A method for improving the static correction imaging accuracy of seismic data based on a vibroseis

Abstract

The present invention discloses a method for improving the imaging accuracy of seismic data static correction based on a vibrator, which includes the following steps: 1. First, perform minimum-phase processing on the vibrator data; 2. Manually and finely pick the first arrival jump point of single-shot data to obtain near-surface geological information; 3. Perform first-arrival wave refraction static correction calculation on the data; 4. Apply the datum static correction in step 3 to the original single-shot data; 5. Modify the first-arrival trace headers of the data picked in step 2 to ensure consistency with the data in step 4; 6. Perform first-arrival wave residual static correction calculation on the data, and jointly use the first-arrival wave refraction static correction to improve the focusing of the imaging quality; 7. Separate the high and low frequencies of the datum static correction, and ensure the authenticity of the underground structure morphology with the low-frequency component of the static correction; the high-frequency component of the datum static correction is combined with the first-arrival wave residual static correction as the high-frequency component of the static correction. The present invention can eliminate the problem of in-phase axis imaging jitter caused by the thickness and velocity variation of the low-velocity layer.

Description

Technical Field

[0001] The present invention relates to the technical field of urban geological seismic exploration imaging, and specifically refers to a method for improving the imaging accuracy of seismic data static correction based on a controllable seismic source. Background Art

[0002] The working area of urban geological seismic exploration is often covered by the Quaternary system, with loose strata. Inside the Quaternary strata, there are strata with different lithologies such as sand layers, clay layers, and silt clay layers with different particles, which will generate several wave impedance interfaces. At the same time, due to the large differences in the near-surface sedimentary conditions, the thickness of the low-velocity layer ranges from a few meters to over a hundred meters, and the surface velocity varies drastically horizontally and vertically. The static correction problem caused by the low-velocity layer affects the imaging quality of seismic data, and even generates false structures, seriously interfering with the determination of the underground stratigraphic distribution, fracture characteristics, and special geological lithology bodies. At the same time, there is a lack of micro-logging and small refraction data in urban geological seismic exploration. Applying micro-logging and small refraction to generate field static correction is costly, and only applying elevation static correction is difficult to solve the imaging accuracy of urban geological seismic exploration.

[0003] Taking the seismic exploration in a certain area as an example for technological innovation work, this project uses an observation system with a 2m trace interval, a 6m shot interval, and a 600m array length for 1ms data acquisition. The spatial bin sampling density is high, and the time bin sampling density interval is small, which can obtain rich velocity information of sand layers, clay layers, silt clay layers, and gravel with different particles in the Quaternary system, and has the conditions for calculating the first arrival refraction wave static correction and the first arrival residual static correction. On the basis of correctly defining the observation system, after performing minimum phase processing on the controllable seismic source to make the mixed phase of the controllable seismic source become the minimum phase after phase processing, and then accurately picking the first arrival jump point, accurate and rich near-surface direct wave information can be obtained, as Figure 1 shown.

[0004] For the first type of first arrival static correction, the thickness and velocity of the near-surface low-velocity layer are obtained from the first arrival travel time first, that is, a near-surface model is established, and then based on the surface consistency principle, the datum plane static correction at each shot point and receiver point is calculated. However, the accuracy of the calculated short-wavelength static correction is not high.

[0005] Another type does not require determining the thickness and velocity of the near surface, but directly performs statistical processing on the first arrival wave travel time to obtain the residual static correction values of the shot points and receiver points. The advantage is that it can adapt to complex surface conditions, and the disadvantage is that it cannot solve the authenticity problem of structural imaging.

[0006] Therefore, a method for improving the imaging accuracy of seismic data static correction based on a controllable seismic source has become an urgent problem to be solved in the whole society. Summary of the Invention

[0007] To solve the above technical problems, the technical solution provided by the present invention is: a method for improving the static correction imaging accuracy of seismic data based on a vibrator, including the following method steps,

[0008] (1) First, perform minimum-phase processing on the vibrator data;

[0009] (2) Manually and precisely pick the first arrival takeoff point of single-shot data to obtain near-surface geological information;

[0010] (3) Perform first arrival refraction static correction calculation on the data to improve the static correction accuracy of the datum plane;

[0011] (4) Apply the datum plane static correction in step (3) to the original single-shot data to improve the smoothness of the first arrival;

[0012] (5) Modify the first arrival header of the data picked in step (2) to ensure consistency with the data in step (4);

[0013] (6) Perform first arrival residual static correction calculation on the data, and jointly use the first arrival refraction static correction to improve the focusing of the imaging quality.

[0014] Further, in step (3), perform first arrival refraction static correction calculation on the data to obtain the static correction amounts of the shot point and the geophone point for the datum plane.

[0015] Further, in step (5), ensure matching with the header of the shot gather data in step (4).

