Abstract:In the potential evaluation for the marginal oil-bearing structure in the South China Sea,3 difficulties in research were encouraged,they are the lateral change of the seismic velocity,the seismic data quality for the deep target and the lateral distribution for the sandbody reservoir.Regarding the 3 difficulties the different strategies and techniques were used,the corresponding research and application were conducted for different oilfields.For the lateral change of the seismic velocity,several velocity methods were used to conduct structure sensitivity research,every factor which affects velocity change was studied,the changing trend and law for the velocity space were understood,the depth-time relation which reflects the real geological conditions was established,for the poor seismic data quality of the deep target,several geophysical methods were used to conduct integrated technological research,post-stack and pre-stack seismic data structure research and oilgas hydrocarbon detection were combined and validated with each other,for the lateral distribution of the sandbody reservoir seismic sedimentology analysis method was used and the concept of the sequence stratigraphy was brought into seismic data interpretation,guided by geological mode,the seismic inversion,stratigraphic slicing and seismic attribute extraction were utilized to conduct detailed studies and to predict reservoir and the characteristics of the sandbody distribution in the oilfield.