A method and system for formation absorption compensation based on seismic signal space

Abstract

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

Description

Technical Field

[0001] This invention relates to the field of seismic data processing for oil and gas geophysical exploration, and particularly to a method and system for formation absorption compensation based on seismic signal space. Background Technology

[0002] Seismic exploration is a geophysical method for detecting underground structures. This method artificially generates seismic waves, receives reflected signals from the subsurface at the Earth's surface, and then analyzes and processes these reflected signals to detect and predict the geological structure. However, the subsurface medium is not an ideal elastic medium, but rather a viscoelastic medium with an absorption effect. Seismic waves experience frequency absorption and velocity dispersion during propagation in viscoelastic media, severely reducing the resolution and amplitude preservation of seismic signals.

[0003] Compensating for seismic wave absorption and dispersion in viscoelastic media is a crucial research area in high-resolution seismic signal processing. Currently, there are two main types of absorption compensation methods: one based on viscoelastic medium wavefield extension, and the other based on unsteady-state inversion. Seismic wave absorption is a frequency-dependent exponential decay process; the higher the frequency and the longer the propagation time, the more severe the absorption attenuation. Absorption compensation, as the inverse process of formation absorption, is a frequency-dependent exponential amplification process. Noise interference is unavoidable in seismic records, and this noise interference is also exponentially amplified during absorption compensation. Therefore, absorption compensation exhibits strong instability and amplification effect on high-frequency noise. While improving seismic data resolution, absorption compensation also significantly reduces the signal-to-noise ratio of seismic records, severely limiting the application effectiveness of these two methods in practical seismic data processing.

[0004] In practice, gain limiting and frequency limiting strategies are frequently employed to enhance the stability of the compensation process and suppress the amplification effect of high-frequency noise. Gain limiting involves setting a threshold value for the compensation magnitude; once this threshold is exceeded, the compensation stops increasing. Frequency limiting is similar in concept to gain limiting; for seismic signals with frequencies higher than a certain threshold, absorption compensation is no longer performed. Clearly, both of these limiting strategies are compromises made out of necessity, enhancing the stability of the compensation process while reducing the actual accuracy of the seismic signal compensation. Summary of the Invention

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

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

[0007] Acquire seismic signals;

[0008] The coherence direction of the seismic signal is determined using the tilt scanning method, and a spatial prediction error filter with signal recognition capability is designed.

[0009] Construct an unsteady-state filter to characterize the absorption effect of seismic signals;

[0010] An objective functional for non-steady-state inversion of seismic signals after absorption compensation is established, and the spatial coherence of the seismic signals is introduced into the regularization condition of the inversion system.

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

[0012] Optionally, the unsteady-state filter describes the frequency and phase changes of the seismic signal in the viscoelastic medium.

[0013] Optionally, acquiring the seismic signal specifically includes:

[0014] Step S1: Input the seismic record u(x,t), where t is the reflection time and x is the location on the Earth's surface;

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

[0016] Optionally, determining the coherence direction of the seismic signal using the tilt 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 spatial prediction error filter with signal recognition capability specifically includes:

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

[0020]

[0021] Optionally, the construction of the non-steady-state filter characterizing the seismic signal absorption effect specifically includes:

[0022] The specific steps for calculating the unsteady-state filter d(t,τ) describing the formation absorption effect are as follows: Calculate the amplitude spectrum of the formation absorption filter.

[0023] Calculate the phase spectrum of the formation absorption filter Wherein, the symbol H() represents the Hilbert transform;

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

[0025] Performing an inverse Fourier transform on the frequency response yields the unsteady filter d(t,τ).

[0026] Optionally, the construction of the non-steady-state filter characterizing the seismic signal absorption effect further includes:

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

[0028] Step S7: Construct a large sparse block matrix d consisting of unsteady filters d(t,τ), specifically in the form of...

[0029]

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

[0031] Step S8: Use Helix transform to construct matrix a, which consists of spatial prediction error filter a(x).