[0016] The advantages of the invention compared with the prior art are as follows:

[0017] By adopting the above technical solution, the present invention can eliminate the problem of in-phase axis imaging jitter caused by the thickness and velocity variation of the low-velocity layer, and at the same time improve the accuracy and focusing of shallow engineering seismic imaging in urban geology, resulting in good social and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a diagram of picking the first arrival takeoff point of shot gather data;

[0019] Figure 2 is a schematic diagram of the static correction technical process for urban seismic geological data;

[0020] Figure 3 is a single-shot effect diagram of joint static correction of first arrivals;

[0021] Figure 4 is a stacked effect diagram of joint static correction of first arrivals;

[0022] Figure 5 is a comparison diagram before and after the application of joint high-frequency static correction of first arrivals. DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention will be further described in detail below with reference to the accompanying drawings.

[0024] The present invention will be introduced in detail with reference to the accompanying drawings.

[0025] When the present invention is specifically implemented, a method for improving the static correction imaging accuracy of seismic data based on a vibrator is provided.

[0026] (1) First, perform observation system definition and small-phase processing on the data.

[0027] (2) Fine-pick the first arrival jump point of the seismic data to obtain near-surface geological information.

[0028] (3) Perform first arrival wave refraction static correction calculation to obtain the static correction amounts of the shot point and receiver datum planes.

[0029] (4) Apply the first arrival wave refraction datum plane static correction to the shot gather data to improve the smoothness of the first arrival wave.

[0030] (5) Modify the first arrival trace headers picked in step 2 to match the trace headers of the shot gather data in step 4.

[0031] (6) Perform first arrival wave residual static correction calculation to improve the high-frequency accuracy of the static correction and improve the imaging quality.

[0032] (7) Separate the high and low frequencies of the datum plane static correction. The low-frequency component of the datum plane static correction ensures the authenticity of the underground structure morphology; the high-frequency component of the datum plane static correction is combined with the first arrival wave residual static correction as the high-frequency component of the static correction, and the combined application jointly improves the focusing of the imaging in-phase axis, providing technical support for subsequent velocity analysis and other work.

[0033] Example:

[0034] Taking a certain area as an example, the acquisition parameters of the work area can be seen in Table 1, and the schematic diagram of the technical process can be seen Figure 2 .

[0035] As Figure 3 shown, it can be seen from the single-shot monitoring of applying elevation static correction and the single-shot monitoring of applying first arrival wave joint static correction that after the application of the first arrival wave joint static correction, the jitter phenomenon of the first arrival wave disappears, the first arrival is smooth, and it conforms to the law of surface velocity change; through Figure 4 stacking comparison shows that the imaging effect of the first arrival wave joint static correction stacking section is improved, and the in-phase axis focusing is stronger; Figure 5 This is the effect after the joint application of high-frequency static correction, which better solves the problem of high-frequency imaging of static correction, and the hyperbola characteristic law is obvious, laying a solid foundation for subsequent urban geological seismic imaging.

[0036] Parameter Table of Shallow (Two-Dimensional) Seismic Acquisition Observation System for Fault Geological Survey in a Certain Area of a Certain District - Table 1

[0037] Name Parameter Name Parameter Observation system 2D survey line Arrangement mode 300-0-2-0-300 Trace interval (m) 2 Number of receiver traces (traces) 300 CMP (m) 1 Coverage times 50 Shotpoint interval (m) 6 Shot method Vibroseis Recording length (s) 2 Project number 11000022210200001649-XM002-2

[0038] The above describes the present invention and its implementation manners. Such description is not restrictive. What is shown in the drawings is only one of the implementation manners of the present invention, and the actual structure is not limited thereto. Generally speaking, if those of ordinary skill in the art are inspired by it and, without departing from the gist of the present invention, design similar structural manners and embodiments to this technical solution without creative efforts, they shall fall within the protection scope of the present invention.

Claims

1. A method for improving the static correction imaging accuracy of seismic data based on a vibrator, characterized in that, Including the following method steps, (1) First, perform minimum-phase processing on the vibroseis data; (2) Manually and precisely pick the first arrival jump point of the single-shot data to obtain near-surface geological information; (3) Perform first-arrival wave refraction static correction calculation on the data to obtain the static correction amounts of the shot point and geophone datum, and improve the static correction accuracy of the datum; (4) Apply the datum static correction in step (3) to the original single-shot data to improve the smoothness of the first arrival wave; (5) Modify the first arrival trace headers of the data picked in step (2) to ensure consistency with the data in step (4); (6) Perform first-arrival wave residual static correction calculation on the data, and jointly use the first-arrival wave refraction static correction to improve the focusing of the imaging quality; (7) Separate the high and low frequencies of the datum static correction. The low-frequency component of the static correction ensures the authenticity of the underground structure morphology; the high-frequency component of the datum static correction is combined with the first-arrival wave residual static correction as the high-frequency component of the static correction, and the joint application jointly improves the focusing of the imaging in-phase axis; The method for the static correction imaging accuracy of the seismic data is used to improve the accuracy and focusing of the shallow engineering seismic imaging of urban geology.

2. The method for improving the static correction imaging accuracy of seismic data based on a vibrator according to claim 1, characterized in that: In step (5), ensure the matching of the trace headers of the shot gather data with those in step (4).

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