Orthotropic parameter calculation method and device, electronic equipment and medium

Abstract

The application provides a method and device for calculating orthotropic anisotropy parameters, electronic equipment and a medium. The method for calculating orthotropic anisotropy parameters comprises the following steps: extracting residual moveout of an azimuthal gather; using the residual moveout to invert anisotropy parameters of an HTI medium; performing moveout correction on the azimuthal gather; and using amplitude inversion to invert anisotropy parameters of a VTI medium. The application considers the HTI medium and the VTI medium respectively from the azimuthal prestack gather, and inverts them respectively, thereby solving the problem of mutual interference and mutual influence in conventional one-time inversion, and further solving the problem of inaccurate inversion results, and opening up another road for stable, fast and high signal-to-noise ratio development of two-group fracture anisotropy prediction technology.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of seismic exploration, and is a kind of orthogonal fracture anisotropy parameter calculation method based on pre-stack azimuth gather, which separates HTI medium / VTI medium in orthogonal medium and respectively inverts. BACKGROUND

[0002] Fracture is an important migration channel and reservoir space of unconventional oil and gas reservoir, and therefore, the inversion of the azimuthal anisotropy of the fracture type reservoir is crucial for the prediction of reservoir production and the selection of favorable drilling areas. The development of fractures will make the reservoir show azimuthal anisotropy, which is reflected in the difference in amplitude and other properties of seismic data in different directions. Therefore, the pre-stack seismic inversion method based on azimuthal seismic data can obtain the parameters related to the reservoir fracture, and then predict the reservoir fracture.

[0003] The existing pre-stack fracture anisotropy inversion is mostly based on the assumption of HTI medium, and there are also assumptions based on TTI medium and orthogonal medium. The former two belong to single anisotropic medium, while the orthogonal medium belongs to two groups of orthogonal anisotropic medium assumption (see Figure 2 ), and is more complex. The use of traditional inversion methods similar to single medium assumption (such as AVAZ inversion method, Bayesian-based stochastic inversion method, etc.) will bring mutual influence of anisotropic medium, and due to the smaller difference in azimuthal amplitude, it will bring more complicated inversion steps, lower inversion accuracy, and weaker uniqueness.

[0004] Therefore, there is a need in the art to develop an orthogonal anisotropy parameter calculation method based on the difference of pre-stack azimuth gather, which considers HTI medium and VTI medium respectively from the azimuthal pre-stack gather, and respectively inverts, which solves the problem of mutual interference and mutual influence in one inversion, and further causes inaccurate inversion results, which opens up a new way for stable, fast and high signal-to-noise ratio two-group fracture anisotropy prediction technology. SUMMARY

[0005] In order to solve the problems of the prior art, the present application develops an orthogonal anisotropy parameter calculation method based on the difference of pre-stack azimuth gather, which considers HTI medium and VTI medium respectively from the azimuthal pre-stack gather, and respectively inverts, which solves the problem of mutual interference and mutual influence in one inversion, and further causes inaccurate inversion results, which opens up a new way for stable, fast and high signal-to-noise ratio two-group fracture anisotropy prediction technology, and provides a new solution for the efficient exploration and development of two-group fractures (such as vertical fractures developed in horizontal bedding in shale area) in actual exploration.

[0006] According to one aspect of the present invention, a method for calculating orthogonal anisotropy parameters is provided, comprising:

[0007] Extract the remaining time difference of the azimuth gather;

[0008] The anisotropy parameters of the HTI medium are retrieved using the remaining time difference;

[0009] Time difference correction is performed on the aforementioned azimuth gather;

[0010] The anisotropic parameters of the VTI medium are inverted using amplitude.

[0011] Furthermore, the method also includes azimuth confirmation and correction of the final inverted crack development orientation.

[0012] Furthermore, by using the fracture development direction in the well to correspond to the fracture development direction of the HTI medium, a 90° correction is performed to obtain the fracture development direction of the ORT orthogonal medium.

[0013] Furthermore, the remaining time difference is extracted from the offset front-side gather.

