柴达木盆地西北部新近系上干柴沟组烃源岩生物标志化合物特征及意义  

Characteristics and implication of biomarker in source rocks of the Upper Ganchaigou Formation of Neogene in northwestern Qaidam Basin

作　　者：夏洋 曲江秀[1] 丁修建 XIA Yang;QU Jiangxiu;DING Xiujian(School of Geosciences,China University of Petroleum,Qingdao,Shandong 266580,China)

机构地区：[1]中国石油大学(华东)地球科学与技术学院,山东青岛266580

出　　处：《天然气勘探与开发》2024年第5期55-63,共9页Natural Gas Exploration and Development

摘　　要：柴达木盆地西北部古近系—新近系烃源岩是我国西部典型的咸化湖相烃源岩,针对研究目的层(柴达木盆地西北部新近系中新统上干柴沟组)烃源岩,通过气相色谱-质谱分析技术,分析了烃源岩的生物标志化合物对有机质来源、沉积环境及热演化程度的地质意义。结果表明:(1)研究目的层烃源岩正构烷烃轻重比■较低,萜烷化合物参数(C_(24)TeT/C_(26)TT)比值较高,规则甾烷以C_(27)和C_(29)含量较高,呈不对称的“V”字形分布,结合相应判识图版显示,烃源岩有机质来源为低等水生生物和陆源高等植物的混合输入。(2)环境判识参数,姥植比(Pr/Ph)较低,伽马蜡烷指数(Ga/C_(30)H)和β胡萝卜烷相关参数(β胡萝卜烷/C_(max))均较高,芳香烃数据显示在三芴系列中以硫芴含量相对较高,DBT/Phen比值较低,结合相应判识图版认为,烃源岩沉积环境为还原—强还原环境。(3)正构烷烃无明显碳优势和奇偶优势,三降藿烷参数(Ts/Tm)比值较高,甾烷成熟度参数C_(29)-ααα20S/(20S+20R)和C_(29)-αββ/(αββ+ααα)的平均值分别为0.46和0.52,反映烃源岩热演化程度基本达到成熟阶段。结论认为,本次研究基于气相色谱-质谱分析技术结果,探讨了部分常用生物标志化合物参数及其意义,为进一步的烃源岩发育等研究提供参考,为柴达木盆地的油气勘探提供助力。Paleogene-Neogene source rocks in northwestern Qaidam Basin are classic saline lacustrine facies source rocks in West China.Taken such rocks of the Neogene Miocene Upper Ganchaigou Formation in the study area as examples,the geological implication of biomarker in these rocks for organic-matter origin,sedimentary environment and thermal evolution was discussed using both gas chromatography and mass spectrometry technologies.Results show that(i)the source rocks exhibit a lower light-to-heavy ratio of n-alkanes,a higher C_(24)TeT/C_(26)TT value of terpane,and rich content of both C_(27) and C_(29) in regular sterane,presenting an asymmetric V-shaped extension.Combined with discrimination charts,their organic matter are believed to have originated from hybrid input of lower hydrobiont and higher terrigenous plants;(ii)among some environmental proxies,there exists a lower ratio of pristane to phytane(Pr/Ph)as well as a higher gammacerane index(Ga/C_(30)H)and the other parameter ofβ-carotene/C_(max).According to the data of arene,the content of dibenzothiophen in trifluorene series is high,and the DBT/Phen value is low.Coupling with the charts,it is considered that the source rocks are deposited in a transitional setting from reduction to strong reduction;and(iii)the n-alkanes are observed with no evident predominance in both carbon and odd-even,and exhibit a high Ts/Tm ratio for trisnorhopane,and both C_(29)-αββ/(αββ+ααα)and C_(29)-ααα20S/(20S+20R)for sterane maturity are averaged at 0.52 and 0.46,respectively,suggesting that for the rocks,the thermal evolution almost reaches a mature stage.In conclusion,this study discusses some parameters of regular biomarker and their implication,which may provide references for further probing into the source rocks and is conducive to both hydrocarbon exploration and development in Qaidam Basin.

关 键 词：上干柴沟组 生物标志化合物 烃源岩 柴达木盆地 

分 类 号：P618.13[天文地球—矿床学]