Acoustic wave vector reverse time migration imaging method without reflection angle influence

Abstract

The invention belongs to the field of exploration geophysics, and discloses a reflection angle influence-free sound wave vector reverse time migration imaging method, which comprises the following steps of: presetting seismic wavelets and an initial speed model, and realizing forward extrapolation of a sound wave field by utilizing a first-order sound wave equation to obtain a sound wave source wave field; according to observed seismic data and a preset initial velocity model, using a first-order sound wave equation to realize sound wave field reverse extrapolation to obtain a sound wave detection wave field; based on the sound wave source wave field and the sound wave detection wave field, an imaging angle is determined by using the constructed energy norm-based imaging angle extraction function; and based on the imaging angle, imaging is carried out by using the constructed dot product cross-correlation imaging condition without the influence of the reflection angle, and a scalar imaging result without the influence of the reflection angle is obtained. According to the method disclosed by the invention, the problem of polarity inversion caused by the imaging angle under the acoustic vector dot product imaging condition can be eliminated, and the polarity consistency of the acoustic imaging event is improved, so that a guarantee is provided for the accuracy of geologic structure imaging in a complex environment.

Description

Technical Field

[0001] The invention belongs to the field of exploration geophysics, and in particular relates to an acoustic wave vector reverse time migration imaging method without reflection angle influence. Background Art

[0002] The acoustic wave vector reverse time migration imaging method is based on the two-way wave equation to extend the wave field. It has no dip angle restriction and can accurately image complex structural areas. It has shown superior performance in improving the imaging quality of complex media. Different from the acoustic wave reverse time migration method, the acoustic wave vector reverse time migration method can comprehensively utilize the spatial information of the acoustic wave particle vibration velocity vector to provide imaging results with richer information for subsequent geological interpretation and other work. However, when extracting scalar imaging results from the vector seismic wave field based on the dot product cross-correlation imaging condition, the imaging angular coefficient term introduced by the dot product operation is The impact of the incident angle is When the reflection coefficient is different from that of the reflection coefficient, the polarity reversal problem of the imaging event will occur. When the data are stacked, this abnormal polarity reversal problem will interfere with the coherence of the imaging event to a certain extent, making it difficult to serve the subsequent geological interpretation and other work. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides an acoustic wave vector reverse time migration imaging method without the influence of reflection angle, so as to eliminate imaging errors such as polarity reversal caused by the imaging angle at the imaging point, and obtain accurate reflection coefficient characterization scalar imaging results.

[0004] To achieve the above object, the technical solution of the present invention is as follows: A method for acoustic wave vector reverse time migration imaging without reflection angle influence comprises the following steps: Step 1: Given the seismic wavelet and initial velocity model in advance, the acoustic wave field forward vector extension operator is constructed using the first-order acoustic wave equation to realize the forward extrapolation of the acoustic wave field and obtain the acoustic source wave field; Step 2: Based on the observed seismic data and the pre-given initial velocity model, the first-order acoustic wave equation is used to construct the acoustic wave field reverse vector extension operator to realize the reverse extrapolation of the acoustic wave field and obtain the acoustic wave detection wave field; Step 3, based on the acoustic source wave field and the acoustic detection wave field at the same imaging time, the imaging angle is determined by using the energy norm-based imaging angle extraction function; Step 4: Based on the determined imaging angle, imaging is performed using the constructed dot product cross-correlation imaging condition without the influence of the reflection angle to obtain a scalar imaging result without the influence of the reflection angle.

[0005] In the above scheme, step 1 is as follows: given a seismic wavelet and the initial velocity model , using the first-order acoustic wave equation to construct the acoustic wave field forward vector extension operator, including the acoustic wave confining pressure wave field at the source end and the acoustic wave particle vibration velocity vector wave field, to achieve the forward extrapolation of the acoustic wave field, obtain the acoustic wave source wave field, and store it in the hard disk; the constructed acoustic wave field forward vector extension operator is as follows: ; Among them, the superscript and Indicates the whole time point, and is a half-time node, , represents the number of discrete points corresponding to the total time of earthquake records, represents the time sampling interval, and Respectively and The acoustic wave confining pressure field at the source end at time t, the subscript s represents the acoustic wave field index at the source end, represents the velocity vector of the acoustic wave particle vibration, and They represent the x-direction and z-direction components of the particle vibration velocity vector, respectively. and Respectively and The x-direction component of the velocity vector field of the acoustic wave particle at the source end at time, and Respectively and The z-component of the velocity vector field of the acoustic wave particle at the source end at time, is the boundary absorption coefficient, in the target area , in the boundary absorption region , , is the absorption layer thickness, represents the background velocity field density parameter model, represents the velocity model of the background velocity field, and denote the spatial derivatives in the x and z directions respectively, represents the source wavelet, represents the earthquake wavelet function, represents the spatial attenuation function of the earthquake source.

