The Prestack Time Migration Method Based On Wave Theory

In view of the disadvantages of the prestack depth migration: building velocity modelwas difficult and computational efficiency was low. In this paper, a prestack time migrationapproach based on wave equation was given. With the one way wave equation andstationary-phase theory, the travel time and the analytic formula for the amplitude of imagingconditions for prestack depth migration were gain. The adaptive time-varying migrationaperture and amplitude-preservation imaging algorithm could be determined. Simulating themaximum inclined angle of the structure by controlling impulse response may realize thetime-varying migration aperture.This method not only speeded up the processing, but alsosuppressed the migration noise and improves the signal to noise ratio. We adopt imagingcondition of depth migration for calculating the weighted coefficient to get the amplitude. Itpartially compensated the geometric diffusion and restored the deep energy to preserveamplitude. In this scheme, the table-driven technique was used to avoid calculating traveltime and amplitude repeatedly which could enhance the computational efficiency.In3D seismic data preprocessing stage, according to the energy difference in differentblocks, the paper combined the geometric spreading amplitude compensation, surfaceconsistent amplitude compensation and residual amplitude analysis compensation to solve thelongitudinal energy compensation and lateral equilibrium problems. By combining thetomographic static correction and the micro-logging static correction method, the staticcorrection problems were resolved. With the velocity analysis and the iterative of residualstatic correction, the influence of the residual static correction was eliminated and the accuratevelocity field was determined.The processed results showed that this paper gave the reasonable process design, properthe selection of parameters, natural waveform, obvious characteristics of waves, the richinformation between the layers, clear and reliable breakpoint and section. In addition, it couldbe found that the processed profiles have high signal-to-noise ratio and resolution and it isbeneficial to the understanding of the unity of the regional geological rules.