A method and system for obtaining seismic tuning frequencies

Abstract

The present invention provides a method and a system for obtaining seismic tuning frequencies, belonging to the field of seismic data processing. The method uses a Gaussian function to fit the frequency-divided amplitude scatter points of actual seismic data, and calculates the accurate seismic tuning frequencies. In view of the problems such as low calculation efficiency of frequency division processing and limited number of frequency divisions in actual production, the present invention establishes a model and conducts forward frequency division simulation to calculate the frequency-divided amplitude scatter point values, uses the Gaussian function for scatter point fitting, determines the Gaussian function parameter values, demonstrating the accuracy of the method of the present invention; given a small parameter perturbation range, the Gaussian function is used to fit the actual frequency-divided amplitude values, and the accurate tuning frequency values are calculated, reducing the requirement for the number of frequency division data volumes, improving the research accuracy of the target geological body, and having good application prospects.

Description

Technical Field

[0001] The present invention belongs to the field of seismic data processing, and particularly relates to a method and a system for obtaining seismic tuning frequencies. Background Art

[0002] The tuning frequency of a geological body is of great significance for determining the scale characteristics of the geological body. The existing conventional method is to calculate multiple frequency-divided data volumes, and then visually observe the changes of the geological body on different frequency-divided data volumes to study the thickness characteristics of the geological body. This method has strong human interference factors, and the tuning frequency cannot be accurately determined, causing great difficulties in the study of geological bodies.

[0003] Therefore, it is necessary to establish a method for automatically calculating the tuning frequency using limited scatter points to lay a foundation for the subsequent study of geological body reservoirs. Summary of the Invention

[0004] The purpose of the present invention is to solve the problems existing in the above-mentioned prior art, and provide a method and a system for obtaining seismic tuning frequencies, which solve the problem that the calculation of the tuning frequency of geological bodies in the existing method is inaccurate.

[0005] The present invention is realized by the following technical solutions:

[0006] In a first aspect of the present invention, a method for obtaining a seismic tuning frequency is provided, which fits the frequency-divided amplitude scatter points of actual seismic data using a Gaussian function to calculate an accurate seismic tuning frequency.

[0007] A further improvement of the present invention lies in:

[0008] The method specifically includes the following steps:

[0009] (1) Collect actual seismic data to obtain the frequency-divided amplitude scatter points of actual seismic data;

[0010] (2) Obtain the model parameter values;

[0011] (3) On the basis of the model parameter values, given a parameter perturbation range, perform Gaussian fitting on the frequency-divided amplitude scatter points of actual seismic data within the range to obtain the parameter values of the actual seismic data fitting;

[0012] (4) Obtain the tuning frequency value.

[0013] A further improvement of the present invention lies in:

[0014] In the step (1), the actual seismic data includes the frequency-divided frequency and the amplitude values of the wave peaks and wave valleys relative to the frequency division.

[0015] A further improvement of the present invention lies in:

[0016] The specific operation of step (2) for obtaining the model parameter values includes:

[0017] (21) Establish a geological model with a certain thickness for the target to be studied;

[0018] (22) Conduct forward modeling using Ricker wavelets with different dominant frequencies to obtain the synthetic seismic records of frequency division forward modeling of the model;

[0019] (23) Based on the seismic tuning theory, extract the relative amplitude values of the wave peaks and wave valleys of the synthetic seismic records to obtain frequency division amplitude scatter points;

[0020] (24) Fit the frequency division amplitude scatter points with a Gaussian function to obtain the model parameter values.

[0021] A further improvement of the present invention lies in:

[0022] In step (23), based on the seismic tuning theory, extracting the relative amplitude values of the wave peaks and wave valleys of the synthetic seismic records to obtain frequency division amplitude scatter points, the specific operation is:

[0023] Extract the relative amplitude values of the wave peaks and wave valleys within each frequency band of the synthetic seismic records, and mark all the relative amplitude values of the wave peaks and wave valleys on a coordinate graph with frequency as the abscissa and relative amplitude value as the ordinate to form frequency division amplitude scatter points.

