A base stretch frequency modulation synchronous extrusion seismic reservoir prediction method

Abstract

The application discloses a base stretching frequency modulation synchronous extrusion seismic reservoir prediction method, which comprises the following steps: S1, inputting original two-dimensional seismic profile signal s(x;t) to be analyzed; S2, decomposing the original two-dimensional seismic profile signal s(x;t) by using base stretching adaptive frequency modulation transformation to obtain time-frequency transformation result SBCT(x;f,t); S3, estimating the instantaneous frequency of the xth seismic signal at each time-frequency position according to the time-frequency transformation result SBCT(x;t,f); S4, constructing a synchronous extrusion operator with the signal instantaneous frequency as the curve center on the time-frequency domain according to the synchronous extrusion principle, which is used for extruding the original time-frequency spectrum energy to the curve to obtain new time-frequency coefficients; S5, taking the modulus of the time-frequency coefficients to obtain the time-frequency spectrum after base stretching frequency modulation synchronous extrusion transformation; S6, calculating the main frequency range of the original seismic signal by using Fourier transformation to determine the high-frequency value and the low-frequency value; extracting the spectrum corresponding to the high-frequency value and the low-frequency value from the time-frequency spectrum obtained in S5 to obtain two common frequency profiles; and finally, determining whether the reservoir exists in the seismic profile by comparing the attenuation of the seismic signals in the two common frequency profiles. The application can significantly improve the time-frequency energy focusing property and improve the identification precision of the seismic reservoir.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of signal processing, and particularly relates to a base stretching frequency modulation synchronous extrusion seismic reservoir prediction method. BACKGROUND

[0002] Time-frequency analysis is a powerful tool for seismic data processing, which provides a method for us to explain the time-frequency characteristics of seismic signals from a two-dimensional perspective, that is, a one-dimensional time signal can be expressed as a joint distribution function of time domain and frequency domain through time-frequency processing. In addition, as an effective means of signal processing, time-frequency analysis clearly describes the close relationship between signal frequency and time. As an important means of seismic reservoir prediction, time-frequency analysis method can effectively characterize the non-stationary characteristics of seismic signals and reveal the relationship between signal frequency and time.

[0003] However, most time-frequency characterization methods cannot process complex multi-component signals without prior conditions. The SBCT method can adaptively match multi-component signals by constructing basis functions. By scaling the time center and its surrounding basis functions within a certain window length range to expand the chirp rate, a linear frequency modulation varying with time and frequency is generated, so that the multi-component signals within the entire window length range can match the slope of each instantaneous frequency track. Compared with existing methods, the time-frequency characterization obtained by the SBCT method can achieve higher time-frequency energy concentration.

[0004] The basic idea of the base stretching frequency modulation synchronous extrusion seismic reservoir prediction method is to first obtain the time-frequency characterization result of the signal through SBCT, and then construct a synchronous extrusion operator in the time-frequency domain to estimate the real instantaneous frequency of the signal for extruding the original time-frequency spectrum energy and rearranging the time-frequency energy to the real instantaneous frequency ridge line of the signal to significantly improve the focusing of the energy distribution of the signal time-frequency characterization. SUMMARY

[0005] In view of the above deficiencies in the prior art, the base stretching frequency modulation synchronous extrusion seismic reservoir prediction method provided by the present application can significantly improve the time-frequency energy focusing and improve the identification accuracy of the seismic reservoir.

