Seismic Characteristics Analysis Of Anomalous Amplitudes And Research On Suppression Methods

With the development and application of prestack migration technology,the seismic data processing requires higher signal-to-noise ratio of prestack data,and improving the signal-to-noise ratio is still a hot topic in seismic data processing.The anomalous amplitudes in seismic data,especially those caused by magnetic tape drop off,would cover the valid signal,and reduce the signal to noise ratio of seismic data.Those noises lead to uneven energy change from vertical and horizontal direction,and would cause arc phenomenon in the prestack migration processing,interfering with the seismic interpretation work.Aiming at strong energy anomalous amplitudes of raw seismic data,the paper studies the anomalous amplitudes suppression methods,to eliminate the influence of the strong energy noise on the migration processing and improve the quality of seismic processing.It is a common method to suppress anomalous amplitudes by identifying anomalous amplitudes and separating those noises from effective signal.However,due to the limitation of the available methods,when there are large scope and strong energy anomalous amplitudes in seismic data,the available methods does not work very well.Thus,it is necessary to find a reasonable method to suppress this kind of anomalous amplitudes,and maximize the signal to noise ratio of prestack seismic data.The paper discussed the principles for anomalous amplitudes suppression including the artificial edit,frequency-dependent amplitude attenuation,2D medium filtering and adaptive amplitude attenuation.On the basis of previous studies,an anomalous amplitudes suppression method based on seismic wave attenuation theory is proposed.By using average absolute amplitude discrimination method,it could get a threshold for identifying the anomalous amplitudes,and the novel attenuation function could suppress those data with strong energy amplitudes noise.Taking the model data as example,the proposed method has achieved better results,compared with other methods.The results show that the proposed method overcomes the shortcomings of the conventional methods.By the field data processing,several methods are used to suppress the anomalous amplitudes of seismic data.The difference of seismic data in frequency spectrum,single channel autocorrelation and signal to noise ratio spectrum before and after noise suppression is compared and analyzed.The comparison results show that the suppression method based on seismic wave attenuation theory is effective.Based on the detailed analysis of physical characteristics in anomalous amplitude,it is concluded that the anomalous amplitudes have the characteristics of wide frequency bandwidth,strong energy and poor spatial correlation.By apply the methods in model and real data,analyzing the conventional suppression methods,we found that for a large area of anomalous amplitudes,the conventional method would be restricted by factors of assumptions and scope of application,and there are some deficiency in suppression result.The method based on seismic wave attenuation theory this paper proposed could well compensate for this problem.It does not damage the valid reflection signal while suppressing large scope and strong energy anomalous amplitudes.