Study On Processing And Interpretation Of 3-D Prestack Time Migration In Complex Geologic Areas

Because of the lateral velocity varying in complex geologic areas, some conventional imaging methods can not fulfill the correct image of complex fault blocks. So we have to adopt the technique of 3-D prestack time migration(PSTM), we can solve the image problem of seismic data in complex geologic areas. Seismic data processing is a system engineering. Selecting a good migration method is very necessary. But if we want to make the result of 3-D Prestack time migration better, the study on some corresponding assorted 3-D Prestack time migration processing techniques is essential. In the paper, after analyzing the principle of four kinds of migration methods and comparing with their character, the study on 3-D Prestack time migration processing and interpretation has been done by using Kirchhoff integration migration and corresponding assorted techniques in the Baxian depression Yanling～Maoxi area. Firstly, the paper shows migration concepts and migration classifications. Four kinds of 3-D Prestack time migration methods which are Kirchhoff integration migration, Fourier finite-difference migration,pseudo-screen migration and Finite-difference migration in frequency space domain are introduced and briefly commented on. The paper puts forward the application conditions and accommodations of the four migration methods in practice which can supply the evidence for the selection of migration methods and effective applications. Secondly, in order to do better the study on 3-D Prestack time migration processing and interpretation in the Baxian depression Yanling～Maoxi area, the paper analyses carefully the original data and previous sections of the research area. Then the problems in the data are clear and the corresponding measures solving the problems are taken. Thirdly, the study on 3-D Prestack time migration processing is the main content of the paper. At the meantime, corresponding assorted processing techniques are studied. In the course of the study, the following key techniques are adopted. (1) the energy consistent processing technique in time domain; (2) the technique of founding 3D migration velocity filed; (3) the frequency splitting processing technique. Fourthly, in the course of data interpretation, through the method of opening, improving the cognition, by using drilling data and some different interpretation software, some new discoveries are found. Through the study on 3-D Prestack time migration processing in the Yanling～Maoxi area, a series of reasonable and effective processing flow of 3-D prestack time migration , which is also used in the other areas, has been generalized. After processing, the sections on which 3-D Prestack time migration processing technique is adopted have the following merits: clear geologic structure, accurate breakpoint position, high resolution of the goal layers(improved 5-10HZ). After the interpretation, the flat sheet of the T4,T5,T6'layers are finished. Eleven oil traps are found. Their total area is 23.5km2. Predictive oil geology storage capacity is 2114×104t. Three wells are determined. PSTM is a system engineering of conjoined theory with practice tightly and each step directly affects imaging appreciation. Selecting methods and the standard of people's seismic data processing and interpretation are the key factor which can improve the quality of the processing and interpretation. The studied result shows that the methods we advocated in the paper are feasible and effective.