Application Of Multichannel Seismic Imaging Method In Southwest Taiwan Basin

The southwest Taiwan Basin is located in the northeast of the South China Sea and southwest of Taiwan.It is a Cenozoic basin developed in the northern continental margin of the South China Sea.It is of great significance for the study of the structural attributes of the northern continental margin of the South China Sea and the exploration and development of oil and gas resources.However,among the many petroliferous basins in the northern continental margin of the South China Sea,the research on the geological structure and oil and gas resources in the southwest Taiwan Basin is relatively backward.Marine multi-channel seismic exploration is an important means for the study of geological structures and oil and gas resources.Based on the multi-channel seismic data of the southwestern Taiwan Basin,this paper has applied Kirchhoff migration(poststack time migration,prestack partial migration and prestack time migration).The differences of different imaging methods in the imaging of faults,magmatic intrusions,anticlines and shallow strata are compared,and their effects on the study of geological structures and the exploration and development of oil and gas resources in the southwestern Taiwan Basin are analyzed.The influence of the key imaging parameters of each imaging method on the imaging of the above typical structures is further discussed.All the three imaging methods can image the main faults in the southwestern Taiwan Basin,but prestack time migration can accurately image the number and nature of faults,while there is a gap between poststack time migration and prestack partial migration.Prestack partial migration and prestack time migration image the magmatic intrusion as a lenticular complex,while poststack time migration images the magmatic intrusion as a tabular bedrock.Post stack time migration and prestack partial migration imaged the core of the anticline as circular fold,while prestack time migration imaged the core of the anticline as small fold with sharp angle.In prestack partial migration and prestack time migration,the continuity of shallow strata is relatively good and the resolution is high.The resolution of shallow strata in post stack time migration is low.Although the above three imaging methods have achieved certain results in the imaging of typical geological structures in the southwestern Taiwan Basin,their imaging results will be affected by the key imaging parameters.As the key imaging parameter of the three methods,migration velocity has an important impact on the imaging results.When the migration velocity error occurs,the imaging effect of prestack time migration decreases the most,and the imaging resolution is significantly lower than the other two imaging methods.Prestack partial migration takes the second place,and poststack time migration is relatively less affected by velocity error.DMO formation dip angle is the key imaging parameter of prestack partial migration.Setting different angles(set as 5 ° ?35 °)has little impact on this data.In the range of 1000m?9000m,different migration aperture settings have little effect on prestack time migration imaging,and the shallow formation resolution increases slightly with the increase of migration aperture.The error of migration maximum dip angle has obvious influence on the imaging effect of prestack time migration.When the maximum dip angle of migration is too small,prestack time migration can not accurately image faults and anticlines.As mentioned above,although the imaging effect of prestack time migration is good,it is greatly affected by key parameters,and a small error can lead to a significant decline in imaging effect.Although the imaging effect of prestack partial migration method is slightly worse than that of prestack time migration,it is significantly better than poststack time migration,and the influence of parameter changes is less than that of prestack time migration.Compared with the other two methods,the imaging effect of poststack time migration has some shortcomings,but it is less affected by parameter changes.