[0024] A further improvement of the present invention lies in:

[0025] The Gaussian function fitting expression in step (24) is:

[0026]

[0027] where a, b, and c are real constants, and a > 0, f(x) represents the amplitude, and x is the frequency.

[0028] A further improvement of the present invention lies in:

[0029] In step (4), obtain the tuning frequency value, that is, calculate the frequency value corresponding to the position of the maximum amplitude, and the calculation formula is:

[0030] f t = b' × f max

[0031] where b' is the parameter value fitted from the actual seismic data, and f max is the maximum frequency value in the actual seismic data.

[0032] In the second aspect of the present invention, a system for obtaining the tuning frequency is provided, and the system includes:

[0033] A data acquisition unit for acquiring actual seismic data to obtain the frequency-divided amplitude scatter points of the actual earthquake. The actual seismic data includes the frequency-divided frequency and the amplitude values of the wave peaks and wave troughs relative to the frequency division.

[0034] A model parameter acquisition unit for obtaining model parameter values.

[0035] A first Gaussian function fitting unit, connected to the data acquisition unit and the model parameter acquisition unit respectively, for performing Gaussian function fitting on the frequency-divided amplitude scatter points of the actual earthquake within a given parameter perturbation range based on the model parameter values to obtain the parameter values of the actual seismic data fitting.

[0036] A tuning frequency acquisition unit, connected to the Gaussian function fitting unit, for obtaining the tuning frequency value.

[0037] A further improvement of the present invention lies in:

[0038] The model parameter acquisition unit includes

[0039] A model establishment unit for establishing a geological model with a certain thickness for the target to be studied.

[0040] A forward modeling unit, connected to the model establishment unit, for performing forward modeling using Ricker wavelets with different dominant frequencies to obtain the synthetic seismic record of the frequency-divided forward modeling of the model.

[0041] A second Gaussian function fitting unit, connected to the forward modeling unit respectively, for extracting the relative amplitude values of the wave peaks and wave troughs of the synthetic seismic record based on the seismic tuning theory to obtain the frequency-divided amplitude scatter points; and performing Gaussian function fitting on the frequency-divided amplitude scatter points to obtain the model parameter values.

[0042] In a third aspect of the present invention, there is provided a computer-readable storage medium storing at least one computer-executable program, and when the at least one program is executed by the computer, the computer is caused to execute the steps in the method for obtaining the tuning frequency described above.

[0043] Compared with the prior art, the beneficial effects of the present invention are:

[0044] Aiming at the problems such as low calculation efficiency of frequency division processing and limited number of frequency divisions in actual production, the present invention establishes a model and conducts frequency-divided forward modeling, calculates the frequency-divided amplitude scatter point values, uses the Gaussian function for scatter point fitting, determines the Gaussian function parameter values, demonstrating the accuracy of the method of the present invention; given a small parameter perturbation range, performing Gaussian function fitting on the actual frequency-divided amplitude values, calculating the accurate tuning frequency value, and laying a foundation for the fine research of the reservoir.

[0045] The method of the present invention can improve the calculation accuracy of the tuning frequency, reduce the requirement for the number of frequency-divided data volumes, improve the research accuracy of the target geological body, and has good application prospects.

[0046] In the application in a certain exploration area in the northwest, the process designed by the present invention can calculate relatively accurate tuning frequency values, providing valuable research ideas and results for the fine description of fracture-cavity bodies in this oilfield. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 is a flow chart of the seismic tuning frequency calculation method of the present invention;

[0048] Figure 2 is the established geological model;

[0049] Figure 3 is the forward synthetic seismic record;

[0050] Figure 4a is the scatter plot of the model frequency-divided amplitude interval of 1 Hz;

[0051] Figure 4b is the scatter plot of the model frequency-divided amplitude interval of 5 Hz;

[0052] Figure 5a is the Gaussian function fitting graph of the model frequency-divided amplitude interval of 1 Hz;

[0053] Figure 5b is the Gaussian function fitting graph of the model frequency-divided amplitude interval of 5 Hz;

[0054] Figure 6 is the Gaussian function fitting graph of the actual seismic frequency-divided amplitude. DETAILED DESCRIPTION OF THE INVENTION

[0055] The present invention will be further described in detail below with reference to the accompanying drawings:

[0056] The present invention uses a Gaussian function to fit the scatter points of the frequency-divided amplitude and calculates accurate seismic tuning frequency values.

