准噶尔盆地乌-夏地区油气成藏期次分析

Research on the Stages of Reservoir Formation in Wuerhe-Xiazijie Area in Junggar Basin

乌-夏地区发育佳木河组、风城组和下乌尔禾组3套烃源岩,它们的热演化程度和排烃高峰期具有明显差异。由于多期的构造运动,使得该区断裂发育。以侏罗系底界为限,纵向上可划分为深、浅两套断裂体系,其中深层断裂的持续活动为油气的垂向运移提供了良好通道。依据地化特征,可将乌-夏地区的原油分为Ⅰ～Ⅳ类,不同类型的原油分布在不同层系和区域。多套烃源岩、不同的排烃期、持续的断裂活动和多种类型的原油显示该区油气成藏过程复杂。根据流体包裹体均一温度分析,三叠系具有三叠纪末和白垩纪末两期油气成藏,而二叠系具有二叠纪末、三叠纪末和白垩纪末3期油气成藏。多期的油气充注,预示着乌-夏地区乃至西北缘二叠系仍具有巨大的勘探潜力。

Three sets of source rocks including Jiamuhe Formation, Fengcheng Formation and Lower Wuerhe Formation were developed in Wuerhe-Xiazijie Area. Their thermal evolution grades and peak-times of hydrocarbon expulsion were obviously difference. Because of multi-periods tectonic movements, faults were developed in the area. By the limitation of Jurassic system, faults could be divided into deep fault systems and the shallow fault systems. The everlasting movement of the deep faults provided good ways to vertical migration of oil and gas. By the character of geochemistry, the crude oil in Wuerhe-Xiazijie Area can be divided into I-IV types. Different types of crude oil are distributed in different layers and areas. Several sets of source rocks, different times of hydrocarbon expulsion, everlasting fault movements and multi types of crude oil indicate that the hydrocarbon accumulation process in Wuerhe-Xiazijie Area are very complex. The homogenization temperature of fluid inclusions indicates that Triassic has two formation stages of oil-gas reservoirs - late Triassic and late Cretaceous, and Permian has three formation stages of oil-gas reservoirs- late Permian, late Triassic and late Cretaceous. Hydrocarbon accumulation of many times indicates that the northwestern margin of Junggar Basin, especially Wuerhe-Xiazijie Area still holds great exploratory potential.