冀中坳陷饶阳凹陷留西地区沙三上亚段层序地层与隐蔽油藏

Sequence stratigraphy of the upper third member of the Shahejie Formation in Liuxi area of the Raoyang Sag,the Jizhong Depression and exploration of subtle reservoirs

根据层序地层学基本原理,利用地震、测井、岩相等资料,对冀中坳陷饶阳凹陷留西地区古近系沙三上亚段进行了层序地层学研究,建立了全区的层序地层格架。研究表明,沙三上亚段为一个完整的三级层序,可分为低位、湖侵和高位3个体系域。在此基础上,分析了层序格架内各体系域的沉积相平面展布特征。沙三上亚段主要发育辫状河三角洲沉积相,其中前缘亚相分布面积最广。区内低位体系域砂体与湖侵体系域烃源岩形成了十分有利的生储盖组合,具有优越的隐蔽圈闭发育条件。结合区域构造特征,综合分析认为中南部沙三上亚段低位体系域辫状河三角洲前缘砂体是下一步隐蔽油藏勘探的有利区域。

Exploration of subtle reservoirs is a hot topic and one of the future directions in oil exploration. In this paper,research on sequence stratigraphy of the upper third member of the Shahejie Formation （Es^3） in the Liuxi area of the Raoyang Sag, the Jizhong Depression is made based on basic principles of sequence stratigraphy and by using seismic, logging and lithofacies and other data. Sequence stratigraphic framework of the Liuxi area is established. According to the research, the upper Es^3 is a complete third-order sequence which can be divided into lowstand,lake transgression and highstand system tract. Based on these results, the plane distribution features of sedimentary facies in each system tract are analyzed under the sequence stratigraphic framework. The upper Es^3 is dominated by braided river delta facies, of which the delta front subfacies is the most extensive. The sandstone in the lowstand system tract and the source rock in the lake transgression system tract form an excellent source-reservoir-seal combination, which is favorable for the development of subtle reservoirs. Considering the regional structure features, it is suggested that the favorable exploration targets for subtle reservoirs should be the sand body in the braided river delta front of the lowstand system tract in the upper Es^3 in the central and southern parts of the study area.