Complex karst fracture-vuggy systems formed during early Hercynian of Tahe Oilfield show greatly disparities in scales and distributions in the east (blocks of interests) and west (peripheral area) parts of the oilfield.Karst water was thought to be the key factor during the karstification under varying hydrogeomorphology and hydrokinetic conditions against different geological settings.To deeper understand and interpret the mechanisms behind the development of karst reservoirs in western China

the authors restored paleokarst geomorphology and hydrology networks buried in a depth less than 5000m with modern karst theories as guidance

and high-precision 3D seismic data

seismic attribute abstraction and seismic images

as basis.A fine description of hydrogeomorphology of the east and west parts of the oilfiled were also carried out to help define the evolution stages of the karstification.The results show that the east part was developed into karst plateau with high-relief peak clusters and karst mounds as the primary landform units.Typical landscape combinations consisting of dry valleys

blind valleys

swallet steams

canyons and natural bridges

were formed by strong vertical erosion from surface water.Integrated drainage systems made up of both surface and underground hydrologic networks were also formed there.These features reveal that the part had gone through a long and stable period of karstification.The results also point out that the west part is mostly a karst depression holding gentle topography gradient and karst mounds with relatively lower relief.The surface water network was observed to erode largely laterally into snaking networks in the part.However

continuous underground water networks failed to come into being

indicating a shorter period of karsitification in the part.Combining these observations with regional tectonic evolution data

the authors suggests that the karst re-servoirs in the east of the oilfield are still in their stage of maturity and those in the west are during their adolescence phase.