[0057] Examples of the method of the present invention are as follows:

[0058]

Example 1

[0059] As Figure 1 shown, the method specifically includes the following steps:

[0060] (1), Collect actual seismic data to obtain the scatter points of the frequency-divided amplitude of the actual seismic.

[0061] The actual seismic data includes the frequency-divided frequency and the amplitude values of the wave peaks and wave valleys relative to the frequency division.

[0062] (2), Obtain the model parameter values;

[0063] Obtain model parameter values. The specific operations include:

[0064] (21) For the target to be studied, establish a geological body with a certain thickness to obtain a theoretical model that conforms to the actual situation;

[0065] Use software to design a model with a certain thickness (as shown in Figure 2 ), for example, if the designed model has a set of geological bodies developed at the position of 500m - 530m and the thickness is 30m, then the target is to study the response characteristics of this 30m geological body. Therefore, such a model needs to be designed. After parameterizing this model later, subsequent analysis will be carried out.

[0066] This is a conventional method in geophysics and will not be elaborated here.

[0067] (22) Use Ricker wavelets with different dominant frequencies for forward modeling to obtain the synthetic seismic records of frequency - division forward modeling of the model.

[0068] (23) Based on the seismic tuning theory, extract the relative amplitude values of the wave peaks and wave valleys of the synthetic seismic records to obtain frequency - division amplitude scatter points.

[0069] The specific operation is as follows: Extract the relative amplitude values of the wave peaks and wave valleys within each frequency band of the synthetic seismic records, and mark all the relative amplitude values of the wave peaks and wave valleys on a coordinate graph with frequency as the abscissa and relative amplitude value as the ordinate to form frequency - division amplitude scatter points. For example, if the model has a total of 16 frequencies (20 - 35Hz, with an interval of 1Hz), the abscissa is these 16 frequencies, and the ordinate is the relative amplitude values of the wave peaks and wave valleys, thus forming a frequency - division amplitude scatter plot.

[0070] The relative amplitude value = wave peak value + absolute value of wave valley. For example, if the wave peak is a positive value, say 5, and the wave valley is a negative value, say - 4, the relative amplitude value refers to the wave peak value + absolute value of wave valley, that is, 5 + 4 = 9.

[0071] (24) Fit the frequency - division amplitude scatter points with a Gaussian function to obtain the model parameter values.

[0072] Through method testing and optimization, a Gaussian function is preferably used for scatter point fitting. The expression of the Gaussian function is:

[0073]

[0074] where a, b, and c are real - number constants, and a > 0, f(x) represents the amplitude, and x is the frequency.

[0075] The three parameter values obtained by automatic matching through the fitting algorithm in this step are that a, b, and c are real - number constants, and a > 0.

[0076] (3) Based on the model parameter values, a parameter perturbation interval range is given. Within this interval range, Gaussian function fitting is performed on the frequency-divided amplitude scatter points of the actual earthquake to obtain the parameter values fitted from the actual earthquake data.

[0077] Given parameter perturbation interval range: Generally, the parameter perturbation interval range is set to 10 - 20%. If the effect is not good, the perturbation interval range can be appropriately expanded.

[0078] (4) Obtain the frequency value corresponding to the maximum amplitude position, which is the tuning frequency value f t , to achieve accurate calculation. The calculation formula is:

[0079] f t = b′ × f max

[0080] where b′ is the parameter value fitted from the actual earthquake data, and f max is the maximum frequency value in the actual earthquake data.

[0081] The following further illustrates the method of the present invention through an application example.

[0082]

Example 2

[0083] In a certain exploration area in the northwest, the longitudinal scale research of carbonate rock karst caves is relatively small and difficult. Therefore, the seismic tuning frequency calculation method based on Gaussian function fitting is used to convert and obtain the longitudinal scale of the karst cave. The flow chart is as shown in the appendix Figure 1 shown.

