The Rule Of Sandbodies Distribution And Sedimentary Characteristics Of The 9th Member Of Yan Chang Formation In The Longdong Area Of Ordos Basin

on the basis of sedimentary geology, geophysics, lithofacies ancient geography and paleontology and other related materials,carried out a detailed study on the rule of sandbodies distribution and sedimentary characteristics of the 9th member of YanChang formation in the Longdong area of Ordos basin.the types of the parent rocks and directions of sediment supply are discussed on the basis of imaging logging paleocurrent, the types and compositions of the sandstones, light mineral and heavy mineral assemblages and palaeogeographic framework during the deposition of the 9th Member of the Yan Chang Formation in The Long-Dong area. The results of research in this study have disclosed that the clastic debris in the LongDong area is mainly controlled by Qi Lian-Qin Ling Fold belt and ancient Qinling, the main sedimentary provenance of the 9th Member of the Yan Chang Formation was detailed divide three sources, which are from north-east,south-west and south. The parent rocks is mainly comprise of metamorphic rock fragments, and igneous rock is accounted for a part. Studies of the typical sign,nature of fluvial depositional and lake depositional systems was deposited in the studied area,including delta plain subfacies in south-west, delta-front subfacies in middle,small part of shallow lake subfacies in north-east and several microfacies.According to the lithology, sedimentary structures, palaeontology, logging and other features, we can find the ancient lake shoreline position. Studies show that the9 th Member of the Yan Chang Formation's early structure is very stable, and it Occur in retrograding period of the lake basin, water deepening, mainly developed delta and semi-deep lacustrine facies. Among them, the most developed in the southwest, they are belong to delta plains and delta front sediments, mainly in the southwest and northeast. The sedimentary center is located in Fuxian-HuangLong area,it mainly developed semi-deep lake sedimentary. The Chang 91 is Similar to the Chang 92 interval of the Yan Chang Formation. Compared with the Chang 92 interval, its lakeshore line began to fall back, but its semi-deep lake faciesexpanded.Chang 9 interval mainly developed delta shallow lake, semi-deep lake facies. Among them, the sedimentary center is located in Zhidan-Ganquan area, and it mainly belongs to semi-deep lake facies. Finally,we established a completely sedimentary model on the Chang 9 interval of the Longdong area.Therefore,we can study the spatiotemporal distribution of sandbodies, the delta plain and delta front sand bodies overall were belt-like distributed., in the southwest,North West, North and south direction.The deposition center is in Wuqi-Yizheng area. The sand bodies of Chang 9 interval on the whole are well developed, mainly developed the six branches of sand bodies.Overall they are toward to the south,West, North and East. And the elta plain facies distributary channel sandbodies and the sand bodies of subaquatic distributary channels in delta fronts are the better reservoir of the study area.