鄂尔多斯盆地陇东地区长9油层组层序-岩相古地理

Sequence-based lithofacies and palaeogeographic characteristics of Chang 9 oil reservoir set in Longdong area, Ordos Basin

通过岩心描述、岩石薄片鉴定、古生物、物源区及测井曲线等资料的综合分析,对鄂尔多斯盆地陇东地区三叠系延长组长9油层组沉积相和层序地层学特征进行了详细研究,确定长9油层组属于浅水三角洲沉积体系,可划分为1个长期、2个中期和4个短期旋回层序。以古盐度的定量计算和盐度分区为依据,进一步确定了陇东地区长9油层组沉积期的古湖岸线位置。在此基础上,以物源区、沉积相和层序分析等资料为基础,选取中期旋回层序的上升和下降相域作为等时地层单元编制陇东地区长9油层组各时期层序-岩相古地理图。结果表明,各时期古地理面貌和砂体展布格局主要受湖平面升降和物源区方向控制,最有利储层发育的水上和水下分流河道主要出现在各中期旋回的湖侵相域,砂体的延伸方向与西南部的主物源方向相平行。该研究成果对陇东地区长9油藏的后续勘探具有一定的指导意义。

base level phases of middle-term sequence cycles were selected as the isochronic＇ stratigraphic unit to draw up dw sequence-based lithofaeies and paleogeography map of Chang 9 oil reservoir set in Longdong at^a. It is concluded that paleogeography features and sand body distribution are controlled by lake level flu~.tuation and source direction. Distributary channels and underwater distributary channels during the transgressive phases are thw^rable for reservoir development, and the sand body direction is parallel to the major source direction. The resuhs canl guide the followingexploration for the Chang 9 reservoirs in Longdong area.