[0006] In the above scheme, step 2 is as follows: Based on the observed earthquake data And the pre-given initial velocity model , the first-order acoustic wave equation is used to construct the reverse vector extension operator of the acoustic wave field, including the acoustic wave confining pressure wave field and the acoustic wave particle vibration velocity vector wave field at the detection end, to realize the reverse extrapolation of the acoustic wave field and obtain the acoustic wave detection wave field; the constructed acoustic wave field reverse vector extension operator is as follows: ; Among them, the subscript Indicates the acoustic wave field index of the detector end. and Respectively and The x-direction component of the velocity vector field of the acoustic wave particle vibration at the detector end at time, and Respectively and The z-component of the velocity vector field of the acoustic wave particle vibration at the detector end at time, Indicates a given The vector field of earthquake records at time Indicates a given Time along The seismic record component of the direction, Indicates a given Time along The seismic record component of the direction, Indicates the buried depth when the seismic record was collected. and Respectively and The sound wave surrounding pressure field at the earthquake source at all times.

[0007] In the above scheme, in step 3, the energy norm-based imaging angle extraction function is constructed as: ; in, Indicates the corresponding imaging time Based on the imaging angle determined by the energy norm, represents the sound wave propagation speed of the initial velocity model, Indicates the corresponding imaging time The acoustic stress field at the source end of Indicates the corresponding imaging time The acoustic stress field at the detection end, " represents the dot product operation," " indicates gradient operation, and the superscript "." indicates time derivative.

[0008] In the above scheme, step 4 is as follows: at each imaging moment, based on the imaging angle determined in step 3 , the vibration velocity vector field of the acoustic wave particle at the source end stored in step 1 and the velocity vector field of the acoustic wave particle vibration at the detection end in step 2 , use the constructed dot product cross-correlation imaging condition without the influence of reflection angle to perform imaging, and obtain the scalar imaging result without the influence of reflection angle at the current imaging moment; superimpose all the shot gathers at all imaging moments to obtain the final scalar imaging result without polarity inversion; the constructed dot product cross-correlation imaging condition without the influence of reflection angle is: ; in, represents the acoustic wave dot product cross-correlation imaging condition without the influence of reflection angle, represents the vibration velocity vector field of the particle at the source end, represents the vibration velocity vector field of the particle at the detection end, represents the coordinate index of the source end, Indicates the detector coordinate index, represents the imaging time index, represents the shot gather index, represents the acoustic wave stress field at the source end, Represents the acoustic wave stress field at the detection end, " represents the dot product operation," " indicates gradient operation, and the superscript "." indicates time derivative.

[0009] Through the above technical solution, the acoustic wave vector reverse time migration imaging method without reflection angle influence provided by the present invention has the following beneficial effects: The present invention first uses the first-order acoustic wave equation in the time domain to realize the construction of the source wave field and the detection wave field. Then, the time derivative field and the space derivative field of the source end confining pressure field and the detection end confining pressure field are used to derive the imaging reflection angle extraction function at all imaging points at all imaging moments based on the acoustic wave energy norm. Finally, based on the principle of time consistency and the extracted imaging reflection angle information, the acoustic wave point product cross-correlation imaging condition without the influence of the reflection angle is constructed, which realizes the polarity reversal problem of eliminating the influence of the imaging angle and extracts the scalar imaging information with the amplitude and phase information effectively maintained.

[0010] In the conventional acoustic wave vector imaging method, the present invention derives the imaging angle data at the imaging point by using the spatial information and time information of the acoustic wave confining pressure scalar field based on the energy norm, so as to eliminate the polarity reversal error introduced by the reflection angle during dot product cross-correlation imaging, thereby ensuring the consistency of the polarity of the event axis of the scalar imaging result extracted from the vector data, and providing a certain guarantee for the accuracy of geological structure imaging under complex geological conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below.

