庙西北洼东营组烃源岩地球化学特征及意义

Geochemical Characteristics and the Significance of the Source Rocks in Dongying Formation of the Northern Depression of Miaoxi Sag

通过对庙西北洼东营组(Ed)74个烃源岩样品研究以及15个样品烃类抽提物饱和烃色谱-色质(GC-MS)的分析表明:Ed烃源岩自上而下依次为差、中等-好、优质级别的烃源岩,尤其是其下部烃源岩有机质十分富集,母质类型好,具有良好的生烃前景;研究区正构烷烃碳数分布范围为nC_(14)~nC_(33),主峰碳数分布范围为nC_(16)~nC_(20),呈前峰型分布,Pr/Ph介于1.28~2.58,表明烃源岩发育于弱还原-弱氧化的沉积环境;ΣnC_(21)^-/ΣnC_(22)^+为1.05~16.02,C_(27)、C_(28)、C_(29)规则甾烷均呈"V"字型分布,表明为低等水生生物与陆源高等植物的混合有机母质;CPI(碳优势指数)、OEP(奇偶优势)以及C_(29)αββ/(ααα+αββ)、C_(29)20S/(20S+20R)等成熟度参数,揭示其有机质处于低熟-成熟阶段。庙西北洼Ed优质烃源岩的确定为该区油气勘探部署提供了新的依据。

Based on the study of 74 samples of source rocks and GC-MS analysis of saturated hydrocarbon of 15 hydrocarbon extraction samples in Dongying Formation(Ed)of the northern sag of Miaoxi Sag,the results indicated that source rocks in Dongying Formation from the top to bottom was poor,medium-fine,high quality level respectively,especially in the lower Dongying Formation,there existed abundant organic matter with good type of parent material and good prospects of the source generation.The carbon number distribution of n-alkanes in the study area ranged from nC14 to nC33,maximizing was at nC_(16) to nC_(20),it was n-alkanes distribution of a front peak mode,and the Pr/Ph ratios varied from 1.28 to 2.58,it indicated the hydrocarbon was in weak oxidation-reduction depositional environment,ΣnC_(21)^-/ΣnC_(22)^+ ratios were between 1.05 and 16.02,and C_(27),C_(28) and C_(29) regular steranes presented'V'pattern,it indicated that the dual input of the aquatic organisms and terrigenous were higher plants;through the value of CPI,OEP,C_(29)αββ/(ααα+αββ),C_(29)20S/(20S+20R)and other maturity parameters,it indicated that the organic matter in the research area was at low mature-mature stage in the evolution process.The confirmation of high quality hydrocarbon source rocks in Dongying Formation provides a new basis for the oil and gas exploration and deployment in the northern sag of the Miaoxi Area.