Three-dimensional seismic forward modeling method and system for carbonate karst cave reservoir

Abstract

The application discloses a kind of three-dimensional seismic forward modeling methods and systems for carbonate karst cave reservoir, belong to the field of oil and gas exploration seismic forward modeling.The method of fusing the three-dimensional P-wave velocity body of the carved-out karst cave reservoir quantitatively into seismic interval velocity establishes three-dimensional seismic forward modeling P-wave velocity model for karst cave reservoir, and the method of carrying out seismic forward modeling based on the model;In the process of three-dimensional seismic forward modeling for carbonate karst cave reservoir, the seismic inversion P-wave impedance body after carving by well logging petrophysical analysis is introduced into the process of establishing P-wave velocity model for the first time, so that the established karst model is more in line with geological understanding and actual situation, and the established seismic forward modeling P-wave velocity model is more accurate.The three-dimensional seismic forward modeling P-wave velocity model of carbonate karst cave reservoir obtained by the application can more truly represent the shape and size of actual carbonate karst cave reservoir compared with the model made by other traditional methods.

Description

Technical Field

[0001] This invention belongs to the field of seismic forward modeling in oil and gas exploration, and relates to a three-dimensional seismic forward modeling method and system for carbonate karst reservoirs. Background Technology

[0002] Seismic forward modeling is a technique used in seismic interpretation to identify unusual seismic anomalies. It involves simulating earthquakes using an ideal geological model, guided by seismic theory, to achieve the forward modeling of the seismic response of geological bodies. [1] The P-wave velocity model, as the most fundamental model data in seismic forward modeling, directly affects the quality of the seismic forward modeling results. Typically, a P-wave velocity model is established based on actual geological knowledge, and then seismic forward modeling is carried out based on the established P-wave velocity model to obtain the final seismic data. This allows for an understanding of the seismic response of geological bodies and the acquisition of useful conclusions to guide oil and gas reservoir exploration and development.

[0003] Cavern reservoirs are the main reservoir type for fractured-cavity oil and gas reservoirs in carbonate rocks. [3] For three-dimensional seismic forward modeling of carbonate karst reservoirs, it is common practice to add regularly shaped three-dimensional volumes to conventional well interpolated P-wave velocity volumes, seismic layer velocity volumes, or P-wave velocity volumes based on layer filling to represent the karst reservoir. [2] Then, based on this, seismic forward modeling is carried out to simulate the seismic response of the three-dimensional cave reservoir model. Although this method can solve the problem of three-dimensional seismic forward modeling of cave reservoirs to a certain extent, the cave reservoir in the established P-wave velocity model is quite different from the actual cave reservoir. It is just a simple substitute for the actual cave reservoir. The shape and size of the cave reservoir are quite different from the actual cave reservoir. The results of seismic forward modeling based on this three-dimensional P-wave velocity model cannot simulate the seismic response of the actual cave reservoir. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing three-dimensional seismic forward modeling method, which cannot establish a model that is more consistent with the actual karst reservoir and cannot numerically simulate the seismic response of the actual karst reservoir, the present invention aims to provide a three-dimensional seismic forward modeling method and system for carbonate karst reservoirs.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] A three-dimensional seismic forward modeling method for carbonate karst cave reservoirs includes the following steps:

[0007] Step 1) Obtain seismic data and seismic layer velocity data within the study area, and perform seismic inversion based on the seismic data within the study area to obtain the inverted P-wave impedance volume;

[0008] Step 2) Determine the range and threshold of the longitudinal wave impedance of the cavern reservoir;

[0009] Step 3) Quantitatively sculpt the cavern reservoir by inverting the P-wave impedance volume according to the threshold, and obtain the three-dimensional P-wave velocity volume of the cavern reservoir;

[0010] Step 4) Fuse the three-dimensional P-wave velocity volume of the karst reservoir with the seismic layer velocity data to obtain a three-dimensional seismic forward modeling P-wave velocity model;

[0011] Step 5) Based on the three-dimensional seismic forward modeling P-wave velocity model, select a numerical simulation method to perform three-dimensional seismic forward modeling simulation.