[0006] In order to achieve the above-mentioned application purposes, the technical scheme adopted by the present application is as follows: a base stretching frequency modulation synchronous extrusion seismic reservoir prediction method, comprising the following steps:

[0007] S1, inputting an original two-dimensional seismic profile signal s(x;t) to be analyzed;

[0008] S2, decomposing the original two-dimensional seismic profile signal s(x;t) by using the base stretching adaptive frequency modulation transform to obtain a time-frequency transform result SBCT(x;f,t);

[0009] S3, estimating the instantaneous frequency of the xth seismic signal at each time-frequency position according to the obtained time-frequency transform result SBCT(x;f,t);

[0010] S4, constructing a synchronous squeezing operator with the instantaneous frequency of the signal as the curve center in the time-frequency domain to squeeze the original time-frequency spectrum energy onto the curve to obtain new time-frequency coefficients according to the synchronous squeezing principle;

[0011] S5, taking the modulus of the time-frequency coefficients to obtain the time-frequency spectrum after the base-stretch adaptive frequency modulation synchronous squeezing transform;

[0012] S6, calculating the main frequency range of the original seismic signal by using the Fourier transform, setting 85% of the maximum frequency value in the main frequency range as the high frequency value and setting the minimum frequency value in the main frequency range as the low frequency value, then extracting the spectrum corresponding to the high frequency value from the time-frequency spectrum obtained in S5 to obtain the common frequency profile of the high frequency value, and extracting the spectrum corresponding to the low frequency value from the time-frequency spectrum obtained in S5 to obtain the common frequency profile of the low frequency value. Whether there is a reservoir in the seismic profile is determined by comparing the attenuation of the seismic signal in the two common frequency profiles.

[0013] Preferably, the time-frequency transform result of the base-stretch adaptive frequency modulation transform of the original two-dimensional seismic profile signal s(x; t) in step S2 is:

[0014]

[0015] wherein t represents time, f represents the frequency center, and h(x; τ) represents a Gaussian function. represents a phase function, τ is a time variable, and the phase function is:

[0016]

[0017] wherein k = 1, 2,..., n, n is the order of the phase function, (a1, a2,..., an) is an adaptive parameter of the phase function, and can be determined according to the kurtosis theory, i.e.: n

[0018]

[0019] wherein argmax(·) represents the parameter set when the function takes the maximum value.

[0020] Preferably, the instantaneous frequency of the signal at each time-frequency position (t, f) is estimated according to the obtained time-frequency transform result SBCT(x; t, f):

[0021] ​​

[0022] wherein, denotes the partial derivative of the window function h(x;t) with respect to t, denotes the SBCT result under the window function h(x;t). The SBCT result under the function t k h(x;t) is shown.

[0023] As a preference, the specific method of obtaining the new time-frequency coefficient in the step S4 is: according to the synchronous squeezing principle, a synchronous squeezing operator STO(x;f,t) with the signal instantaneous frequency as the curve center is constructed on the time-frequency domain to squeeze the original time-frequency spectrum energy onto the curve to obtain the new time-frequency coefficient T(x;f,t), and the synchronous squeezing operator STO(x;f,t) satisfies:

[0024]

[0025] wherein, δ(·) is a unit impulse function. The new time-frequency coefficient T(x;f,t) is:

[0026]

[0027] As a preference, the step S5 can perform inverse transformation on T(x;f,t) in the formula (6) to reconstruct the seismic signal s(x;t).

[0028]

[0029] wherein

[0030] The idea of the present application is:

[0031] Firstly, input the original two-dimensional seismic profile signal s(x;t) to be analyzed;

[0032] Secondly, perform the basis stretching and self-adaptive frequency modulation transformation on the input signal s(x;t) to obtain the time-frequency transformation result SBCT(x;t,f)

[0033]

[0034] wherein, t represents time, f represents the frequency center, h(x;τ) represents a Gaussian function, φ(t) represents a phase function, and τ is a time variable.

[0035] Thirdly, estimate the instantaneous frequency of the xth seismic signal at each time-frequency position (t,f) according to the obtained time-frequency transformation result SBCT(x;t,f)

[0036] Fourth, according to the principle of synchronous extrusion, a synchronous extrusion operator STO(x;f,t) is constructed in the time-frequency domain with the signal instantaneous frequency curve as the center to extrude the original time-frequency spectrum energy onto the curve to obtain new time-frequency coefficients;

[0037] Fifth, the time-frequency coefficients obtained in the fourth step are taken as a modulus to obtain the time-frequency spectrum after the base-stretching frequency-modulation synchronous extrusion.

