鄂尔多斯盆地东缘柳林—子洲地区本溪组富有机质泥页岩发育影响因素与发育模式

鄂尔多斯盆地东缘上石炭统本溪组海陆过渡相泥页岩是该区潜在的页岩气勘探目标。在盆地东缘柳林—子洲地区本溪组代表性剖面和重点探井的系统观测和采样分析基础上,对该区本溪组富有机质泥页岩的发育影响因素与发育模式进行了研究,并建立了本溪组“缓慢沉降、陆源供给、封闭保存”的海陆过渡相富有机质泥页岩的发育模式。结果表明:鄂尔多斯盆地柳林—子洲地区本溪组富有机质泥页岩主要发育在晋祠段和畔沟段,以黏土质泥页岩为主,含少量硅质泥页岩; 其有机质丰度高,有机质类型主要为腐殖型; 本溪期炎热潮湿的气候导致区域内成煤植物繁盛,沉积水体有机质供应充足; 在鄂尔多斯盆地东缘整体缓慢沉降的海侵背景下,障壁岛-瀉湖-浅海泥质陆棚体系在水体底层形成较高盐度的缺氧还原性水体,为沉积有机质的保存和富集提供了良好场所。

Influencing Factors and Development Pattern of Organic-rich Shale in Benxi Formation of Liulin-Zizhou Area,the Eastern Ordos Basin,China

The marine-continent transitional mud shale in Upper Carboniferous Benxi Formation is a potential shale gas exploration target in the eastern Ordos Basin. Based on the systematic observation and sampling analysis of representative profiles and key well, the influencing factors and development pattern of organic-rich mud shale in Benxi Formation of Liulin-Zizhou area, the eastern Ordos Basin were studied, and the development pattern “slow subsidence, terrigenous organic matter supply, and enclosed preservation” of marine-continent transitional organic-rich mud shale was established. The results show that the organic-rich mud shale in Benxi Formation of Liulin-Zizhou area, the eastern Ordos Basin mainly belongs to Jinci and Pangou members, and the lithofacies is mainly clay mud shale with a small amount of siliceous mud shale; the abundance of organic matter is high, and the type is mainly humic; the coal-forming plants flourish in the region because of the hot and humid climate in Benxi depositional period, and result in an abundant supply of organic matter for the sedimentary water; the transgression occurs in the eastern Ordos Basin under the tectonic background of slow subsidence; the high salinity of anoxic water at the bottom maintains reduction environment in the barrier island-lagoon-neritic muddy shelf sedimentary system, which provides a favorable zone for the preservation and enrichment of sedimentary organic matter.