[0012] Preferably, step 2) specifically involves: obtaining the well logging rock physics analysis results within the research area, and determining the range and threshold of the longitudinal wave impedance of the cavern reservoir based on the well logging rock physics analysis results.

[0013] Preferably, the specific process of step 3) is as follows:

[0014] Based on the threshold, the P-wave impedance volume obtained by seismic inversion is used to quantitatively sculpt the cavern reservoir, resulting in the three-dimensional P-wave impedance volume of the cavern reservoir.

[0015] Obtain the average density of the karst reservoirs statistically analyzed on the surface within the research area;

[0016] The three-dimensional P-wave velocity volume of the cavern reservoir is obtained by dividing the three-dimensional P-wave impedance volume of the cavern reservoir by the average density of the cavern reservoir.

[0017] Preferably, in step 3), the specific process of quantitative carving of the karst reservoir is as follows:

[0018] The P-wave impedance values ​​within the range of the karst reservoir are retained, while other values ​​are discarded, thus obtaining the three-dimensional P-wave impedance volume of the karst reservoir.

[0019] Preferably, the specific process of step 5) is as follows:

[0020] Based on a 3D seismic forward modeling P-wave velocity model, 3D seismic forward modeling simulation is carried out.

[0021] When only the vertical resolution of the karst cave exists, a convolution-based numerical simulation method is used;

[0022] When only the lateral resolution of the cave exists, or when both the longitudinal and lateral resolutions of the cave exist simultaneously, a forward modeling method based on the wave equation is used.

[0023] A three-dimensional seismic forward modeling system for carbonate karst cave reservoirs includes:

[0024] The data acquisition module is used to acquire seismic data and seismic layer velocity data within the research area;

[0025] The seismic inversion module interacts with the data acquisition module to perform seismic inversion based on seismic data within the research area, and obtain the inverted P-wave impedance volume.

[0026] The longitudinal wave impedance module for cavern reservoirs is used to determine the range and threshold of longitudinal wave impedance in cavern reservoirs.

[0027] The quantitative carving module interacts with the longitudinal wave impedance module of the karst reservoir to quantitatively carve the karst reservoir based on the inverted longitudinal wave impedance volume, thereby obtaining the three-dimensional longitudinal wave velocity volume of the karst reservoir.

[0028] The model building module interacts with the quantitative carving module and the data acquisition module respectively, and fuses the three-dimensional P-wave velocity volume of the karst reservoir with the seismic layer velocity to obtain a three-dimensional seismic forward modeling P-wave velocity model.

[0029] The simulation module interacts with the model building module. Based on the three-dimensional seismic forward modeling P-wave velocity model, it selects numerical simulation methods to perform three-dimensional seismic forward modeling simulations for carbonate karst cave reservoirs.

[0030] Preferably, the quantitative engraving module includes an engraving unit, a density acquisition unit, and a data processing unit;

[0031] The carving unit is used to quantitatively carve the cavern reservoir based on the P-wave impedance volume obtained from seismic inversion according to the threshold, and obtain the three-dimensional P-wave impedance volume of the cavern reservoir.

[0032] The density acquisition unit is used to obtain the average density of the cavern reservoir statistically analyzed on the surface within the research area.

[0033] The data processing unit is used to obtain the three-dimensional P-wave velocity volume of the cavern reservoir by dividing the three-dimensional P-wave impedance volume of the cavern reservoir by the average density of the cavern reservoir.

[0034] An apparatus includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the steps of the method described above.

