The internal structure of fault zone in extensional normal fault consists of fault core and damage zone. There may be several slip surfaces and kinds of fault rock in fault core which the permeability of them depends on both the shale content in the fault zone and the type of fault rock. Damage zone which is characterized by high density of fractures shearing the surrounding rock has relative higher permeability than fault core. Hence, the lateral permeability of fault zone is decided by the development of both fault core and damage zone. While, shale content in the fault zone dominant its lateral seal capacity .There are five seal types including juxtaposition seal, cataclastic rock seal（SGR＜15%）, framework—phyllosilicate fault rocks seal（15%＜SGR<50%）, clay smears seal (SGR>50%)and cemented seal. Juxtaposition seal is the dominant seal mechanism in smallscale fault and fault which developed in brittle layer. This seal pattern decide that the hydrocarbon which is dominated by normal fault enrich in footwall. The height of hydrocarbon column is equivalence with the minimal displacement of the controlling fault in fault trap area. Hydrocarbon in footwall and hanging wall distribute as “sine curve” is the result of the “silk ribbon effect” of strikeslip fault .Based on the relationship between the SGR value of sealing fault in fault zone and the pressure difference between footwall and hanging wall, the quantitative relationship is established between SGR value and height of hydrocarbon column sealed by lateral fault seal. Use of actual distribution of OWC and the height of hydrocarbon column can be made to conclude d value for no calibrating area, and then the relationship between the height of hydrocarbon column and SGR value can be made sure. Therefore, lateral fault seal capacity can be estimated quantitatively according as above. Fault trap can be classified as entirety efficient trap， partly efficient trap and entirety inefficient trap according to the height of hydrocarbon column and its scope. Entirety efficient trap is full of hydrocarbon，the gas/oil runoff from the spilling point. The height of hydrocarbon column is smaller than trap scope in partly efficient trap and gas/oil runoff from fault laterally. There have only water in entirety inefficient trap.