[0012] Figure 1 It is a flow chart of a method for reverse time migration of acoustic wave vector without the influence of reflection angle disclosed in the present invention; Figure 2 It is a schematic diagram of the imaging angle calculated by the energy norm at the imaging point at a certain imaging moment; Figure 3 Pre-given source wavelet; Figure 4 A predetermined initial sound wave velocity; Figure 5 A pre-given seismic acoustic pressure record; Figure 6 yes The signal at the source end propagating forward at all times; (a) is the acoustic pressure wave field, (b) is the x-direction component of the acoustic pressure particle vibration velocity vector field, and (c) is the z-direction component of the acoustic pressure particle vibration velocity vector field; Figure 7 yes The detection end signal propagating in the opposite direction at all times; (a) is the sound pressure wave field, (b) is the x-direction component of the sound pressure particle vibration velocity vector field, and (c) is the z-direction component of the sound pressure particle vibration velocity vector field; Figure 8 yes Imaging angle distribution information determined by the imaging angle extraction function is used at all times; Fig. 9 for The results of using the acoustic wave particle vibration velocity vector field extraction at all times; (a) is the dot product imaging result; (b) is the dot product imaging result without the influence of the reflection angle; Fig.10 The single shot result extracted using the acoustic wave particle vibration velocity vector field; (a) is the dot product imaging result; (b) is the dot product imaging result without the influence of the reflection angle; Fig.11 This is a comparison chart of the reflection results of a single shot point product imaging result at z=1800m and the point product cross-correlation imaging result without the influence of reflection angle. DETAILED DESCRIPTION

[0013] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0014] The present invention provides a method for acoustic wave vector reverse time migration imaging without the influence of reflection angle, such as Figure 1 As shown, the following steps are included: Step 1: Given the seismic wavelet and initial velocity model in advance, the first-order acoustic wave equation is used to construct the acoustic wave field forward vector extension operator to realize the forward extrapolation of the acoustic wave field and obtain the acoustic source wave field.

[0015] The details are as follows: Pre-given seismic wavelet and the initial velocity model , using the first-order acoustic wave equation to construct the acoustic wave field forward vector extension operator, including the acoustic wave confining pressure wave field at the source end and the acoustic wave particle vibration velocity vector wave field, to achieve the forward extrapolation of the acoustic wave field, obtain the acoustic wave source wave field, and store it in the hard disk; the constructed acoustic wave field forward vector extension operator is as follows: ; Among them, the superscript and Indicates the whole time point, and is a half-time node, , represents the number of discrete points corresponding to the total time of earthquake records, represents the time sampling interval, and Respectively and The acoustic wave confining pressure field at the source end at time t, the subscript s represents the acoustic wave field index at the source end, represents the velocity vector of the acoustic wave particle vibration, and They represent the x-direction and z-direction components of the particle vibration velocity vector, respectively. and Respectively and The x-direction component of the velocity vector field of the acoustic wave particle at the source end at time, and Respectively and The z-component of the velocity vector field of the acoustic wave particle at the source end at time, is the boundary absorption coefficient, in the target area , in the boundary absorption region , , is the absorption layer thickness, represents the background velocity field density parameter model, represents the velocity model of the background velocity field, and denote the spatial derivatives in the x and z directions respectively, represents the source wavelet, represents the earthquake wavelet function, represents the spatial attenuation function of the earthquake source.

[0016] Step 2: Based on the observed seismic data and the pre-given initial velocity model, the first-order acoustic wave equation is used to construct the acoustic wave field reverse vector extension operator to realize the reverse extrapolation of the acoustic wave field and obtain the acoustic wave detection wave field.

[0017] The details are as follows: Based on the observed earthquake data And the pre-given initial velocity model , the first-order acoustic wave equation is used to construct the reverse vector extension operator of the acoustic wave field, including the acoustic wave confining pressure wave field and the acoustic wave particle vibration velocity vector wave field at the detection end, to realize the reverse extrapolation of the acoustic wave field and obtain the acoustic wave detection wave field; the constructed acoustic wave field reverse vector extension operator is as follows: ; Among them, the subscript Indicates the acoustic wave field index of the detector end. and Respectively and The x-direction component of the velocity vector field of the acoustic wave particle vibration at the detector end at time, and Respectively and The z-component of the velocity vector field of the acoustic wave particle vibration at the detector end at time, Indicates a given The vector field of earthquake records at time of Indicates along The seismic record component of the direction, Indicates along The seismic record component of the direction, Indicates the buried depth when the seismic record was collected. and Respectively and The sound wave surrounding pressure field at the earthquake source at all times.

