鄂尔多斯盆地伊盟隆起上古生界天然气成藏条件

利用含油气系统的概念与方法研究伊盟隆起上古生界天然气成藏要素及成藏作用,总结其成藏模式.伊盟隆起上古生界天然气主要来自隆起南部及乌审旗地区的太原组和山西组烃源岩;山西组和下石盒子组冲积扇相辫状水道砂体,河流相河道砂坝砂体及三角洲平原亚相分流河道砂体为最有利储集层;上石盒子组和石千峰组厚层泥岩构成区域性盖层,另有众多局部盖层;生、储、盖层具有良好的组合关系,形成自生自储式(隆起南部)和下生上储式(隆起南部、北部)生储盖组合.天然气主要通过优势输导砂体、不整合面、断层和裂缝组成的输导体系向北部运移;隆起北部地区以局部构造圈闭、远源成藏为主,而南部地区以岩性圈闭、近源成藏为主.

Upper Palaeozoic gas accumulations of the Yimeng uplift, Ordos Basin

This paper analyzes the Upper Palaeozoic gas accumulations and conditions of the study area by using the definition and method of petroleum system, and concludes the natural gas accumulation pattern. The Upper Palaeozoic natural gas in the Yimeng uplift is mainly from the source rock of Taiyuan and Shanxi Formations in the southern part and Wushenqi area. Braided channel sandbodies of alluvial fan, river channel sandbodies and distributary channel sandbodies of delta plain in the Shanxi and Xiashihezi Formations are the most favorable reservoirs. The thick mudstone layers of the Shangshihezi and Shiqianfeng Formations which cover the whole region constitute the regional seal rock, and there are also many local seal rocks. Oil source, reservoir and seal rocks form a good relationship in time and space and they form two types of assemblage which are self-generating and self-preserving assemblage in the southern part of the Yimeng uplift and the lower-generating and upper-preserving assemblage in the southern and northern parts. Natural gas migrated to the north through the migration pathways composed by advantageous sandbody, unconformity, faults and cracks. Structural traps and the distal accumulation pattern dominate in the northern part, while the southern part is characterized by lithologic traps and the proximal accumulation pattern. The favorable gas accumulation zones are predicted in the study area.