[0014] Furthermore, cross-correlation calculations are performed on the other azimuth gathers and the gather at 0 degrees azimuth, and the extracted time difference is the remaining time difference.

[0015] Furthermore, cross-correlation calculations or the remaining time difference are used for time difference correction.

[0016] Furthermore, the method of using amplitude inversion to retrieve the anisotropy parameters of the VTI medium includes substituting the anisotropy parameters of the HTI medium into the reflection coefficient equation representing the amplitude of the ORT medium to obtain the anisotropy parameters of the VTI medium. The specific equation is as follows:

[0017]

[0018]

[0019] Among them, I p and I s These represent the longitudinal wave impedance and the transverse wave impedance, respectively. All other terms in the formula are known terms, yielding the corresponding T. x T y , is the final anisotropic characterization parameter of the ORT medium.

[0020] According to another aspect of the present invention, an orthogonal anisotropy parameter calculation apparatus is provided, comprising:

[0021] Extraction unit, extract the remaining time difference of the azimuth gather;

[0022] The first inversion unit uses the remaining time difference to invert the anisotropic parameters of the HTI medium;

[0023] The leveling unit performs time difference correction on the azimuth gather;

[0024] The second inversion unit uses amplitude to invert the anisotropic parameters of the VTI medium.

[0025] According to another aspect of the present invention, an electronic device is provided, the electronic device comprising:

[0026] Memory, which stores executable instructions;

[0027] A processor that executes the executable instructions in the memory to implement the orthogonal anisotropy parameter calculation method.

[0028] According to another aspect of the present invention, a computer-readable storage medium is provided, the computer-readable storage medium storing a computer program that, when executed by a processor, implements the aforementioned method for calculating orthogonal anisotropy parameters.

[0029] The method of this invention starts from the pre-stack gather in the azimuth orientation and considers the HTI medium and VTI medium separately, and inverts them separately. This solves the problem of mutual interference and influence in conventional single inversion, which leads to inaccurate inversion results. This also opens up another way for stable, fast and high signal-to-noise ratio technology to carry out anisotropy prediction of two sets of fractures. Attached Figure Description

[0030] The above and other objects, features and advantages of this disclosure will become more apparent from the more detailed description of exemplary embodiments thereof taken in conjunction with the accompanying drawings, wherein like reference numerals generally denote like parts.

[0031] Figure 1 This is a flowchart of the two-step orthogonal anisotropy parameter calculation method of the present invention.

[0032] Figure 2 This is a pre-stack azimuth CRP gather for an orthogonal medium model according to an embodiment of the present invention.

[0033] Figure 3 These are the anisotropy parameters of the HTI medium obtained by inversion according to an embodiment of the present invention.

[0034] Figure 4 This is a pre-stack CRP gather after secondary time difference correction according to an embodiment of the present invention.

[0035] Figure 5 The results of orthogonal medium fracture prediction based on pre-stack azimuth CRP gathers according to an embodiment of the present invention are shown. Detailed Implementation

[0036] Preferred embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0037] This invention is a two-step crack anisotropy parameter inversion technique based on pre-stack gather data, which considers HTI and VTI media separately and inverts them separately.

[0038] Specifically, TI (Transverse Isotroic) is short for transversely isotropic medium, HTI (Horizontal Transverse Isotroic) is short for transversely isotropic medium with a horizontal axis of symmetry, VTI (Vertical Transverse Isotroic) is short for transversely isotropic medium with a vertical axis of symmetry, and ORT (orthogonal Isotroic) is an orthogonal medium. There are various types of orthogonal media. The orthogonal medium of this invention refers to the type that is orthogonal to HTI and TTI.

[0039] Furthermore, the front-stack azimuth gather in this invention can be either an azimuth angle gather or an azimuth offset gather. In practical applications, azimuth angle gathers and azimuth offset gathers are often two different representations of the same gather data, and they can be converted to each other: the first-hand seismic data collected in actual field seismic exploration is in the form of azimuth offset gathers, but azimuth angle gathers are often used in later inversion applications. Azimuth offset gathers can be converted into azimuth angle gathers using velocity data from seismic exploration.

