鄂尔多斯地区西部和南部奥陶纪海槽边缘沉积特征与天然气成藏潜力分析

鄂尔多斯地区自中—晚元古代至早古生代继承性地发育区域性海相沉积,大体经历了中—晚元古代大陆裂谷及拗拉槽、寒武纪陆表海台地、奥陶纪局限海台地及构造转换等三个主要演化阶段。分析认为,奥陶纪在盆地西部和南部存在对天然气成藏较为有利的海槽/台地边缘沉积相带。中—上奥陶统平凉组—背锅山组是盆地西部和南部下古生界天然气成藏的主要烃源层;奥陶系礁滩体岩性圈闭是最主要的圈闭类型。盆地西部的天环北段和南部的麟游北为两个近期天然气勘探的有利目标。

Sedimentary Characteristics and Gas Accumulation Potential along Margin of Ordovician Trough in Western and Southern Parts of Ordos

Inherited regional marine sediments developed in Ordos region from middle-late Proterozoic to early Paleozoic erathems,during which three major evolution stages went through,including middle-late Proterozoic continental rifts and aulacogens,Cambrian epicontinental platform and Ordovician restricted platform and tectonic conversion.It is deemed that there was a sedimentary facies belt favorable for gas accumulation along the margin of troughs/platform in the western and southern parts of Ordos Basin.The Middle-Upper Ordovician Pingliang and Beiguo Formations are the main source rock beds for the Lower Paleozoic gas accumulation in the western and southern parts of Ordos Basin.Ordovician reef/shoal lithologic traps are common reservoirs and two areas,the northern Tianhuan area in the western part of basin and the northern Youling area,are the recent object ones favorable for gas exploration.