Seismic data quality effective evaluation method based on mixed waves

Abstract

The invention provides a seismic data quality effective evaluation method based on hybrid waves, and the method comprises the steps: 1, building a typical forward model of a work area in combination with a near-surface interpretation result; 2, analyzing whether mixed waves exist in the seismic data or not and the characteristics of the mixed waves; step 3, carrying out signal-to-noise ratio quantization on mixed wave regions at different positions; and 4, drawing signal-to-noise ratio trend charts of mixed wave regions at different positions. According to the seismic data quality effective evaluation method based on the hybrid waves, the evaluation method of the hybrid waves can be quickly identified, and scientific basis and technical reference are provided for optimizing optimal excitation factors and later interference wave suppression and analyzing and improving data quality.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield seismic exploration, and in particular to an effective evaluation method for seismic data quality based on mixed waves. Background Art

[0002] Through a large amount of preliminary research and analysis, fruitful results and outstanding achievements have been made in the quality analysis and interference wave suppression of seismic records containing traditional interference waves such as surface waves, acoustic waves, and shallow refraction waves, and mature experience and scientific seismic data evaluation methods have gradually been formed. However, the "mixed waves" generated by the interface between the low-velocity reduction zone and the high-speed layer have not received enough attention, and there are relatively few analytical studies. There is a lack of data analysis and evaluation methods for mixed waves, which has caused certain limitations in the current seismic data evaluation, and often results in the designed and implemented drilling failing to achieve the ideal effect. Combining factors such as the virtual reflection interface, the mixed waves generated by the virtual reflection interface, and the single-shot signal-to-noise ratio to comprehensively consider and determine the optimal well depth is the key to high-quality excitation and obtaining high-quality seismic data in this area.

[0003] There are a lot of desert surfaces in the ZZ deep depression area. The thick overlying strata in the desert area have serious absorption and attenuation problems, strong interference, low signal-to-noise ratio, weak energy, and difficulty in identifying deep targets. To solve these problems, it is necessary to improve the deep signal-to-noise ratio and resolution. To improve the signal-to-noise ratio, we must first suppress the noise and highlight the effective information. At present, the quality of some original single-shot data in this area is generally low, mainly manifested in many types of interference and low signal-to-noise ratio, resulting in serious interference and low signal-to-noise ratio.

[0004] Among the many interference waves, traditional interference waves such as surface waves, acoustic waves, and shallow refraction waves are generated along with the surface and near the surface. The wave field characteristics are familiar, easy to identify, and well controlled and suppressed. However, there is a special interference wave in the desert, commonly known as "mixed wave", which is a mixed wave of multiple direct waves and multiple reflected waves, strong or weak, existing in the near, middle and far channels. Compared with other traditional shallow interference waves, the wave field characteristics of mixed waves are more obvious in the deep information recorded by a single shot. Mixed waves are generated along with the interface. From the simulation of seismic wave fields of low-velocity layer excitation and ground channel reception, it can be seen that mixed waves are mainly generated by the influence of low-velocity reduction layers. The wave field of mixed waves is chaotic and complex, especially in the low-velocity reduction layer, where the energy is strong, which is the aliasing of secondary interference generated by the interface and effective waves. The mixed wave excited near the 0.5m interface of the high-speed layer is greatly affected and the mixed wave energy is strong. In the seismic record, it appears as a mixed wave affected by the interface, which makes the seismic wave waveform fatter, causes the effective wave reflection phase axis to be distorted, the wave resistance characteristics are not obvious, and the signal-to-noise ratio is greatly reduced, which has a great impact on the seismic data.

[0005] In the Chinese patent application with application number: CN201310749379.1, a prestack inversion method based on seismic constrained modeling is involved. The results of prestack inversion are directly controlled by the quality of its constrained model, but methods such as "phase-controlled modeling", "karst modeling" and "reservoir phase modeling" cannot quantitatively establish models for highly heterogeneous carbonate reservoirs, and their conventional basic data have errors, resulting in inaccurate subsequent inversion and reservoir prediction. Based on prestack amplitude-preserved gathers, the invention first uses pure longitudinal wave extraction technology to remove the AVO effect to improve data accuracy, and then uses the relative impedance obtained by color inversion and logging data to establish a quantitative model reflecting the distribution law of secondary reservoirs to guide inversion. Actual data application confirms that the prestack inversion results based on seismic constrained modeling have clearer details of the development of secondary carbonate reservoirs. The advantage of this invention is that it can be directly applied to actual data, especially more accurately describing the development law of reservoirs in deep well-free areas.

