Research The Methods Of Deep Layer Seismic Signal Phase Consistency Processing

Signal-to-noise ratio and resolution of the seismic section is the important content in seismic data processing. The stack technique can obviously improve signal-to-noise ratio of seismic section, but the hypothetical condition is that the amplitude and phase of seismic wavelet are same in the same traces after NMO(normal moveout) and static correction. But in the factual, this hypothetical condition is not satisfied. In seismic data processing, the effects of near surface anomalies are important and should not be ignored. These factors include the near-surface low, declining speed strip mantlerock horizontal layer thickness and the speed of change, and, shot and geophone coupling condition difference. The amplitude and phase differences caused by these factors impact the in-phase stack of seismic data. The problem of phase difference is one of the most important factors affecting the in-phase stack for the effective reflectors. In the place of shot and geophone wavelet form inconsistent, it not only needs to carry out time and amplitude correction but also to carry out phase correction. By this means, it can make the amplitude, time and phase consistency in all traces in pre-stack CMP(common mid-point) gathers. Only by this we can get good stack section. Phase correction can eliminate the phase differences of seismic wavelet, to make the seismic wavelet become or approximate to zero-phase wavelet, eliminate the residual phase influence and improve the stacked section quality. This paper summarizes the phase correction methods and different phase correction criterions. Two phase correction methods are carried out in this paper. The strongpoint and shortcomings of these criterions and applying range are analyzed in this paper. The obvious shortcoming of the varimax norm method is the low efficiency. And the analogical criterion has high efficiency, but the precision is not enough. Because of these we give out a new correction criterion. In the new method, the varimax norm method is used to elimination the residual phase in the model gather first, then the analogical criterion is used in CMP gathers to get the phase-correction angle in each gather, that can achieve precision phase correction. The model and real seismic data processed results indicate that the improved method has enhanced the calculation efficiency, kept the precision and has obvious effect in the residual phase elimination, signal-noise ratio improvement, the event continuity enhancement and stacked section quality improvement.