鄂尔多斯盆地里151油藏延8—延10油组沉积特征及其与油气的关系

Sedimentary microfacies study for Yan8-Yan10 layers of Yan'an formation in Li151 oilfield,Ordos Basin

鄂尔多斯盆地里151油藏尚处于开发前期，储层沉积微相及砂体展布规律认识不清。为指导后续开发，结合岩心观察、薄片鉴定、测井及生产动态等资料进行了沉积微相划分，确定了微相空间展布规律及其与油气富集的关系。结果表明：延安组延8-延9油组为三角洲平原沉积，可进一步划分出分流河道、河道砂坝、决口扇和河间沼泽4种沉积微相；发育1-3条南西-北东向分流河道，随着基准面变化河道发生了横向摆动，不同时期分流河道的数量、规模也发生变化。延10油组为辫状河沉积，可划分出辫状河道、心滩和泛滥平原3种沉积微相；心滩发育，砂体厚度大。基准面下降晚期的延10—1、延9-2、延8-3和延8-1小层储层发育，有利于油气富集；分流河道、河道砂坝、辫状河心滩微相对油气富集有利。

As a result of confusion about the reservoir sedimentary microfacies and the distribution rule of sand body in early the development of Li151 oilfield,the core,thin section,logging data and well performance definitely indicate the conclusion of division of microfacies,the spatial distributing of sedimentary facies and the relationship between sedimentary facies and oil-gas enrichment,which provide guidance for subsequence development.The results show that the Yan8-Yan9 layers are developed in sedimentary system of delta plain with 1-3 from SW to NE distributary channel(s),which laterally swung,as well as the number and dimension of distributary channe(ls)at different periods changed along with the fluctuation of base level.The Yan10 layer is developed in sedimentary system as braided river with developed channel bar and thick sand body.The distributary channels,sand bar in channels,channel bar of braided river are favorable for the oil-gas enrichment.These achievements are of valuable significance to direct the progressive development of the reservoir.