in an anisotropic VTI medium.

[0087] In addition, compared with isotropic elastic wave migration imaging, the present invention can make the travel time, path, and dynamic parameter information of elastic wave tracing in an anisotropic VTI medium more accurate, so that the reflection wave attribution in the elastic anisotropic VTI medium is more accurate and the diffraction wave convergence is more complete. Whether for the qPqP wave result or the qPqSV wave result, an offset result with accurate imaging position and good convergence is obtained. In addition, the present invention can be applied to strongly anisotropic media and is suitable for imaging of complex anisotropic elastic wave VTI media, providing a new solution for elastic wave migration imaging of complex anisotropic VTI media. BRIEF DESCRIPTION OF THE DRAWINGS

[0088] To more clearly illustrate the technical solutions in the embodiments of the present invention or in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other embodiments can be obtained based on these drawings.

[0089] Figure 1 Schematic diagram of an embodiment of an elastic wave Gaussian beam migration imaging method for anisotropic VTI media provided by the present invention;

[0090] Figure 2 In (a), it is a schematic diagram of the vertical P-wave velocity v of the elastic wave tomography model for anisotropic VTI media provided by the present invention; P0 Schematic diagram;

[0091] Figure 2 In (b), it is a schematic diagram of the vertical S-wave velocity v of the elastic wave tomography model for anisotropic VTI media provided by the present invention; S0 Schematic diagram;

[0092] Figure 2 In (c), it is a schematic diagram of the anisotropic parameter ε of the elastic wave tomography model for anisotropic VTI media provided by the present invention;

[0093] Figure 2 In (d), it is a schematic diagram of the anisotropic parameter δ of the elastic wave tomography model for anisotropic VTI media provided by the present invention;

[0094] Figure 3 In (a), it is a schematic diagram of the x-component of the seismic record of the elastic wave tomography model for anisotropic VTI media provided by the present invention;

[0095] Figure 3 In (b), it is a schematic diagram of the z-component of the seismic record of the elastic wave tomography model for anisotropic VTI media provided by the present invention;

[0096] Figure 4 In (a), it is a schematic diagram of the imaging result of the elastic wave Gaussian beam migration PP wave obtained by using the isotropic medium algorithm provided by the present invention;

[0097] Figure 4 In (b), it is a schematic diagram of the imaging result of the elastic wave Gaussian beam migration PS wave obtained by using the isotropic medium algorithm provided by the present invention;

[0098] Figure 4 In (c), it is a schematic diagram of the imaging result of the qPqP wave of the elastic wave Gaussian beam for anisotropic VTI media obtained by using the elastic wave Gaussian beam migration imaging method and system for anisotropic VTI media provided by the present invention;

[0099] Figure 4 Figure (d) is a schematic diagram of the qPqSV wave imaging result of elastic wave Gaussian beam imaging in anisotropic VTI media obtained by the elastic wave Gaussian beam migration imaging method and system provided by the present invention;

[0100] Figure 5 Figure (a) is the vertical longitudinal wave velocity v of the Hess model of elastic waves in anisotropic VTI media provided by the present invention P0 Schematic diagram;

[0101] Figure 5 Figure (b) is the vertical shear wave velocity v of the Hess model of elastic waves in anisotropic VTI media provided by the present invention S0 Schematic diagram;

[0102] Figure 5 Figure (c) is a schematic diagram of the anisotropy parameter ε of the Hess model of elastic waves in anisotropic VTI media provided by the present invention;

[0103] Figure 5 Figure (d) is a schematic diagram of the anisotropy parameter δ of the Hess model of elastic waves in anisotropic VTI media provided by the present invention;

[0104] Figure 6 Figure (a) is a schematic diagram of the x-component of the seismic record of the Hess model of elastic waves in anisotropic VTI media provided by the present invention;

[0105] Figure 6 Figure (b) is a schematic diagram of the z-component of the seismic record of the Hess model of elastic waves in anisotropic VTI media provided by the present invention;

[0106] Figure 7 Figure (a) is a schematic diagram of the PP wave imaging result of elastic wave Gaussian beam migration obtained by using the isotropic medium algorithm provided by the present invention;

[0107] Figure 7 Figure (b) is a schematic diagram of the PS wave imaging result of elastic wave Gaussian beam migration obtained by using the isotropic medium algorithm provided by the present invention;

[0108] Figure 7 Figure (c) is a schematic diagram of the qPqP wave imaging result of elastic wave Gaussian beam imaging in anisotropic VTI media obtained by the elastic wave Gaussian beam migration imaging method and system provided by the present invention;

[0109] Figure 7 Figure (d) is a schematic diagram of the qPqSV wave imaging result of elastic wave Gaussian beam imaging in anisotropic VTI media obtained by the elastic wave Gaussian beam migration imaging method and system provided by the present invention;

[0110] Figure 8 Schematic diagram of an embodiment of an anisotropic VTI medium elastic wave Gaussian beam migration imaging device provided by the present invention. Detailed implementation manners

[0111] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the following further describes the embodiments of the present invention in detail with reference to specific embodiments and the accompanying drawings.

[0112] It should be noted that all the expressions using "first" and "second" in the embodiments of the present invention are used to distinguish two entities or parameters with the same name but different, and it can be seen that "first" and "second" are only for the convenience of expression and should not be construed as a limitation on the embodiments of the present invention. This will not be elaborated one by one in the subsequent embodiments.

[0113] Based on the above objectives, in the first aspect of the embodiments of the present invention, an embodiment of an anisotropic VTI medium elastic wave Gaussian beam migration imaging method is proposed. Figure 1 Shown is a schematic diagram of an embodiment of an anisotropic VTI medium elastic wave Gaussian beam migration imaging method provided by the present invention. As Figure 1 shown, the method may include S101-S105 (where some steps are optional steps). Specifically, S101-S105 may specifically be:

[0114] S101. Obtain the shear wave velocity information, longitudinal wave velocity information, anisotropic parameter information, and single-shot elastic wave seismic record of the anisotropic VTI medium elastic wave required in the tracking.