[0006] In the Chinese patent application with application number: CN201911293960.0, a method for separating mixed wave fields of multi-source earthquakes is involved, and the method includes: obtaining mixed seismic data of multi-source earthquakes, and creating a geological model based on the mixed seismic data; performing multi-directional scanning on the mixed seismic data in each layer segment in the geological model to obtain the corresponding dip angle of each layer segment; performing median filtering on the mixed seismic data using the corresponding dip angle for each layer segment; after all layers have completed the median filtering, wave field separated seismic data is obtained. Through the scheme of this invention, the separation accuracy of the multi-source mixed wave field of earthquakes is improved through geological constraints, multi-directional scanning and median filtering, and high-fidelity seismic data is obtained.

[0007] In the Chinese patent application with application number: CN201210316989.8, a vector wave field synthesis and separation method based on VSP time-varying polarization analysis is involved, which belongs to the field of petroleum geophysical exploration. The method comprises the following steps: (1) reading in two records of horizontal Hp component and vertical z component; (2) automatically selecting a time window in the frequency domain to obtain a polarization analysis time window; (3) using the covariance matrix method to determine the wave field type of the two records within the polarization analysis time window obtained in step (2); if the judgment result is a single wave field, the energy criterion method is used to perform polarization analysis to obtain the wave field of the separated and synthesized P wave and SV wave; if the judgment result is a mixed wave field, the Cho and Spencer method is used to perform polarization analysis to obtain the wave field of the separated and synthesized P wave and SV wave. The method of the invention can better separate the P wave and SV wave fields, and can restore the vector wave field from the scalar wave field.

[0008] In the Chinese patent application with application number: CN201710160037.4, a system and method for elastic wave least squares reverse time migration based on wavefield separation is involved, which belongs to the field of oil exploration. The invention can use multi-component seismic exploration data for multi-parameter imaging. By providing a least squares migration operator and anti-migration operator based on wavefield separation, and a gradient formula based on wavefield separation, it can overcome the imaging noise existing in the traditional elastic wave reverse time migration imaging method, obtain the multi-component imaging profile of the true amplitude, and suppress the crosstalk noise caused by the mutual influence between the longitudinal and transverse waves. The elastic wave least squares reverse time migration technology based on wavefield separation is developed to provide a high-precision imaging basis for the subsequent interpretation of seismic data of multi-component seismic exploration.

[0009] The above existing technologies are all significantly different from the present invention and fail to solve the technical problem we want to solve. Therefore, we have invented a new effective evaluation method for seismic data quality based on mixed waves. Summary of the invention

[0010] The purpose of the present invention is to provide an effective evaluation method for seismic data quality based on mixed waves, which can quickly identify mixed waves, optimize the best excitation factors and later interference wave suppression, and provide a scientific basis and technical reference for analyzing and improving data quality.

[0011] The object of the present invention can be achieved by the following technical measures: an effective evaluation method for seismic data quality based on mixed waves, the effective evaluation method for seismic data quality based on mixed waves comprising:

[0012] Step 1: Combine the near-surface interpretation results to establish a typical forward model of the work area;

[0013] Step 2, analyzing whether there are mixed waves and the characteristics of mixed waves in the seismic data;

[0014] Step 3, quantify the signal-to-noise ratio of the mixed wave area at different positions;

[0015] Step 4: Draw the signal-to-noise ratio trend graph of the mixed wave area at different locations.

[0016] The purpose of the present invention can also be achieved by the following technical measures:

[0017] In step 1, a typical forward model of the work area is established in combination with the near-surface interpretation results, and the excitation simulation is carried out with the actual observation system parameters of the work area to clarify the mixed wave response characteristics of the low-speed zone, the deceleration zone, and the high-speed layer interface.

[0018] In step 1, the surface data interpretation results are used to extract key parameters such as near-surface velocity and thickness, establish a precise micro-logging model, and analyze the propagation law of seismic waves; based on the five approximation principles of approximating actual seismic acquisition parameters, approximating actual seismic main frequency, approximating actual seismic effective bandwidth, approximating real geological model, and approximating actual reservoir depth, a typical forward model of the work area is established.

