A method for automatically reassigning domains for seismic thin interbed thickness analysis

Abstract

This invention discloses a method for analyzing the thickness of thin interbedded layers in seismic earthquakes with automatic redistribution of the domain, comprising the following steps: S1, inputting the seismic signal to be analyzed x(t), where t is time; S2, setting a preset window function, where σ t It is the standard deviation, used to calculate the short-time Fourier transform G of the seismic signal. e (t,ω), where ω represents frequency; S3, give the criterion for judging local maximum value and define the effective window width D; S4, based on the relevant parameters defined in step S3, propose the automatic redistribution transformation ART(t,η); S5, based on the automatic redistribution transformation ART(t,η) in step S4, analyze the thickness of thin interlayers in seismic earthquakes.

Description

Technical Field

[0001] This invention belongs to the field of seismic signal processing, specifically relating to a method for automatically redistributing the thickness of thin interlayers in seismic regions. Background Technology

[0002] Thin interbedded layer analysis is a crucial aspect of oil and gas exploration, playing a vital guiding role in reservoir prediction. However, due to the low resolution of seismic wavelet, directly predicting the thickness of thin interbedded layers is challenging. As a signal processing tool, time-frequency analysis provides joint time-frequency distributions and is widely used in geophysics. Practice has shown that variations in the thickness of thin interbedded layers can be characterized by the time-frequency features of seismic signals. However, limited by Heisenberg's uncertainty principle, traditional time-frequency analysis methods such as Short-Time Fourier Transform (STFT), wavelet transform, S-transform, generalized S-transform, and W-transform cannot simultaneously achieve optimal time and frequency resolution, resulting in unclear descriptions of the thickness variation trends of thin interbedded layers.

[0003] In recent years, many post-processing methods have been proposed to improve the energy concentration of original time-frequency analysis methods. Among them, the redistribution method (RM) redistributes time-frequency energy simultaneously along the time and frequency directions. However, RM cannot reconstruct the original signal. Based on the "redistribution" technique, Synchronous Compression Transform (SST) was developed. Unlike RM, SST simply compresses the time-frequency coefficients from the frequency direction into the instantaneous frequency trajectory. It not only greatly improves the time-frequency resolution of classical time-frequency analysis methods but also allows for signal reconstruction. Due to the limitation of instantaneous frequency estimation accuracy, SST exhibits energy ambiguity when processing high-frequency signals. Therefore, second-order and higher-order SSTs have been proposed to sharpen time-frequency characterization, successfully highlighting detailed geological structures. In addition, Synchronous Extraction Transform (SET) has also been used to improve time-frequency focusing. Unlike the SST algorithm, SET only extracts the time-frequency coefficients most relevant to the instantaneous frequency. Due to the good focusing ability of SET, its extended methods, such as higher-order SET, SEWT, and TEGCT, are widely used in channel characterization and reservoir identification. The above methods differ in their processing of time-frequency energy but are essentially the same. Their core idea is to calculate the instantaneous frequency and then process the time-frequency coefficients based on the instantaneous frequency. However, this approach always suffers from drawbacks such as weak time-frequency energy focusing and unclear characterization of thin interlayer thickness. Summary of the Invention

[0004] To overcome the aforementioned shortcomings, this invention provides an Automatic Redistribution Domain (ART) method for seismic thin interbedded layer thickness analysis. Unlike other methods that redistribute time-frequency coefficients by calculating instantaneous frequencies, ART automatically redistributes energy to the instantaneous frequency trajectory by exploring the energy distribution of the STFT time spectrum. The proposed ART provides satisfactory time-frequency characterization results, enabling better analysis of the variation trend of seismic thin interbedded layer thickness.

[0005] To achieve the above-mentioned objectives, the technical solution adopted by this invention is: a method for analyzing the thickness of thin interlayers in seismic formations with automatic redistribution of domains, comprising the following steps:

[0006] S1. Input the seismic signal x(t) to be analyzed, where t is time;

[0007] S2, Preset window function Where, σ t It is the standard deviation, used to calculate the short-time Fourier transform G of the seismic signal. e (t,ω):

[0008]

[0009] in, ω is the imaginary part of a complex number, and ω represents frequency.

