鄂尔多斯盆地大牛地气田山西组沉积相研究

Study of the sedimentary facies of Shanxi formation in Daniudi Gasfield of Ordos Basin

目的研究鄂尔多斯盆地大牛地气田山西组沉积微相及其时空展布特征,为天然气勘探寻找有利储层。方法综合运用岩心观察、薄片鉴定、测井相分析,以及稀土元素配分模式(REE)分析等手段,辅之以优势相编图法进行研究。结果划分出1个相(辨状河三角洲)、1个亚相(辫状河三角洲平原)和3个微相(分流河道、泛滥平原、沼泽沉积微相),并确定物源区主要是活动性特征的再旋回造山物源区。结论山西组内部各小层沉积相平面展布有很好的继承性,河道砂体总体都呈南北向展布,有利储层为辫状河三角洲平原分流河道。研究区主要受到北东方向物源的控制。

Aim To study the sedimentary facies of Shanxi formation in Daniudi Gasfield of Ordos Basin and clarify the microfacies and the spatial-temporal distribution,in order to search favorable reservoir for gas exploration.Methods Using different methods including the core observation,thin section analysis,electrofacies analysis,and the rare earth element distributing pattern（REE） analysis,assistant with dominant facies mapping.Results 1 facies and 1 subfacies and 3 microfacies were identified,that is,braided river delta,braided river delta plain,distributary channel,flood plain,and swamp deposit;and the geological characteristics and its identification of every microfacies were discussed.Besides,the sedimentary source comes from recycled-orogenic source.Conclusion Internal various subzones of Shanxi formation have good succession,and the channel sand body distributes by north-south way,the favorable reservoir is distributary channel of braided river delta plain.The study area is mainly controlled by northeastern sedimentary source area.