[0032] Optionally, the establishment of the objective functional for non-steady-state inversion of the seismic signal after absorption compensation specifically includes:

[0033] Step S9: Establish the absorption compensation objective functional ε(v), which has the following specific form:

[0034]

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

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

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

[0038] This invention also provides a seismic signal spatial-based formation absorption compensation system, which applies the aforementioned seismic signal spatial-based formation absorption compensation method. The compensation system specifically includes:

[0039] Seismic signal acquisition module, used to acquire seismic signals;

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

[0041] The unsteady-state filter construction module is used to construct unsteady-state filters that characterize the absorption effect of seismic signals;

[0042] The objective functional establishment module is used to establish the objective functional for non-steady-state 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 objective function using the conjugate gradient method to obtain the seismic record after absorption compensation.

[0044] This invention provides a seismic signal spatial stratum absorption compensation method. The compensation method includes: 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 capability; constructing a non-steady-state filter characterizing the seismic signal absorption effect; establishing an objective functional for non-steady-state inversion of the absorption-compensated seismic signals and incorporating the spatial coherence of the seismic signals into the regularization conditions of the inversion system; and using the conjugate gradient method to invert the objective function to obtain the absorption-compensated seismic record. The method is simple to operate, stable in operation, and has significant effects, effectively suppressing the influence of noise interference on absorption compensation and improving the compensation accuracy of seismic signals.

[0045] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0046] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 A flowchart illustrating a ground absorption compensation method based on seismic signal space, provided for an embodiment of the present invention;

[0048] Figure 2 The earthquake record prior to absorption compensation provided in this embodiment of the invention;

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

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

[0051] Figure 5 The earthquake record after absorption compensation provided in the embodiments of the present invention;

[0052] Figure 6 The amplitude spectrum after absorption compensation is provided in the embodiment of the present invention. Detailed Implementation

[0053] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0054] The terms "comprising" and "having," and any variations thereof, in the specification, embodiments, claims, and drawings of this invention are intended to cover non-exclusive inclusion, such as including a series of steps or units.

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

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

[0057] Acquire seismic signals;

[0058] The coherence direction of seismic signals is determined using methods such as dip scanning, and a spatial prediction error filter with signal recognition capability is designed.

[0059] An unsteady-state filter is constructed to characterize the absorption effect of seismic signals. The unsteady-state filter describes the frequency and phase changes of seismic signals in viscoelastic media.

[0060] An objective functional for non-steady-state inversion of seismic signals after absorption compensation is established, and the spatial coherence of the seismic signals is introduced into the regularization condition of the inversion system.

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

[0062] The specific steps of the formation absorption compensation method based on the spatial coherence of seismic signals described in this invention are as follows:

[0063] Step S1: Input the seismic record u(x,t), where t is the reflection time and x is the location on the Earth's surface.

[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) of length 3L, in the following specific form:

[0067] Step S5: Calculate the unsteady-state filter d(t,τ) describing 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 the 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 an inverse Fourier transform on the frequency response to obtain the unsteady filter d(t,τ).

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

[0073] Step S7: Construct a large sparse block matrix d consisting of unsteady filters d(t,τ), specifically in the form of...

[0074]

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

[0076] Step S8: Use Helix transform to construct matrix a, which consists of spatial prediction error filter a(x).

[0077] Step S9: Establish the absorption compensation objective functional ε(v), which has the following specific form:

[0078]

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

[0080] Step S10: Solve the absorption compensation objective functional ε(v) using the conjugate gradient method 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 three-dimensional block of Shengli Oilfield. Figure 2 This is the seismic record of the three-dimensional work area before absorption compensation. Figure 3 This is the subsurface quality factor model corresponding to the earthquake record. The quality factor describes the strength of the formation's absorption; the smaller the quality factor, the stronger the formation's absorption of seismic waves.

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

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

[0085] Figure 6 This is the amplitude spectrum after absorption compensation. It can be seen that, due to the introduction of seismic signal coherence constraints in this invention, the impact of noise interference on absorption compensation is effectively suppressed. After absorption compensation, the dominant frequency of the seismic signal increases from 20Hz to 30Hz. While maintaining the signal-to-noise ratio, the resolution of the seismic record is significantly improved.