[0018] Step 3: Based on the acoustic source wave field and acoustic detection wave field at the same imaging time, the imaging angle is determined using the energy norm-based imaging angle extraction function. .

[0019] The details are as follows: Each imaging moment Based on the acoustic confining pressure wave field at the source end stored in step 1 and the acoustic confining pressure wave field at the receiver end obtained in step 2, the imaging angle is determined using the energy norm-based imaging angle extraction function. The energy norm-based imaging angle extraction function is constructed as follows: ; in, Indicates the corresponding imaging time Based on the imaging angle determined by the energy norm, represents the sound wave propagation speed of the initial velocity model, Indicates the corresponding imaging time The acoustic stress field at the source end of Indicates the corresponding imaging time The acoustic stress field at the detection end, " represents the dot product operation," " indicates gradient operation, and the superscript "." indicates time derivative.

[0020] Specifically, in the embodiment of the present invention, the plane wave theory is used to derive the imaging angle extraction function in the frequency domain.

[0021] Under the plane wave assumption, the sound pressure field of the incident sound wave at the source end in the frequency domain is expressed as: ; in, is the incident acoustic wave stress field at the source end, represents the incident acoustic wave stress amplitude at the source end, It represents the wave number vector of the incident sound wave at the source end, that is, the propagation direction of the incident sound wave (such as Figure 2 ), represents the coordinate index, Indicates frequency, represents time, where the wave number vector satisfies , Represents the sound wave propagation speed of the initial velocity model.

[0022] Similarly, under the plane wave assumption, the sound pressure field of the incident sound wave at the detection end in the frequency domain is expressed as: ; in, is the stress field of the acoustic wave reflected at the detection end, It represents the stress amplitude of the reflected sound wave at the detection end. Indicates the wave number vector of the reflected sound wave at the detection end, that is, the propagation direction of the reflected sound wave (such as Figure 2 ), whose wave number vector satisfies .

[0023] At a certain imaging moment, the spatial derivative of the sound pressure of the incident sound wave satisfies , the time derivative satisfies , the spatial derivative of the sound pressure of the reflected sound wave satisfies , the time derivative satisfies .

[0024] According to the energy norm expression , we can derive the energy expression in the frequency domain as: ; Since the incident sound wave number satisfies and the reflected sound wave number satisfies ,So .in, represents the reflection angle of the incident sound wave and the reflected sound wave, is the imaging angle at the current imaging moment, satisfying Substituting the acoustic wave number into the energy norm expression, it is expressed as: ; Through the energy norm expression, it is not difficult to find that in the energy norm, the potential energy part related to the space derivative and the kinetic energy part related to the time derivative have and only have Therefore, we construct the imaging angle extraction function based on the energy norm: ; In the time-space domain, at a certain imaging moment The imaging angle extraction function can be expressed as: ; In the formula, For a certain imaging moment The imaging angle is determined based on the energy norm.

[0025] Step 4: Based on the determined imaging angle, imaging is performed using the constructed dot product cross-correlation imaging condition without the influence of the reflection angle to obtain a scalar imaging result without the influence of the reflection angle.

[0026] The details are as follows: At each imaging moment, based on the imaging angle determined in step 3 , the vibration velocity vector field of the acoustic wave particle at the source end stored in step 1 and the velocity vector field of the acoustic wave particle vibration at the detection end in step 2 , use the constructed dot product cross-correlation imaging condition without the influence of reflection angle to perform imaging, and obtain the scalar imaging result without the influence of reflection angle at the current imaging moment; superimpose all the shot gathers at all imaging moments to obtain the final scalar imaging result without polarity inversion; the constructed dot product cross-correlation imaging condition without the influence of reflection angle is: ; in, represents the acoustic wave dot product cross-correlation imaging condition without the influence of reflection angle, represents the vibration velocity vector field of the particle at the source end, represents the vibration velocity vector field of the particle at the detection end, represents the coordinate index of the source end, Indicates the detector coordinate index, represents the imaging time index, represents the shot gather index, represents the acoustic wave stress field at the source end, Represents the acoustic wave stress field at the detection end, " represents the dot product operation," " indicates gradient operation, and the superscript "." indicates time derivative.