[0040] The method of this invention separates the HTI medium and VTI medium in orthogonal media and performs inversion step by step. For the two sets of anisotropic media (HTI medium / VTI medium) in orthogonal media, pre-stack gathers are used to treat the seismic responses of the gathers of the two media differently and invert them separately, thereby obtaining the two sets of anisotropic parameters in the entire orthogonal media. This is a core innovation of this invention.

[0041] Specifically, such as Figure 1 As shown, the present invention provides a method for calculating orthogonal anisotropy parameters, comprising:

[0042] Extract the remaining time difference of the azimuth gather;

[0043] The anisotropy parameters of the HTI medium are retrieved using the remaining time difference;

[0044] Time difference correction is performed on the aforementioned azimuth gather;

[0045] The anisotropic parameters of the VTI medium are inverted using amplitude.

[0046] Specifically, in orthogonal (HTI / VTI) media, for pre-stack seismic gathers, velocity azimuth anisotropy (also known as velocity-azimuth anisotropy) is only related to the HTI medium, while amplitude anisotropy is closely related to both the HTI and VTI media. Therefore, the approach of this invention is to first invert the time difference (velocity) in the pre-stack seismic gathers to calculate the anisotropy parameters of the HTI medium, and then use amplitude inversion to retrieve the anisotropy parameters of the VTI medium. This two-step inversion method is simple, convenient, and easy to understand, and can greatly reduce the uncertainty caused by directly using a single amplitude anisotropy inversion.

[0047] Further, the pre-stack azimuth gathers after migration are first selected to extract the remaining time difference. Commonly selected pre-stack azimuth gathers include: pre-stack azimuth CMP gathers (azimuth hidden in the trace head, azimuth angles unevenly distributed), pre-stack azimuth-specific CRP gathers (azimuth angles in the trace head, azimuth angles evenly distributed), and pre-stack all-around imaging gathers (azimuth angles in the trace head, azimuth angles unevenly distributed). All of these azimuth gathers can be used in this invention. The preferred prerequisite is that the seismic data is wide-azimuth, large-offset seismic exploration data, i.e., it has a wide range of incident and azimuth angles (generally requiring at least four azimuth angles within 180 degrees and an incident angle of at least 30 degrees).

[0048] Next, the residual time difference of the azimuth gathers is extracted. From the basic theories of VTI and HTI media, we know that for a single VTI medium, there is no time difference for any azimuth incident gathers. Therefore, whether it's a 0-degree azimuth gather or a 90-degree azimuth gather, there is no residual time difference at either the far or near offset for the reflection point (imaging point). In other words, all seismic waves are straight. For a single HTI medium, there is also no time difference for azimuth gathers at 0 degrees. As the azimuth angle increases, the time difference increases to its maximum (vertical direction) at 90 degrees; from 90 degrees to 180 degrees, the residual time difference gradually decreases again.

[0049] In actual seismic data, it may not be possible to obtain seismic gathers with an absolute azimuth of 0 degrees. According to the theory of HTI medium, as long as the azimuth is perpendicular to the azimuth of the maximum time difference, it can be regarded as a 0-degree azimuth. This treatment is appropriate in actual seismic data.

[0050] The anisotropy parameter η of the HTI medium can be derived by using the time difference, and it is a non-ellipticity.

[0051] To calculate all anisotropic parameters of orthogonal media using azimuth amplitude, a second time-difference correction (gather flattening) is required for the front-stack azimuth gather. Amplitude inversion of anisotropic parameters is based on the azimuth difference of anisotropy. If there is a time difference, the time difference itself will cause differences in amplitude, thus leading to inaccuracies in the inversion results. Therefore, time-difference correction is necessary.

[0052] The flattening algorithm can be consistent with the steps described above for extracting the remaining time difference, using cross-correlation calculation. Cross-correlation involves performing correlation calculations on each pair of seismic traces using a sliding time window. The maximum correlation value indicates the best correlation between the two seismic traces. This time difference is recorded and used to correct the calculated seismic traces. Alternatively, when flattening the traces after extracting the remaining time difference, the remaining time difference can be directly used to flatten the traces. However, for ease of understanding, practical application, and standardization in real-world data, and because trace flattening is crucial for subsequent inversion, a secondary time difference correction (trace flattening) is performed on the pre-stack traces.