[0035] A computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the above-described method.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] This invention discloses a three-dimensional seismic forward modeling method for carbonate karst reservoirs. It proposes for the first time a method to integrate the quantitatively sculpted three-dimensional P-wave velocity volume of the karst reservoir into the seismic layer velocity to establish a three-dimensional seismic forward modeling P-wave velocity model for karst reservoirs, and then perform seismic forward modeling based on this model. In the three-dimensional seismic forward modeling process for carbonate karst reservoirs, for the first time, the seismic inversion P-wave impedance volume sculpted through well logging rock physics analysis is introduced into the P-wave velocity model establishment process, making the established karst model more consistent with geological understanding and actual conditions. The P-wave velocity model is more accurate because, based on well logging data, cavernous reservoir sections are generally short and the amount of logging data obtained is limited, making it difficult to statistically determine a strict linear relationship between wellbore P-wave impedance and P-wave velocity. Therefore, in the process of converting the sculpted three-dimensional P-wave impedance volume of the cavernous reservoir into a P-wave velocity volume, the method of dividing the three-dimensional P-wave impedance volume of the cavernous reservoir by the average density statistically obtained from the wellbore reservoir section is used to obtain the three-dimensional P-wave velocity volume of the cavernous reservoir. Compared with the traditional method of converting using the linear relationship between wellbore P-wave impedance and P-wave velocity, this method better preserves the relative relationship of the P-wave velocity volume and is also simpler. The three-dimensional seismic forward modeling P-wave velocity model of carbonate cavernous reservoirs obtained by this invention can more realistically represent the morphology and size of actual carbonate cavernous reservoirs compared to models produced by other traditional methods.

[0038] Furthermore, in the process of establishing a three-dimensional seismic forward modeling P-wave velocity model for karst reservoirs, this invention employs a method of converting the quantitatively sculpted three-dimensional P-wave impedance volume of the karst reservoir into a P-wave velocity volume. This method enables the determination of the boundary and P-wave velocity values ​​of the three-dimensional P-wave velocity volume of the karst reservoir. The boundary and P-wave velocity values ​​of the karst reservoir quantitatively characterized by this method are more accurate, providing good basic data for the subsequent establishment of a three-dimensional seismic forward modeling P-wave velocity model for karst reservoirs.

[0039] Furthermore, in order to overcome the problems of limited logging in karst reservoirs and the difficulty in statistically determining the linear relationship between P-wave velocity and P-wave impedance in karst reservoir sections, a method is proposed to obtain the three-dimensional P-wave velocity volume of karst reservoirs by dividing the three-dimensional P-wave impedance volume of the karst reservoir by the average density statistically obtained from the karst reservoir section above ground. This method maintains the relative relationship of velocity values ​​within the three-dimensional P-wave velocity volume of the karst reservoir and is also simpler. Attached Figure Description

[0040] Figure 1 Histogram of P-wave impedance distribution in cavern reservoir and surrounding rock sections, as statistically analyzed from wells in a carbonate rock research area.

[0041] Figure 2 A three-dimensional display of the inverted P-wave impedance and the three-dimensional P-wave velocity volume of the cave reservoir quantitatively sculpted based on the seismically inverted P-wave impedance;

[0042] Figure 3 A three-dimensional display of the seismic velocity volume in the work area;

[0043] Figure 4 This is a three-dimensional seismic forward modeling P-wave velocity model of carbonate karst reservoirs obtained by integrating the three-dimensional P-wave velocity volume of the karst reservoir into the seismic layer velocity.

[0044] Figure 5 Based on Figure 4 One of the seismic profiles obtained from the forward seismic modeling of the medium velocity model. Detailed Implementation

[0045] The present invention will now be described in further detail with reference to the accompanying drawings:

[0046] Example 1

[0047] A three-dimensional seismic forward modeling method for carbonate karst cave reservoirs includes the following steps:

[0048] Step 1) Obtain seismic data within the study area, perform seismic inversion based on the seismic data within the study area, and obtain the inverted P-wave impedance volume;

[0049] Step 2) Determine the range and threshold of the longitudinal wave impedance of the cavern reservoir;

[0050] Step 3) Quantitatively sculpt the cavern reservoir by inverting the P-wave impedance volume according to the threshold, and obtain the three-dimensional P-wave velocity volume of the cavern reservoir;

[0051] Step 4) Fuse the three-dimensional P-wave velocity volume of the karst reservoir with the seismic layer velocity to obtain a three-dimensional seismic forward modeling P-wave velocity model;

[0052] Step 5) Perform three-dimensional seismic forward modeling based on the three-dimensional seismic forward modeling P-wave velocity model.