[0019] In step 1, receivers are arranged according to the actual track distance, face element and coverage times of the work area. Combined with the actual data, a 30 Hz main frequency is used for excitation simulation, and the simulated single shot record is compared and analyzed with the actual single shot record.

[0020] In step 1, 35 excitation points near the interface of the low-speed reduction zone and the high-speed layer are used for ground reception with a track spacing of 25m to conduct excitation simulation reception analysis, and the mixed wave response characteristics of the simulated records near different parts and interfaces and the characteristics of the reflected wave group with or without mixed waves are analyzed; from the forward analysis results, the single-shot data collected in the field contain mixed waves, especially in the single-shot records generated when excited near the interface, the mixed waves are more obvious.

[0021] In step 2, based on the understanding of seismic response characteristics, actual data and simulated records are compared to analyze whether there are mixed waves in the seismic data, as well as the strength, distribution pattern, periodicity and wave field characteristics of the mixed waves.

[0022] In step 3, in the seismic record, the mixed waves generated by the interface between the low-velocity reduction zone and the high-velocity layer, i.e., the virtual reflection interface, have a time difference in front of the sub-source waves excited by different phases. The superposition of different phases seriously affects the data quality and will produce a large number of mixed waves with low-frequency characteristics, making the waveform fatter.

[0023] In step 3, the mixed wave shows the characteristics of low main frequency, low speed and different directions in both the low velocity reduction zone and the high velocity layer. According to the characteristics of the mixed wave in the actual data, the parameters and characteristics of the interference waves excited at different well depths and different parts are determined.

[0024] In step 3, the seismic data is analyzed for data quality by combining the traditional interference wave and mixed wave characteristics, and the quality of the seismic data is evaluated based on the presence or absence of mixed waves in the seismic records, the location, strength, and distribution characteristics of the mixed waves.

[0025] In step 3, the quality of the forward simulation record and the actual seismic data is compared to determine the drilling depth and relative position to the interface in the design or implementation.

[0026] In step 4, the signal-to-noise ratio at the mixed wave of the seismic record is quantitatively calculated, and a quantitative analysis of the well depth and the signal-to-noise ratio is plotted to obtain a quantitative calculation formula for the well depth and the signal-to-noise ratio at the mixed wave.

[0027] In step 4, forward modeling and actual data are combined to quantitatively analyze the signal-to-noise ratio of mixed waves at different depths in the low-speed reduction zone and high-speed layer, perform data fitting analysis on energy values ​​at different locations, draw the energy value trend line, and fit the corresponding fitting formula.

[0028] In step 4, the quality of the forward simulation record and the actual seismic data is compared to determine the drilling depth and relative position to the interface in the design or implementation.

[0029] The effective evaluation method of seismic data quality based on mixed waves in the present invention determines the optimal well depth by comprehensively considering factors such as virtual reflection interface, mixed waves generated by virtual reflection interface and single shot signal-to-noise ratio, and provides a scientific basis and technical reference for optimizing the optimal excitation factors and suppressing interference waves in the later stage, and obtaining high-quality seismic data. The present invention can quickly identify the evaluation method of mixed waves, and provides a scientific basis and technical reference for optimizing the optimal excitation factors and suppressing interference waves in the later stage, and for analyzing and improving data quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a flowchart of a specific embodiment of the method for effectively evaluating the quality of seismic data based on mixed waves of the present invention;

[0031] Figure 2 A schematic diagram of a typical near-surface geological model of a study area in a specific embodiment of the present invention;

[0032] Figure 3 It is a schematic diagram of a single shot simulation record at different excitation depths from an interface in a study area in a specific embodiment of the present invention;

[0033] Figure 4 It is a schematic diagram of single shot recording at different excitation depths from the interface in a study area in a specific embodiment of the present invention;

[0034] Figure 5 It is a schematic diagram of the signal-to-noise ratio analysis of a mixed wave region at different excitation depths from an interface in a research area in a specific embodiment of the present invention;

[0035] Figure 6 This is a trend diagram of the signal-to-noise ratio at different locations in a mixed wave zone in a study area in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0036] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0037] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations and / or combinations thereof.

