Self-adaptive variable grid reverse time migration imaging method, system, equipment and medium

Abstract

The invention belongs to the technical field of petroleum geophysical exploration, and relates to a self-adaptive variable grid reverse time migration imaging method, system and device and a medium. The method comprises the following steps of: respectively carrying out wave field continuation along a forward propagation direction and a reverse propagation direction of time by applying a two-dimensional constant-density acoustic wave equation of an adaptive variable grid technology to obtain a forward propagation wave field and a reverse propagation wave field, and realizing grid discretization automation and self-adaption through the adaptive variable grid technology, so as to obtain a two-dimensional constant-density acoustic wave field. False reflection is effectively avoided, and the problem that the reverse time migration technology is low in efficiency when applied to ultra-deep reservoir imaging is solved. And carrying out seismic source normalization imaging on the forward propagation wave field and the reverse propagation wave field at the same moment. And linear interpolation processing is carried out on the normalized imaging result to obtain a reverse time migration imaging profile, so that the imaging precision is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of petroleum geophysical exploration, and relates to an adaptive variable grid reverse time migration imaging method, system, equipment and medium. Background Art

[0002] The ultra-deep oil and gas reservoirs in the western exploration area are deeply buried, with complex underground geological structures, large changes in shallow and deep velocity, weak deep signals, large reverse time migration calculation and storage requirements, and high production costs. Developing model variable grid generation and wave equation solving technology based on compact differences for ultra-deep oil and gas reservoirs, and developing efficient and high-precision reverse time migration imaging technology will help reduce production costs and obtain high-quality migration profiles, which is of great research significance for the exploration and development of ultra-deep oil and gas in the western exploration area of ​​my country.

[0003] Traditional variable grid technology achieves the purpose of reducing computational efficiency by artificially dividing grids of different coarseness and fineness. However, it needs to use different differential formats in grid areas of different coarseness and fineness, or use interpolation technology to achieve transition in the connection area between coarse and fine grids. The implementation method is relatively complicated and is prone to false reflection, which affects the imaging effect. Summary of the invention

[0004] In order to overcome the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide an adaptive variable grid reverse time migration imaging method, system, device and medium, which avoids the phenomenon of false reflection during imaging and can improve imaging accuracy.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention discloses an adaptive variable grid reverse time migration imaging method, comprising the following steps:

[0007] The two-dimensional constant density acoustic wave equation using adaptive variable grid technology is extended along the forward propagation direction and the reverse propagation direction of time to obtain the forward propagation wave field and the reverse propagation wave field.

[0008] Perform source normalization imaging on the forward propagating wave field and the reverse propagating wave field at the same time;

[0009] The normalized imaging results are subjected to linear interpolation to obtain the reverse time migration imaging section.

[0010] Furthermore, the process of obtaining the two-dimensional constant density acoustic wave equation using the adaptive variable grid technology is as follows:

[0011] The adaptive variable grid discretization technology is combined with the initial migration velocity field to obtain the variable grid migration velocity field, and the mapping relationship between the initial migration velocity field and the variable grid migration velocity field is recorded;

[0012] Combining the mapping relationship and the two-dimensional constant density acoustic wave equation, the two-dimensional constant density acoustic wave equation based on adaptive variable grid technology is obtained.

[0013] Furthermore, the process of obtaining the initial migration velocity field is as follows:

[0014] Search for the minimum velocity at each depth layer along the depth direction;

[0015] The theoretically optimal longitudinal grid spacing dz(z) is calculated based on the minimum velocity in each depth layer and the number of sampling points in each wavelength;

[0016]

[0017] Where z is the depth, n is the number of sampling points in each wavelength, f is the frequency, and v is the sampling point. min is the minimum velocity for each depth layer;

[0018] Take the depth z m , so that z m -z m-1 =dz(m), where m is a positive integer greater than 1 and equal to 1, and the initial migration velocity field is obtained.

