尼日尔Agadem区块古近系层序地层及沉积体系研究
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摘要
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 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.
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.
引文
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[18]Zanguina M,Bruneton A,Gonnard R.Opportunities seen inthree petroleum systems in Niger[J].Oil&Gas Journal,1996,94(19):126-128.
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[20]操应长,姜在兴,夏斌,等.利用测井资料识别层序地层界面的几种方法[J].石油大学学报:自然科学版,2003,27(2):23-26.
[21]王林,姜在兴,冯磊,等.深水湖盆层序地层单元识别方法:以Muglad盆地Fula坳陷为例[J].大庆石油地质与开发,2007,26(6):1-4.
[2]Lambiase J J.The framework of African rifting during thePhanerozoic[J].Journal of African Earth Sciences,1989,8(2/3/4):183-190.
[3]Fairhead J D.Green C M.Controls on rifting in Africa andthe regional tectonic model for the Nigeria and East Niger riftbasins[J].Journal of African Earth Sciences,1989,8(2/3/4):231-249.
[4]Fairhead J D,Binks R M.Differential opening of the Centraland South Atlantic Oceans and the opening of the West Afri-can rift system[J].Tectonophysics,1991,187:191-203.
[5]Nüberg D,Müller R D.The tectonic evolution of the SouthAtlantic from Late Jurassic to present[J].Tectonophysics,1991,191:21-53.
[6]Binks R M,Fairhead J D.A plate tectonic setting for Meso-zoic rifts of West and Central Africa[J].Tectonophysics,1992,213(1/2):141-151.
[7]Guiraud R,Maurin J C.Early Cretaceous Rift of Westernand Central Africa:An overview[J].Tectonophysics,1992,213(1/2):153-168.
[8]Genik G J.Regional framework,structural and petroleumaspects of rift basins in Niger,Chad and the Central AfricanRepublic(C.A.R.)[J].Tectonophysics,1992,213(1/2):169-185.
[9]Wilson M,Guriaud R.Magmatism and rifting in Westernand Central Africa,from Late Jurassic to Recent times[J].Tectonophysics,1992,213(1/2):203-225.
[10]Guriaud R,Binks R M,Fairhead J D,et al.Chronology andgeodynamic setting of Cretaceous-Cenozoic rifting in Westand Central Africa[J].Tectonophysics,1992,213(1/2):227-234.
[11]Maurin J C,Guriaud R.Basement control in the developmentof the Early Cretaceous West and Central African Rift Sys-tem[J].Tectonophysics,1993,228(1/2):81-95.
[12]Olsen K H.Continental Rifts:Evolution,Structure,Tec-tonics[M].Amsterdam:Elsevier,1995:437-449.
[13]Bumby A J,Guiraud R.The geodynamic setting of the Phan-erozoic basins of Africa[J].Journal of African Earth Sci-ences,2005,43:1-12.
[14]Guiraud R,Bosworth W,Thierry J,et al.Phanerozoic geologicalevolution of Northern and Central Africa:An overview[J].Jour-nal of African Earth Sciences,2005,43:83-143.
[15]Bruneton A.Niger,with new oil legislation,offers littledrilled acreage for exploration[J].Oil&Gas Journal,1991,89(37):102-106.
[16]Genik G J.Petroleum geology of Cretaceous-Tertiary rift ba-sins in Niger,Chad,and Central African Republic[J].AAPG Bulletin,1993,77(8):1405-1434.
[17]Perrodon A.Overview of African petroleum systems[J].Oil&Gas Journal,1993,91(28):115-118.
[18]Zanguina M,Bruneton A,Gonnard R.Opportunities seen inthree petroleum systems in Niger[J].Oil&Gas Journal,1996,94(19):126-128.
[19]Zanguina M,Bruneton A,Gonnard R.An introduction tothe petroleum potential of Niger[J].Journal of PetroleumGeology,1998,21(1):83-103.
[20]操应长,姜在兴,夏斌,等.利用测井资料识别层序地层界面的几种方法[J].石油大学学报:自然科学版,2003,27(2):23-26.
[21]王林,姜在兴,冯磊,等.深水湖盆层序地层单元识别方法:以Muglad盆地Fula坳陷为例[J].大庆石油地质与开发,2007,26(6):1-4.
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