[0038] Sixth, the main frequency range of the original seismic signal is calculated by using Fourier transform, 85% of the maximum frequency value in the main frequency range is set as a high frequency value, and the minimum frequency value in the main frequency range is set as a low frequency value, then the spectrum corresponding to the high frequency value is extracted from the time-frequency spectrum obtained in the fifth step to obtain a common frequency profile of the high frequency value, and the spectrum corresponding to the low frequency value is extracted from the time-frequency spectrum obtained in the fifth step to obtain a common frequency profile of the low frequency value. Whether the reservoir exists in the seismic profile is determined by comparing the attenuation of the seismic signal in the two common frequency profiles.

[0039] The working principle of the present application is as follows: collecting an original two-dimensional seismic profile signal s(x;t) to be analyzed; decomposing the original two-dimensional seismic profile signal s(x;t) by using base-stretching adaptive frequency modulation transformation to obtain a time-frequency transformation result SBCT(x;f,t); estimating the instantaneous frequency of the xth signal at each time-frequency position according to the time-frequency transformation result SBCT(x;f,t); constructing a synchronous extrusion operator with the signal instantaneous frequency curve as the center in the time-frequency domain according to the principle of synchronous extrusion to extrude the original time-frequency spectrum energy onto the curve to obtain new time-frequency coefficients; and taking the time-frequency coefficients as a modulus to obtain the time-frequency spectrum after base-stretching frequency-modulation synchronous extrusion. The present application can significantly improve the time-frequency energy focusing and the identification accuracy of the seismic reservoir.

[0040] The present application is aimed at the problems of unclear identification and poor aggregation of the synchronous extrusion transformation and the base-stretching adaptive frequency modulation transformation in the multi-component non-stationary nonlinear complex signal, and proposes a base-stretching frequency-modulation synchronous extrusion seismic reservoir prediction method. First, the signal is processed by base-stretching adaptive frequency modulation transformation to obtain its representation result, then the instantaneous frequency of the signal at each time-frequency position is estimated according to the phase information of the time-frequency spectrum. Then, according to the principle of synchronous extrusion, a synchronous extrusion operator for estimating the real instantaneous frequency of the signal is constructed in the time-frequency domain to extrude the original time-frequency spectrum energy to obtain new time-frequency coefficients. Finally, the time-frequency coefficients are taken as a modulus to obtain the time-frequency spectrum after base-stretching frequency-modulation synchronous extrusion. The present application has good effects in reconstruction ability and calculation efficiency, can significantly improve the time-frequency energy focusing, and improve the identification accuracy of the seismic reservoir. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 The flowchart of the present application is shown in the figure;

[0042] Figure 2 A profile for the Sichuan Basin in the central and western regions of China

[0043] Figure 3 A low-frequency common frequency profile for the Sichuan Basin in the central and western regions of China treated by the method of the present application

[0044] Figure 4 A high-frequency common frequency profile for the Sichuan Basin in the central and western regions of China treated by the method of the present application DETAILED DESCRIPTION

[0045] The present application will be further described below with reference to the accompanying drawings.

[0046] Example 1: see Figure 1 A base-stretching frequency-modulation synchronous extrusion seismic reservoir prediction method, comprising the following steps:

[0047] S1, inputting a raw two-dimensional seismic profile signal s(x; t) to be analyzed;

[0048] S2, decomposing the raw two-dimensional seismic profile signal s(x; t) using a base-stretching adaptive frequency-modulation transform to obtain a time-frequency transform result of the base-stretching adaptive frequency-modulation transform of the raw two-dimensional seismic profile signal s(x; t);

[0049] S3, estimating an instantaneous frequency of the signal at each time-frequency position according to the time-frequency transform result SBCT(x; t, f);

[0050] S4, constructing a synchronous extrusion operator STO(x; f, t) with the instantaneous frequency of the signal as the center of the curve in the time-frequency domain according to the synchronous extrusion principle, and using the synchronous extrusion operator STO(x; f, t) to extrude the original time-frequency spectrum energy onto the curve to obtain new time-frequency coefficients;

[0051] S5, taking the modulus of the time-frequency coefficients to obtain a time-frequency spectrum after base-stretching frequency-modulation synchronous extrusion transformation.