[0019] Furthermore, the two-dimensional constant density acoustic wave equation based on adaptive variable grid technology is obtained by combining the mapping relationship and the two-dimensional constant density acoustic wave equation as follows:

[0020] The mapping relation is differentiated to obtain its derivative, and the derivative of the mapping relation and the two-dimensional constant density acoustic wave equation are applied to obtain the two-dimensional constant density acoustic wave equation using an adaptive variable grid technology for extending the forward propagation wave field and the reverse propagation wave field.

[0021] Furthermore, the two-dimensional constant density acoustic wave equation used to extend the forward propagating wave field is as follows:

[0022]

[0023] The two-dimensional constant density acoustic wave equation used to extend the back-propagating wave field is as follows:

[0024]

[0025] Among them, v p (x,z) is the initial 2D migration velocity field, s(t) is the source wavelet, F(t) is the shot record source, x is the depth direction, z is the depth direction, and t is the time.

[0026] Furthermore, the two-dimensional constant density acoustic wave equation for the adaptive variable grid technology used to extend the forward propagating wave field is as follows:

[0027]

[0028] The two-dimensional constant density acoustic wave equation for the adaptive variable grid technique used to extend the back-propagating wave field is as follows:

[0029]

[0030] in, is the derivative of the mapping relationship, v pnew (x,z) is the variable grid offset velocity field.

[0031] Furthermore, the formula for source normalization imaging of the forward propagating wave field and the reverse propagating wave field at the same time is as follows:

[0032]

[0033] Among them, F(x,z,t) is the wave field propagating forward along time, B(x,z,t) is the wave field propagating backward along time, and R im (x,z) is the imaging result.

[0034] Based on the method of the present invention, the present invention proposes an adaptive variable grid reverse time migration imaging system, comprising:

[0035] Wavefield extension module: It is used to extend the wavefield of the two-dimensional constant density acoustic wave equation along the forward propagation direction and the reverse propagation direction of time using the adaptive variable grid technology to obtain the forward propagation wavefield and the reverse propagation wavefield;

[0036] Normalized imaging module: used to perform source normalized imaging on the forward propagating wave field and the reverse propagating wave field at the same time;

[0037] Interpolation processing module: used to perform linear interpolation processing on the normalized imaging results to obtain the reverse time migration imaging section.

[0038] An electronic device comprises: a processor; a memory for storing computer program instructions; and a memory for implementing the steps of an adaptive variable grid reverse time migration imaging method when executing the computer program.

[0039] A storage medium stores computer program instructions. When the computer program instructions are loaded and run by a processor, the processor executes an adaptive variable grid reverse time migration imaging method.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The present invention discloses an adaptive variable grid reverse time migration imaging method, which is specifically as follows: the two-dimensional constant density acoustic wave equation using the adaptive variable grid technology is used to perform wave field extension along the forward propagation direction and the reverse propagation direction of time, respectively, to obtain the forward propagation wave field and the reverse propagation wave field. The adaptive variable grid technology is used to realize grid discretization automation and adaptability, effectively avoiding false reflections, solving the problem of low efficiency of reverse time migration technology when imaging ultra-deep reservoirs, and reducing storage requirements. The source normalization imaging of the forward propagation wave field and the reverse propagation wave field at the same time can balance the imaging amplitude and improve the imaging accuracy. The normalized imaging result is subjected to linear interpolation processing to obtain the reverse time migration imaging profile, that is, to obtain the correct imaging result, and improve the imaging accuracy.

[0042] The present invention discloses an adaptive variable grid reverse time migration imaging system, which includes a wave field extension module, a normalized imaging module and an interpolation processing module. The wave field extension module is used to apply the two-dimensional constant density acoustic wave equation of the adaptive variable grid technology to perform wave field extension along the forward propagation direction and the reverse propagation direction of time respectively, so as to obtain the forward propagation wave field and the reverse propagation wave field. The normalized imaging module is used to perform source normalized imaging on the forward propagation wave field and the reverse propagation wave field at the same time. The interpolation processing module is used to perform linear interpolation processing on the normalized imaging result to obtain the reverse time migration imaging profile. The various modules cooperate with each other to avoid the phenomenon of false reflection during imaging, improve imaging accuracy and reduce storage requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is a flow chart of the method of the present invention;

