| Karst caved reservoir is a main types of reservoir space in fractured/vuggy reservoirs in Lungu Oilfield, in which most efficient wells met large karst caved reservoirs in drills. Based on analysis of a large number of data of drilled wells in the western part of Lungu Oilfield, it is shown that the karst caves in Ordovician buried-hill reservoirs can be divided into filled, partly filled and unfilled ones in type. Combined with fine depiction of paleogeomor phology and the cognition of vertical karst zoning, it is accounted that the positions of paleolandforms decrease lower with transition from karst platforms to karst gentle slopes and karst basins, and meanwhile development and fillings of caves tend to increase in extent. The unfilled and partly filled karst caves are mainly distributed in (1) karst plat
forms, (2) the side slopes of karst hills in karst gentle slopes, and (3) the slopes in ravines and depressions. The karst cave reservoirs develop most in frequence in epigenic karst zones and runoff dissolved zones, and next common in vertical percolation dissolved zones and groundwater flow zones. The unfilled and partly filled karst caves develop mainly in epigenic karst zones. |
