鄂尔多斯盆地上古生界天然气成藏特征

Natural gas accumulation in the Upper Paleozoic of Ordos Basin, China

鄂尔多斯盆地上古生界具有含气丰富和低孔、低渗、低压的特征。通过储集层流体包裹体均一温度、包裹体激光拉曼光谱、沥青分布与成因、岩石薄片等分析,结合天然气组分、C5—C8轻烃、单体碳同位素实验数据,分析了鄂尔多斯盆地上古生界天然气成藏基本特征和成藏过程,总结了高效储集层的主控因素,划分出3种上古生界天然气成藏组合,即源内成藏组合(山2段—太原组)、源顶成藏组合(山1段—盒8段)、源外成藏组合(石千峰组)。并应用上述方法剖析了不同类型气藏天然气成藏过程及成藏主控因素。

The natural gas pools developed within the Upper Paleozoic of Ordos Basin are of low porosity, low permeability and low pressure. The gas accumulation characters and processes were analyzed through the study of fluid inclusion homogeneous temperature, fluid inclusion laser-Raman spectrum, bitumen distribution and genesis, and rock slices, together with the experimental data of the composition of the natural gases, light hydrocarbons from C5 to C8 and individual carbon isotope. Three gas plays were identified as inside source play, P： s2-C3 t; top source play, P1 s1-P1 x8 ; and outside source play, P2 s. Four gas pool-forming stages developed in Upper Paleozoic, including CO2 injection, light liquid hydrocarbon injection, extensive gases injection and the dynastic stage between the gain from coal-absorbed gas and the loss from cumulative natural gas. The accumulation processes and key factors of different types of gas pools were also studied.