[0044] Figure 2 is a detailed flow chart of the method of the present invention;

[0045] Figure 3a is the initial migration velocity field;

[0046] Figure 3b Adaptive variable grid offset velocity field;

[0047] Figure 4a This is a reverse time migration profile imaging diagram of the present invention;

[0048] Figure 4b It is the migration profile imaging diagram after linear interpolation processing of the present invention;

[0049] Figure 5 It is a system module diagram of the present invention. DETAILED DESCRIPTION

[0050] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0051] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0052] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0053] See also Figure 1 The present invention discloses an adaptive variable grid reverse time migration imaging method, comprising the following steps:

[0054] S1. Apply the adaptive variable grid technology to extend the wave field of the two-dimensional constant density acoustic wave equation along the forward propagation direction and the reverse propagation direction of time to obtain the forward propagation wave field and the reverse propagation wave field;

[0055] The process of obtaining the two-dimensional constant density acoustic wave equation using adaptive variable grid technology is as follows:

[0056] The adaptive variable grid discretization technology is combined with the initial migration velocity field to obtain the variable grid migration velocity field, and the mapping relationship between the initial migration velocity field and the variable grid migration velocity field is recorded;

[0057] The process of obtaining the initial migration velocity field is as follows:

[0058] Search for the minimum velocity at each depth layer along the depth direction;

[0059] The theoretically optimal longitudinal grid spacing dz(z) is calculated based on the minimum velocity in each depth layer and the number of sampling points in each wavelength;

[0060]

[0061] Where z is the depth, n is the number of sampling points in each wavelength, f is the frequency, and v is the sampling point. min is the minimum velocity for each depth layer;

[0062] Take the depth z m , so that z m -z m-1 =dz(m), where m is a positive integer greater than 1 and equal to 1, and the initial migration velocity field is obtained.

[0063] Combining the mapping relationship and the two-dimensional constant density acoustic wave equation, the two-dimensional constant density acoustic wave equation based on adaptive variable grid technology is obtained.

[0064] Combining the mapping relationship and the two-dimensional constant density acoustic wave equation, the two-dimensional constant density acoustic wave equation based on adaptive variable grid technology is obtained as follows:

[0065] The mapping relation is differentiated to obtain its derivative, and the derivative of the mapping relation and the two-dimensional constant density acoustic wave equation are applied to obtain the two-dimensional constant density acoustic wave equation using an adaptive variable grid technology for extending the forward propagation wave field and the reverse propagation wave field.

[0066] The two-dimensional constant density acoustic wave equation used to extend the forward propagating wave field is as follows:

[0067]

[0068] The two-dimensional constant density acoustic wave equation used to extend the back-propagating wave field is as follows:

[0069]

[0070] Among them, v p (x,z) is the initial 2D migration velocity field, s(t) is the source wavelet, F(t) is the shot record source, x is the depth direction, z is the depth direction, and t is the time.

[0071] The two-dimensional constant density acoustic wave equation for the adaptive variable grid technique used to extend the forward propagating wave field is as follows:

[0072]

[0073] The two-dimensional constant density acoustic wave equation for the adaptive variable grid technique used to extend the back-propagating wave field is as follows:

[0074]

[0075] in, is the derivative of the mapping relationship, v pnew (x,z) is the variable grid offset velocity field.

[0076] The time second-order central finite difference format is used to solve the two-dimensional constant density acoustic wave equation using the adaptive variable grid technology. The discrete format formula of the two-dimensional constant density acoustic wave equation using the adaptive variable grid technology is as follows:

[0077]

[0078]

[0079] In the formula, and At n moments and The discrete value of ψ j for discrete value of .