[0115] The single-shot elastic wave seismic record of the anisotropic VTI medium is used to obtain the wave field information from the source point to the geophone point. The wave field information includes the total travel time from the source point to the geophone point. For example, the single-shot elastic wave seismic record of the anisotropic VTI medium may include the x component and the z component.

[0116] The shear wave velocity information may include the shear wave vertical velocity v S0 ; the longitudinal wave velocity information may include the longitudinal wave vertical velocity v P0 .

[0117] The anisotropic parameter information may include the anisotropic parameters of the anisotropic VTI medium. For example, the anisotropic parameter ε of the anisotropic medium and the anisotropic parameter δ of the anisotropic medium.

[0118] S102. Determine the kinematic ray tracing equation and the dynamic ray tracing equation of the anisotropic VTI medium elastic wave according to the shear wave velocity information, longitudinal wave velocity information, and anisotropic parameter information.

[0119] In some embodiments, S102 can be specifically implemented as follows:

[0120] S1021. Determine the kinematic ray tracing equation of elastic waves in the anisotropic VTI medium and the dynamic ray tracing equation of elastic waves in the anisotropic VTI medium according to the vertical P-wave velocity v P0 , the vertical S-wave velocity v S0 , the anisotropic parameter ε of the anisotropic VTI medium, and the anisotropic parameter δ information of the anisotropic VTI medium.

[0121] Among them, the kinematic ray tracing equation of elastic waves (qP waves) in the anisotropic VTI medium is determined according to the following expression, and this expression can be:

[0122]

[0123]

[0124]

[0125]

[0126] Among them, x qP , z qP are the x-component and z-component of the qP-wave ray tracing path respectively, and s qP represents the qP-wave phase slowness scalar; are the x-component and z-component of the qP-wave slowness vector p qP respectively; E qP , F qP , L qP , G qP , K qP are the vertical P-wave velocity v P0 , the vertical S-wave velocity v S0 , the anisotropic parameter ε of the anisotropic VTI medium, the anisotropic parameter δ of the anisotropic VTI medium, and the x-component qP and z-component and z-component of the qP-wave slowness vector p

[0127] Among them,

[0128] Among them, the kinematic ray tracing equation of elastic waves (qSV waves) in the anisotropic VTI medium is determined according to the following expression, and this expression can be:

[0129]

[0130]

[0131]

[0132]

[0133] Among them, x qSV , z qSV are the x-component and z-component of the qP-wave ray tracing path respectively, and s qSV represents the qSV-wave phase slowness scalar; p x qSV , p z qSV are the x-component and z-component of the qSV-wave slowness vector p qSV respectively; E qSV , F qSV , L qSV , G qSV , K qSV are the vertical velocity v P0 of the longitudinal wave, the vertical velocity v S0 of the shear wave, the anisotropic parameter ε of the anisotropic VTI medium, the anisotropic parameter δ of the anisotropic VTI medium, and the x-component qSV and z-component of the qSV-wave slowness vector p respectively, which constitute the parameter variables;

[0134] Among them,

[0135] Among them, the dynamic ray tracing equation of elastic waves (including qP waves) in the anisotropic VTI medium is determined according to the following expression, and this expression can be:

[0136]

[0137]

[0138] Among them, and represent the qP-wave dynamic ray parameters; M and N represent the coordinate variables in the ray center coordinate system. For a two-dimensional medium, M and N take the value of 1; i and j represent the coordinate variables in the Cartesian coordinate system. For a two-dimensional medium, i and j can take the values of 1 and 3; represents the qP-wave dynamic ray tracing calculation coefficient, and there are respectively:

[0139]

[0140]

[0141]

[0142]

[0143] Among them, the dynamic ray tracing equations of elastic waves (including qSV waves) in anisotropic VTI media are determined according to the following expressions, which can be:

[0144]

[0145]

[0146] Among them, and represent the dynamic ray parameters of qSV waves; M and N represent the coordinate variables in the ray center coordinate system. For two-dimensional media, M and N take the value of 1; i and j represent the coordinate variables in the Cartesian coordinate system. For two-dimensional media, i and j can take the values of 1 and 3; represent the calculation coefficients for dynamic ray tracing of qSV waves, respectively:

[0147]

[0148]

[0149]

[0150]

[0151] S103. Determine the central ray travel time and path information of elastic waves in anisotropic VTI media according to the kinematic ray tracing equations of elastic waves in anisotropic VTI media, shear wave velocity information, longitudinal wave velocity information, and anisotropic parameter information.

[0152] Specifically, determine the central ray travel time and path information of elastic waves (including qP waves and qSV waves) according to the kinematic ray tracing equations of elastic waves (including qP waves and qSV waves) in anisotropic VTI media.

[0153] S104. Determine the dynamic ray tracing parameters of elastic waves (including qP waves and qSV waves) according to the dynamic ray tracing equations of elastic waves (including qP waves and qSV waves) in anisotropic VTI media, shear wave velocity information, longitudinal wave velocity information, and anisotropic parameter information.

[0154] S105. Determine the Gaussian beam source displacement wave field of elastic waves in anisotropic VTI media according to the central ray travel time, path information, dynamic ray tracing parameters, shear wave velocity information, longitudinal wave velocity information, and anisotropic parameter information.

