桂中坳陷泥盆系碳酸盐岩烃源岩特征

Characteristics of carbonate source rocks of the Devonian strata in Guizhong depression Guangxi,China

通过对桂中坳陷泥盆系野外地质剖面的实际丈量和烃源岩样品的室内分析,完成了桂中坳陷泥盆系烃源岩岩石类型、地层厚度和分布的调查及总体有机地球化学特征的分析,在此基础上详细论述了各层位烃源岩特点,指出了泥盆系的主力烃源岩层段。研究结果表明:桂中坳陷泥盆系是以海相碳酸盐岩为主的连续地层,平均有机质丰度偏低,有机碳含量平均值为O.21%;有机质类型以Ⅰ型干酪根为主,部分为Ⅱ_1型;镜质组反射率为0.937%～2.03%,有机质总体上处于成熟—过成熟阶段。烃源岩综合评价结果显示:中泥盆统唐家湾组中段是桂中坳陷的主力烃源岩层段,该层段的烃源岩厚度为374.7m,有机碳含量平均值为0.29%,有机质类型以Ⅰ型干酪根为主,镜质组反射率为0.937%～1.115 3%,有机质处于中等成熟阶段。

According to the survey of the stratigraphic profiles in field of Devonian strata in the Guizhong depression and laboratory experiments of source rock samples,the investigation on rock types,thickness,distribution of source rock and the analysis of the total organic geochemical characteristics are summarized herein.On the basis of study above,this paper discusses the characteristics of source rock in each formation in detail,and points out the most effective source rock layer of Devonian strata in the Guizhong depression.The results show that Devonian strata in the Guizhong depression consists mainly of continuous marine deposited carbonates,the total organic carbon(TOC) of carbonate source rock is low,averagely 0.21%;and the main type of organic matter is the typeⅠ,a few typeⅡ_1;the vitrinite reflectance (R_o) of kerogen ranges from 0.937%to 2.03%,indicating the maturated and super-maturated stages.According to the comprehensive evaluation of carbonate source rock,the middle segment of Tangjiawan Formation in the central stage of Devonian system is the most effective source rock in the Guizhong depression,with an effective thickness of 374.7m,and average TOC of 0.29%,and the main type of organic matter is typeⅠwith R_o values ranging from 0.937%to 1.1153%,the organic matter is at middle-maturity stage.