羌塘盆地托纳木地区上侏罗统雪山组沉积相与储集层评价

Sedimentary Facies and Reservoir Evaluation of Xueshan Formation of Upper Jurassic in Tuonamu Area, Qiangtang Basin, Tibet

西藏羌塘盆地双湖托纳木地区地处羌北坳陷与中央隆起带毗连地带,广泛发育上侏罗统雪山组沉积,其岩石地层垂向上由3个沉积组合构成,总体显示为一个向上变粗的充填序列。雪山组一段发育三角洲相,二段发育冲积扇相。三角洲相包括三角洲前缘和三角洲平原两个亚相,三角洲前缘亚相发育分流河道、河口坝、远砂坝和分流间湾,三角洲平原亚相发育天然堤和分流河道,冲积扇相包括外扇和中扇两个亚相。储集层分析表明,上侏罗统雪山组二段碎屑岩储集层的储集性能较佳,可达中等水平,其次为雪山组一段碎屑岩,为中等偏差储集层。

Shuanghu-Tuonamu area in Qiangtang basin is situated in northern Tibet plateau, along Qiangbei depression and central uplift zone, with widespread Xueshan formation deposits of Upper Jurassic. Two sedimentary associations in its vertical structure appear one coarsen-upward filling sequence. Delta and alluvial fan facies are developed in the first member and second member of Xueshan formation, respectively. The delta facies includes two subfacies of delta front and delta plain. The subfacies of delta front consists of the microfacies of distributary channel, mouth bar, distal bar and interdistributary bay; the subfacies of delta plain consists of the microfacies of natural levee and distributary channel. The alluvial fan facies include the subfacies of outside fan and middle fan. The reservoir analysis shows that the reservoir quality of the second member of Xueshan formation belongs to medium reservoir, better than that of the first member of Xueshan formation.