[0155] In a specific implementable manner, S105 can be specifically implemented as follows:

[0156] S1051. Determine the dynamic ray parameters of elastic waves (including qP waves and qSV waves) according to the dynamic ray tracing equations of elastic waves (including qP waves and qSV waves) in the anisotropic VTI medium and

[0157] S1052. Determine the Gaussian beam source displacement wave field of elastic waves in the anisotropic VTI medium according to the ray paths of elastic waves (including qP waves and qSV waves), the dynamic ray parameters of elastic waves (including qP waves and qSV waves) and the vertical velocity v of the longitudinal wave P0 and the vertical velocity v of the shear wave S0 and the anisotropy parameter ε of the anisotropic VTI medium and the anisotropy parameter δ of the anisotropic VTI medium

[0158] Among them, the expression of the Gaussian beam source displacement wave field of elastic waves in the anisotropic VTI medium can be:

[0159]

[0160] where x s is the source point, x is the underground imaging point, and the superscript ν represents different types of waves, including qP waves and qSV waves is a complex constant, v ν (s) is the phase velocity of different types of waves (qP waves and qSV waves), ρ(s) is the density, τ ν (s) is the travel time of different types of waves (qP waves and qSV waves), i represents the imaginary number, ω is the angular frequency, Q ν represents the dynamic tracking parameter of different types of waves (qP waves and qSV waves), e ν is the polarization vector of different types of waves (qP waves and qSV waves) at x, and M ν (s) is the second-order partial derivative of the travel time corresponding to different types of waves (qP waves and qSV waves) with respect to the coordinates (s, n) of the ray center coordinate system, s represents the coordinate in the tangent direction of ray propagation, and n represents the coordinate in the normal direction of ray propagation

[0161] S106. Determine the Gaussian beam migration imaging value of elastic waves in the anisotropic VTI medium corresponding to the single-shot elastic wave seismic record of the anisotropic VTI medium according to the forward-propagating wave field and the backward-propagating wave field of the Gaussian beam source displacement wave field of elastic waves in the anisotropic VTI medium, and the cross-correlation result between the forward-propagating wave field and the backward-propagating wave field and the backward-propagating wave field at the Gaussian beam center

[0162] In a specific implementable manner, S106 can be specifically implemented as follows:

[0163] S1061. Use elastic wave Gaussian beams to determine the displacement vectors of elastic wave Gaussian beams at the imaging points underground excited at the source point in the anisotropic VTI medium calculated.

[0164] S1062. Determine the forward-propagating wavefield of elastic wave Gaussian beams in the anisotropic VTI medium and the backward-propagating wavefield of elastic wave Gaussian beams in the anisotropic VTI medium according to the displacement vectors of elastic wave Gaussian beams in the anisotropic VTI medium.

[0165] Among them, the expression of the forward-propagating wavefield of the source displacement wavefield of elastic wave Gaussian beams in the anisotropic VTI medium can be:

[0166]

[0167] Among them, i represents an imaginary number; the initial beam width of the elastic wave Gaussian beam is defined as w0; the underground density at the source x s is defined as ρ(x s ); the displacement vector of elastic waves in the anisotropic VTI medium (qP wave at the source) is defined as The x and z components of the slowness vector of the qP wave at the source are defined as

[0168] S1063. Based on the cross-correlation imaging condition, determine the migration imaging value of the elastic wave Gaussian beam in the anisotropic VTI medium corresponding to the single-shot elastic wave seismic record in the anisotropic VTI medium through the forward-propagating wavefield of the elastic wave Gaussian beam in the anisotropic VTI medium and the backward-propagating wavefield of the elastic wave Gaussian beam in the anisotropic VTI medium.

[0169] Specifically, on the basis of Gaussian window decomposition and phase shift correction, perform dip stacking to transform the seismic record into the Tau-P domain. Then, according to different slowness magnitudes, decompose it into local plane waves in different directions, and use the displacement of the elastic wave Gaussian beam to perform wavefield continuation to obtain the source displacement wavefield of the elastic wave Gaussian beam in the anisotropic VTI medium, and its expression can be:

[0170]

[0171] Among them, ΔL is the horizontal interval; N L is the number of Gaussian windows; are respectively the x component and z component of the slowness vector of different wave types (qP wave and qSV wave); are respectively the x component and z component of the weight coefficient corresponding to different types of waves (qP wave and qSV wave) at the beam center x L ; and They are the x - component and z - component of the local tilt stack corresponding to different types of waves (qP - wave and qSV - wave) respectively.

[0172] Based on the Clearbout (1976) imaging rule, using the cross - correlation imaging condition, the qPqP - wave imaging and qPqSV - wave imaging are obtained respectively, and their expressions can be:

[0173]

[0174]

[0175] Where I qPqP is the qP - qP wave imaging result, I qPqSV is the qP - qSV wave imaging result; are the x - component and z - component of the qP - wave weight coefficient at the beam center x L respectively, are the x - component and z - component of the qSV - wave weight coefficient at the beam center x L respectively, and sgn(α) is the sign function for polarity correction; and are the x - component and z - component of the local tilt stack of the qP - wave respectively; and are the x - component and z - component of the local tilt stack of the qSV - wave respectively.

[0176] S107. Superimpose the anisotropic VTI medium elastic - wave Gaussian beam migration imaging values corresponding to all single - shot seismic records to determine the anisotropic VTI medium elastic - wave Gaussian beam migration imaging.

[0177] The final anisotropic VTI medium elastic - wave Gaussian beam migration imaging result is obtained by adding all the imaging values.

[0178] To illustrate the correctness and effectiveness of the method in the present invention, the present invention uses an anisotropic VTI medium complex structure model and an anisotropic VTI medium elastic - wave Hess model for migration imaging tests.

