鄂尔多斯盆地东南部二叠系碎屑岩物源分析

Provenance Analysis of Clastic Rocks in Permian System at Southeast Area of Ordos Basin

鄂尔多斯盆地东南部二叠系碎屑岩具有巨大的天然气勘探潜力。为确定该区二叠系的物源方向,探索沉积体系和天然气储层的分布规律,从盆地周缘古陆特征、岩石类型、构造属性、石英阴极发光特征、岩屑类型、重矿物组合、古流向及地球化学等方面对鄂尔多斯盆地东南部二叠系碎屑岩进行了源区分析。结果表明:该区二叠系物源分别来自北东、北西和南部三个方向,即阴山古陆东部的太仆寺旗-集宁地区、阴山古陆中部的渣尔泰山-乌拉山地区及东秦岭古陆。沉积体系的分布受源区控制,储集砂体主要分布在坪桥-安塞地区、绥德-清涧-子长-延长-延安地区及富县-宜川一带。

The clastic rocks in Permian System at the southeast area of Ordos Basin contain tremendous potential in exploration of natural gas. In order to ascertain provenance of Permian system in the studied area and grope for distribution regulation of depositional systems and gas reservoirs, provenance analysis of clastic rocks in Permian System at southeast area of Ordos Basin is conducted from the features of peripheral ancient land of the basin, lithology, tectonic property, cathodoluminescence features of quartz, types of detritus, combination of heavy crop, direction of palaeoflow, and geochemistry, etc.. Results show that the provenance of Permian System in this area comes from the northeast, northwest and south directions, respectively. That is to say, provenance includes Taipusiqi-Ji＇ning region in the east of Yinshan ancient land, Zha＇ertai-Wulashan region in the middle of Yinshan ancient land and the east Qinling ancient land. Distribution of depositional systems is under the control of provenance. Reservoirs are distributed mainly in the region of Pingqiao-Ansai, region of Suide-Qingjian-Zichang-Yanchang-Yan＇ an and the strip of Fuxian-Yichuan.