[0027] Specifically, taking a simple flat layer model as an example, given in advance: Figure 3 Seismic wavelets generated by offshore airguns are shown ,like Figure 4 The initial velocity model shown He Ru Figure 5 The seismic acoustic pressure record shown in the figure is respectively extended along the forward time to obtain the vector wave field at the source end and along the reverse time to obtain the vector wave field at the detector end. Figure 6 (a) is The wave field and acoustic pressure field at the source end at time, Figure 6 (b) is The x-direction component of the velocity vector field of the acoustic wave particle vibration at the source end at time , Figure 6 (c) The component of the z-direction of the vibration velocity vector field of the acoustic wave particle at the source end at time , Figure 7 (a) is The wave field and sound pressure field of the detector at each moment, Figure 7 (b) is The x-direction component of the velocity vector field of the wave field particle at the detector end at time, Figure 7 (c) The component of the z-direction of the wave field particle vibration velocity vector field at the detector end at time . It can be found that the wave fronts of the source wave field and the detection wave field are inconsistent, and the information carried by different components in the vector field is inconsistent.

[0028] Pre-set checkpoints and use them as imaging times , according to the pre-set imaging time The acoustic source wavefield and the acoustic receiver wavefield are stored in the hard disk. At each imaging time, the imaging angle distribution information at the current imaging moment can be determined using the imaging angle extraction function based on the energy norm. Figure 8 for The imaging angle distribution information determined by the imaging angle extraction function is used at all times. Fig. 9 (a) is The dot product imaging results are extracted by using the acoustic wave particle vibration velocity vector field at all times. Fig. 9 (b) is The point product imaging result without the influence of reflection angle is extracted by using the velocity vector field of the acoustic wave particle vibration at all times. It can be found that the imaging angle distribution information at different positions is different, and at non-specific imaging angles, that is, When the reflection angle is 0.04, the difference between the dot product imaging result extracted by the acoustic wave particle vibration velocity and the dot product imaging result without the influence of the reflection angle is not obvious.

[0029] The imaging results of all pre-set checkpoints are superimposed to obtain the single-shot reverse time migration imaging result. Fig.10 (a) is the single shot point product imaging result extracted by using the acoustic wave particle vibration velocity vector field; Fig.10 (b) is the point product imaging result of a single shot without the influence of reflection angle extracted by using the velocity vector field of the acoustic wave particle vibration. Right now ,distance At , the dot product imaging results gradually show polarity reversal, but the dot product imaging results without the influence of reflection angle have no polarity reversal. To further illustrate the imaging results, the dot product imaging results and the dot product imaging results without the influence of reflection angle are extracted at a depth of z = 1800m for trajectory comparison. Fig.11 The figure is a comparison of the single shot dot product imaging result at z=1800m and the dot product cross-correlation imaging result without the influence of the reflection angle. The comparison results show that the dot product imaging result without the influence of the reflection angle has a polarity reversal problem, but the dot product imaging result has a polarity reversal problem. The acoustic wave vector reverse time migration method without the influence of the reflection angle can eliminate the polarity reversal problem introduced by the reflection angle, effectively maintain the polarity of the event axis under different offset distances, reduce the dependence of the imaging method on the offset distance and the incident angle, and improve the imaging accuracy of the vector reverse time migration method in complex environments.

[0030] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for acoustic wave vector reverse time migration imaging without reflection angle influence, characterized in that: The steps include: Step 1: Given the seismic wavelet and initial velocity model in advance, the acoustic wave field forward vector extension operator is constructed using the first-order acoustic wave equation to realize the forward extrapolation of the acoustic wave field and obtain the acoustic source wave field; Step 2: Based on the observed seismic data and a pre-given initial velocity model, a first-order acoustic wave equation is used to construct an acoustic wave field reverse vector extension operator to achieve reverse extrapolation of the acoustic wave field and obtain an acoustic wave detection wave field; Step 3, based on the acoustic source wave field and the acoustic detection wave field at the same imaging time, the imaging angle is determined by using the energy norm-based imaging angle extraction function; Step 4: Based on the determined imaging angle, imaging is performed using the constructed dot product cross-correlation imaging condition without the influence of the reflection angle to obtain a scalar imaging result without the influence of the reflection angle.

