Stratum absorption compensation method and system based on seismic signal space

Abstract

The invention provides a seismic signal space-based stratum absorption compensation method and system. The compensation method comprises the following steps: acquiring a seismic signal; determining a coherent direction of the seismic signal by using an inclination angle scanning method, and designing a space prediction error filter with a signal identification capability; constructing an unsteady filter representing the seismic signal absorption effect; establishing a target functional for performing unsteady-state inversion on the seismic signal after absorption compensation, and introducing the spatial coherence of the seismic signal into a regularization condition of an inversion system; and performing inversion on the target function by adopting a conjugate gradient method to obtain the seismic record after absorption compensation. The method is simple in operation, stable in operation and obvious in effect, effectively inhibits the influence of noise interference on absorption compensation, and improves the compensation precision of seismic signals.

Description

Technical Field

[0001] The present invention relates to the field of oil and gas geophysical exploration seismic data processing, and in particular to a formation absorption compensation method and system based on seismic signal space. Background Art

[0002] Seismic exploration is a geophysical method for detecting subsurface structures. This method artificially excites seismic waves at the surface, receives reflected signals from the subsurface, and analyzes and processes these signals to detect and predict the structure of the strata. The subsurface medium is not an ideal elastic medium, but rather a viscoelastic medium with an absorbing effect. Seismic waves propagating in viscoelastic media experience frequency absorption and velocity dispersion, significantly reducing the resolution and amplitude preservation of the seismic signal.

[0003] Compensating for the absorption and dispersion of seismic waves in viscoelastic media is a crucial research topic in high-resolution seismic signal processing. Currently, there are two main types of absorption compensation methods: those based on wavefield continuation in viscoelastic media and those based on non-stationary inversion. Seismic wave absorption is a frequency-dependent exponential decay process: higher frequencies and longer propagation times result in greater absorption attenuation. Absorption compensation, the inverse of formation absorption, is a frequency-dependent exponential amplification process. Noise interference, which is inherently present in seismic recordings, is also exponentially amplified during the absorption compensation process. Consequently, absorption compensation suffers from significant instability and amplifies high-frequency noise. While improving seismic data resolution, absorption compensation also significantly reduces the signal-to-noise ratio (SNR), severely limiting the effectiveness of these two methods in practical seismic data processing.

[0004] In practice, gain limiting and frequency limiting strategies are often employed to enhance the stability of the compensation process and suppress the amplification effect of high-frequency noise. Gain limiting imposes a threshold on the compensation level, preventing further increases above this threshold. Frequency limiting, similar to gain limiting, eliminates absorption compensation for seismic signals above a certain frequency. Clearly, both of these limiting strategies are compromises, enhancing the stability of the compensation process while also reducing the accuracy of the actual seismic signal. Summary of the Invention

[0005] In view of the above problems, the present invention is proposed to provide a formation absorption compensation method and system based on seismic signal space, which overcomes the above problems or at least partially solves the above problems.

[0006] According to one aspect of the present invention, a method for compensating for formation absorption based on seismic signal space is provided, the compensation method comprising:

[0007] Acquire seismic signals;

[0008] Determining the coherence direction of the seismic signal using a dip scanning method and designing a spatial prediction error filter with signal recognition capability;

[0009] Constructing a non-stationary filter to characterize the absorption effect of seismic signals;

[0010] Establish a target functional for non-stationary inversion of seismic signals after absorption compensation, and introduce the spatial coherence of seismic signals into the regularization condition of the inversion system;

[0011] The conjugate gradient method is used to invert the objective function and obtain the seismic records after absorption compensation.

[0012] Optionally, the non-stationary filter describes the frequency variation and phase variation of the seismic signal in the viscoelastic medium.

[0013] Optionally, the acquiring of seismic signals specifically includes:

[0014] Step S1: Input seismic record u(x,t), where t is the reflection time and x is the surface position;

[0015] Step S2: Input the formation absorption quality factor Q(t).

[0016] Optionally, the determining the coherence direction of the seismic signal by using the dip scanning method specifically includes:

[0017] Step S3: Determine the dip angle p(x, t) on the seismic record u(x, t) using conventional methods such as dip scanning.

