Abstract: Comprehensive study of seismic, geologic, formation testing and production testing data indicates that the No. 9 fault, previously delineated in west block of Wangji oilfield, should be divided into two faults, i. e. No. 9 and No. 10. The reservoirs in this area mainly are NW - trending Wangji delta sandbodies, which can be further divided into subfacies including underwater distributary channel, mouth bar, front sand sheet and predelta. Oil layers are mainly distributed in Ⅳ - Ⅵ oil units of the 3rd member of Hetaoyuan Fm, of which Ⅴ - Ⅶ oil units are the major ones. Reservoirs are mainly of structural types under control of No. 91 fault. Oil layers distribute along this fault and are characterized by poor overlapping, low oil column and narrow oil - bearing width. However, it is believed that this area has relatively large potential to add reserves.