[0038] The effective evaluation method of seismic data quality based on mixed waves of the present invention, in combination with the near-surface interpretation results, establishes a typical forward model of the work area, performs excitation simulation with the actual observation system parameters of the work area, and clarifies the mixed wave response characteristics of the low, deceleration zone and high-speed layer interfaces; on the basis of the understanding of the seismic response characteristics, compares the actual data with the simulation records, and analyzes whether there are mixed waves in the seismic data, as well as the strength, distribution law, periodic law and wave field characteristics of the mixed waves; in the seismic records, the mixed waves generated at the interface between the low deceleration zone and the high-speed layer (virtual reflection interface) have a time difference in front of the sub-source waves excited by different phases, and the superposition of different phases seriously affects the data quality, and a large number of mixed waves will be generated, with low-frequency characteristics, making the waveform fatter. It can be seen from the wave field that the mixed waves are mainly generated by the influence of the low deceleration layer, and have a greater impact on the ground channel and the channel inside the low deceleration layer. The unstable mixed interference waves generated in the deceleration layer are stimulated, and the strong mixed waves are generated at the interface of the high-speed layer. The farther away from the interface in the high-speed layer, the weaker the mixed wave energy; the signal-to-noise ratio of the seismic recorded mixed waves is quantitatively calculated, and the quantitative analysis of the well depth and the signal-to-noise ratio is drawn, and the quantitative calculation formula of the well depth and the signal-to-noise ratio at the mixed wave is obtained.

[0039] The following are several specific embodiments of the present invention.

[0040] Example 1

[0041] In a specific embodiment 1 of the present invention, the effective evaluation method of seismic data quality based on mixed waves of the present invention includes the following steps:

[0042] (1) In combination with the near-surface interpretation results, a typical forward model of the work area was established based on the five approaching principles of "approaching actual seismic acquisition parameters, approaching actual seismic main frequency, approaching actual seismic effective bandwidth, approaching real geological model, and approaching actual reservoir depth". The excitation simulation was carried out with the actual observation system parameters of the work area to clarify the mixed wave response characteristics of the low-speed, deceleration zone, and high-speed layer interface.

[0043] ① In the desert area, the surface data interpretation results are used to extract key parameters such as near-surface velocity and thickness, establish a precise micro-logging model, and analyze the propagation law of seismic waves. A typical forward model of the work area is established based on the five approaching principles of "approaching actual seismic acquisition parameters, approaching actual seismic main frequency, approaching actual seismic effective bandwidth, approaching real geological model, and approaching actual reservoir depth".

[0044] ② Arrange the receivers according to the actual track distance, face element, coverage times and other observation parameters in the work area, conduct excitation simulation based on actual data, and compare and analyze the simulated single-shot records with the actual single-shot records.

[0045] ③ The excitation points were set up near the interface of the low-speed zone, the deceleration zone and the high-speed layer, and the ground track was received with a track spacing of 25m. The excitation simulation reception analysis was carried out to analyze the mixed wave response characteristics of the simulated records near different parts and different interfaces and the characteristics of the reflected wave group with or without mixed waves. From the forward analysis results, the single-shot data collected in the field contains mixed waves, especially in the single-shot records generated when excited near the interface, the mixed waves are more obvious.

[0046] (2) Based on the understanding of seismic response characteristics, compare the actual data with the simulated records to analyze whether there are mixed waves in the seismic data, as well as the strength, distribution pattern, periodicity and wave field characteristics of the mixed waves.

[0047] (3) In seismic records, the mixed waves generated at the interface between the low-velocity reduction zone and the high-velocity layer (virtual reflection interface) have a time difference in front of the sub-source waves excited by different phases. The superposition of different phases seriously affects the data quality and will produce a large number of mixed waves, resulting in low-frequency characteristics and making the waveform fatter.

[0048] ① According to the simulation analysis principle, it can be seen from the wave field that the mixed wave is mainly generated by the influence of the low deceleration layer, and has a greater impact on the ground track and the track in the low deceleration layer. The unstable mixed interference wave generated in the deceleration layer and the strong mixed wave generated at the interface of the high-speed layer can obtain relatively stable waves in the high-speed layer. The farther the distance from the interface in the high-speed layer is, the weaker the mixed wave energy is.

[0049] ②Analyze the characteristics of low main frequency, low speed and different directions of mixed waves in low-velocity reduction zones and high-velocity layers. According to the characteristics of mixed waves in actual data, determine the parameters and characteristics of interference waves excited at different well depths and different parts. Combined with the characteristics of traditional interference waves and mixed waves, analyze the quality of seismic data, and evaluate the quality of seismic data based on whether there are mixed waves in seismic records, their location, strength and distribution characteristics.

[0050] ③ Compare the quality of forward simulation records and actual seismic data to determine the drilling depth and relative position to the interface during design or implementation.

