吉木萨尔凹陷吉页1井区二叠系芦草沟组沉积环境及有机质富集机理

通过X射线衍射、有机碳测试、主微量元素测试和饱和烃色谱等分析对吉木萨尔凹陷二叠系芦草沟组烃源岩的古环境、古生产力及其有机质富集机理进行了研究。研究结果表明：①吉木萨尔凹陷吉页1井区二叠系芦草沟组烃源岩主要为长英质混合细粒沉积岩和黏土质混合细粒沉积岩，有机质来源包括陆源有机质和海相藻类，其中海相藻类贡献较大；芦一段TOC值平均为5.93%，芦二段TOC值平均为5.69%。②研究区岩样中Ba元素含量较高，平均质量分数为12 052.89×10^-6；烃源岩正构烷烃多呈单峰型，芦一段主峰碳为C₁₇和C₁₉，具有较弱的奇碳优势，芦二段主峰为主峰碳为C₁₉，具有奇碳优势，整体类异戊二烯烃中Pr和Ph含量丰富。③研究区整体为干旱-咸化还原沉积背景，芦一段沉积期为干旱气候，古水体较浅，古盐度较高，水体分层形成稳定的还原环境，古生产力比芦二段强；芦二段沉积期为半潮湿—半干旱气候，古水体较深，古盐度较低，还原环境好。④研究区烃源岩有机质富集受控于陆源碎屑供给、古生产力和古气候等因素，还原环境稳定，是典型的“生产力富集模式”，古气候、古盐度和陆源碎屑的影响导致芦二段TOC含量较低。

Sedimentary environment and organic matter enrichment mechanism of Permian Lucaogou Formation in Jiye-1 well area,Jimsar Sag

The paleoenvironment,paleoproductivity and organic matter enrichment mechanism of hydrocarbon source rocks of Permian Luchaogou Formation in Jimsar Sag were investigated by X-ray diffraction,organic carbon testing, major and trace element testing and saturated hydrocarbon chromatography. The results show that:(1)The source rocks of Permian Lucaogou Formation in Jiye-1 well area of Jimsar Sag are dominated by feldspars-quartz mixed fine-grained sedimentary rocks and clayey mixed fine-grained sedimentary rocks. The sources of organic matter include terrestrial organic matters and marine algae,with a greater contribution from marine algae. The average TOC values are 5.93% and 5.69% in the first and second(Lu-1 and Lu-2)members of Lucaogou Formation respectively.(2)The content of Ba element in rock samples in the study area is high,with an average mass fraction of 12 052.89×10^-6. The n-alkane curve of the source rock shows unimodal distribution. The main peak carbon of Lu-1 member is C₁₇ and C₁₉,with weak odd carbon predominance,and the main peak carbon of Lu-2 member is C 19,with odd carbon predominance,and the overall isoprene-like hydrocarbons are rich in Pr and Ph.(3)The Luchaogou Formation in the study area has an overall arid-saline reductive depositional background. During the depositional period of Lu-1 member,the overall depositional environment was arid,with shallow palaeohydric depth and high palaeo-salinity,and the water was stratified to form a stable reduction environment with stronger palaeo-productivity than Lu-2 member. During the depositional period of Lu-2 member,t he depositional environment was semi-wet to semi-arid,with deeper palaeohydric depth,lower palaeo-salinity and good reduction environment.(4)The organic matter enrichment of source rocks in the study area is controlled by terrigenous clastic supply,paleoproductivity and paleoclimate. Throughout the sedimentary period of Lucaogou Formation,it was in a stable reducing environment,which is a typical "productivity enrichment mode". The influence of palaeoclimate, palaeosalinity and terrigenous debris resulted in the low TOC content of Lu-2 member.