Abstract: Karst caves are widely developed in Ordovician reservoirs in block-12 of Tahe Oilfield,but affected by filling of the underground river sediments and later denudation,the filled cave drilling rate of Upper Ordovician in denuded area is as high as 33%, which brings great difficulties such as well completion selection and completion method requirements. In order to improve the prediction level of filling cave,deepen the understanding of filling mechanism and clear the potential tapping direction of filling cave,based on drilling and logging data of 36 drilled wells,the filling caves were studied by using the methods of karst geology,seismic attributes,seismic reflection features and ancient landform restoration. The results show that the Ordovician in block-12 developed four types of karst cave filling, including underground river sediment, river lateral stacking, unconfined and collapse. The karst cave fillings can be divided into four types:siltstone,mudstone,collapse breccia and calcite. At the same time, three geophysical prediction methods for filling karst cave were established:seismic reflection contrast method,Middle and Lower Ordovician top surface shape comparison method and ancient landform restoration method. Three potential tapping directions were pointed out:intraformational potential, interlamination potential and interwell potential.