[0179] 1) Anisotropic VTI medium elastic - wave tomography model. The model has 1500 horizontal sampling points with a sampling interval of 10 m, 500 sampling points in the depth direction with a sampling interval of 10 m; the seismic data is received in a full - receiving manner, and the forward simulation is carried out using the anisotropic VTI medium elastic - wave finite - difference method, with a total of 301 shots, a shot interval of 50 m; a trace interval of 10 m; the sampling time of the seismic record is 6 s, and the time sampling interval is 2 ms. Figure 2 In (a) is the longitudinal - wave vertical velocity v P0 schematic diagram of the anisotropic VTI medium elastic - wave tomography model provided by the present invention;Figure 2 In (b), it is a schematic diagram of the transverse wave vertical velocity v of the anisotropic VTI medium elastic wave tomography model provided by the present invention; S0 Schematic diagram; Figure 2 In (c), it is a schematic diagram of the anisotropy parameter ε of the anisotropic VTI medium elastic wave tomography model provided by the present invention; Figure 2 In (d), it is a schematic diagram of the anisotropy parameter δ of the anisotropic VTI medium elastic wave tomography model provided by the present invention;

[0180] Figure 3 In (a), it is a schematic diagram of the x-component of the seismic record of the anisotropic VTI medium elastic wave tomography model provided by the present invention; Figure 3 In (b), it is a schematic diagram of the z-component of the seismic record of the anisotropic VTI medium elastic wave tomography model provided by the present invention;

[0181] Figure 4 In (a), it is a schematic diagram of the elastic wave Gaussian beam migration PP wave imaging result obtained by using the isotropic medium algorithm provided by the present invention; Figure 4 In (b), it is a schematic diagram of the elastic wave Gaussian beam migration PS wave imaging result obtained by using the isotropic medium algorithm provided by the present invention; Figure 4 In (c), it is a schematic diagram of the anisotropic VTI medium elastic wave Gaussian beam imaging qPqP wave imaging result obtained by using the anisotropic VTI medium elastic wave Gaussian beam migration imaging method and system provided by the present invention; Figure 4 In (d), it is a schematic diagram of the anisotropic VTI medium elastic wave Gaussian beam imaging qPqSV wave imaging result obtained by using the anisotropic VTI medium elastic wave Gaussian beam migration imaging method and system provided by the present invention.

[0182] It can be found by comparison that due to not considering the anisotropic influence, Figure 4 For the isotropic elastic wave Gaussian beam PP wave imaging result shown in (a) in 4 and the isotropic elastic wave Gaussian beam PS wave imaging result shown in (b) in 4, the reflection wave migration is inaccurate, the diffraction wave convergence is incomplete, the continuity of the event is poor, and the overall signal-to-noise ratio is low. However, for the anisotropic VTI medium elastic wave Gaussian beam qPqP wave imaging result obtained by using the present invention as shown in Figure 4 In (c), and for the anisotropic VTI medium elastic wave Gaussian beam qPqSV wave imaging result obtained by using the present invention as shown in Figure 4 In (d), whether for the qPqP wave result ( Figure 4 in (c)), or for the qPqSV wave result ( Figure 4 in (d)), the imaging results obtained by using the present invention are more ideal in terms of the accuracy of imaging migration, the diffraction wave convergence is more complete, the event is more continuous, and the signal-to-noise ratio is effectively improved.

[0183] 2) Elastic wave Hess model for anisotropic VTI media. The number of horizontal sampling points in this model is 1809, the sampling interval is 10 m, the number of sampling points in the depth direction is 750, and the sampling interval is 6 m; the seismic data is received in full, and the forward simulation is carried out by using the finite difference method of elastic waves in anisotropic VTI media, with a total of 362 shots, the shot interval is 50 m; the trace interval is 6 m; the sampling time of the seismic record is 4.0 s, and the time sampling interval is 2 ms. Among them, Figure 5 (a) in it is the schematic diagram of the vertical P-wave velocity v of the elastic wave Hess model for anisotropic VTI media provided by the present invention P0 Schematic diagram; Figure 5 (b) in it is the schematic diagram of the vertical S-wave velocity v of the elastic wave Hess model for anisotropic VTI media provided by the present invention S0 Schematic diagram; Figure 5 (c) in it is the schematic diagram of the anisotropy parameter ε of the elastic wave Hess model for anisotropic VTI media provided by the present invention; Figure 5 (d) in it is the schematic diagram of the anisotropy parameter δ of the elastic wave Hess model for anisotropic VTI media provided by the present invention. Figure 6 (a) in it is the schematic diagram of the x-component of the seismic record of the elastic wave Hess model for anisotropic VTI media provided by the present invention; Figure 6 (b) in it is the schematic diagram of the z-component of the seismic record of the elastic wave Hess model for anisotropic VTI media provided by the present invention; Figure 7 (a) in it is the schematic diagram of the imaging result of the elastic wave Gaussian beam migration PP wave obtained by using the isotropic medium algorithm provided by the present invention; Figure 7 (b) in it is the schematic diagram of the imaging result of the elastic wave Gaussian beam migration PS wave obtained by using the isotropic medium algorithm provided by the present invention; Figure 7 (c) in it is the schematic diagram of the imaging result of the qPqP wave of the elastic wave Gaussian beam imaging for anisotropic VTI media obtained by using the elastic wave Gaussian beam migration imaging method and system for anisotropic VTI media provided by the present invention; Figure 7 (d) in it is the schematic diagram of the imaging result of the qPqSV wave of the elastic wave Gaussian beam imaging for anisotropic VTI media obtained by using the elastic wave Gaussian beam migration imaging method and system for anisotropic VTI media provided by the present invention.

