Abstract: The author of this paper studied the effects of lithology and the property of pore fluids on seismic velocity through the analysis of the data of acoustic loggings, vertical seismic sections and stacking velocity. It is suggested that the analysis can be carried out on the mudstone compaction and oil/gas migration by using seismic data and information. Based on the calculations of the formational fluid pressure by the data of seismic velocity with equivalent depth method, the hydrodynamics can be analysed. Finally, the orientation of oil/gas migration and possible oil/gas accumulation belts could be inferred with combination of the geological background in a certain area.