[0051] (4) The signal-to-noise ratio of the mixed wave in the seismic record is quantitatively calculated, and a quantitative analysis of the well depth and the signal-to-noise ratio is plotted to obtain a quantitative calculation formula for the well depth and the signal-to-noise ratio at the mixed wave.

[0052] ① Combining forward simulation with actual data, the signal-to-noise ratio of mixed waves at different depths in the low-velocity reduction zone and high-velocity layer is quantitatively analyzed, and the data is collated.

[0053] ② Use EXCEL to perform data fitting analysis on energy values ​​at different positions, draw the energy value trend line, and fit the corresponding fitting formula.

[0054] ③ Use empirical formulas to select the appropriate well depth based on the quality of regional seismic data and other evidence.

[0055] Example 2

[0056] In a specific embodiment 2 of the present invention, as Figure 1 FIG. 1 is a flow chart of an effective method for evaluating seismic data quality based on mixed waves according to the present invention.

[0057] In step 101, in combination with the near-surface interpretation results, a typical forward model of the work area is established based on the five approaching principles of "approaching actual seismic acquisition parameters, approaching actual seismic main frequency, approaching actual seismic effective bandwidth, approaching real geological model, and approaching actual reservoir depth", and the excitation simulation is carried out with the actual observation system parameters of the work area to clarify the mixed wave response characteristics of the low, deceleration zone, and high-speed layer interface.

[0058] In step 102, based on the knowledge of seismic response characteristics, actual data and simulation records are compared to analyze whether there are mixed waves in the seismic data, as well as the strength, distribution pattern, periodicity and wave field characteristics of the mixed waves.

[0059] In step 103, the parameters and characteristics of the interference waves excited at different well depths and different locations are determined according to the characteristics of the mixed waves in the actual data. The data quality analysis is performed on the seismic data in combination with the characteristics of the traditional interference waves and mixed waves, and the quality of the seismic data is evaluated according to whether there are mixed waves in the seismic records, the location, strength and distribution characteristics of the mixed waves.

[0060] In step 104, the signal-to-noise ratio at the mixed wave of the seismic record is quantitatively calculated, and a quantitative analysis of the well depth and the signal-to-noise ratio is plotted to obtain a quantitative calculation formula for the well depth and the signal-to-noise ratio at the mixed wave.

[0061] Embodiment 3:

[0062] In the specific embodiment 3 of the present invention, a typical forward model of the work area is established based on the five-imminent principle in combination with the near-surface interpretation results, such as Figure 2 As shown in the figure, the excitation simulation is carried out with the actual observation system parameters in the work area to clarify the mixed wave response characteristics of the low, velocity reduction zone and high-velocity layer interface; through the forward simulation of seismic data at different excitation depths, it can be seen from the wave field that Figure 3As shown in the figure, the unstable mixed interference wave generated in the deceleration layer, the strong mixed wave generated at the interface of the high-speed layer, and the relatively stable wave can be obtained in the high-speed layer. The farther the distance from the interface in the high-speed layer is, the weaker the mixed wave energy is. According to the characteristics of the mixed wave in the actual data, the interference wave parameters and characteristics excited at different well depths and different parts are determined ( Figure 4 ). Combined with the characteristics of traditional interference waves and mixed waves, the seismic data quality analysis is carried out on the seismic data. The quality of the seismic data is evaluated according to whether there are mixed waves in the seismic records, the location, strength and distribution characteristics of the mixed waves ( Figure 5 ); Quantitative calculation of the signal-to-noise ratio at the mixed wave of the seismic record is performed, and a quantitative analysis of the well depth and the signal-to-noise ratio is plotted, and a quantitative calculation formula for the well depth and the signal-to-noise ratio at the mixed wave is obtained ( Figure 6 ).

[0063] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions recorded in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0064] Except for the technical features described in the specification, all other technical features are known technologies to those skilled in the art.

Claims

1. An effective evaluation method for seismic data quality based on mixed waves, characterized in that: The effective evaluation method of seismic data quality based on mixed waves includes: Step 1: Combine the near-surface interpretation results to establish a typical forward model of the work area; Step 2, analyzing whether there are mixed waves and the characteristics of mixed waves in the seismic data; Step 3, quantify the signal-to-noise ratio of the mixed wave area at different positions; Step 4: Draw the signal-to-noise ratio trend graph of the mixed wave area at different locations.

