Prestack Time Migration Technique Applied Research

At present, the routine seismic data processing is prostack time migration, it just canmoves dipping reflector to their true subsurface positions and collapses diffractions. But itcannot solve the problem that the points on dipping interface engaging in stacking are not theCRP. The improved way is prestack partial migration. It can avoid the influence of tiltedstratum and yield an improved stacked section. But DMO is just prestack partial migration,velocity analysis using CMP gathers after DMO is still influenced by the dipping reflectorunderside the velocity analysis points, so the result of velocity analysis is not exact. So, itmust use prestack migration imaging technology. If we want to make the result of 3-Dprestack time migration better, the study on some corresponding assorted 3-D prestack timemigration processing techniques is essential.Firstly, the paper shows the migration concepts, the basic theory of migration and so on,then I briefly introduce two kinds of prestack time migration methods which are kirchhoffintegration migration and wave equation migration, compare their merits and disadvantageswhich can supply the evidence for the selection of migration methods and effectiveapplications. In addition, the two velocity analysis methods of prestack time migration andhow to operate are briefly introduced, which can supply the evidence for the establishment ofvelocity field.Through the study on 3-D prestack time migration processing in the first well area ofDaqing xu sheng, the method of establishing velocity mode for 3-D prestack time migrationaiming at the deep layer of Daqing has formed, the prestack time migration processing flowaiming at the deep layer of Daqing also has formed. The profiles after prestack time migrationprocessing have great improvement than the old ones. In addition, through participating inthis processing project, I summarize some recognitions and conclusions:â… .When the change of transverse velocity is not great, 3-D prestack time migration is agood substitution of 3-D prestack depth migration. In present, it's the best technology ofimproving imaging precision that can be put into large scale production.â…¡.Prestack time migration is not an independent process, and its imaging result is tightlyrelated with the basic process.â…¢.Velocity filed is a key aspect which directly affects migration result. Rational andhigh precise velocity model closed to the real geology is precondition to get high quality byprestack time migration. Besides choosing arithmetic, prestack time migration work includesbuilding velocity model and it is a complex and taking time iteration process.â…£.We can tack both the migration quality and migration efficiency into account andchoose the best value of migration aperture in the experiment.â…¤.In different area, the processing flow should be used flexibly. In data processing, theestablishment of processing flow, the choosing of migration method and parameter must adaptto the characteristic of different workplace. And purposefully resolving some problemsexiting in data processing is required.