[0052] S6, calculating a main frequency range of the original seismic signal using Fourier transform, setting 85% of the maximum frequency value in the main frequency range as a high-frequency value, setting the minimum frequency value in the main frequency range as a low-frequency value, then extracting the spectrum corresponding to the high-frequency value from the time-frequency spectrum obtained in S5 to obtain a high-frequency common frequency profile, and extracting the spectrum corresponding to the low-frequency value from the time-frequency spectrum obtained in S5 to obtain a low-frequency common frequency profile. Whether a reservoir exists in the seismic profile is determined by comparing the attenuation of the seismic signal in the two common frequency profiles.

[0053] As a preferred, the time-frequency spectrum of the base-stretching adaptive frequency-modulation transform of the two-dimensional seismic profile signal s(x; t) in step S2 is:

[0054]

[0055] where t represents time, f represents frequency center, h(x; t) represents Gaussian function, represents phase function, and t is time variable;

[0056] The phase function is:

[0057]

[0058] where k = 1, 2,..., n, n is the order of the phase function, (a1, a2,..., an) is the adaptive parameter of the phase function, which can be determined according to the kurtosis theory, that is: n

[0059]

[0060] where argmax(·) represents the parameter set when the function takes the maximum value.

[0061] As preferred, the step S3 of estimating the instantaneous frequency of the signal at each time-frequency position (t, f) according to the time-frequency spectrum phase information is:

[0062]

[0063] where represents the partial derivative of the window function h(x; t) with respect to t, represents the SBCT result under the window function . represents the SBCT result under the function t k h(x; t).

[0064] As preferred, the specific method of obtaining the new time-frequency coefficient in the step S4 is: according to the principle of synchronous squeezing, a synchronous squeezing operator STO(x; f, t) with the instantaneous frequency of the signal as the curve center is constructed on the time-frequency domain to squeeze the original time-frequency spectrum energy onto the curve to obtain the new time-frequency coefficient T(x; f, t), and the synchronous squeezing operator STO(x; f, t) satisfies:

[0065]

[0066] where δ(·) is the unit impulse function. The new time-frequency coefficient T(x; f, t) is:

[0067]

[0068] As preferred, the step S5 can perform inverse transformation on T(x; t, η) in equation (6) to reconstruct the seismic signal s(x; t) by using the following formula: ​​

[0069]

[0070] wherein The present application is suitable for reconstructing seismic signals.

[0071] Referring to Figures 1 to 4 , we specifically take a seismic profile as an example, and the two-dimensional seismic profile is shown in Figure 2 . Figures 3-4 respectively are low-frequency value common frequency profile and high-frequency value common frequency profile extracted from time-frequency spectrum obtained by performing base-stretching self-adapting frequency modulation transform on the seismic profile. In the figure, the horizontal coordinate represents seismic trace number, the vertical coordinate represents time, and the right color bar represents energy value. The embodiment proves that the result graph obtained after processing by the method of the present application has higher time-frequency resolution and more concentrated energy, and improves the identification precision of seismic reservoirs.

