3D VSP (three-dimensional video signal processor) pre-stack imaging technology organically integrating optimization of migration aperture with avoidance of wavelet distortion

Abstract

The invention provides a 3D VSP (three-dimensional video signal processor) pre-stack imaging technology organically integrating the optimization of migration aperture with the avoidance of wavelet distortion. The method comprises the following three links of: (1) decomposing data; (2) migrating; and (3) rebuilding. The method organically integrates the optimization of the migration aperture and the whole prolongation of the wavelet into three links of the beam deviation to simultaneously solve the problems such as the wavelet distortion and the migration aperture instead of purely considering the optimization of the migration aperture or solving the problem of the wavelet distortion, so that the organic integration between the optimization of migration aperture and the avoidance of the wavelet distortion can be realized in the three links of the beam deviation. The 3D VSP theoretical wave field and measured data process result shows that the 3D VSP well periphery accurate imaging can be realized by the technology.

Description

technical field [0001] The invention relates to a 3D VSP pre-stack imaging technology which organically combines optimal offset aperture and wavelet distortion free. The invention belongs to a processing method for 3D VSP seismic signals, and relates to a 3D VSP wave field atomic decomposition technology, an atomic directional extension technology and a wave field selective reconstruction technology. Background technique [0002] As a borehole seismic observation technology, vertical seismic profiling (VSP) has the advantages of high signal-to-noise ratio, high resolution, rich wave field information, and is conducive to underground imaging and seismic attribute analysis compared with surface seismic. 3D VSP is a three-dimensional borehole seismic observation technology developed in order to overcome the limitation of a certain angle in the coverage area of ​​two-dimensional VSP. The 3D VSP data has high resolution, and can image small structures that cannot be imaged by su...

AI Technical Summary

Problems solved by technology

[0007] Existing problems: the above 3D VSP imaging technologies have their own advantages and disadvantages: ①. VSP-CDP conversion method: advantages: simple and easy to implement; disadvantages: mainly based on one-dimensional velocity model, cannot be used for two-dimensional or even three-dimensional velocity model, only It is suitable for horizontally layered media or medium distribution with slow lateral velocity change. When the formation dip angle is large, the structural imaging will be distorted, and the waveform is also susceptible to stretching and compression

②.Kirchhoff migration method: advantages: flexible target processing function, high-efficiency numerical calculation ability, adaptable to spatially irregular sampling data, strong anti-noise ability, suitable for large dip angle structure imaging; disadvantage: excessive loss of wave field dynamics information , can only be used in slow-changing media. Under complex media conditions, it is difficult to deal with multi-valued travel time and caustics, and it is impossible to adjust the offset aperture in real time.

③.Wave equation-like migration method: Advantages: rich wave field information, no high-frequency approximation assumptions, adapt to strong lateral speed changes, no caustics and multi-path phenomena in complex structural areas, and the operator is relatively more amplitude-preserving; Disadvantages: Not suitable for space irregular sampling (such as 3D VSP observation system), high accuracy requirements for velocity model, too much calculation (especially reverse time migration), unable to adjust the migration aperture in real time

④.Gaussian beam migration method: advantages: suitable for irregular sampling in space; small amount of calculation, fast calculation speed; suitable for imaging structures with strong lateral changes in velocity and steep dip angles; good radiation protection; low requirements for the accuracy of velocity models ;With optimal migration aperture, the migration noise is small; Disadvantages: In the decomposition process, it is based on oblique superposition decomposition. This decomposition method based on energy summation is not strong enough to detect the event, so the calculation accuracy is not high enough , will affect the accuracy of the selection of the migration aperture in the second link. In addition, it is easy to cause wavelet distortion, and the amount of data after decomposition is large; The time domain is still the traditional single-point shift, which will lead to wavelet distortion in the imaging results, which will mislead the subsequent seismic attribute extraction; generate some offset noise