Research And Application On High-precision Imaging Of Prestack Time Migration

As the difficulty of modern seismic exploration is increasing, the faced geological conditions are more and more difficult, the regional structures are more and more complicated,and the demand for imaging precision is higher and higher. As the dominant technology of seismic migration imaging, prestack time migration(PSTM) has always been the primary choice to deal with the image problem of seismic data in complex geological areas. Therefore,the research on high-precision imaging of PSTM has its practice significance.The signal-to-noise(S/N) ratio of raw data of research areas is low and the quality is poor. The imaging precision of previous processing sections is low, the wave group characters are fuzzy, and the migration is inaccurate. Therefore, under the premise that high- precision noise suppression technologies are used to improve the S/N ratio, we put forward the following research ideas:(1) The optimization analysis of velocity——the key parameter of PSTM will be done.(2) Study the influence of the other parameters such as migration aperture and the max dip of migration.Firstly, introduce the project overview and data information of Langgu depression Liuheying area. Secondly, study comparatively the principle of two kinds of PSTM methods, discuss deeply their characters, and choose Kirchhoff integration migration as theory basis of the research on high- precision imaging of PSTM. Thirdly,the optimization analysis in velocity parameter of PSTM has been done on the basis of high-quality common middle point(CMP) gathers. Fourthly, study the influence of the other parameters on imaging precision. Finally, Analyze the processing effects.Through the study on high-precision imaging of PSTM in the Langgu depression Liuheying area, We find out the following conclusions:(1) shot gathers with high S/N ratio is the basis to improve the imaging precision of PSTM.(2) On the condition that the underground media is horizontal layered media, stack velocity can be used as the initial migration velocity. Whereas DMO velocity is suitable for underground strata with certain angle, and the imaging precision of PSTM sections is higher when DMOvelocity is used as initial migration velocity. Therefore, DMO velocity is more suitable as initial migration velocity, and DMO is necessary to be well done before PTSM.(3) During the procedure of optimization analysis of migration velociy,P-Sonic curve in well logging data has been used to monitor the trend of migration velocity, and the accurate migration velocity field has been quickly built.(4)Except migration velocity, migration aperture and the max dip are also important parameters of Kirchhoff prestack time migration.High-precision PSTM processing procedure has been applied in Langgu depression Liuheying area, and the imaging precision had been indeed improved. The wave group characters is clear, the migration is accurate, the break-point’s location is accurate, and the feature of tectonics is outstanding. Therefore, the research method introduced in the paper is so feasible that it can really enhance the imaging precision.