[0184] It can be found by comparing the imaging results: Figure 7 The imaging result of the PP wave of the elastic wave Hess model for anisotropic VTI media obtained by using the isotropic elastic wave Gaussian beam migration shown in (a) in it, Figure 7Figure (b) shows the PS-wave imaging result of the elastic wave Hess model in an anisotropic VTI medium obtained by using isotropic elastic wave Gaussian beam migration. Since anisotropy is not considered, problems such as inaccurate migration positioning, incomplete convergence of diffracted waves at the fault, and unsatisfactory energy focusing occur at the right fault. Overall, the signal-to-noise ratio of the imaging profile is low and the imaging quality is not ideal. Figure 7 The qPqP-wave migration result of the elastic wave Gaussian beam migration in the anisotropic VTI medium provided by the present invention shown in Figure (c). Figure 7 The qPqSV-wave migration result of the elastic wave Gaussian beam in the anisotropic VTI medium provided by the present invention shown in Figure (d). The result obtained by using the elastic wave Gaussian beam migration imaging method in the anisotropic VTI medium of the present invention has been improved in terms of migration positioning accuracy, fault diffracted wave convergence, and energy focusing. At the same time, comparing the qPqP-wave migration result ( Figure 7 Figure (c)) obtained by using the elastic wave Gaussian beam migration imaging method in the anisotropic VTI medium of the present invention and the qPqSV-wave migration result ( Figure 7 Figure (d)) obtained by using the elastic wave Gaussian beam migration imaging method in the anisotropic VTI medium of the present invention, the qPqSV-wave migration result ( Figure 7 Figure (d)) obtained by using the elastic wave Gaussian beam migration imaging method in the anisotropic VTI medium of the present invention has certain advantages in imaging resolution compared with the qPqP-wave migration result ( Figure 7 Figure (c)).

[0185] Based on the above, the results of the model trial calculation illustrate that the elastic wave Gaussian beam migration imaging in the anisotropic VTI medium provided by the present invention can be applied to the imaging of complex work areas in the anisotropic VTI medium, can solve the problem of elastic wave migration imaging of complex geological structures in the anisotropic VTI medium, and can provide a new solution for the elastic wave migration imaging of complex anisotropic VTI media.

[0186] In addition, in the embodiments of the present invention, the dependence on the weak anisotropy assumption of the prior art is broken through; the elastic wave ray tracing algorithm in the anisotropic VTI medium is applied to the elastic wave Gaussian beam migration imaging in the anisotropic VTI medium, and the elastic wave Gaussian beam migration imaging method in the anisotropic VTI medium is realized. This method can be applied to the imaging of elastic wave data in the anisotropic VTI medium. By using the method of the present invention, the reflected waves in the elastic wave work area of the anisotropic VTI medium can be migrated more accurately and the diffracted waves can converge more completely, and an elastic wave migration result with higher imaging quality in the anisotropic VTI medium can be obtained.

[0187] In addition, in the embodiments of the present invention, compared with the conventional isotropic elastic wave Gaussian beam migration method, the present invention can make the migration of reflected waves in complex anisotropic VTI elastic media more accurate, the diffracted energy better converge, enhance the continuity of the in-phase axis, thereby improving the imaging signal-to-noise ratio and obtaining high-quality elastic wave imaging results. Therefore, the method of the present invention can solve the problem of elastic wave migration imaging of geological structures in complex anisotropic VTI media, especially the problem of elastic wave migration imaging in strongly anisotropic VTI media, and can provide a new solution for elastic wave migration imaging in complex anisotropic VTI media.

[0188] In addition, the present invention provides a new elastic wave ray tracing equation and algorithm for VTI media. This algorithm overcomes the limitations of the prior art's weak anisotropy assumption and improves the adaptability of the elastic wave ray tracing algorithm to complex anisotropic VTI media. On this basis, an elastic wave Gaussian beam migration imaging method for anisotropic VTI media is realized. The main advantage of this method is that it can be applied to elastic wave migration imaging in strongly anisotropic VTI media, can provide a new solution for elastic wave migration imaging in complex anisotropic VTI media, and provides important technical support for elastic wave migration imaging in complex anisotropic VTI media.

[0189] Based on the above objectives, in the second aspect of the embodiments of the present invention, an elastic wave Gaussian beam migration imaging device for anisotropic VTI media is proposed. Figure 8 The following shows a schematic diagram of an embodiment of the elastic wave Gaussian beam migration imaging device for anisotropic VTI media provided by the present invention. As Figure 8 shown, the elastic wave Gaussian beam migration imaging device 800 for anisotropic VTI media may include: an acquisition module 801 and a determination module 802, wherein,

[0190] The acquisition module 801 is used to acquire the shear wave velocity information, longitudinal wave velocity information, anisotropic parameter information required in the tracking of elastic waves in anisotropic VTI media, and the single-shot elastic wave seismic record of anisotropic VTI media.

[0191] The determination module 802 is used for:

[0192] According to the shear wave velocity information, longitudinal wave velocity information, and anisotropic parameter information, determine the central ray travel time, path information, and dynamic ray parameters of elastic waves in anisotropic VTI media;

[0193] According to the central ray travel time, path information, dynamic ray parameters, shear wave velocity information, longitudinal wave velocity information, and anisotropic parameter information, determine the elastic wave Gaussian beam source displacement wave field in anisotropic VTI media;

[0194] Based on the forward-propagating wave field and backward-propagating wave field of the elastic wave Gaussian beam source displacement wave field in the anisotropic VTI medium, and the cross-correlation results between the forward-propagating wave field and backward-propagating wave field and the backward-propagating wave field at the Gaussian beam center, determine the anisotropic VTI medium elastic wave Gaussian beam migration imaging value corresponding to the single-shot elastic wave seismic record of the anisotropic VTI medium;

[0195] Superimpose the anisotropic VTI medium elastic wave Gaussian beam migration imaging values corresponding to all single-shot seismic records to determine the anisotropic VTI medium elastic wave Gaussian beam migration imaging.