[0084] First, a geological body with a thickness of 30m is established, with a velocity of 3600m / s and a surrounding rock velocity of 6000m / s, as shown in the appendix Figure 2 shown. Forward modeling is carried out using a zero-phase Ricker wavelet, with the wavelet frequency ranging from 20Hz - 35Hz at intervals of 1Hz. The final forward modeling profile is obtained, with a total of 16 channels of data, as shown in the appendix Figure 3 shown. Extract the relative amplitude values of the wave peaks and wave troughs of the waveform to obtain a scatter plot, as shown in the appendix Figure 4a shown. At the same time, for method reliability verification, amplitude values are extracted at intervals of 5Hz to obtain 4 scatter points, as shown in the appendix Figure 4b . Based on the above scatter points, Gaussian function is used for scatter fitting, as shown in the appendix Figure 5a and Figure 5b shown, Figure 5a is the fitting result at intervals of 1Hz (16 points), Figure 5b is the fitting result at intervals of 5Hz (a total of 4 points). The tuning frequency calculated in Figure 5a is 28.2Hz, Figure 5bThe calculated tuning frequency is 28.4 Hz, with a very small error. This shows that when fitting with a Gaussian function at a limited number of points (when the number of points is small), a relatively accurate tuning frequency value can still be obtained, laying a foundation for the fitting of scattered points of divided-frequency amplitudes of actual data and the calculation of tuning frequencies. Figure 5a The obtained Gaussian function parameters are a = 0.9985, b = 0.807, and c = 0.5535.

[0085] The following is the analysis of actual data processing. In actual production, due to requirements such as calculation efficiency and construction period, it is impossible to set the divided-frequency interval to 1 Hz. Most of the cases are intervals of 5 Hz, and 3 - 5 data volumes are output. Pre-stack divided-frequency imaging has been carried out in this study area, and there are three divided-frequency data volumes, which are 25 Hz, 30 Hz, and 45 Hz respectively. For the target position of the geological body, the relative amplitude values of its wave peaks and wave valleys are extracted, which are 5504, 5676, and 5121 respectively. Gaussian function fitting is carried out for these three divided-frequency amplitude values. In order to maintain the consistency between the characteristics of actual data and the laws of the model, based on the parameters obtained in model fitting, the parameter perturbation ranges are given, which are 1.1 > a > 0.9, 0.9 > b > 0.7, and 0.65 > c > 0.45. Gaussian function fitting is carried out for the three actual divided-frequency amplitudes within this range, as shown in the appendix Figure 6 As shown, the final fitting parameters are a' = 1.005, b' = 0.7177, and c' = 0.608. It can be seen that the fitting effect of the scattered points in the appendix Figure 6 is better, and the parameter values are within the given interval range, indicating that the characteristics of the Gaussian curve have a high degree of consistency, and the laws of actual data and model data have a high degree of consistency, verifying the reliability and applicability of the method.

[0086] In the last step, according to the obtained parameters, the tuning frequency is calculated. b' = 0.7177, f max = 45 Hz, f t = b' × f max = 32.3 Hz, and an accurate tuning frequency value is obtained, laying a foundation for the calculation of tuning thickness and the fine analysis of reservoirs.

[0087] The present invention also provides a system for obtaining a tuning frequency. The embodiments of the system are as follows:

[0088]

Embodiment 3

[0089] The system includes:

[0090] A data acquisition unit, configured to acquire actual seismic data to obtain scattered points of divided-frequency amplitudes of actual seismic data. The actual seismic data includes divided-frequency frequencies and relative amplitude values of wave peaks and wave valleys of divided frequencies;

[0091] A model parameter acquisition unit, configured to acquire model parameter values;

[0092] The first Gaussian function fitting unit, which is respectively connected to the data acquisition unit and the model parameter acquisition unit, is configured to, on the basis of the model parameter value, given a parameter perturbation interval range, perform Gaussian function fitting on the frequency-divided amplitude scatter points of the actual earthquake within the interval range, and obtain the parameter value of the actual earthquake data fitting;

[0093] The tuning frequency acquisition unit, which is connected to the Gaussian function fitting unit, is configured to obtain the tuning frequency value. The tuning frequency value f t , that is, the frequency value corresponding to the maximum amplitude position, and the calculation formula is:

[0094] f t = b' × f max

[0095] where b' is the parameter value of the actual earthquake data fitting, and f max is the maximum frequency value in the actual earthquake data.