[0018] Optionally, the designing of a spatial prediction error filter having signal recognition capability specifically includes:

[0019] Step S4: Design a spatial prediction error filter a(x) with a length of 3L, which is in the form of

[0020]

[0021] Optionally, constructing a non-stationary filter for characterizing the seismic signal absorption effect specifically includes:

[0022] Calculate the unsteady filter d(t,τ) that describes the ground absorption effect. The specific steps are as follows: Calculate the amplitude spectrum of the ground absorption filter

[0023] Calculating the Phase Spectrum of the Ground Absorption Filter Wherein, the symbol H() represents Hilbert transform;

[0024] Calculate the frequency response of the formation absorption filter D(t,f)=A(t,f)e iφ(t,f) ;

[0025] Perform inverse Fourier transform on the frequency response to obtain the non-stationary filter d(t,τ).

[0026] Optionally, constructing a non-stationary filter for characterizing the seismic signal absorption effect further includes:

[0027] Step S6: Connect all input seismic records u(x, t) end to end to form an input seismic record vector u;

[0028] Step S7: Construct a large sparse block matrix d composed of non-stationary filters d(t,τ), which is in the form of

[0029]

[0030] Where n is the number of earthquake records, and each subarray d i The elements in are d(t,τ);

[0031] Step S8: Use Helix transform to construct a matrix a consisting of spatial prediction error filters a(x).

[0032] Optionally, the step of establishing a target functional for performing non-stationary inversion on the seismic signal after absorption compensation specifically includes:

[0033] Step S9: Establish the absorption compensation target functional ε(v), which is in the form of

[0034]

[0035] Where v is a vector formed by connecting the seismic records v(x,t) end to end after absorption compensation, and λ1 and λ2 are two regularization parameters.

[0036] Optionally, the inversion of the objective function using the conjugate gradient method to obtain the seismic record after absorption compensation specifically includes:

[0037] Step S10: using the conjugate gradient method to solve the absorption compensation target functional ε(v) to obtain the seismic record v(x, t) after absorption compensation.

[0038] The present invention also provides a stratum absorption compensation system based on seismic signal space, which applies the above-mentioned stratum absorption compensation method based on seismic signal space. The compensation system specifically includes:

[0039] A seismic signal acquisition module, used for acquiring seismic signals;

[0040] A coherence direction determination module is used to determine the coherence direction of the seismic signal using a dip scanning method and to design a spatial prediction error filter with signal recognition capability;

[0041] Unsteady filter building module, used to build unsteady filters that characterize the absorption effect of seismic signals;

[0042] A target functional establishment module is used to establish a target functional for non-stationary inversion of seismic signals after absorption compensation, and to introduce the spatial coherence of seismic signals into the regularization conditions of the inversion system;

[0043] The inversion module is used to invert the target function using the conjugate gradient method to obtain the seismic record after absorption compensation.

[0044] The present invention provides a method for compensating for formation absorption based on seismic signal space. The method comprises: acquiring seismic signals; determining the coherence direction of the seismic signals using a dip scanning method and designing a spatial prediction error filter with signal recognition capabilities; constructing a non-stationary filter to characterize the absorption effect of the seismic signals; establishing a target functional for non-stationary inversion of the seismic signals after absorption compensation, and introducing the spatial coherence of the seismic signals into the regularization conditions of the inversion system; and inverting the target function using a conjugate gradient method to obtain seismic records after absorption compensation. The method is simple to operate, stable in operation, and effective, effectively suppressing the influence of noise interference on absorption compensation and improving the compensation accuracy of seismic signals.

[0045] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are specifically listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0047] Figure 1 A flow chart of a formation absorption compensation method based on seismic signal space provided by an embodiment of the present invention;

[0048] Figure 2 Seismic records before absorption compensation provided by embodiments of the present invention;

[0049] Figure 3The underground medium quality factor model provided by the embodiment of the present invention;

[0050] Figure 4 The amplitude spectrum before absorption compensation provided by the embodiment of the present invention;

[0051] Figure 5 Seismic records after absorption compensation provided by an embodiment of the present invention;

[0052] Figure 6 This is the amplitude spectrum after absorption compensation provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0053] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0054] The terms "comprises" and "comprising" and any variations thereof in the description, embodiments, claims and drawings of the present invention are intended to cover non-exclusive inclusions, for example, including a series of steps or units.

[0055] The technical solution of the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0056] like Figure 1 As shown, the present invention provides a formation absorption compensation method based on seismic signal space, comprising:

[0057] Acquire seismic signals;

[0058] Determine the coherence direction of seismic signals using methods such as dip scanning, and design a spatial prediction error filter with signal recognition capabilities;

[0059] Construct an unsteady filter to characterize the absorption effect of seismic signals. The unsteady filter describes the frequency and phase changes of seismic signals in viscoelastic media.