[0010] S3. Give the criteria for judging local maximum values ​​and define the effective window width D;

[0011] S4. Based on the relevant parameters defined in step S3, the time-frequency coefficients in the effective window width are automatically redistributed to the corresponding instantaneous frequency trajectories, and an automatic redistribution transformation ART(t,η) is proposed.

[0012] S5. Analyze the thickness of thin interlayers in the earthquake according to the automatic redistribution transformation ART(t,η) in step S4.

[0013] Preferably, the criterion for determining local maxima in step S3 is:

[0014]

[0015] Among them, |G e (t,ω)| is G e The magnitude of (t,ω), where dω is the discrete frequency interval. It is a threshold.

[0016] Preferably, the threshold Take 0.01.

[0017] Preferably, the effective window width D in step S3 is defined as:

[0018]

[0019] Where, σ t It is the standard deviation of the window function g(t).

[0020] Preferably, the automatic redistribution transformation ART(t,η) in step S4 is defined as:

[0021]

[0022] The concept of this invention is as follows:

[0023] First, input the seismic signal x(t) to be analyzed, where t is time;

[0024] Second, preset window function Where, σ t It is the standard deviation, used to calculate the short-time Fourier transform G of the seismic signal. e (t,ω), where ω represents the frequency;

[0025] Third, the criteria for judging local maxima are given, and the effective window width D is defined;

[0026] Fourth, based on the calculated parameters, the time-frequency coefficients in the effective window width are automatically redistributed to the corresponding instantaneous frequency trajectories, and an automatic redistribution transformation ART(t,η) is proposed.

[0027] Fifth, the thickness of thin interbedded layers in earthquakes is analyzed based on the aforementioned automatic redistribution transformation ART(t,η).

[0028] The working principle of this invention is as follows: input the seismic signal x(t) to be analyzed, where t is time; preset the window function. Where, σ t It is the standard deviation, used to calculate the short-time Fourier transform G of the seismic signal. e (t, ω), where ω represents the frequency; a criterion for determining local maxima is given, and an effective window width D is defined; based on the calculated relevant parameters, the time-frequency coefficients in the effective window width are automatically redistributed to the corresponding instantaneous frequency trajectories, and an automatic redistribution transformation ART(t, η) is proposed; based on the automatic redistribution transformation ART(t, η), the thickness of thin interbedded layers in seismic earthquakes is analyzed. This invention provides a time-frequency characterization method with highly focused energy for analyzing the thickness of thin interbedded layers in seismic earthquakes.

[0029] This invention proposes an automatic redistribution domain method for analyzing the thickness of thin interbedded layers in seismic earthquakes. First, the seismic signal to be analyzed is input and its short-time Fourier transform result is calculated. Then, a criterion for determining local maxima is given, and an effective window width is defined. Finally, based on the calculated parameters, the time-frequency coefficients within the effective window width are automatically redistributed to the corresponding instantaneous frequency trajectories, thus proposing an automatic redistribution transformation. This invention demonstrates excellent time-frequency characterization capabilities, significantly improving the energy focusing of the time-frequency distribution and enabling better analysis of variations in the thickness of thin interbedded layers in seismic earthquakes. Attached Figure Description

[0030] Figure 1 This is a flowchart of the present invention;

[0031] Figure 2 This is a seismic profile, and the input seismic signal is the seismic signal corresponding to the well-passing seismic trace in the figure;

[0032] Figure 3 The time-frequency spectra are processed by (a) short-time Fourier transform, (b) synchronous squeezing transform, (c) redistribution method and (d) the method of the present invention, respectively. Detailed Implementation

[0033] The invention will now be further described with reference to the accompanying drawings.