[0053] Example 2

[0054] A three-dimensional seismic forward modeling method for carbonate karst cave reservoirs includes the following steps:

[0055] Step 1: Perform seismic inversion on the seismic data within the study area to obtain the inverted P-wave impedance volume;

[0056] Step 2: Based on the results of well logging rock physics analysis in the study area, determine the range and threshold of the longitudinal wave impedance of the karst reservoir;

[0057] Step 3: Quantitatively sculpt the cavern reservoir by using the P-wave impedance volume obtained from seismic inversion based on the threshold. That is, P-wave impedance values ​​within the P-wave impedance range of the cavern reservoir are retained, while other values ​​are discarded, thus obtaining the three-dimensional P-wave impedance volume of the cavern reservoir.

[0058] Step 4: Divide the three-dimensional P-wave impedance volume of the cavern reservoir by the average density of the cavern reservoir section statistically analyzed on the surface within the work area to obtain the three-dimensional P-wave velocity volume of the cavern reservoir.

[0059] Step 5: Fuse the obtained three-dimensional P-wave velocity volume of the karst reservoir with the seismic layer velocity to obtain the final three-dimensional seismic forward modeling P-wave velocity model of the carbonate karst reservoir.

[0060] It should be noted that this invention allows for the selection of numerical simulation methods based on actual needs and efficiency. If only the vertical resolution of the cave is considered, a convolution-based numerical simulation method is used. If the lateral resolution of the cave is considered, or both the vertical and lateral resolutions are considered simultaneously, a wave equation-based numerical simulation method is used.

[0061] Example 3

[0062] This embodiment utilizes seismic data from a specific work area. First, well logging rock physics analysis is performed on the wells within the work area. Histogram analysis is used to determine the threshold corresponding to the boundary between the P-wave impedance of the cavernous reservoir and the P-wave impedance of the surrounding rock. 16000 g / cm³*m / s is the threshold for the P-wave impedance of the cavernous reservoir; values ​​less than 16000 g / cm³*m / s indicate a cavernous reservoir. Figure 1 As shown. Figure 1 In the diagram, the horizontal axis represents the longitudinal wave impedance, with units of g / cm. 3 *m / s, the vertical axis represents the frequency of P-wave impedance values. It can be seen that the distribution range of P-wave impedance values ​​in cavernous reservoirs is significantly different from that in the surrounding rock. Using the threshold obtained from well logging rock physics analysis to sculpt the seismic inversion P-wave impedance volume, the P-wave impedance volume and boundary of the cavernous reservoir are obtained, as shown below. Figure 2 As shown. The three-dimensional P-wave impedance volume of the karst reservoir is then divided by the average density of the karst reservoir segment obtained from well statistics in the work area to obtain the seismic forward modeling P-wave velocity volume of the karst reservoir. Figure 3 To study the seismic layer velocities collected within the work area, a three-dimensional P-wave velocity volume of the sculpted cavern reservoir was integrated into the seismic layer velocities, based on these velocities. Specifically, the areas where the seismic layer velocity volume overlapped with the sculpted cavern reservoir P-wave velocity volume were replaced with the sculpted cavern reservoir P-wave velocity volume, forming the final three-dimensional seismic forward model of the carbonate cavern reservoir. Figure 4 As shown. This example requires simulating the effect of actual seismic imaging, that is, considering both longitudinal and lateral resolution. Therefore, a seismic forward modeling method based on the wave equation is used, as follows: Figure 5 As shown, it is based on Figure 4 A seismic profile obtained from forward seismic modeling using a medium-velocity model.

[0063] Example 4

[0064] A three-dimensional seismic forward modeling system for carbonate karst cave reservoirs includes:

[0065] The data acquisition module is used to acquire seismic data within the research area;

[0066] The seismic inversion module interacts with the data acquisition module to perform seismic inversion based on seismic data within the research area, and obtain the inverted P-wave impedance volume.