[0060] Establish a target functional for non-stationary inversion of seismic signals after absorption compensation, and introduce the spatial coherence of seismic signals into the regularization condition of the inversion system;

[0061] The conjugate gradient method is used to invert the objective function and obtain the seismic records after absorption compensation.

[0062] The present invention provides a method for compensating for formation absorption based on spatial coherence of seismic signals, and its specific steps are as follows:

[0063] Step S1: Input the seismic record u(x,t), where t is the reflection time and x is the surface position.

[0064] Step S2: Input the formation absorption quality factor Q(t).

[0065] Step S3: Determine the dip angle p(x, t) on the seismic record u(x, t) using conventional methods such as dip scanning.

[0066] Step S4: Design a spatial prediction error filter a(x) with a length of 3L, which is in the form of

[0067] Step S5: Calculate the unsteady filter d(t,τ) that describes the formation absorption effect. The specific steps are as follows:

[0068] (1) Calculate the amplitude spectrum of the formation absorption filter

[0069] (2) Calculate the phase spectrum of the formation absorption filter Here, the symbol H() represents Hilbert transform.

[0070] (3) Calculate the frequency response of the formation absorption filter D(t,f) = A(t,f)e iφ( t,f ) .

[0071] (4) Perform inverse Fourier transform on the frequency response to obtain the non-steady-state filter d(t,τ).

[0072] Step S6: Connect all input seismic records u(x, t) end to end to form an input seismic record vector u.

[0073] Step S7: Construct a large sparse block matrix d composed of non-stationary filters d(t,τ), which is in the form of

[0074]

[0075] Where n is the number of earthquake records, and each subarray d i The elements in are d(t,τ).

[0076] Step S8: Use Helix transform to construct a matrix a consisting of spatial prediction error filters a(x).

[0077] Step S9: Establish the absorption compensation target functional ε(v), which is in the form of

[0078]

[0079] Where v is a vector formed by connecting the seismic records v(x,t) end to end after absorption compensation, and λ1 and λ2 are two regularization parameters.

[0080] Step S10: using the conjugate gradient method to solve the absorption compensation target functional ε(v) to obtain the seismic record v(x, t) after absorption compensation.

[0081] Step S11: Output the seismic record v(x, t) after absorption compensation.

[0082] This embodiment is an application example of the present invention in a certain three-dimensional block in Shengli Oilfield. Figure 2 It is the earthquake record before the absorption compensation of the 3D work area. Figure 3 is the underground quality factor model corresponding to the earthquake record. The quality factor describes the strength of the ground absorption. The smaller the quality factor, the stronger the ground absorbs seismic waves.

[0083] Figure 4 It is the amplitude spectrum of the earthquake record before absorption compensation. Due to the absorption of seismic waves by the underground medium, the frequency of the seismic signal is relatively low, with the main frequency being around 20 Hz.

[0084] Figure 5 This is an earthquake record after absorption compensation is performed using the present invention.

[0085] Figure 6 This is the amplitude spectrum after absorption compensation. As can be seen, the present invention effectively suppresses the impact of noise interference on absorption compensation by introducing seismic signal coherence constraints. After absorption compensation, the dominant frequency of the seismic signal increases from 20 Hz to 30 Hz. While maintaining the signal-to-noise ratio, the resolution of the seismic recording is significantly improved.

[0086] Beneficial Effects: The present invention provides a formation absorption compensation method based on the spatial coherence of seismic signals. It is simple to operate, stable in operation, and effective in suppressing the influence of noise interference on absorption compensation, thereby improving the compensation accuracy of seismic signals.

[0087] The present invention provides a stratum absorption compensation method based on the spatial coherence of seismic signals, which suppresses the amplification effect of high-frequency noise in the compensation process and improves the resolution of seismic records while maintaining the signal-to-noise ratio of seismic records.

[0088] This paper proposes a method for compensating for formation absorption based on the spatial coherence of seismic signals. Unlike noise interference, seismic signals exhibit spatial continuity and coherence. This method incorporates spatial coherence into the regularization conditions for the absorption compensation problem. Under the constraints of spatial coherence, the method inverts and recovers seismic records after absorption compensation, suppressing the amplification effect of high-frequency noise and improving the accuracy of seismic signal compensation.