[0196] In some embodiments, based on the shear wave velocity information, compressional wave velocity information, anisotropic parameter information, and seismic record, determine the kinematic ray tracing equation of the elastic wave qP wave in the anisotropic VTI medium:

[0197]

[0198]

[0199]

[0200]

[0201] where x qP , z qP are the x-component and z-component of the qP wave ray tracing path respectively, and s qP represents the qP wave phase slowness scalar; are the x-component and z-component of the qP wave slowness vector p qP respectively; E qP , F qP , L qP , G qP , K qP are the compressional wave vertical velocity v P0 , the shear wave vertical velocity v S0 , the anisotropic parameter ε of the anisotropic VTI medium, the anisotropic parameter δ of the anisotropic VTI medium, and the parameter variables composed of the x-component qP and z-component of the qP wave slowness vector p respectively;

[0202] where,

[0203] In some embodiments, based on the shear wave velocity information, compressional wave velocity information, anisotropic parameter information, and seismic record, determine the kinematic ray tracing equation of the elastic wave qSV wave in the anisotropic VTI medium:

[0204]

[0205]

[0206]

[0207]

[0208] where x qSV , z qSV are the x - component and z - component of the qSV - wave ray - tracing path respectively, and s qSV represents the qSV - wave phase slowness scalar; are the x - component and z - component of the qSV - wave slowness vector p qSV respectively; E qSV , F qSV , L qSV , G qSV , K qSV are the vertical velocity of the P - wave v P0 , the vertical velocity of the S - wave v S0 , the anisotropic parameter ε of the anisotropic VTI medium, the anisotropic parameter δ of the anisotropic VTI medium, and the x - component qSV and z - component of the qSV - wave slowness vector p constitute the parameter variables;

[0209] where

[0210] In some embodiments, according to the shear - wave velocity information, the P - wave velocity information, the anisotropic parameter information, and the seismic record, the dynamic ray - tracing equation of the elastic wave qP - wave in the anisotropic VTI medium is determined:

[0211]

[0212]

[0213] where and represent the dynamic ray parameters of the qP - wave; M and N represent the coordinate variables in the ray - centered coordinate system. For a two - dimensional medium, M and N take the value of 1; i and j represent the coordinate variables in the Cartesian coordinate system. For a two - dimensional medium, i and j can take the values of 1 and 3; represents the calculation coefficient of the dynamic ray - tracing of the qP - wave, and there are respectively:

[0214]

[0215] In some embodiments, according to the shear wave velocity information, the compressional wave velocity information, the anisotropy parameter information, and the seismic record, the dynamic ray tracing equation of the elastic wave qSV wave in the anisotropic VTI medium is determined:

[0216]

[0217]

[0218] Wherein, and represent the dynamic ray parameters of the qSV wave; M and N represent the coordinate variables in the ray center coordinate system. For a two-dimensional medium, the values of M and N are 1; i and j represent the coordinate variables in the Cartesian coordinate system. For a two-dimensional medium, i and j can take the values of 1 and 3; represent the calculation coefficients of the dynamic ray tracing of the qSV wave, and are respectively:

[0219] In some embodiments, according to the central ray travel time, the path information, the dynamic ray parameters, the shear wave velocity information, the compressional wave velocity information, and the anisotropy parameter information, the Gaussian beam source displacement wave field of the elastic wave in the anisotropic VTI medium is determined, and the expression is:

[0220]

[0221] Wherein, x s is the source point, x is the underground imaging point, and the superscript ν represents different types of waves, including the qP wave and the qSV wave, is a complex constant, v ν (s) is the phase velocity of different types of waves (qP wave and qSV wave), ρ(s) is the density, τ ν (s) is the travel time of different types of waves (qP wave and qSV wave), i represents the imaginary number, ω is the angular frequency, Q ν represents the dynamic tracking parameters of different types of waves (qP wave and qSV wave), e ν is the polarization vector of different types of waves (qP wave and qSV wave) at x, M ν (s) is the second-order partial derivative of the travel time corresponding to different types of waves (qP wave and qSV wave) with respect to the coordinates (s, n) in the ray center coordinate system, s represents the coordinate in the tangent direction of the ray propagation, and n represents the coordinate in the normal direction of the ray propagation.

[0222] In some embodiments, the determining module 802 is configured to:

[0223] Using elastic wave Gaussian beams to determine the displacement vector of elastic wave Gaussian beams at the imaging points underground excited at the source point in an anisotropic VTI medium;

[0224] According to the displacement vector of elastic wave Gaussian beams in an anisotropic VTI medium, determine the forward-propagating wavefield of elastic wave Gaussian beams in an anisotropic VTI medium and the backward-propagating wavefield of elastic wave Gaussian beams in an anisotropic VTI medium;

[0225] Based on the cross-correlation imaging condition, through the forward-propagating wavefield of elastic wave Gaussian beams in an anisotropic VTI medium and the backward-propagating wavefield of elastic wave Gaussian beams in an anisotropic VTI medium, determine the migration imaging value of elastic wave Gaussian beams corresponding to a single-shot elastic wave seismic record in an anisotropic VTI medium.

[0226] In some embodiments, a single-shot elastic wave seismic record in an anisotropic VTI medium is used to obtain wavefield information from the source point to the geophone, and the wavefield information includes the total travel time from the source point to the geophone.

[0227] In some embodiments, the shear wave velocity information includes the vertical shear wave velocity; the compressional wave velocity information includes the vertical compressional wave velocity.

[0228] In some embodiments, the anisotropic parameter information includes the anisotropic parameters of the anisotropic VTI medium.

[0229] The present invention can achieve accurate ray tracing in an anisotropic VTI medium, and then achieve elastic wave migration imaging in an anisotropic VTI medium. The present invention can be applied to strongly anisotropic media, solve the problem of elastic wave imaging in an anisotropic VTI medium, and improve the quality of elastic wave migration imaging in an anisotropic VTI medium.

