断陷湖盆层序界面的成因类型及其与油气藏的关系

Relationship between hydrocarbon reservoir and genetic types of sequence boundary in rift lacustrine basin

利用湖盆沉积作用基本方程,对断陷湖盆层序界面的成因机制进行了研究,并对东营凹陷的断陷湖盆进行了实例分析。结果表明,气候变化和构造运动是层序界面形成的关键因素。按照成因机制,东营凹陷沙河街组的层序界面可分为构造型(T型)和构造气候综合型(TC型)。T型界面一般对应于三级层序界面,且根据沉积物的供给特征可进一步分为3种类型;TC型界面一般对应于二级或一级层序界面。不同成因机制的层序界面具有不同的结构特征和地层分布模式,砂体和油气的富集程度与界面的成因类型存在着密切的关系。TC型界面附近砂体发育,砂体成藏率低;T型界面附近砂体发育程度低,砂体成藏率高。

Based on the sedimentary basic equation, the genetic mechanism of sequence boundaries in rift lacustrine basin was discussed. The characters of the rift lacustrine basin in Dongying Depression were exemplified. The analysis results show that the tectonic movement and climate are the key factors for generating sequence boundary. The sequence boundaries in Shahejie Formation of Dongying Depression can be divided into two types of tectonic boundary (T type) and tectonic-climate synthetic boundary (T_C type) according to the genetic mechanism. The T type boundary usually corresponds to the third order sequence boundary and can be divided into three sub-types according to the characteristics of sediment supply. The T_C type boundary corresponds to the second or first order sequence boundary. There are different sequence stratigraphic structures and modes for the sequence boundary resulted from different genetic mechanism. The genetic type of sequence boundary is relative to the distribution of sandbody and oil reservoir. The sandbody was developed in a great degree nearby the T_C type boundary, which has a little probability for forming reservoir. The sandbody was developed in a small degree nearby the T type boundary, which has a great probability for forming reservoir.