The Ordovician buried-hill reservoirs in Lungu oilfield belong to the typical heterogeneous carbonate reservoirs.The paleogeomorphology of this area was resumed by impressing and residual thickness methods，and the 2nd-grade pa?leogeomorphology of Lungu oilfield is divided into gentle karst slope，karst platform，karst highland，peak-cluster valley and karst basin from west to east. The type of Ordovician karst reservoir is dominated by cave reservoir，which can be further divided into high mountain with large caves type and interconnecting underground river type. At present，the caves found by exploration and development are mainly distributed less than 135 m below Ordovician buried hill surface，but the cave filling characteristics differ significantly in different burial-depths and different zones. The cave filling facies are divided into 4 types which are chemical deposition facies，transposition lithofacies，collapse-breccia facies and vadose filling facies；the cave filling models are also divided into 4 types：cave filling models of underflow along the river in gorge districts，flood backwater of swallet stream and cave collapse filling models of deep underflow in gorge districts，sinkhole filling models caused by collapse of underflow along the river and vertical shaft unfilling models of deep underflow. Oil and gas are mainly enriched in the upper part of the monadnock of Ordovician buried hill in Lungu oilfield. The trend surface of valleys can indicate the original oil-water interface，but the valleys that control the oil-water interface differ in different well blocks.