Three-dimensional Synthesized Shot-record Interactive Residual Migration Velocity Analysis

In this paper,a 3-D residual migration velocity analysis based on the synthesized source -record prestack depth migration is studied.We also extend the study to some other related topics including seismic numerical forward modeling and seismic data migration.Seismic numerical modeling,based on the assumption that the structure and parameters of the subsurface media are known,simulate the wavefield and calculate the numerical seismic record that should be observerd,is applied extensively in seismic exploration and earthquake seismology.In the process of seismic data,seismic numerical modeling can be used to test some inverse methods.The accuracy and the efficiency are the two issues to develop for the wavefied modeling. The Fourier transform method is used widespread for its high efficiency and accuracy.In the paper,the method is discussed and developed.Further,the Fourier transform method is replaced by the Hartley transform method in many cases.Theses schemes are to utilize current computer facilities to provide seismic data efficiently for testing purposes.However, to provide 3-D data for testing some seismic processing methods such as the 3-D residual migration velocity analysis is still time consuming.To overcome the obstacle,we present modeling with synthesized areal sources and linear sources.The data from modeling of the synthesized areal sources can be used to test some methods that deal with the synthesized area record without the synthesis,while the data from modeling of the linear source can be used to test some schemes in which the controlled illumination is necessary.Since the Hartley transform has advantages over the Fourier transform,we also bring the method into zero-offset forward modeling and migration.The prestack depth migration methods based on the wave equation are accurate. However,they are restricted by the low efficiency,especially for the 3-D cases.In the areal shot-record migration,the extrapolations need not be done for all the individual shot records,but for the areal shot record only.We use a large step to extrapolate the wavefields in the migration,and use the method in the limited-frequencies method to further improve the migration efficiencies.The numerical examples on the Marmousi model,filed data and 3-D SEG model demonstrate the method is feasible and efficient. The 3-D residual migration velocity analysis method based on the synthesized areal shot-record prestack depth migration is established on the idea of residual curvature.And the controlled illumination technique is brought in.The migration method adopted is the above mentioned efficient methods.After the migration,the common image gathers can be extracted directly.The utilization of the controlled illumination avoids the wave distortion during the propagation in the inhomogeneous media and make the hypothesis of the correction formula hold.With Qt programming technique and the lower libraries developed by Dongfang Geophysical Petroleum Exploration Corporation,we develpe a software package.