[0080] S2. Perform source normalization imaging on the wave field propagating forward and the wave field propagating backward at the same time;

[0081] The formula for source normalization imaging of the forward propagating wave field and the reverse propagating wave field at the same time is as follows:

[0082]

[0083] Among them, F(x,z,t) is the wave field propagating forward along time, B(x,z,t) is the wave field propagating backward along time, and R im (x,z) is the imaging result.

[0084] S3. Perform linear interpolation processing on the normalized imaging results to obtain the reverse time migration imaging section.

[0085] Preferably, an adaptive variable grid reverse time migration imaging method disclosed in the present invention is specifically as follows: the two-dimensional constant density acoustic wave equation using the adaptive variable grid technology is used to perform wave field extension along the forward propagation direction and the reverse propagation direction of time respectively, to obtain the wave field of forward propagation and the wave field of reverse propagation, and the grid discretization automation and adaptability are realized through the adaptive variable grid technology, which effectively avoids false reflections, solves the problem of low efficiency of reverse time migration technology when applied to imaging ultra-deep reservoirs, and can reduce storage requirements. The source normalization imaging of the wave field of forward propagation and the wave field of reverse propagation at the same time can balance the imaging amplitude and improve the imaging accuracy; the normalized imaging result is subjected to linear interpolation processing to obtain the reverse time migration imaging profile, that is, to obtain the correct imaging result, and improve the imaging accuracy. The purpose of the present invention is to solve the problem of high cost and low accuracy of reverse time migration imaging of ultra-deep oil and gas reservoirs in the western exploration area of ​​my country. The traditional variable grid method is complex to implement and has false reflections. The present invention aims to achieve grid discretization automation and adaptability by developing adaptive variable grid subdivision technology, effectively avoid false reflections, and improve imaging accuracy by normalized imaging and linear interpolation of normalized imaging results.

[0086] Embodiment 1:

[0087] See also Figure 1 This embodiment discloses an adaptive variable grid reverse time migration imaging method, comprising the following steps:

[0088] S1. Input the initial 2D migration velocity field v p (x,z), search for the minimum speed of each depth layer along the depth z direction, and convert v p The minimum velocity along the depth direction in (x,z) is denoted as v min Given the horizontal and vertical grid spacing dx and dz, the source wavelet s(t), and the number of sampling points n in each wavelength, the adaptive variable grid discretization technique is applied to the initial migration velocity field to obtain the variable grid migration velocity field v pnew (x,z) and record the initial migration velocity field and the variable grid migration velocity field v pnew The mapping relationship between (x,z) Its derivative is

[0089] Get the variable grid offset velocity field v pnew The processing steps for (x,z) are as follows:

[0090] Search for the minimum velocity at each depth layer along the depth direction;

[0091] The theoretically optimal longitudinal grid spacing dz(z) is calculated based on the minimum velocity in each depth layer and the number of sampling points in each wavelength;

[0092]

[0093] Where z is the depth, n is the number of sampling points in each wavelength, f is the frequency, and v is the sampling point. min is the minimum velocity for each depth layer;

[0094] Take the depth z m , so that z m -z m-1 =dz(m), where m is a positive integer greater than 1 and equal to 1, and the initial migration velocity field is obtained as follows:

[0095] A trial step size of 0.1 times the vertical grid spacing is given, and the trial step size is continuously increased until the depth z1 is reached, so that z1 = dz(z1);

[0096] Starting from point z1, a trial step size of 0.1 times the vertical grid spacing is given, and the trial step size is continuously increased until the depth z2 is reached, so that z2-z1=dz(z2);

[0097] Repeat the above steps until the maximum depth z of the model is reached. m , m is a positive integer greater than 1 and equal to 1, and all grid points are obtained, namely the initial offset velocity field. The grid discretization automation and adaptability are realized, and false reflections are effectively avoided.

[0098] Along the forward propagation direction of time, the compact finite difference scheme with fourth order in space and the central finite difference scheme with second order in time are used to solve the two-dimensional constant density acoustic wave equation:

[0099]

[0100] Among them, s(t) is the source wavelet.