2. The method for acoustic wave vector reverse time migration imaging without reflection angle influence according to claim 1, characterized in that: Step 1 is as follows: given the seismic wavelet and the initial velocity model , using the first-order acoustic wave equation to construct the acoustic wave field forward vector extension operator, including the acoustic wave confining pressure wave field at the source end and the acoustic wave particle vibration velocity vector wave field, to achieve the forward extrapolation of the acoustic wave field, obtain the acoustic wave source wave field, and store it in the hard disk; the constructed acoustic wave field forward vector extension operator is as follows: ； Among them, the superscript and Indicates the whole time point, and is a half-time node, , represents the number of discrete points corresponding to the total time of earthquake records, represents the time sampling interval, and Respectively and The acoustic wave confining pressure field at the source end at time t, the subscript s represents the acoustic wave field index at the source end, represents the velocity vector of the acoustic wave particle vibration, and They represent the x-direction and z-direction components of the particle vibration velocity vector, respectively. and Respectively and The x-direction component of the velocity vector field of the acoustic wave particle at the source end at time, and Respectively and The z-component of the velocity vector field of the acoustic wave particle at the source end at time, is the boundary absorption coefficient, in the target area , in the boundary absorption region , , is the absorption layer thickness, represents the background velocity field density parameter model, represents the velocity model of the background velocity field, and denote the spatial derivatives in the x and z directions respectively, represents the source wavelet, represents the earthquake wavelet function, represents the spatial attenuation function of the earthquake source.

3. The method for acoustic wave vector reverse time migration imaging without reflection angle influence according to claim 1, characterized in that: Step 2 is as follows: Based on the observed earthquake data And the pre-given initial velocity model , the first-order acoustic wave equation is used to construct the reverse vector extension operator of the acoustic wave field, including the acoustic wave confining pressure wave field and the acoustic wave particle vibration velocity vector wave field at the detection end, to realize the reverse extrapolation of the acoustic wave field and obtain the acoustic wave detection wave field; the constructed acoustic wave field reverse vector extension operator is as follows: ； Among them, the subscript Indicates the acoustic wave field index of the detector end. and Respectively and The x-direction component of the velocity vector field of the acoustic wave particle vibration at the detector end at time, and Respectively and The z-component of the velocity vector field of the acoustic wave particle vibration at the detector end at time, Indicates a given The vector field of earthquake records at time Indicates a given Time along The seismic record component of the direction, Indicates a given Time along The seismic record component of the direction, Indicates the buried depth when the seismic record was collected. and Respectively and The sound wave surrounding pressure field at the earthquake source at all times.

4. The method for acoustic wave vector reverse time migration imaging without reflection angle influence according to claim 2, characterized in that: In step 3, the energy norm-based imaging angle extraction function is constructed as: ； in, Indicates the corresponding imaging time Based on the imaging angle determined by the energy norm, represents the sound wave propagation speed of the initial velocity model, Indicates the corresponding imaging time The acoustic stress field at the source end is Indicates the corresponding imaging time Acoustic stress field at the detector end, " " represents the dot product operation, " ” indicates the gradient operation, and the superscript “.” indicates the time derivative.

5. The method for acoustic wave vector reverse time migration imaging without reflection angle influence according to claim 1, characterized in that: Step 4 is as follows: At each imaging moment, based on the imaging angle determined in step 3 , the acoustic wave particle vibration velocity vector field at the source end stored in step 1 and the velocity vector field of the acoustic wave particle vibration at the detection end in step 2 , use the constructed dot product cross-correlation imaging condition without the influence of reflection angle to perform imaging, and obtain the scalar imaging result without the influence of reflection angle at the current imaging moment; superimpose all the shot gathers at all imaging moments to obtain the final scalar imaging result without polarity inversion; the constructed dot product cross-correlation imaging condition without the influence of reflection angle is: ； in, represents the acoustic wave dot product cross-correlation imaging condition without the influence of reflection angle, represents the vibration velocity vector field of the particle at the source end, represents the vibration velocity vector field of the particle at the detection end, represents the coordinate index of the source end, Indicates the detector coordinate index, represents the imaging time index, represents the shot gather index, represents the acoustic wave stress field at the source end, represents the acoustic stress field at the detection end, " " represents the dot product operation, " ” indicates the gradient operation, and the superscript “.” indicates the time derivative.

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