层序地层学在秦南凹陷东南斜坡隐蔽油气藏勘探中的应用

探讨隐蔽油气藏在层序格架内的展布规律及预测方法。在层序地层学理论指导下,综合运用钻井、测井以及地震资料,对渤海秦南凹陷东南斜坡区古近系东营组层序地层特征进行了精细研究,把东营组划分为3个Ⅲ级层序:东三、东二和东一层序,并建立东三层序的沉积模型,总结了隐蔽油气藏成藏模式。研究结果表明:在东三层序晚期水体下降,物源供给充足,储层十分发育并且分布范围广,与东二层序稳定分布的泥岩相配合可形成大规模的地层油气藏;早期水体逐渐上升,可形成超覆尖灭岩性油气藏。东二层序厚层泥岩之下,受湖平面变化控制的砂体展布特征和油气输导条件是隐蔽油气藏的成藏主控因素。秦南凹陷隐蔽油气藏勘探潜力巨大。

Application of sequence stratigraphy to subtle oil and gas reservoir exploration in southeast slope of Qinnan depression of Bohai Bay,China

This paper discusses the distribution laws and prediction methods of the subtle oil and gas reservoir in a sequence framework.Guided by the sequence stratigraphic theories,this paper studies the sequence stratigraphy features of Paleogene Dongying Formation in the southeast slope of the Qinnan depression in Bohai Bay in detail by using well drilling,logging and seismic data.Dongying Formation is divided into 3 third-order sequences,that is Sequence Dong 3 ,Sequence Dong 2 and Sequence Dong 1 .The depositional model of Sequence Dong 3 is constructed and the petroleum accumulation model of the subtle oil and gas reservoir is concluded.The research results show that in the late period of Sequence Dong 3 reservoir well developed and widely distributed with water level falling and the abundant material supplying, which can form a large-scale formation reservoir combined with the stable distribution of mudstone in Sequence Dong 2 .In the early stage,the water gradually rises and an overlap pinch-out lithologic reservoir can be formed.Below the thick mudstone of Sequence Dong 2 ,the main controlling factors of the petroleum accumulation for the subtle oil and gas reservoir are the sand distribution characteristics controlled by the change of lake level.The exploration potential is great in subtle reservoirs of the Qinnan depression.