[0101] Using the derivative of the mapping relationship between the initial migration velocity field and the variable grid migration velocity field The formula of the two-dimensional constant density acoustic wave equation is modified to obtain a new two-dimensional constant density acoustic wave equation for extending the forward propagating wave field with adaptive variable grid technology:

[0102]

[0103] In the reverse propagation direction of time, the fourth-order compact finite difference format in space and the second-order central finite difference format in time are used to reversely extend the wave field at the detection point to solve the two-dimensional constant density acoustic wave equation:

[0104]

[0105] where F(t) is the shot recording source.

[0106] Using the derivative of the mapping relationship between the initial migration velocity field and the variable grid migration velocity field The formula of the two-dimensional constant density acoustic wave equation is modified to obtain a new two-dimensional constant density acoustic wave equation for extending the back-propagating wave field with adaptive variable grid technology:

[0107]

[0108] The processing steps for solving the two-dimensional constant density acoustic wave equation using fourth-order compact finite differences in space and second-order central finite differences in time are as follows:

[0109] Solve using the spatial fourth-order compact finite difference format formula The spatial fourth-order compact finite difference format formula is as follows:

[0110]

[0111] In the formula, a=0.1, b=1.2, u″ *,j Indicates the point (*,j) The discrete value of u *,j Represents the discrete value of the wave field at point (*, j);

[0112] Solve using the spatial fourth-order compact finite difference format formula The spatial fourth-order compact finite difference format formula is as follows:

[0113]

[0114] In the formula, u″ i,* Indicates point (i,*) Discrete value of u i,* Represents the discrete value of the wave field at point (i,*).

[0115] The time second-order central finite difference format is used to solve the two-dimensional constant density acoustic wave equation of the adaptive variable grid technology. The discretization format of the two-dimensional constant density acoustic wave equation of the adaptive variable grid technology is as follows:

[0116]

[0117]

[0118] In the formula, and At n moments and The discrete value of ψ j for discrete value of .

[0119] S2. Performing source normalization imaging on the wave fields propagating forward and backward at the same time is beneficial to improving the imaging accuracy. The imaging conditions are shown in the formula:

[0120]

[0121] Among them, F(x,z,t) is the wave field propagating forward along time, B(x,z,t) is the wave field propagating backward along time, and R im (x,z) is the imaging result.

[0122] S3. Perform linear interpolation processing on the normalized imaging results to obtain the reverse time migration imaging section, thereby improving the imaging accuracy.

[0123] The purpose of the present invention is to solve the difficult problems of high cost and low precision of reverse time migration imaging of ultra-deep oil and gas reservoirs. The traditional variable grid method is complex to implement and has false reflections. The method proposed in the present invention solves the problem of low efficiency of reverse time migration technology when imaging ultra-deep reservoirs by optimizing the offset velocity field through adaptive variable grids. By using compact difference technology to solve the wave equation, the resolution of the imaging results is significantly improved. Compared with the traditional central difference technology, the compact difference technology has high calculation accuracy, low boundary condition requirements, and small storage requirements, and can meet the production needs of high-precision reverse time migration imaging. That is, the implementation of this method is simple and easy, and can effectively avoid false reflections, while taking into account production costs and imaging quality.

[0124] Embodiment 2:

[0125] See also Figure 1 and Figure 2 This embodiment discloses an adaptive variable grid reverse time migration imaging method, comprising the following steps:

[0126] S1. The two-dimensional constant density acoustic wave equation using adaptive variable grid technology is extended along the forward propagation direction and the reverse propagation direction of time to obtain the forward propagation wave field and the reverse propagation wave field, as follows:

[0127] Search for the minimum velocity at each depth layer along the depth direction;

[0128] The theoretically optimal longitudinal grid spacing dz(z) is calculated based on the minimum velocity in each depth layer and the number of sampling points in each wavelength;

[0129]

[0130] Where z is the depth, n is the number of sampling points in each wavelength, f is the frequency, and v is the sampling point. min is the minimum velocity for each depth layer;