[0089] The above specific implementation methods further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific implementation methods of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A formation absorption compensation method based on seismic signal space, characterized in that: The compensation method includes: Acquire seismic signals; Determining the coherence direction of the seismic signal using a dip scanning method and designing a spatial prediction error filter with signal recognition capability; Constructing a non-stationary filter to characterize the absorption effect of seismic signals; Establish a target functional for non-stationary inversion of seismic signals after absorption compensation, and introduce the spatial coherence of seismic signals into the regularization condition of the inversion system; The conjugate gradient method is used to invert the objective function and obtain the seismic records after absorption compensation.

2. The method for compensating for formation absorption based on seismic signal space according to claim 1, characterized in that: The non-stationary filter describes the frequency variation and phase variation of the seismic signal in the viscoelastic medium.

3. The method for compensating for formation absorption based on seismic signal space according to claim 1, characterized in that: The obtaining of seismic signals specifically includes: Step S1: Input the seismic record u(x,t), where t is the reflection time and x is the surface position. Step S2: Input the formation absorption quality factor Q(t).

4. The method for compensating for formation absorption based on seismic signal space according to claim 1, characterized in that: The method of determining the coherence direction of the seismic signal by using the dip scanning method specifically includes: Step S3: Determine the dip angle p(x, t) on the seismic record u(x, t) using conventional methods such as dip scanning.

5. The method for compensating for formation absorption based on seismic signal space according to claim 1, characterized in that: The design of the spatial prediction error filter with signal recognition capability specifically includes: Step S4: Design a spatial prediction error filter a(x) with a length of 3L, which is in the form of 6. The method for compensating for formation absorption based on seismic signal space according to claim 1, characterized in that: The construction of the non-stationary filter characterizing the seismic signal absorption effect specifically includes: Calculate the unsteady filter d(t,τ) that describes the ground absorption effect. The specific steps are as follows: Calculate the amplitude spectrum of the ground absorption filter Calculating the Phase Spectrum of the Ground Absorption Filter Wherein, the symbol H() represents Hilbert transform; Calculate the frequency response of the formation absorption filter D(t,f)=A(t,f)e i φ( t,f) ; Perform inverse Fourier transform on the frequency response to obtain the non-stationary filter d(t,τ).

7. The method for compensating for formation absorption based on seismic signal space according to claim 1, characterized in that: The constructing of the non-stationary filter characterizing the seismic signal absorption effect further comprises: Step S6: Connect all input seismic records u(x, t) end to end to form an input seismic record vector u; Step S7: Construct a large sparse block matrix d composed of non-stationary filters d(t,τ), which is in the form of Where n is the number of earthquake records, and each subarray d i The elements in are d(t,τ); Step S8: Use Helix transform to construct a matrix a consisting of spatial prediction error filters a(x).

8. The method for compensating for formation absorption based on seismic signal space according to claim 1, characterized in that: The establishment of a target functional for performing non-stationary inversion on the seismic signal after absorption compensation specifically includes: Step S9: Establish the absorption compensation target functional ε(v), which is in the form of Where v is a vector formed by connecting the seismic records v(x,t) end to end after absorption compensation, and λ1 and λ2 are two regularization parameters.

9. The method for compensating for formation absorption based on seismic signal space according to claim 1, characterized in that: The method of inverting the objective function using the conjugate gradient method to obtain the seismic record after absorption compensation specifically includes: Step S10: using the conjugate gradient method to solve the absorption compensation target functional ε(v) to obtain the seismic record v(x, t) after absorption compensation.

10. A formation absorption compensation system based on seismic signal space, applying the formation absorption compensation method based on seismic signal space according to any one of claims 1 to 9, characterized in that: The compensation system specifically includes: A seismic signal acquisition module, used for acquiring seismic signals; A coherence direction determination module is used to determine the coherence direction of the seismic signal using a dip scanning method and to design a spatial prediction error filter with signal recognition capability; Unsteady filter building module, used to build unsteady filters that characterize the absorption effect of seismic signals; A target functional establishment module is used to establish a target functional for non-stationary inversion of seismic signals after absorption compensation, and to introduce the spatial coherence of seismic signals into the regularization conditions of the inversion system; The inversion module is used to invert the target function using the conjugate gradient method to obtain the seismic record after absorption compensation.

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