[0086] Beneficial effects: This invention provides a formation absorption compensation method based on the spatial coherence of seismic signals. It is simple to operate, stable in operation, and yields significant results, effectively suppressing the impact of noise interference on absorption compensation and improving the compensation accuracy of seismic signals.

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

[0088] This invention proposes a stratigraphic absorption compensation method based on the spatial coherence of seismic signals. Unlike noise interference, seismic signals possess spatial continuity and coherence. This invention incorporates spatial coherence characteristics into the regularization conditions of the absorption compensation problem, performing inversion and reconstruction of the absorption-compensated seismic record under spatial coherence constraints. This suppresses the amplification effect of high-frequency noise and improves the accuracy of seismic signal compensation.

[0089] The above specific embodiments further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are merely specific embodiments 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 within the scope of protection of the present invention.

Claims

1. A ground absorption compensation method based on seismic signal space, characterized in that, The compensation method includes: Acquire seismic signals; The coherence direction of the seismic signal is determined using the tilt scanning method, and a spatial prediction error filter with signal recognition capability is designed. Its specific form is ； Constructing a non-steady-state filter to characterize the absorption effect of seismic signals, including: Calculate the unsteady-state filter that describes the formation absorption effect. The specific steps are as follows: Calculate the amplitude spectrum of the formation absorption filter ; Calculate the phase spectrum of the formation absorption filter , where the symbol Represents the Hilbert transform; Calculate the frequency response of the formation absorption filter ; Performing an inverse Fourier transform on the frequency response yields the unsteady-state filter. ; Step S6: Put all input seismic records Connecting the beginning and end, they form the input seismic record vector. ; Step S7: Construct a filter from an unsteady state. Large sparse block matrix Its specific form is in, It is the number of earthquake records, for each subarray. The elements in are ; Step S8: Construct a spatial prediction error filter using the Helix transform. The matrix formed ; An objective functional for non-steady-state inversion of seismic signals after absorption compensation is established, and the spatial coherence of the seismic signals is introduced into the regularization condition of the inversion system. Step S9: Establish the absorption compensation objective functional Its specific form is in, Earthquake records after absorption compensation A vector formed by connecting the first and last ends. and These are two regularization parameters; The conjugate gradient method is used to invert the objective function to obtain the seismic record after absorption compensation.

2. The ground absorption compensation method based on seismic signal space according to claim 1, characterized in that, The unsteady-state filter describes the frequency and phase changes of the seismic signal in the viscoelastic medium.

3. The ground absorption compensation method based on seismic signal space according to claim 1, characterized in that, The acquisition of seismic signals specifically includes: Step S1: Input seismic records ,in, It is the reflection time. It refers to the location on the Earth's surface; Step S2: Input formation absorption quality factor .

4. The ground absorption compensation method based on seismic signal space according to claim 1, characterized in that, The determination of the coherence direction of the seismic signal using the tilt scanning method specifically includes: Step S3: Determining the seismic record using the conventional tilt scanning method. The angle of inclination .

5. The ground absorption compensation method based on seismic signal space according to claim 1, characterized in that, The process 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 invert the objective function after absorption compensation. The solution is performed to obtain the seismic record after absorption compensation. .

6. A seismic signal spatial-based formation absorption compensation system, employing the seismic signal spatial-based formation absorption compensation method according to any one of claims 1-5, characterized in that, The compensation system specifically includes: Seismic signal acquisition module, used to acquire seismic signals; The coherence direction determination module is used to determine the coherence direction of the seismic signal using the tilt scanning method, and to design a spatial prediction error filter with signal recognition capability. The unsteady-state filter construction module is used to construct unsteady-state filters that characterize the absorption effect of seismic signals; The objective functional establishment module is used to establish the objective functional for non-steady-state 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 objective function using the conjugate gradient method to obtain the seismic record after absorption compensation.

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