As a mature oilfield developed for over 40 years in the northern part of the Langgu Sag, the Wanzhuang area is dominated by normal faults. Fault cutting has resulted in complex oil-water relationships, including the "water above oil" distribution, with unclear reservoir-forming models. To identify the controlling factors of oil-water distribution and the reservoir-forming model in the upper and middle sub-members of the third member of the Shahejie Formation (Es?? and Es??) in the Wanzhuang area, this study is based on the exploration results of three blocks (A12, B87, and A21). Through comprehensive analysis of reservoir-forming characteristics, it focuses on examining the relationships between lateral fault sealing, sandbody thickness, caprock thickness, sandbody dip angle and oil testing production, clarifies the oil-water distribution and main controlling factors of reservoir formation, and establishes the reservoir-forming model.The reservoir prediction model constructed by multivariate fitting of various reservoir-forming elements and reservoir anatomy indicate that the vertical difference in fault-sandbody configuration among different oil groups is the main controlling factor for the "water above oil" phenomenon and reservoir formation in the Es?? in the study area. Lateral fault sealing and high-dip-angle sandbodies are the primary controlling factors for reservoir formation in the Es??.Based on the analysis of various reservoir-forming conditions, the reservoir-forming model of the Wanzhuang area is defined as follows: Oil and gas generated from the source rocks of the lower sub-member of the third member of the Shahejie Formation (Es??) and the upper sub-member of the fourth member of the Shahejie Formation (Es??) migrate vertically along the transporting faults. After being blocked by the overlying caprocks, the hydrocarbons diverge into reservoirs in contact with secondary faults. Subsequently, the oil and gas continuously adjust to higher positions along the fault-sandbody transportation system until accumulating in traps formed by laterally sealed faults or lithologic pinchouts.