[0096] The model parameter acquisition unit includes: a model establishment unit, a forward simulation unit, and a second Gaussian function fitting unit that are connected in sequence.

[0097] The model establishment unit is configured to establish a geological model with a certain thickness for the target to be studied;

[0098] Using software to design a model with a certain thickness (as shown in Figure 2 ), for example, if the designed model has a set of geological bodies developed at the position of 500m - 530m and the thickness is 30m, then the target is to study the response characteristics of this 30m geological body, so such a model needs to be designed, and then the model is parameterized for subsequent analysis.

[0099] This is a conventional method in geophysics and will not be elaborated here.

[0100] The forward simulation unit, which is connected to the model establishment unit, is configured to perform forward simulation using Ricker wavelets with different dominant frequencies, and obtain the synthetic seismic record of the frequency-divided forward simulation of the model;

[0101] The second Gaussian function fitting unit, which is respectively connected to the forward simulation unit, is configured to, based on the seismic tuning theory, extract the relative amplitude values of the wave peaks and wave valleys of the synthetic seismic record to obtain frequency-divided amplitude scatter points; and perform Gaussian function fitting on the frequency-divided amplitude scatter points to obtain the model parameter value.

[0102] Based on the seismic tuning theory, the relative amplitude values of the peaks and troughs of the synthetic seismic record are extracted to obtain the frequency-divided amplitude scatter points. The specific operation is as follows: extract the relative amplitude values of the peaks and troughs within each frequency band of the synthetic seismic record, and mark all the relative amplitude values of the peaks and troughs on a coordinate graph with frequency as the abscissa and relative amplitude value as the ordinate, forming the frequency-divided amplitude scatter points. For example, if the model has a total of 16 frequencies (20 - 35 Hz, with an interval of 1 Hz), the abscissa is these 16 frequencies, and the ordinate is the relative amplitude values of the peaks and troughs, thus forming a frequency-divided amplitude scatter plot.

[0103] The relative amplitude value = peak value + absolute value of the trough value. For example, if the peak is a positive value, say 5, and the trough is a negative value, say -4, the relative amplitude value refers to the peak value + the absolute value of the trough value, that is, 5 + 4 = 9.

[0104] The Gaussian function expression is:

[0105]

[0106] Where a, b, and c are real constants, and a > 0, f(x) represents the amplitude, and x is the frequency.

[0107] The three parameter values automatically matched through the fitting algorithm, that is, a, b, and c are real constants, and a > 0.

[0108] The present invention also provides a computer-readable storage medium. The embodiments of the computer-readable medium are as follows:

[0109]

Embodiment 4

[0110] The computer-readable storage medium stores at least one computer-executable program. When the at least one program is executed by the computer, the computer executes the steps in the above method for obtaining the tuning frequency.

[0111] Aiming at the problems such as low calculation efficiency of frequency division processing and limited number of frequency divisions in actual production, the present invention establishes a model and conducts forward simulation of frequency division, calculates the frequency-divided amplitude scatter point values, uses the Gaussian function for scatter point fitting, determines the Gaussian function parameter values, demonstrating the accuracy of the method; given a small parameter perturbation, Gaussian function fitting is performed on the actual frequency-divided amplitude values, and the accurate tuning frequency value is calculated, laying a foundation for the fine research of reservoirs.

[0112] The method of the present invention can improve the calculation accuracy of the tuning frequency, reduce the requirement for the number of frequency division data volumes, improve the research accuracy of the target geological body, and has good application prospects.

[0113] Finally, it should be noted that the above technical solutions are only one implementation manner of the present invention. For those skilled in the art, based on the disclosed application methods and principles of the present invention, it is very easy to make various types of improvements or deformations, not limited to the methods described in the above specific implementation manners of the present invention. Therefore, the manner described above is only preferred and does not have a restrictive meaning.

