Study On Directional Field Filtering In Removal Of Seismic Coherent Noise And Its Application

Noise suppression is a very important part in the indoor processing of seismic data.In seismic data,the coherent noise with good continuity of phase axis and strong energy seriously affects the signal-to-noise ratio(SNR).This paper begins with the basic concept of coherent noise,the causes and characteristics of different types of coherent noise(surface wave,linear interference,acoustic wave,shallow refraction wave),the methods commonly used to suppress coherent noise,as well as their advantages and disadvantages.By introducing the directional field into filtering,a filtering method for suppressing coherent noise is proposed,namely directional field filtering.The experimental results of vertical,oblique and lateral direction spectrum analysis and "Mi" model are used to illustrate the specific scene of direction field filtering in detail and the principle of directional field filtering is described.That is,sampling along the same phase axis direction of the target noise,the sampling data is filtered by the pass high frequency resistive low frequency filter to realize the effect of suppressing the noise in the same phase axis direction of the target noise,and the signal in other directions will not be affected at the same time.In addition,the construction of the direction field and the concrete implementation of the filtering are also introduced in detail(forexample,the direction field is formed by spatial grid interpolation).The key technology is the automatic tracking of the phase axis based on the visual features.The specific usage flow of directional field filtering in this paper is as follows : First,the original data segy format is converted to the dim format which is easy to operate by program(a special seismic modeling format,and the data attribute format based on spatial xyz).Second,in this paper,the in-phase axis is automatically tracked to obtain the confidence value and direction value.Then,the direction samples with high reliability were screened by threshold;Then the direction field of the unit vector is obtained by using spatial gridding interpolation to form the direction field of the unit vector.Finally,the sampling direction determined by the direction field of the unit vector is used for data sampling and high-pass filtering.Finally,the actual data in desert area and loess tableland are used for directional field filtering test,and the filtering effect is compared with f-k filter in Focus seismic data processing system.The results show that: the directional field filtering method can suppress the coherent noise of seismic data,quasilinear coherent noise is especially effective in practical application,moreover,the better the continuity of the phase axis,the better the suppression effect.Meanwhile,the fidelity of the effective signal after filtering is higher than that of f-k filtering.