中国典型盆地油页岩特征及赋存规律

Oil Shale Characteristics and Distribution in Typical Basins of China

我国陆相盆地油页岩矿床特征多样,尚未形成统一的分类体系,本文以典型盆地松辽盆地、抚顺盆地和桦甸盆地、准噶尔盆地以及鄂尔多斯盆地为例,分别开展了离散型大陆裂谷盆地、转换型走滑盆地、汇聚型前陆盆地及板内型克拉通盆地4种类型解剖,总结了各类型盆地油页岩特征及矿床赋存规律。其中:离散型大陆裂谷后热沉降坳陷演化阶段沉积的油页岩具有有机质类型Ⅰ型、含油率中等、厚度中等、分布面积广的特征,易形成特大型油页岩矿床;离散型大陆裂谷同裂谷沉降断陷阶段沉积的油页岩具有有机质类型Ⅱ1-Ⅱ2型、含油率中等、厚度中等、分布面积小的特征,易形成中型油页岩矿床;转换型走滑盆地油页岩具有有机质类型Ⅱ1-Ⅱ2型、矿床赋存特征差异较大的特征,这主要取决于走滑运动断陷的构造沉降量,该类型盆地既发育中等含油率、巨厚的油页岩矿床,也发育高含油率、厚度薄的油页岩矿床,但总体分布范围较小,易形成中小型油页岩矿床;汇聚型前陆盆地陆相磨拉石阶段沉积的油页岩具有有机质类型主要为Ⅰ和Ⅱ1型、含油率较高、厚度大、分布局限、地层产状变化大的特征,易形成大型油页岩矿床;克拉通型盆地陆内坳陷阶段沉积的油页岩具有有机质类型主要为Ⅰ和Ⅱ1型、含油率中等、厚度稳定、分布面积广的特征,易形成特大型油页岩矿床。在所有盆地类型中,半深湖-深湖环境、高水位体系域和水进体系域是油页岩形成的有利场所。

The characteristics of oil shale deposits in continental basins in China are wildly distributed.Taking Songliao basin,Fushun and Huadian Basin in the Dunmi fault zone,Junggar basin,and Ordos basin as examples,the authors analyzed four types of basins:discrete continental rift basin,transitional strike slip basin,convergent foreland basin,and intraplate craton basin,and summarized oil shale characteristics and their distribution.Among them,the oil shale of discrete continental rift basin deposited in the post rift thermal subsidence evolution stage has the characteristics of organic matter typeⅠ,medium oil yield,stable thickness,and wide distribution area,which is easy to form super large oil shale deposits,while the oil shale of discrete continental rift basin deposited in the same rift has the characteristics of organic matter typeⅡ1-Ⅱ2,medium oil yield,medium thickness,and small distribution area,which is easy to form medium oil shale deposits;the oil shale in the conversion strike slip basin has the characteristics ofⅡ1-Ⅱ2 organic matter and medium-small overall distribution range,but the occurrence of deposits is quite different depending on the extent of the structural subsidence of the strike slip movement fault depression,which tends to form not only oil shale deposits with medium oil yield and huge thickness,but also oil shale deposits with high oil yield and thin thickness;the oil shale deposited in the continental molasse stage of convergent foreland basin has the characteristics ofⅠ-Ⅱ1 types of organic matter,high oil yield,large thickness,but limited distribution and large changes in stratigraphic occurrence,which is easy to form large oil shale deposits;the oil shale deposited in the stage of intracontinental depression of craton basin has the characteristics ofⅠ-Ⅱ1 types of organic matter,medium oil yield,stable thickness,and wide distribution area,which is easy to form super large oil shale deposits.Among all types of basins,deep lake environment,high system tract,and transgressive system tract are favorable for oil shale formation.