海相地层无机参数与烃源岩发育环境的相关研究——以鄂尔多斯盆地为例

Study on relation between inorganic parameters in marine deposits and developmental environment of hydrocarbon source rocks:taking Ordos basin as an example

腾格尔 刘文汇 徐永昌 陈践发 胡凯 高长林

Tenger Liu Wenhui Xu Yongchang Chen Jianfa Hu Kai Gao Changlin

运用无机与有机参数组合对鄂尔多斯盆地海相烃源岩发育环境的研究表明,有机碳含量大于0.2%层段其V/(V+Ni)>0.5,Zr/Rb<2,Rb/K>30×10,古盐度大于122,Zn,Mo,Ba等富集,δO,δC正向偏移,指示低能、缺氧环境,具良好的有机质保存条件,有较高的生物生产力和有机质埋藏量,其δC<-28‰,有机质类型好(vi- 型),生烃潜力高,可视为潜在有效烃源岩;有机质碳含量大于等于0.2%层段的有机、无机地化特征均反映高能、氧化环境,有机质保存条件差,埋藏量低,δC值为-28‰～-24‰,多属 型母质,生烃潜力差,属非有效烃源岩。微量元素及碳氧同位素对烃源岩发育的主控因素具良好的表征意义,可作为烃源岩发育环境的判识指标,结合必要的有机参数可以进一步识别有效烃源岩。

The paleoenvironment of Ordovician in southwestern Ordos basin are discussed by using both inorganic and organic parameters,trying to identify potential hydrocarbon source rocks.In the strata with >0.2%,V/(V+Ni)>0.50,Zr/Rb<2,Rb/K>30×10,>122,Zn,Mo and Ba are enriched,and the δO and δC have positive excursion.These characteristics indicate a stagnant and anoxic sedimentary environment with higher organic matter productivity and better preservation condition.These strata have δC<-28‰(iv- type kerogen),and high hydrocarbon-generating potential,so they can be regarded as potential hydrocarbon source rocks.The strata with TOC≤0.2% whose inorganic and organic parameters show a high energy,oxic,littoral-neritic environment with δC between-24% and-28‰(( type kerogen)have low hydrocarbon-generating potential.Such environment is unfavorable for preservation of organic matters,and development of hydrocarbon source rocks.The integration of inorganic parameters(trace element,stable isotope composition etc.) with general organic data can be regarded as important environmental factors for identifying development of effective marine hydrocarbon source rocks.

10.11743/ogg20050403