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.