[0131] Take the depth z m, so that z m -z m-1 =dz(m), where m is a positive integer greater than 1 and equal to 1, and the initial migration velocity field is obtained as follows:

[0132] A trial step size of 0.1 times the vertical grid spacing is given, and the trial step size is continuously increased until the depth z1 is reached, so that z1 = dz(z1);

[0133] Starting from point z1, a trial step size of 0.1 times the vertical grid spacing is given, and the trial step size is continuously increased until the depth z2 is reached, so that z2-z1=dz(z2);

[0134] Repeat the above steps until the maximum depth z of the model is reached. m , m is a positive integer greater than 1 and equal to 1, and all grid points are obtained, namely the initial offset velocity field. The grid discretization automation and adaptability are realized, and false reflections are effectively avoided.

[0135] Figure 3a is the initial migration velocity field, the number of vertical grid points is 701, Figure 3b It is the adaptive variable grid migration velocity field. The number of longitudinal grid points is 449, which is reduced by about 36%.

[0136] Along the forward propagation direction of time, with Ricker wavelet as the source, the four-order compact finite difference format in space and the second-order central finite difference format in time are used to solve the two-dimensional constant density acoustic wave equation based on the adaptive variable grid technology to obtain the discrete format formula, and the second-order central finite difference format in time and the fourth-order compact finite difference format in space are used to discretize the format formula;

[0137] In the reverse propagation direction of time, the shot record is used as the source, and the wave field at the detection point is reversely extended using the fourth-order compact finite difference format in space and the second-order central finite difference format in time.

[0138] S2. Perform source normalization imaging on the forward and reverse propagating wave fields at the same time Figure 4a is the reverse time migration section;

[0139] S3. The migration profile after linear interpolation is as follows Figure 4b shown.

[0140] See also Figure 5 Based on the above method, the present invention discloses an adaptive variable grid reverse time migration imaging system, comprising:

[0141] Wavefield extension module: It is used to extend the wavefield of the two-dimensional constant density acoustic wave equation along the forward propagation direction and the reverse propagation direction of time using the adaptive variable grid technology to obtain the forward propagation wavefield and the reverse propagation wavefield;

[0142] Normalized imaging module: used to perform source normalized imaging on the forward propagating wave field and the reverse propagating wave field at the same time;

[0143] Interpolation processing module: used to perform linear interpolation processing on the normalized imaging results to obtain the reverse time migration imaging section.

[0144] Preferably, the system disclosed in the present invention comprises a wave field extension module, a normalized imaging module and an interpolation processing module. Figure 5 . The wave field extension module is used to apply the two-dimensional constant density acoustic wave equation of the adaptive variable grid technology to perform wave field extension along the forward propagation direction and the reverse propagation direction of time respectively, and obtain the forward propagation wave field and the reverse propagation wave field. The normalized imaging module is used to perform source normalized imaging of the forward propagation wave field and the reverse propagation wave field at the same time. The interpolation processing module is used to perform linear interpolation processing on the normalized imaging results to obtain the reverse time migration imaging profile. The various modules cooperate with each other to avoid the phenomenon of false reflection during imaging, which can improve imaging accuracy and reduce storage requirements.

[0145] An electronic device comprises: a processor; a memory for storing computer program instructions; and a memory for implementing the steps of an adaptive variable grid reverse time migration imaging method when executing the computer program.

[0146] A storage medium stores computer program instructions. When the computer program instructions are loaded and run by a processor, the processor executes an adaptive variable grid reverse time migration imaging method.

[0147] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0148] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0149] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0150] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0151] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. An adaptive variable grid reverse time migration imaging method, characterized in that: The steps include: The two-dimensional constant density acoustic wave equation using adaptive variable grid technology is extended along the forward propagation direction and the reverse propagation direction of time to obtain the forward propagation wave field and the reverse propagation wave field. Perform source normalization imaging on the forward propagating wave field and the reverse propagating wave field at the same time; The normalized imaging results are subjected to linear interpolation to obtain the reverse time migration imaging section.

