Abstract:This paper analyzes the conditions for the formation of sealing of a fault,According to the seismic,geological and log data and by applying the technique of fuzzy comprehen— sive jugement,the fuzzy comprehensive judgement matrix and mathematic model for the sealing of a fault have been established.This model is applied tO the study of the sealing of main faults in the Qiaokou Oil Field,and the barrier of a fault to hydrocarbon accumulation in this area.A set of methods suitable for evaluating the Sealing of a fault in different stages of exploration and development have been set up.