Skylight-type Buried Hill Reservoir To Form A Power Cycle And Basin Deep Water

Lunnan buried hill reservoir is a super carbonate reservoir with 2000m high and 20000km2 area and 4100m depth buried under the ground, Tarim basin. The main reservoir space of the reservoir is Ordovician carbonate ancient weathered crust Karst cave-fractures system. Above the hill, there was a giant thick Ordovician or Carboniferous mudstone onlapped on the slopes of the hill as a capping formation, but a more than 80km2 area in the top of the hill covering with a thick Triassic water-bearing sandstone came into being a top-window area for the hill. It is just because of the top window so that a NEW type of reservoir formed, which called Top-opening Buried Hill Reservoir. In this type of reservoir, the oil and gas accumulated mostly in the slopes surrounding the hill. The upper area near the top of the hill was filled with water or water and little oil. The oil-water interface in such a reservoir was tilting, and the oil-gas accumulating has a unique hydrodynamic features. The genesis of the Lunnan super buried hill reservoir would have likely related with the hydrodynamism due to the Top-window. The main factors dominated the reservoir forming were reservoir, differential dissolution and hydrodynamism. The reservoir controlled the oil and gas accumulating in the surface weathered crust of the buried hill, differential dissolution controlled the oil and gas differential distributing in the hill and the hydrodynamism restrained the oil and gas leaking from the hill and controlled it accumulating in the slope of the hill and controlled the shape of the oil and gas reservoir.Although the top window was unfavorable to the oil and gas preserving, the inverted water dynamic created a sealed zone at the upper of the slope and prevented the oil and gas escaping through the window, which would be the essential reason that the buried hill richly accumulated oil and gas in despite of broken once and again.The hypostasis of differential dissolution is the molecules of oil and gas dissolving and diffusing each other. The differential dissolution made oil and gas mixing and complicated distributing in the reservoir, but in a certain rule:the traps close to the source would be full filled with dry gas or condensate gas, and far away from the source would be oil.There were broad fluids flow in the deep of Tarim Basin, and the flows were shown as the shallow fluid circulation and deep hydrothermal circulation. The driving force driven the deep hydrothermal circulation is the local geothermal discrepancy coming from the difference of thermal flux distributing in the deep of the basin. The hydrodynamic texture would be changed followed the tectonic framework changing, and there would be different driving mechanism at a different hydrogeologic stage and a different hydrogeologic frameworks for the basin fluids. The basin fluids circulation flow supplies vital carriers for matter transport and energy convection, and provides necessary spaces and dynamic for oil, gas and other ores accumulating.