[0067] The longitudinal wave impedance module for cavern reservoirs is used to determine the range and threshold of longitudinal wave impedance in cavern reservoirs.

[0068] The quantitative carving module interacts with the longitudinal wave impedance module of the karst reservoir to quantitatively carve the karst reservoir based on the inverted longitudinal wave impedance volume, thereby obtaining the three-dimensional longitudinal wave velocity volume of the karst reservoir.

[0069] The model building module interacts with the quantitative carving module to fuse the three-dimensional P-wave velocity volume of the karst reservoir with the seismic layer velocity to obtain a three-dimensional seismic forward modeling P-wave velocity model.

[0070] The simulation module interacts with the model building module to perform three-dimensional seismic forward modeling simulations of carbonate karst cave reservoirs based on a three-dimensional seismic forward modeling P-wave velocity model.

[0071] Example 5

[0072] If the method of this invention is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments of this invention can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable storage medium includes permanent and non-permanent, removable and non-removable media, and information storage can be implemented by any method or technology. Information can be computer-readable instructions, data structures, program modules, or other data. It should be noted that the content contained in the computer-readable medium can be appropriately added or subtracted according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electrical carrier signals and telecommunication signals. The computer storage medium can be any available medium or data storage device that a computer can access, including but not limited to magnetic storage (e.g., floppy disk, hard disk, magnetic tape, magneto-optical disk (MO)), optical storage (e.g., CD, DVD, BD, HVD), and semiconductor storage (e.g., ROM, EPROM, EEPROM, non-volatile memory (NAND FLASH), solid-state drive (SSD)).

[0073] Example 6

[0074] In an exemplary embodiment, a computer device is also provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of the deep neural network-based channel estimation method. The processor may be a central processing unit (CPU), or it may be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc.

[0075] In summary, by fusing the quantitatively sculpted three-dimensional P-wave velocity volume of the carbonate karst cavern reservoir with seismic layer velocities, a three-dimensional seismic forward modeling P-wave velocity model of the carbonate karst cavern reservoir is obtained. Compared with models produced by other traditional methods, the three-dimensional seismic forward modeling P-wave velocity model of the carbonate karst cavern reservoir obtained by this invention can more realistically represent the morphology and size of the actual carbonate karst cavern reservoir. This invention employs a quantitative sculpting method of the cavern reservoir based on seismic inversion to characterize the carbonate karst cavern reservoir. The sculpted results are converted into P-wave velocities and fused into the seismic layer velocities of the study area. This achieves the establishment of a three-dimensional seismic forward modeling P-wave velocity model that more closely matches the characteristics of real underground cavern reservoirs. The seismic response obtained by using this model in seismic forward simulation studies is more consistent with the actual seismic response, which is helpful for correctly understanding the seismic response of carbonate karst cavern reservoirs.

[0076] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

[0077] References:

[0078] [1] Zhou Ziqun. 2016. Identification of erosion points in Shahejie Formation in Zhuangxi area using forward model[J]. Oil & Gas Geophysics, 14(4): 39-42.

[0079] [2] Zhang Junhua et al. 2015. Study on the relationship between seismic acquisition parameters and imaging of cavernous reservoirs [J]. Petroleum Geophysical Exploration, 50(4): 573-579.

[0080] [3] Wen Huan. Analysis of the filling properties of karst caves based on forward modeling [J]. Technological Research, 2016(8): 86-87.

