河流相储层基准面旋回划分对比及沉积演化——以港西一区1断块为例

Fluvial Base-level Cycle Division and Correlation and Its Sedimentary Evolution——By Using Block 1 of Region 1 of Gangxi Oilfield for Example

以地质、岩心和测井等资料的综合分析为基础,结合自然伽马曲线频率分析结果,对港西油田一区1断块新近系明二段(Nm2)油组河流相沉积进行基准面旋回划分与对比。Nm2油组可以划分为22个短期基准面旋回(对应于22个单层),根据基准面旋回叠加结构特征,可以将其合并为3个中期基准面旋回。对工区22个单层的沉积微相研究发现,Nm2-7-1、Nm2-3-2和Nm2-1-1单层的沉积微相以多期河道相互叠置切割为特征,反映了较低的A/S比值(可容纳空间与沉积物供应速率之比);而以Nm2-8-2、Nm2-5-2及Nm2-1-3为代表的单层则反映了大面积泛滥平原泥岩背景下孤立河道分布的沉积格局,代表了较高的A/S比值,表明A/S比值在垂向上的旋回性变化控制着沉积微相的发育类型和时空分布模式。精细旋回地层分析和沉积微相研究可以为油田开发中后期有效管理提供地质依据。

Based on integrated analysis of geologic,core and logging and in combination with frequency analysis of GR curves,base-level cycle division and correlation were carried out on No.2 oil group of Gangxi Oilfield.It shows that No.2 oil group could be subdivided into 22 short-term cycles(corresponding to 22 single-layer),which could further be grouped into 3 medium-term cycles.From the research result of sedimentary microfacies on 22 single-layer,it could be concluded that No.2-7-1,No.2-3-2 and No.2-1-1 are characterized by amalgamated multistory channel sandstones in response to lower A/S ratios(accommodation rate to sediment supply rate ratios).In contrast,they are featured by single channel sandstones isolated in the background of extensive mudstone sediments of higher A/S ratios.The vertical different types and distribution modes of the sedimentary microfacies are significantly controlled by A/S ratios.The research of refined cyclic stratigraphic analysis and sedimentary microfacies reconstruction provides geological foundation for reservoir development management at the mid-late stage oilfield development.