[0072] The above merely describes preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, and improvement within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A base-stretch frequency-modulated synchronous extrusion seismic reservoir prediction method, characterized in that, The method comprises the following steps: S1, inputting a raw two-dimensional seismic profile signal s(x;t) to be analyzed; Wherein x represents a seismic trace, and t represents time; S2, performing base-stretching frequency-modulation adaptive transformation on the two-dimensional seismic profile signal s(x;t) input in S1 to obtain a base-stretching frequency-modulation adaptive transformed time-frequency spectrum SBCT(x;t,f) of the raw two-dimensional seismic profile signal s(x;t); The calculation method of SBCT(x;t,f) is as follows: where t denotes time, f denotes the frequency center, h(x; τ) denotes a Gaussian function, denotes a phase function, and τ is a time variable; S3, estimating the instantaneous frequency of the xth seismic signal at each time-frequency location (t, f) from the time-frequency spectrum SBCT(x; t, f) obtained in S2 S4, according to the principle of synchronous squeezing, a synchronous squeezing operator is constructed on the time-frequency spectrum SBCT(x; t, f) obtained in S2, which is centered on the signal instantaneous frequency curve to squeeze the original time-frequency spectrum energy onto the curve to obtain new time-frequency coefficients T(x; f, t); S5, taking the modulus of the time-frequency coefficient obtained in S4 to obtain a time-frequency spectrum after base-stretching frequency-modulation synchronous squeezing transformation; S6, calculating a main frequency range of the raw two-dimensional seismic profile signal s(x;t) by using Fourier transformation, setting 85% of the maximum frequency value in the main frequency range as a high frequency value, setting the minimum frequency value in the main frequency range as a low frequency value, then extracting the frequency spectrum corresponding to the high frequency value from the time-frequency spectrum obtained in S5 to obtain a common frequency profile of the high frequency value, and extracting the frequency spectrum corresponding to the low frequency value from the time-frequency spectrum obtained in S5 to obtain a common frequency profile of the low frequency value. Whether a reservoir exists in the seismic profile is determined by comparing the attenuation of the seismic signals in the two common frequency profiles.

2. The base-stretch frequency-modulated synchronous extrusion seismic reservoir prediction method according to claim 1, characterized in that, The base-stretching frequency-modulation adaptive transformed time-frequency spectrum SBCT(x;t,f) of the two-dimensional seismic profile signal s(x;t) in the step S2; The calculation method of SBCT(x;t,f) is as follows: where t denotes time, f denotes the frequency center, h(x; τ) denotes a Gaussian function, denotes a phase function, τ is a time variable, The phase function is: where k = 1, 2, …, n, n is the order of the phase function (a1, a2, …, a n ) are adaptive parameters of the phase function , which can be determined according to the kurtosis theory, i.e. Wherein, argmax(·) represents the parameter set when the function takes the maximum value.

3. The base-stretch frequency-modulated synchronous extrusion seismic reservoir prediction method according to claim 1, characterized in that, the instantaneous frequency of the signal at each time-frequency position (t,f) is estimated from the time-frequency spectrum SBCT(x; t,f) obtained in S2 in the step S3 wherein denotes the partial derivative of the window function h(x; t) with respect to time t, denotes the SBCT result under the window function h(x; t). denotes the SBCT result computed under the function t k h(x; t).

4. The base-stretch frequency-modulated synchronous extrusion seismic reservoir prediction method according to claim 1, characterized in that, The specific method for obtaining the new time-frequency coefficient T(x;f, t) in step S4 is: according to the principle of synchronous squeezing, a synchronous squeezing operator centered on the signal instantaneous frequency curve is constructed on the time-frequency domain for "squeezing" the original time-frequency spectrum energy onto the curve to obtain a new time-frequency coefficient T(x;f, t), and the new time-frequency coefficient T(x;f, t) is: Wherein, δ(·) is a unit impulse function.

5. The base-stretch frequency-modulated synchronous extrusion seismic reservoir prediction method according to claim 1, characterized in that, The modulus is taken for the time-frequency coefficient obtained in the step S4.

6. The base-stretch frequency-modulated synchronous extrusion seismic reservoir prediction method according to claim 1, characterized in that, In the step S5, the inverse transformation of T(x;t,η) in formula (6) can be performed to reconstruct the two-dimensional seismic profile signal s(x;t) by using the following formula: wherein

Images