2. The effective evaluation method for seismic data quality based on mixed waves according to claim 1, characterized in that: In step 1, a typical forward model of the work area is established in combination with the near-surface interpretation results, and the excitation simulation is carried out with the actual observation system parameters of the work area to clarify the mixed wave response characteristics of the low-speed zone, the deceleration zone, and the high-speed layer interface.

3. The effective evaluation method for seismic data quality based on mixed waves according to claim 2, characterized in that: In step 1, the surface data interpretation results are used to extract key parameters such as near-surface velocity and thickness, establish a precise micro-logging model, and analyze the propagation law of seismic waves; A typical forward model of the work area is established based on the five approximate principles of approximate actual seismic acquisition parameters, approximate actual seismic main frequency, approximate actual seismic effective bandwidth, approximate real geological model, and approximate actual reservoir depth.

4. The effective evaluation method for seismic data quality based on mixed waves according to claim 3, characterized in that: In step 1, receivers are arranged according to the actual track distance, face element and coverage times of the work area. Combined with the actual data, a 30 Hz main frequency is used for excitation simulation, and the simulated single shot record is compared and analyzed with the actual single shot record.

5. The effective evaluation method for seismic data quality based on mixed waves according to claim 4, characterized in that: In step 1, 35 excitation points near the interface of the low-speed reduction zone and the high-speed layer are used for ground channel reception with a channel spacing of 25m to perform excitation simulation reception analysis, and analyze the response characteristics of the simulated recorded mixed waves near different parts and different interfaces and the characteristics of the reflected wave groups with or without mixed waves; From the forward analysis results, it can be seen that the single-shot data collected in the field contain mixed waves, especially in the single-shot records generated when excited near the interface, where the mixed waves are more obvious.

6. The effective evaluation method for seismic data quality based on mixed waves according to claim 1, characterized in that: In step 2, based on the understanding of seismic response characteristics, actual data and simulated records are compared to analyze whether there are mixed waves in the seismic data, as well as the strength, distribution pattern, periodicity and wave field characteristics of the mixed waves.

7. The effective evaluation method for seismic data quality based on mixed waves according to claim 1, characterized in that: In step 3, in the seismic record, the mixed waves generated by the interface between the low-velocity reduction zone and the high-velocity layer, i.e., the virtual reflection interface, have a time difference in front of the sub-source waves excited by different phases. The superposition of different phases seriously affects the data quality and will produce a large number of mixed waves with low-frequency characteristics, making the waveform fatter.

8. The effective evaluation method for seismic data quality based on mixed waves according to claim 7, characterized in that: In step 3, the mixed wave shows the characteristics of low main frequency, low speed and different directions in both the low velocity reduction zone and the high velocity layer. According to the characteristics of the mixed wave in the actual data, the parameters and characteristics of the interference waves excited at different well depths and different parts are determined.

9. The effective evaluation method for seismic data quality based on mixed waves according to claim 8, characterized in that: In step 3, the seismic data is analyzed for data quality by combining the traditional interference wave and mixed wave characteristics, and the quality of the seismic data is evaluated based on the presence or absence of mixed waves in the seismic records, the location, strength, and distribution characteristics of the mixed waves.

10. The effective evaluation method for seismic data quality based on mixed waves according to claim 9, characterized in that: In step 3, the quality of the forward simulation record and the actual seismic data is compared to determine the drilling depth and relative position to the interface in the design or implementation.

11. The effective evaluation method for seismic data quality based on mixed waves according to claim 1, characterized in that: In step 4, the signal-to-noise ratio at the mixed wave of the seismic record is quantitatively calculated, and a quantitative analysis of the well depth and the signal-to-noise ratio is plotted to obtain a quantitative calculation formula for the well depth and the signal-to-noise ratio at the mixed wave.

12. The effective evaluation method for seismic data quality based on mixed waves according to claim 11, characterized in that: In step 4, forward modeling and actual data are combined to quantitatively analyze the signal-to-noise ratio of mixed waves at different depths in the low-speed reduction zone and high-speed layer, perform data fitting analysis on energy values ​​at different locations, draw the energy value trend line, and fit the corresponding fitting formula.

13. The effective evaluation method for seismic data quality based on mixed waves according to claim 12, characterized in that: In step 4, the quality of the forward modeling record and the actual seismic data is compared to determine the drilling depth and relative position to the interface in the design or implementation.

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