[0053] Finally, the anisotropic parameters of the VTI medium are inverted using amplitude. With the previously inverted anisotropic parameters, combined with known information from the local well, such as the P-wave to S-wave velocity ratio, the corresponding anisotropic parameters can be calculated. Substituting these anisotropic parameters for the HTI medium into the reflection coefficient equation representing the amplitude of the ORT medium, the anisotropic parameters of the VTI medium can be obtained, thus characterizing the degree of horizontal fracture development. The specific inversion process can be implemented using various nonlinear inversion methods such as genetic algorithms and simulated annealing.

[0054] Furthermore, since the initial survey line direction is not necessarily true north, a secondary correction is needed to the fracture development orientation obtained from the final inversion. The fracture development orientation in the well can be obtained by using the fracture development orientation in the well to correspond to the fracture development orientation in the inverted HTI medium and performing a 90° correction.

[0055] To facilitate understanding of the solutions and effects of the embodiments of the present invention, specific application examples are given below. Those skilled in the art should understand that these examples are merely for illustrative purposes and any specific details therein are not intended to limit the invention in any way.

[0056] Example 1

[0057] To make the method of the present invention clearer and more understandable, refer to Figures 2-5 The embodiments of the present invention are described in detail below. Figure 2 A schematic diagram showing the distribution of CDP points in post-stack data for a certain seismic work area; Figure 3This is a profile of the attributes of the post-stack seismic data in four different orientations; Figure 4 The inversion yielded the crack development intensity and crack development orientation. Figure 5 The results are based on the orthogonal medium fracture prediction results using pre-stack azimuth CRP gathers.

[0058] like Figure 2 As shown, this embodiment selects a pre-stack azimuth CRP gather of an orthogonal medium model (which is the migration imaging result of the seismic shot record from numerical simulation after normal processing). Figure 1 The image in the middle is a CRP gather after offset imaging, with azimuth angles from left to right being 15°, 30°, 45°...345°. Within one azimuth angle, the incident angles are 0°, 2°, 4°...38°.

[0059] Next, the remaining time difference of the azimuth gather is extracted. This embodiment refers to... Figure 2 This section introduces how to extract the remaining time difference from the azimuth gather.

[0060] contrast Figure 2 As can be seen from several azimuth gathers, the 15-degree azimuth gather is basically flat with no residual time difference. Subsequently, as the azimuth angle increases, the time difference also increases, reaching its maximum at 105 degrees, and then decreasing. The time difference changes from 180 degrees to 360 degrees are consistent with those from 0 degrees to 180 degrees.

[0061] Therefore in Figure 2 In this study, gathers with an azimuth of 15 degrees are selected as standard gathers, and gathers with an azimuth of 105 degrees are selected as 90-degree gathers. In actual seismic data, it may often be impossible to obtain seismic gathers with an absolute azimuth of 0 degrees. According to the theory of HTI medium, as long as the azimuth is perpendicular to the azimuth of the maximum time difference, it can be regarded as a 0-degree azimuth. This treatment is appropriate in actual seismic data.

[0062] Next, the gathers from other azimuths are cross-correlated with the gather from the 0-degree azimuth, and the extracted time difference is the residual time difference required for inversion. The specific process for extracting the time difference can be found in the following patent: Patent No. ZL201010521377.3, A Method for Detecting Pre-stack Fractures in Seismic Reservoir Prediction, which will not be elaborated upon here.

[0063] With the time difference in mind, the anisotropy parameters of the HTI medium can be retrieved. Refer to patent ZL201010521377.3, which describes how the anisotropy parameters of a TI medium at any tilt angle can be calculated. The HTI medium in this invention is a TI medium with a 90-degree tilt angle, a type of fixed-angle TTI medium; therefore, the method described in the cited patent can also be used.

[0064] The anisotropy parameter η of the HTI medium can be derived by using the time difference, and it is a non-ellipticity.