[0230] In addition, compared with isotropic elastic wave migration imaging, the present invention can make the travel time, path, and dynamic parameter information of elastic wave tracing in an anisotropic VTI medium more accurate, so that the reflection waves in the elastic anisotropic VTI medium are grouped more accurately and the diffracted waves converge more completely. Whether for the qPqP wave result or the qPqSV wave result, an offset result with accurate imaging position and good convergence is obtained. In addition, the present invention can be applied to strongly anisotropic media and is suitable for imaging of complex anisotropic elastic wave VTI media, providing a new solution for elastic wave migration imaging of complex anisotropic VTI media.

[0231] Those skilled in the art will also understand that the various exemplary logical blocks, modules, circuits, and algorithm steps described in connection with the disclosure herein can be implemented as electronic hardware, computer software, or a combination of both. To clearly illustrate this interchangeability of hardware and software, functions have been generally described in terms of the functions of various illustrative components, blocks, modules, circuits, and steps. Whether such functions are implemented as software or hardware depends on the particular application and the design constraints imposed on the overall device. The functions that can be implemented in various ways by those skilled in the art for each specific application, but such implementation decisions should not be construed as causing a departure from the scope of the disclosure of the embodiments of the present invention.

[0232] The above are exemplary embodiments disclosed by the present invention. However, it should be noted that various changes and modifications can be made without departing from the scope of the disclosure of the embodiments of the present invention defined by the claims. The functions, steps, and / or actions of the method claims according to the disclosed embodiments herein need not be performed in any specific order. In addition, although the elements disclosed in the embodiments of the present invention can be described or claimed in individual form, they can also be understood as plural unless explicitly limited to the singular.

[0233] It should be understood that, as used herein, unless the context clearly supports exceptions, the singular form "a" is also intended to include the plural form. It should also be understood that the "and / or" used herein refers to any and all possible combinations of one or more of the associated listed items.

[0234] The serial numbers of the disclosed embodiments of the present invention above are only for description and do not represent the superiority or inferiority of the embodiments.

[0235] Those of ordinary skill in the art can understand that all or part of the steps of implementing the above embodiments can be completed by hardware, or can be completed by a program instructing relevant hardware. The program can be stored in a computer-readable storage medium, and the above-mentioned storage medium can be a read-only memory, a disk, an optical disc, etc.

[0236] Those of ordinary skill in the art should understand that: the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the disclosure of the embodiments of the present invention (including the claims) is limited to these examples; under the concept of the embodiments of the present invention, the technical features between the above embodiments or different embodiments can also be combined, and there are many other variations in different aspects of the embodiments of the present invention as above, which are not provided in detail for the sake of brevity. Therefore, any omission, modification, equivalent replacement, improvement, etc. made within the spirit and principle of the embodiments of the present invention shall be included in the protection scope of the embodiments of the present invention.

Claims

1. An elastic wave Gaussian beam migration imaging method for anisotropic VTI media, characterized in that, The method includes: acquiring the shear wave velocity information, the compressional wave velocity information, the anisotropic parameter information required for tracking the elastic wave in the anisotropic VTI medium, and the single-shot elastic wave seismic record of the anisotropic VTI medium; determining the kinematic ray tracing equation of the elastic wave in the anisotropic VTI medium and the dynamic ray tracing equation of the elastic wave in the anisotropic VTI medium according to the shear wave velocity information, the compressional wave velocity information, and the anisotropic parameter information; determining the central ray travel time and path information of the elastic wave in the anisotropic VTI medium according to the kinematic ray tracing equation of the elastic wave in the anisotropic VTI medium, the shear wave velocity information, the compressional wave velocity information, and the anisotropic parameter information; determining the dynamic ray tracing parameters according to the dynamic ray tracing equation of the elastic wave in the anisotropic VTI medium, the shear wave velocity information, the compressional wave velocity information, and the anisotropic parameter information; determining the Gaussian beam source displacement wave field of the elastic wave in the anisotropic VTI medium according to the central ray travel time, the path information, the dynamic ray tracing parameters, the shear wave velocity information, the compressional wave velocity information, and the anisotropic parameter information; determining the Gaussian beam migration imaging value of the elastic wave in the anisotropic VTI medium corresponding to the single-shot elastic wave seismic record of the anisotropic VTI medium according to the forward-propagated wave field and the backward-propagated wave field of the Gaussian beam source displacement wave field of the elastic wave in the anisotropic VTI medium, and the cross-correlation result between the forward-propagated wave field and the backward-propagated wave field and the backward-propagated wave field at the Gaussian beam center; superposing the Gaussian beam migration imaging values of the elastic wave in the anisotropic VTI medium corresponding to all the single-shot elastic wave seismic records of the anisotropic VTI medium to determine the Gaussian beam migration imaging of the elastic wave in the anisotropic VTI medium.

2. The method according to claim 1, characterized in that, The kinematic ray tracing equation of the qP wave of the elastic wave in the anisotropic VTI medium is determined according to the shear wave velocity information, the compressional wave velocity information, and the anisotropic parameter information: Among them, x qP , z qP are the x-component and z-component of the qP-wave ray-tracing path respectively, and s qP represents the qP-wave phase slowness scalar; are the x-component and z-component of the qP-wave slowness vector p qP respectively; E qP , F qP , L qP , G qP , K qP are the parameter variables composed of the vertical velocity v P0 of the P-wave, the vertical velocity v S0 of the S-wave, the anisotropic parameter ε of the anisotropic VTI medium, the anisotropic parameter δ of the anisotropic VTI medium, and the x-component qP and z-component of the qP-wave slowness vector p respectively;​ Among them, 3. The method according to claim 1, characterized in that, The kinematic ray tracing equation of the qSV wave of the elastic wave in the anisotropic VTI medium is determined according to the shear wave velocity information, the compressional wave velocity information, and the anisotropic parameter information: where x qSV , z qSV are the x-component and z-component of the qSV-wave ray-tracing path respectively, and s qSV represents the qSV-wave phase slowness scalar; are the x-component and z-component of the qSV-wave slowness vector p qSV respectively; E qSV , F qSV , L qSV , G qSV , K qSV are the parameter variables composed of the vertical P-wave velocity v P0 , the vertical S-wave velocity v S0 , the anisotropic parameter ε of the anisotropic VTI medium, the anisotropic parameter δ of the anisotropic VTI medium, and the x-component qSV and z-component of the qSV-wave slowness vector p respectively;​ Among them, 4. The method according to claim 1, wherein The dynamic ray tracing equation of the qP wave of the elastic wave in the anisotropic VTI medium is determined according to the shear wave velocity information, the compressional wave velocity information, and the anisotropic parameter information: Among them, and represent the qP-wave dynamic ray parameter; M and N represent the coordinate variables in the ray center coordinate system; i and j represent the coordinate variables in the Cartesian coordinate system; represents the qP-wave dynamic ray tracing calculation coefficient, which are respectively:

