The Yanan Formation is developed throughout the Ordos Basin, and one of most important coal, oil and gas bearing strata in the basin. Based on large amount drilling, logging data, using sedimentological method analyzed Yanan Formation sedimentary system and coal accumulation characteristics in Ailaiwukugou to Taijizhao area in the Dongsheng coalfield. The study considered that the Yanan Formation is braided river, meandering river and braided river deltaic deposits. Sedimentary microfacies mainly have channel lag deposit, channel bar, floodplain, backswamp deposits of braided river system; channel lag deposit, point bar, levee, floodplain, alluvial flat lacustrine deposits of meandering river system; distributary channel, levee and backswamp deposits of braided river delta system. Vertically, the braided river and meandering river deposits present coarse upper part and fine lower part discontinuity normal rhythm or normal cycle, typical river dualistic structural features. The coal accumulation characteristic analysis considered that the backswamp environments of braided and meandering river systems are favor to coal forming, since channel scouring and incision, coal thickness in braided and meandering rivers is rather thin and rather poor lateral continuity; while delta plain in delta system is favorable coal-forming zone, coal seams in the zone have characteristics of rather thick, simpler structure, broader distribution extent and better continuity.%鄂尔多斯盆地延安组在全盆地发育,是盆地内最重要的含煤、油、气地层之一,依据大量的钻井、测井资料,运用沉积学的方法,对东胜煤田艾来五库沟-台吉召延安组沉积体系及聚煤特征进行了分析.研究认为延安组为辫状河、曲流河及辫状河三角洲沉积,沉积微相主要发育有辫状河体系的河床滞留沉积及心滩、河漫滩和河漫沼泽沉积；曲流河体系的河床滞留沉积、边滩、天然堤、河漫滩、河漫沼泽和河漫湖泊沉积；辫状河三角洲体系的分支河道、天然堤和河漫沼泽沉积等.辫状河及曲流河垂向上表现为下粗上细的间断性正韵律或正旋回,为典型的河流二元结构特征.聚煤特征分析认为,辫状河和曲流河体系河漫沼泽环境是有利成煤场所,由于河道的冲刷、下切作用,辫状河道和曲流河道形成的煤层厚度较小、侧向连续性差；三角洲体系的三角洲平原是有利的成煤带,其煤层具有厚度较大、结构较为简单、分布范围较广、连续性较好的特征.
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