[0065] Furthermore, in order to calculate all anisotropic parameters of the orthogonal medium using azimuth amplitude, a secondary time-difference correction (gather flattening) needs to be performed on the pre-stack azimuth gather, such as... Figure 4 As shown.

[0066] The flattening algorithm can be consistent with the steps described above for extracting the remaining time difference, using cross-correlation calculation. Alternatively, when flattening the gathers after extracting the remaining time difference, the gathers can be flattened directly using the remaining time difference. For ease of understanding, operation, and standardization in actual data, and because gather flattening is crucial for subsequent inversion, a secondary time difference correction (gather flattening) is performed on the pre-stack gathers.

[0067] Next, the anisotropy parameters of the VTI medium are inverted using amplitude. With the previously inverted anisotropy parameters, combined with known information from the well in the area, such as the P-wave to S-wave velocity ratio, the corresponding anisotropy parameters can be calculated. Substituting these anisotropy parameters for the HTI medium into the reflection coefficient equation representing the amplitude of the ORT medium, the anisotropy parameters of the VTI medium can be obtained, thus characterizing the degree of horizontal fracture development.

[0068] The specific equation is:

[0069]

[0070]

[0071] Where Ip and Is represent the P-wave impedance and S-wave impedance, respectively, and all other terms in the formula are known terms, which are common parameters in the seismic reflection coefficient equation and are familiar to those skilled in the art; such as R pp The amplitude of the longitudinal wave reflection is θ, the incident angle is φ, and the azimuth angle is φ, which will not be elaborated further in this paper.

[0072] Get the corresponding T x T y , which are the anisotropic characterization parameters of the final ORT medium. The specific inversion process can be implemented using various nonlinear inversion methods such as genetic algorithms and simulated annealing.

[0073] Finally, the orientation is confirmed and corrected. Since the initial survey line direction is not necessarily true north, the orientation of the crack development obtained from the final inversion is corrected a second time.

[0074] For example, the fracture development direction in the well can be used to correspond to the fracture development direction of the inverted HTI medium, and a 90° correction can be performed to obtain the fracture development direction of the ORT orthogonal medium.

[0075] Example 2

[0076] This embodiment discloses an orthogonal anisotropy parameter calculation device, comprising:

[0077] Extraction unit, extract the remaining time difference of the azimuth gather;

[0078] The first inversion unit uses the remaining time difference to invert the anisotropic parameters of the HTI medium;

[0079] The leveling unit performs time difference correction on the azimuth gather;

[0080] The second inversion unit uses amplitude to invert the anisotropic parameters of the VTI medium.

[0081] The extraction unit selects the offset front-stack azimuth gather, extracts the residual time difference of the azimuth gather, and sends the extraction result to the first inversion unit. The residual time difference is used to invert the anisotropy parameters of the HTI medium. The flattening unit performs time difference correction on the azimuth gather. The second inversion unit substitutes the anisotropy parameters of the HTI medium obtained by the first inversion unit into the reflection coefficient equation representing the amplitude of the ORT medium to obtain the anisotropy parameters of the VTI medium, thus characterizing the development degree of horizontal cracks.

[0082] Example 3

[0083] This embodiment provides an electronic device including: a memory storing executable instructions; and a processor that executes the executable instructions in the memory to implement the above-described orthogonal anisotropy parameter calculation method.

[0084] An electronic device according to an embodiment of the present disclosure includes a memory and a processor.

[0085] This memory is used to store non-transitory computer-readable instructions. Specifically, the memory may include one or more computer program products, which may include various forms of computer-readable storage media, such as volatile memory and / or non-volatile memory. The volatile memory may, for example, include random access memory (RAM) and / or cache memory. The non-volatile memory may, for example, include read-only memory (ROM), hard disk, flash memory, etc.

[0086] The processor may be a central processing unit (CPU) or other form of processing unit with data processing capabilities and / or instruction execution capabilities, and may control other components in the electronic device to perform desired functions. In one embodiment of this disclosure, the processor is used to execute computer-readable instructions stored in the memory.

[0087] Those skilled in the art will understand that, in order to solve the technical problem of how to achieve a good user experience, this embodiment may also include well-known structures such as communication buses and interfaces, and these well-known structures should also be included within the protection scope of this disclosure.