[0034] Example 1: See Figure 1 A method for analyzing the thickness of thin interlayered seismic layers with automatic redistribution of the domain includes the following steps:

[0035] S1. Input the seismic signal x(t) to be analyzed, where t is time;

[0036] S2, Preset window function Where, σ t It is the standard deviation, used to calculate the short-time Fourier transform G of the seismic signal. e (t,ω):

[0037]

[0038] in, ω is the imaginary part of a complex number, and ω represents frequency.

[0039] S3. Give the criteria for judging local maximum values ​​and define the effective window width D;

[0040] S4. Based on the relevant parameters defined in step S3, the time-frequency coefficients in the effective window width are automatically redistributed to the corresponding instantaneous frequency trajectories, and an automatic redistribution transformation ART(t,η) is proposed.

[0041] S5. Analyze the thickness of thin interlayers in the earthquake according to the automatic redistribution transformation ART(t,η) in step S4.

[0042] Preferably, the criterion for determining local maxima in step S3 is:

[0043]

[0044] Among them, |G e (t,ω)| is G e The magnitude of (t,ω), where dω is the discrete frequency interval. It is a threshold.

[0045] Preferably, the threshold Take 0.01.

[0046] Preferably, the effective window width D in step S3 is defined as:

[0047]

[0048] Where, σ t It is the standard deviation of the window function g(t).

[0049] Preferably, the automatic redistribution transformation ART(t,η) in step S4 is defined as:

[0050]

[0051] See Figures 1 to 3 We will take a seismic signal from a complex superimposed tight sandstone reservoir as an example. Figure 2 The seismic profile is displayed. The input seismic signal is the well-passing seismic trace signal in the figure. The vertical axis represents time in milliseconds, and the horizontal axis represents the number of traces. Figure 3 The images show the time-frequency spectra processed by (a) Short-Time Fourier Transform, (b) Synchronous Squeeze Transform, (c) Redistribution Method, and (d) the method of this invention. The horizontal axis represents time in milliseconds, and the vertical axis represents frequency in Hertz. Examples demonstrate that the result obtained after processing by the method of this invention exhibits a highly stable, energy-focused time-frequency distribution. Compared to the other three methods, the described time-frequency ridges are also clearer. Increased frequency indicates a thinner interlayer thickness, while decreased frequency indicates a thicker interlayer thickness, allowing for better analysis of changes in interlayer thickness.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for analyzing the thickness of thin interlayered seismic layers with automatic redistribution of the domain, characterized in that, Includes the following steps: S1, Input the seismic signal to be analyzed. ,in For time; S2, Preset window function ,in, It is the standard deviation, used to calculate the short-time Fourier transform of seismic signals. : （ ）； in, The imaginary part of a complex number is the unit. Represents frequency; S3. Provide the criteria for determining local maxima and define the effective window width. ; S4. Based on the relevant parameters defined in step S3, the time-frequency coefficients in the effective window width are automatically redistributed to the corresponding instantaneous frequency trajectories, and an automatic redistribution transformation is proposed. ; S5. Based on the automatic redistribution transformation in step S4. The thickness of thin interbedded layers in earthquakes was analyzed.

2. The method for analyzing the thickness of thin interlayers in seismic formations with automatic redistribution of domains according to claim 1, characterized in that, The criterion for determining the local maximum value in step S3 is as follows: （ ）； in, yes The model, ς is the discrete frequency interval, and ς is the threshold.

3. The method for seismic thin interlayer thickness analysis with automatic redistribution domain as described in claim 2, characterized in that, The threshold ς is set to 0.

01.

4. The method for seismic thin interlayer thickness analysis with automatic redistribution domain as described in claim 1, characterized in that, The effective window width in step S3 Defined as: ；（ ）； in, It is a window function The standard deviation.

5. The method for seismic thin interlayer thickness analysis with automatic redistribution domain according to claim 2, characterized in that, The automatic redistribution transformation in step S4 Defined as: （ ）。

Images