Abstract: On the plane and in vertical direction,the offshore fault block reservoir is characterized by strong heterogeneity and large injection-production well spacing.After long-term water injection development,it is easy to form the preferential pathway and the water-flooding development effect is poor.Due to many commingled injection and production wells,it is not easy to make clear each layer's injection volume and output,and the evaluation accuracy of single preferential pathway is worse.By taking well block-6in northern Weizhou 12-1 oilfield as the example,through comprehensive inter-well dynamic connectivity analysis method,dimensionless PI value method,tracer testing and streamline simulation,the study on preferential pathway identification and quantitative description of the complex fault-block reservoir has been carried out.Combined with the numerical simulation,the results have been verified,which can provide the theoretical basis for follow up remaining oil distribution study and reasonable adjustment programs.