尼日尔Agadem区块古近系层序地层及沉积体系研究

古近系是尼日尔Termit坳陷Agadem区块目前油气勘探的主要目的层位，但研究区目前整体勘探程度低，对古近系有利沉积相带及砂体的展布没有系统的认识，这些都极大制约了进一步的油气勘探。因此在研究区古近系开展层序地层和沉积体系的研究，预测有利砂体分布具有重要的理论及实践意义。文章以层序地层学及沉积学理论为指导，依据录井、测井及地震等资料，运用准层序组叠加样式、ΔlogR、地震反射终止关系及地震时频分析等方法，在Agadem区块古近系识别出2个二级层序界面、4个三级层序界面，将古近系划分为1个二级层序、5个三级层序（ESQ1-ESQ5）。在建立的层序地层格架内，综合岩心相、测井相及地震相特征分析了Agadem区块古近系的沉积环境，认为古近系层序ESQ1-ESQ3沉积时主要发育三角洲湖泊沉积体系，层序ESQ4-ESQ5沉积时主要为湖泊相沉积。在层序格架内沉积体系综合研究的基础上建立起本区古近系的两种沉积模式：层序ESQ1-ESQ3的拗陷期沉积模式及层序ESQ4-ESQ5的断陷期沉积模式。

The study on sequence stratigraphy and sedimentary systems of Paleogene in Agadem Block,Niger

The Paleogene is the main explorative target in the Agadem block of Termit depression in Niger.At present,the exploration degree remains low and the distributions of favorable sedimentary facies and sandbodies haven’t been systematically recognized.It greatly restricts any further exploration of hydrocarbons.Hence,it has great theoretic and practical significance to carry out researches on sequence stratigraphy and sedimentary system of Paleogene and to predict distribution of favorable sandbodies.Guided by the theories of sequence stratigraphy and sedimentology,based on the comprehensive analyses of mud logging,well logging and seismic data,two second-order and four third-order sequence interfaces of Paleogene in Agadem block are identified according to the methods of paraseqence sets stacking patterns,ΔlogR,seismic reflection terminal relations and seismic time-frequency analyses.The Paleogene thus could be divided into one second-order sequence and five third-order sequences(ESQ1-ESQ5).In the framework of sequence stratigraphy,the sedimentary environment of Paleogene in Agadem block is studied on the basis of core,logging and seismic facies.It is considered that sequence ESQ1-ESQ3 mainly developed delta-lacustrine sedimentary system,sequence ESQ4-ESQ5are mainly composed of lacustrine deposits.Through the synthetic study of sedimentary system,two depositional models in Paleogene of the study area are established-the depression model of sequence ESQ1-ESQ3and rift model of sequence ESQ4-ESQ5.