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鄂尔多斯盆地中部气区上古生界煤系气源岩生气强度大 ,大部分地区生气强度大于 40× 1 0 8m3/km2 ;丰富的气源和良好的储盖条件表明中部气区具备形成大型上古生界气藏的条件。气藏的分布受气源、砂体分布、盖层的质量和分布所控制。上古生界天然气藏的形成可分为两个阶段 :第一阶段是三叠纪—早白垩世 ,天然气向北、北东方向大规模运移 ;第二阶段是早白垩世后 ,天然气难以大规模运移 ,上古生界气源岩生成天然气主要就近聚集成藏 ,局部鼻隆构造起到了使天然气相对富集的作用。中部气区上古生界气藏的形成主要与第二阶段天然气的生成、运移和保存有关。今后该区天然气勘探的主攻方向应是中部气区上古生界气藏。

UPPER PALAEOZOIC GAS RESERVOIR FORMATION MECHANISM OF THE CENTRAL GAS FIELD IN E'ERDUOSI BASIN

??The gas generating strengths of Upper Palaeozoic coal measure source rocks at the central gas region in E'erduosi Basin are considerable,most of them being more than 40×10⁸m³/km².It is shown by abundant gas source and fair reservoir caprock assemblage that the central gas region possesses the conditions of forming large sized Upper Palaeozoic gas reservoir,which area is controlled by gas source,the distribution of sand bodies and the quality and distribution of caprocks.The process of forming the Upper Palaeozoic gas reservoir may be divided into two stages:the first stage was Triassic-Early Cretaceous while the natural gas migrated toward the north and the northeast massively;and the second stage was post Early Cretaceous while the natural gas was difficult to migrate massively,the gas originated in the Upper Palaeozoic source rocks was mainly accumulated nearby to form reservoir and local nose structures played an important role in relative gas accumulation.The formation of the Upper Palaeozoic gas reservoir at the central gas region was mainly related to the generation,migration and preservation of the natural gas during the second stage.The major target for natural gas exploration in the future should be the Upper Palaeozoic gas reservoir at the central gas region.