库车坳陷下第三系盖层封闭特征及其对油气成藏的控制作用

Seal Characteristics of Eogene Mudstone Caprock in Kuche Depression and Its Improtance in Controlling Accumulation of Oil and Gas

库车坳陷下第三系泥岩盖层不仅厚度大 ,而且分布广泛 ,具有较强的毛细管、超压封闭能力和较弱的抑制烃浓度封闭能力。综合评价认为 ,克拉苏、东秋立塔克和依南构造为好封盖能力区 ,由此向南封盖能力依次变差。下第三系泥岩盖层的分布控制着白垩系油气的分布 ,天然气藏分布于好封盖区内 ,油气藏则分布于中等封盖区内。下第三系泥岩盖层封闭能力形成时期晚于三叠纪和侏罗纪烃源岩的大量排油期 ,不利于封闭油进行大规模运聚成藏 ;但早于三叠纪和侏罗纪烃源岩的大量排气期 。

The Eogene mudstone caprock in Kuche Depression is very thick and distributed widely in the depression. It is of strong capillary seal ability, overpressure seal ability and weak restraining hydrocarbon concentration seal ability. The comprehensive seal ability of the Eogene mudstone caprock in Kelasu, Dongqiulitake and Yinan Structures is good, its comprehensive seal ability gradually become bad from north to south.The distribution of the mudstone caprock controls the distributions of oil or gas in the Cretaceous system. The gas reservoirs distribute under good caprock,oil reservoirs distribute under middle caprock. The seal period of mudstone caprock of Eogene system is later than the period that a great deal of oil expelled from sourcerock of the Triassic and Jurassic system and is not favor able for a great deal of oil to accumulate. The seal period of mudstone caprock is earlier than the period that a great deal of gas expelled from sourcerock of the Triassic and Jurassic system and is favorable for a great deal of gas to accumulate.