2. The adaptive variable grid reverse time migration imaging method according to claim 1, characterized in that: The process of obtaining the two-dimensional constant density acoustic wave equation of the adaptive variable grid technology is as follows: The adaptive variable grid discretization technology is combined with the initial migration velocity field to obtain the variable grid migration velocity field, and the mapping relationship between the initial migration velocity field and the variable grid migration velocity field is recorded; Combining the mapping relationship and the two-dimensional constant density acoustic wave equation, the two-dimensional constant density acoustic wave equation based on adaptive variable grid technology is obtained.

3. The adaptive variable grid reverse time migration imaging method according to claim 2, characterized in that: The process of obtaining the initial migration velocity field is as follows: Search for the minimum velocity at each depth layer along the depth direction; The theoretically optimal longitudinal grid spacing dz(z) is calculated based on the minimum velocity in each depth layer and the number of sampling points in each wavelength; Where z is the depth, n is the number of sampling points in each wavelength, f is the frequency, and v is the sampling point. min is the minimum velocity for each depth layer; Take the depth z m , so that z m -z m-1 =dz(m), where m is a positive integer greater than 1 and equal to 1, and the initial migration velocity field is obtained.

4. The adaptive variable grid reverse time migration imaging method according to claim 2, characterized in that: The two-dimensional constant density acoustic wave equation based on the adaptive variable grid technology obtained by combining the mapping relationship and the two-dimensional constant density acoustic wave equation is specifically as follows: The mapping relation is differentiated to obtain its derivative, and the derivative of the mapping relation and the two-dimensional constant density acoustic wave equation are applied to obtain the two-dimensional constant density acoustic wave equation using an adaptive variable grid technology for extending the forward propagation wave field and the reverse propagation wave field.

5. The adaptive variable grid reverse time migration imaging method according to claim 4, characterized in that: The two-dimensional constant density acoustic wave equation for extending the wave field of forward propagation is as follows: The two-dimensional constant density acoustic wave equation used to extend the back-propagating wave field is as follows: Among them, v p (x,z) is the initial 2D migration velocity field, s(t) is the source wavelet, F(t) is the shot record source, x is the depth direction, z is the depth direction, and t is the time.

6. The adaptive variable grid reverse time migration imaging method according to claim 4, characterized in that: The two-dimensional constant density acoustic wave equation of the adaptive variable grid technology for extending the wave field of forward propagation is as follows: The two-dimensional constant density acoustic wave equation for the adaptive variable grid technique used to extend the back-propagating wave field is as follows: in, is the derivative of the mapping relationship, v pnew (x,z) is the variable grid offset velocity field.

7. The adaptive variable grid reverse time migration imaging method according to claim 1, characterized in that: The formula for performing source normalization imaging on the wave field propagating forward and the wave field propagating backward at the same time is as follows: Among them, F(x,z,t) is the wave field propagating forward along time, B(x,z,t) is the wave field propagating backward along time, and R im (x,z) is the imaging result.

8. An adaptive variable grid reverse time migration imaging system as claimed in claim 1, characterized in that: include: Wavefield extension module: It is used to extend the wavefield of the two-dimensional constant density acoustic wave equation along the forward propagation direction and the reverse propagation direction of time using the adaptive variable grid technology to obtain the forward propagation wavefield and the reverse propagation wavefield; Normalized imaging module: used to perform source normalized imaging on the forward propagating wave field and the reverse propagating wave field at the same time; Interpolation processing module: used to perform linear interpolation processing on the normalized imaging results to obtain the reverse time migration imaging section.

9. An electronic device, comprising: A processor; a memory for storing computer program instructions; characterized in that it is used to implement the steps of the adaptive variable grid reverse time migration imaging method as described in any one of claims 1 to 7 when executing the computer program.

10. A storage medium storing computer program instructions, characterized in that: When the computer program instructions are loaded and executed by a processor, the processor executes the adaptive variable grid reverse time migration imaging method according to any one of claims 1 to 7.

Images