Abstract:The vertical sealing ability of a fault can be restricted by many geologic factoys:fault category,fault occurrence,static pressure due to the overburden above fault plane,and the type,cementation degree,porosity, permeability etc.of filling materials in the fault belt.Fault sealing research using acoustilog data is mainly based on both the filling materials in fault belt and their compaction.If the filling materials are in normal compaction and then become so compact that they have poor porosity and permeability,the acoustic transit time is low and the fault is open to hydrocarbon.If the filling materials are mainly some poorly compacted mudstones, the acoustic transit time is high and the fault closes hydrocarbon.Filling materials must be poorly compacted mudstones,otherwise they are loose to have good porosity and permeability,thus causing high acoustic transit time and also making the fault open to hydrocarbon.