[0088] For a detailed description of this embodiment, please refer to the corresponding descriptions in the foregoing embodiments, which will not be repeated here.

[0089] Example 4

[0090] This disclosure provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the orthogonal anisotropy parameter calculation method.

[0091] A computer-readable storage medium according to embodiments of the present disclosure stores non-transitory computer-readable instructions. When these non-transitory computer-readable instructions are executed by a processor, all or part of the steps of the methods described in the foregoing embodiments of the present disclosure are performed.

[0092] The aforementioned computer-readable storage media include, but are not limited to: optical storage media (e.g., CD-ROM and DVD), magneto-optical storage media (e.g., MO), magnetic storage media (e.g., magnetic tape or portable hard drive), media with built-in rewritable non-volatile memory (e.g., memory card), and media with built-in ROM (e.g., ROM cartridge).

[0093] Those skilled in the art should understand that the above description of the embodiments of the present invention is only intended to illustrate the beneficial effects of the embodiments of the present invention, and is not intended to limit the embodiments of the present invention to any of the examples given.

[0094] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for calculating orthogonal anisotropy parameters, characterized in that, include: Extract the remaining time difference of the azimuth gather; The anisotropy parameters of the HTI medium are retrieved using the remaining time difference; Time difference correction is performed on the aforementioned azimuth gather; Anisotropic parameters of VTI media are inverted using amplitude; Among them, the other azimuth gathers are cross-correlated with the gathers at 0 degrees azimuth, and the extracted time difference is the remaining time difference. Among them, cross-correlation calculation or time difference correction is performed using the remaining time difference; The method of using amplitude inversion to retrieve the anisotropy parameters of the VTI medium includes substituting the anisotropy parameters of the HTI medium into the reflection coefficient equation representing the amplitude of the ORT medium to obtain the anisotropy parameters of the VTI medium. The specific equation is as follows: Among them, I p and I s These represent the longitudinal wave impedance and the transverse wave impedance, respectively. All other terms in the formula are known terms, yielding the corresponding T. x T y , is the final anisotropic characterization parameter of the ORT medium.

2. The method for calculating orthogonal anisotropy parameters according to claim 1, characterized in that, Further steps include confirming and correcting the orientation of the crack development obtained from the final inversion.

3. The method for calculating orthogonal anisotropy parameters according to claim 2, characterized in that, Using the fracture development direction in the well, corresponding to the fracture development direction of the HTI medium, a 90° correction is performed to obtain the fracture development direction of the ORT orthogonal medium.

4. The method for calculating orthogonal anisotropy parameters according to claim 1, characterized in that, Select the offset front-side gather to extract the remaining time difference.

5. A device for calculating orthogonal anisotropic parameters, characterized in that, include: Extraction unit, extract the remaining time difference of the azimuth gather; The first inversion unit uses the remaining time difference to invert the anisotropic parameters of the HTI medium; The leveling unit performs time difference correction on the azimuth gather; The second inversion unit uses amplitude to invert the anisotropic parameters of the VTI medium; Among them, the other azimuth gathers are cross-correlated with the gathers at 0 degrees azimuth, and the extracted time difference is the remaining time difference. Among them, cross-correlation calculation or time difference correction is performed using the remaining time difference; The method of using amplitude inversion to retrieve the anisotropy parameters of the VTI medium includes substituting the anisotropy parameters of the HTI medium into the reflection coefficient equation representing the amplitude of the ORT medium to obtain the anisotropy parameters of the VTI medium. The specific equation is as follows: Among them, I p and I s These represent the longitudinal wave impedance and the transverse wave impedance, respectively. All other terms in the formula are known terms, yielding the corresponding T. x T y , is the final anisotropic characterization parameter of the ORT medium.

6. An electronic device, characterized in that, The electronic device includes: Memory, which stores executable instructions; A processor that executes the executable instructions in the memory to implement the orthogonal anisotropy parameter calculation method according to any one of claims 1-4.

7. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the orthogonal anisotropy parameter calculation method according to any one of claims 1-4.

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