Multiplicity of hydrocarbon reservoir and accumulation controlling factors within buried hills in Jizhong depression

Key words:  hydrocarbon reservoir of buried hill  inner impermeable bed of buried hill  hydrocarbon transporting  Jizhong depression

Abstract:

Inner hydrocarbon reservoirs of buried hills are the oil pools where hydrocarbon accumulated under the unconformity, but on the essence their traps are irrelevant to the unconformity and are different from those pools trapping by the unconformity. Based on the analysis of the recent exploration achievements in Jizhong depression, the types of inner hydrocarbon reservoir and its accumulation controlling factors were discussed. The results show that the inner hydrocarbon reservoirs are characterized by multiplicity. There are various inner hydrocarbon reservoirs of buried hills including inner fault traps, inner stratigraphic traps, monocline traps and so on. The inner hydrocarbon reservoirs of buried hills are characterized as stratified while the pools trapping by the unconformity are massive. The formation of inner hydrocarbon reservoirs of buried hills is controlled by the transporting conditions and the impermeable beds(caprocks).Commonly, unconformity and boundary faults are the two basic conducting beds, and their permeability becomes lower than those of the inner beds , which is the important reason for the petroleum being forced to migrate into the inner of the buried hills. The development of the inner impermeable layers is controlled by the mud percentage of the inner beds.