Abstract:

Based on a new stratigraphic division and large quantities of drilling，outcrop and core data，the authors have studied in detail the depositional system， lithofacies palaeogeographic characteristics and evolution of the Yan 9 oilbearing interval of the Yanan Formation in Huachi area， Ordos Basin. The results indicate that the Yan 9 oilbearing interval is dominated by fluvial deposits and was inherited and developed from the Yan 10 oilbearing interval. During the deposition of Yan 9， mainly braided fluvial， braided meandering fluvial and anastomosed fluvial facies were developed. Braided fluvial facies was developed in the Y39 interval and Y29 interval inherited the fuvial deposits of Y39， and formed the braided meandering fluvial facies. After the two former stages of filling process， anastomosed fluvial deposits were developed in the Y19 interval in the  peneplain environment. Two fluvial depositional models were developed in the Yan 9 oilbearing interval in Huachi area，namely as， braided fluvialbraided meandering fluvial and anastomosed fluvial depositional models.

Key words: braided fluvial, braided meandering fluvial, anastomosed fluvial, sedimentary facies, fluvial evolution, Yan 9 oilbearing interval, Ordos Basin

摘要：

据新的地层划分方案及大量钻井、露头和岩心资料，详细研究了鄂尔多斯盆地华池地区延安组延9油层组（Y9）沉积体系特征及演化，认为延9油层组主要为河流沉积，是延10油层组的继承与发展，发育有辫状河、辫状型曲流河和网状河3种类型的河流。Y39油层是辫状河发育的油层，Y29油层在继承Y39油层河流的基础上发育辫状型曲流河，Y19油层则是在前两期逐渐填平补齐之后，在准平原条件下发育的网状河沉积。华池地区延9油层组发育辫状河—辫状型曲流河和网状河两种河流沉积模式。

关键词: 辫状河, 辫状型曲流河, 网状河, 沉积相, 河流演化, 延9油层组, 鄂尔多斯盆地