Claims

1. A method for obtaining seismic tuning frequency, characterized in that, The fractional-frequency amplitude scatter points of the actual seismic data are fitted using a Gaussian function to calculate the seismic tuning frequency; The method specifically includes the following steps: (1) Collect actual seismic data to obtain the fractional-frequency amplitude scatter points of the actual seismic data; (2) Obtain the model parameter values; (3) Based on the model parameter values, a parameter perturbation interval range is given, and within this interval, the fractional-frequency amplitude scatter points of the actual seismic data are fitted using a Gaussian function to obtain the parameter values of the actual seismic data fitting; (4) Obtain the tuning frequency value.

2. The method according to claim 1, characterized in that, In step (1), the actual seismic data includes fractional frequencies and the relative amplitude values of the wave peaks and wave valleys of each frequency division.

3. The method according to claim 2, wherein For step (2) to obtain the model parameter values, the specific operations include: (21) For the target to be studied, a geological model with a certain thickness is established; (22) Forward modeling is performed using Ricker wavelets with different dominant frequencies to obtain the synthetic seismic records of the fractional-frequency forward modeling of the model; (23) Based on the seismic tuning theory, the relative amplitude values of the wave peaks and wave valleys of the synthetic seismic records are extracted to obtain the fractional-frequency amplitude scatter points; (24) The fractional-frequency amplitude scatter points are fitted using a Gaussian function to obtain the model parameter values.

4. The method according to claim 3, wherein For step (23), based on the seismic tuning theory, to extract the relative amplitude values of the wave peaks and wave valleys of the synthetic seismic records to obtain the fractional-frequency amplitude scatter points, the specific operation is: Extract the relative amplitude values of the wave peaks and wave valleys within each frequency band of the synthetic seismic records, and mark all the relative amplitude values of the wave peaks and wave valleys on a coordinate graph with frequency as the abscissa and relative amplitude value as the ordinate to form the fractional-frequency amplitude scatter points.

5. The method according to claim 4, wherein The Gaussian function fitting expression in step (24) is: where a, b, and c are real constants, and a > 0, f(x) represents the amplitude, and x is the frequency.

6. The method according to claim 5, characterized in that, For step (4), to obtain the tuning frequency value, that is, to obtain the frequency value corresponding to the position of the maximum amplitude, the calculation formula is: f t = b' × f max where b′ is the parameter value of the actual seismic data fitting, and f max is the maximum frequency value in the actual seismic data.

7. A system for obtaining a tuning frequency, characterized in that, The system includes: A data acquisition unit for collecting actual seismic data to obtain the fractional-frequency amplitude scatter points of the actual seismic data, where the actual seismic data includes fractional frequencies and the relative amplitude values of the wave peaks and wave valleys of each frequency division; A model parameter acquisition unit for obtaining the model parameter values; A first Gaussian function fitting unit, connected to the data acquisition unit and the model parameter acquisition unit respectively, for, based on the model parameter values, giving a parameter perturbation interval range, and within this interval, fitting the fractional-frequency amplitude scatter points of the actual seismic data using a Gaussian function to obtain the parameter values of the actual seismic data fitting; A tuning frequency acquisition unit, connected to the Gaussian function fitting unit, for obtaining the tuning frequency value.

8. The system according to claim 7, wherein The model parameter acquisition unit includes: A model establishment unit for establishing a geological model with a certain thickness for the target to be studied; A forward modeling unit, connected to the model establishment unit, for performing forward modeling using Ricker wavelets with different dominant frequencies to obtain the synthetic seismic records of the fractional-frequency forward modeling of the model; The second Gaussian function fitting unit is respectively connected to the forward modeling unit, and is used to extract the relative amplitude values of the wave peaks and wave valleys of the synthetic seismic record based on the seismic tuning theory to obtain frequency-divided amplitude scatter points; and perform Gaussian function fitting on the frequency-divided amplitude scatter points to obtain model parameter values.

9. A computer-readable storage medium, characterized in that The computer-readable storage medium stores at least one computer-executable program, and when the at least one program is executed by the computer, the computer is caused to execute the steps in the method for obtaining the tuning frequency according to any one of claims 1-6.

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