5. The method according to claim 1, characterized in that, The dynamic ray tracing equation of the qSV wave of the elastic wave in the anisotropic VTI medium is determined according to the shear wave velocity information, the compressional wave velocity information, and the anisotropic parameter information: Among them, and represent the qSV wave dynamic ray parameter; M and N represent the coordinate variables in the ray center coordinate system; i and j represent the coordinate variables in the Cartesian coordinate system; represent the qSV wave dynamic ray tracing calculation coefficients, respectively:

6. The method according to any one of claims 1-5, characterized in that, The Gaussian beam source displacement wave field of the elastic wave in the anisotropic VTI medium is determined according to the central ray travel time, the path information, the dynamic ray parameters, the shear wave velocity information, the compressional wave velocity information, and the anisotropic parameter information, and the expression is: where, x s is the source point, x is the subsurface imaging point, and the superscript ν represents different types of waves, including qP waves and qSV waves. is a complex-valued constant, v ν (s) is the phase velocity of different types of waves, ρ(s) is the density, and τ ν (s) is the travel time of different types of waves, i represents the imaginary number, ω is the angular frequency, and Q ν represents the dynamic tracking parameter of different types of waves, and e ν is the polarization vector of different types of waves at x, and M ν (s) is the second-order partial derivative of the travel time corresponding to different types of waves with respect to the coordinates (s, n) of the ray-centered coordinate system. s represents the coordinate in the tangent direction of ray propagation, and n represents the coordinate in the normal direction of ray propagation.

7. The method according to claim 1, characterized in that, Determining the Gaussian beam migration imaging value of the elastic wave in the anisotropic VTI medium corresponding to the single-shot elastic wave seismic record of the anisotropic VTI medium includes: Using elastic wave Gaussian beams to determine the elastic wave Gaussian beam displacement vectors calculated at the imaging points underground excited at the source point; According to the elastic wave Gaussian beam displacement vectors of the anisotropic VTI medium, determining the forward-propagating wave field of the elastic wave Gaussian beam of the anisotropic VTI medium and the backward-propagating wave field of the elastic wave Gaussian beam of the anisotropic VTI medium; Based on the cross-correlation imaging condition, determining the elastic wave Gaussian beam migration imaging values of the anisotropic VTI medium corresponding to the single-shot elastic wave seismic records of the anisotropic VTI medium through the forward-propagating wave field of the elastic wave Gaussian beam of the anisotropic VTI medium and the backward-propagating wave field of the elastic wave Gaussian beam of the anisotropic VTI medium.

8. The method according to claim 1, characterized in that, The single-shot elastic wave seismic records of the anisotropic VTI medium are used to obtain the wave field information from the source point to the geophone, and the wave field information includes the total travel time from the source point to the geophone.

9. The method according to claim 1, characterized in that The shear wave velocity information includes the vertical shear wave velocity; the P-wave velocity information includes the vertical P-wave velocity; and the anisotropy parameter information includes the anisotropy parameters of the anisotropic VTI medium.

10. An anisotropic VTI medium elastic wave Gaussian beam migration imaging device, characterized in that, The device includes: an acquisition module and a determination module, where the acquisition module is used to acquire the shear wave velocity information, P-wave velocity information, anisotropy parameter information required in the tracking of the elastic waves of the anisotropic VTI medium, and the single-shot elastic wave seismic records of the anisotropic VTI medium; the determination module is used for: determining the kinematic ray tracing equation of the elastic waves of the anisotropic VTI medium and the dynamic ray tracing equation of the elastic waves of the anisotropic VTI medium according to the shear wave velocity information, the P-wave velocity information, and the anisotropy parameter information; determining the central ray travel time and path information of the elastic waves of the anisotropic VTI medium according to the kinematic ray tracing equation of the elastic waves of the anisotropic VTI medium, the shear wave velocity information, the P-wave velocity information, and the anisotropy parameter information; determining the dynamic ray tracing parameters according to the dynamic ray tracing equation of the elastic waves of the anisotropic VTI medium, the shear wave velocity information, the P-wave velocity information, and the anisotropy parameter information; determining the elastic wave Gaussian beam source displacement wave field of the anisotropic VTI medium according to the central ray travel time information, the path information, the dynamic ray parameters, the shear wave velocity information, the P-wave velocity information, and the anisotropy parameter information; determining the elastic wave Gaussian beam migration imaging values of the anisotropic VTI medium corresponding to the single-shot elastic wave seismic records of the anisotropic VTI medium according to the forward-propagating wave field and backward-propagating wave field of the elastic wave Gaussian beam source displacement wave field of the anisotropic VTI medium, and the cross-correlation result between the forward-propagating wave field and backward-propagating wave field and the backward-propagating wave field at the center of the Gaussian beam; superposing the elastic wave Gaussian beam migration imaging values of the anisotropic VTI medium corresponding to all the single-shot elastic wave seismic records of the anisotropic VTI medium to determine the elastic wave Gaussian beam migration imaging of the anisotropic VTI medium.

Images