Claims

1. A three-dimensional seismic forward modeling method for carbonate karst cave reservoirs, characterized in that, Includes the following steps: Step 1) Obtain seismic data and seismic layer velocity data within the study area, and perform seismic inversion based on the seismic data within the study area to obtain the inverted P-wave impedance volume; Step 2) Determine the range and threshold of the longitudinal wave impedance of the cavern reservoir; Step 3) Quantitatively sculpt the cavern reservoir by inverting the P-wave impedance volume according to the threshold, and obtain the three-dimensional P-wave velocity volume of the cavern reservoir; Step 4) Fuse the three-dimensional P-wave velocity volume of the karst reservoir with the seismic layer velocity data to obtain a three-dimensional seismic forward modeling P-wave velocity model; Step 5) Based on the three-dimensional seismic forward modeling P-wave velocity model, select a numerical simulation method to perform three-dimensional seismic forward modeling simulation; The specific process of step 3) is as follows: Based on the threshold, the P-wave impedance volume obtained by seismic inversion is used to quantitatively sculpt the cavern reservoir, resulting in the three-dimensional P-wave impedance volume of the cavern reservoir. Obtain the average density of the karst reservoirs statistically analyzed on the surface within the research area; The three-dimensional P-wave velocity volume of the cavern reservoir is obtained by dividing the three-dimensional P-wave impedance volume of the cavern reservoir by the average density of the cavern reservoir.

2. The three-dimensional seismic forward modeling method for carbonate karst cave reservoirs according to claim 1, characterized in that, Step 2) Specifically, it involves obtaining the well logging rock physics analysis results within the research area, and determining the range and threshold of the longitudinal wave impedance of the cavern reservoir based on the well logging rock physics analysis results.

3. The three-dimensional seismic forward modeling method for carbonate karst cave reservoirs according to claim 1, characterized in that, In step 3), the specific process of quantitative carving of the karst reservoir is as follows: The P-wave impedance values ​​within the range of the karst reservoir are retained, while other values ​​are discarded, thus obtaining the three-dimensional P-wave impedance volume of the karst reservoir.

4. The three-dimensional seismic forward modeling method for carbonate karst cave reservoirs according to claim 1, characterized in that, The specific process of step 5) is as follows: Based on the three-dimensional seismic forward modeling P-wave velocity model, three-dimensional seismic forward modeling simulation is carried out; When only the vertical resolution of the cavern exists, a convolution-based numerical simulation method is used. When only the lateral resolution of the cave exists, or when both the longitudinal and lateral resolutions of the cave exist simultaneously, a forward modeling method based on the wave equation is used.

5. A three-dimensional seismic forward modeling system for carbonate karst cave reservoirs, characterized in that, include: The data acquisition module is used to acquire seismic data and seismic layer velocity data within the research area; The seismic inversion module interacts with the data acquisition module to perform seismic inversion based on seismic data within the research area, and obtain the inverted P-wave impedance volume. The longitudinal wave impedance module for cavern reservoirs is used to determine the range and threshold of longitudinal wave impedance in cavern reservoirs. The quantitative carving module interacts with the longitudinal wave impedance module of the karst reservoir to quantitatively carve the karst reservoir based on the inverted longitudinal wave impedance volume, thereby obtaining the three-dimensional longitudinal wave velocity volume of the karst reservoir. The model building module interacts with the quantitative carving module and the data acquisition module respectively, and fuses the three-dimensional P-wave velocity volume of the karst reservoir with the seismic layer velocity to obtain a three-dimensional seismic forward modeling P-wave velocity model. The simulation module interacts with the model building module. Based on the three-dimensional seismic forward modeling P-wave velocity model, it selects numerical simulation methods to perform three-dimensional seismic forward modeling simulations for carbonate karst cave reservoirs. The quantitative engraving module includes an engraving unit, a density acquisition unit, and a data processing unit; The carving unit is used to quantitatively carve the cavern reservoir based on the P-wave impedance volume obtained from seismic inversion according to the threshold, and obtain the three-dimensional P-wave impedance volume of the cavern reservoir. The density acquisition unit is used to obtain the average density of the cavern reservoir statistically analyzed on the surface within the research area. The data processing unit is used to obtain the three-dimensional P-wave velocity volume of the cavern reservoir by dividing the three-dimensional P-wave impedance volume of the cavern reservoir by the average density of the cavern reservoir.

6. An apparatus comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method as described in any one of claims 1 to 4.

7. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method as described in any one of claims 1 to 4.

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