准噶尔盆地南缘侏罗系八道湾组富藻类体煤系源岩的发现及其沉积背景  

Discovery of alginite-rich coal measures in the Lower Jurassic Badaowan Formation at the southern margin of the Junggar Basin and its depositional setting

作　　者：王俊[1] 何毓新 刘敏[1] 高遥 魏凌云[1] 孙永革[2] WANG Jun;HE Yuxin;LIU Min;GAO Yao;WEI Lingyun;SUN Yongge(Geological Branch,Exploration and Production Research Institute,Xinjiang Oilfield Ltd.,PetroChina,Urumqi 830013,Xinjiang,China;Organic Geochemistry Unit,School of Earth Sciences,Zhejiang University,Hangzhou 310027,Zhejiang,China)

机构地区：[1]中国石油新疆油田分公司勘探开发研究院地球物理研究所,新疆乌鲁木齐830013 [2]浙江大学地球科学学院有机地球化学研究组,浙江杭州310027

出　　处：《地球化学》2024年第3期339-350,共12页Geochimica

基　　金：中国石油科技重大专项(2021DJ2101)资助。

摘　　要：通过沉积有机质中生物标志化合物组合分析,并结合荧光显微组分镜检结果,本研究首次在准噶尔盆地南缘建功剖面下侏罗统八道湾组上段识别出一套富藻类有机质输入的煤系沉积。该套煤系源岩主体处于低成熟–成熟早期演化阶段,镜质组反射率为0.5%~0.6%;有机碳(TOC)含量主要介于2.0%~4.0%之间,局部发育碳质泥岩和煤线;生烃潜量(S_(1)+S_(2))值普遍为3.0~5.0 mg/g,碳质泥岩段最高达18.4 mg/g;氢指数(HI)主要为100~150 mg/g,碳质泥岩段达280 mg/g,属于Ⅱ2型有机质。沉积有机质中生物标志化合物组合表现为姥鲛烷优势,中、短链正构烷烃含量较高,C_(27)~C_(29)规则甾烷呈“V”型分布,Ts、C_(29)Ts、C_(30)H藿烷含量较高,C同位素组成较轻。全岩荧光显微镜镜检结果表明,源岩中壳质组主要为孢子体和藻类(屑)体。结合沉积背景综合判断,该套富藻类体煤系沉积形成于水体较深的湖泊沼泽化早期阶段,浮游藻类等低等水生生物对沉积有机质存在显著贡献,有望成为区域潜在的优质烃源岩。Based on the biomarker assemblage of sedimentary organic matters in the source rocks and fluorescence microscope observations,a set of alginite-rich coal-bearing source rocks has been identified for the first time in the Lower Jurassic source rocks in the Jiangong Section at the southern margin of the Junggar Basin.This set of source rocks is in a low mature stage,with vitrinite reflectance of 0.5%to 0.6%.The TOC contents of the source rocks mostly range from 2.0%to 4.0%,and carbonaceous mudstone and coal line developed locally.Most of the source rocks have hydrocarbon generation potentials(S_(1)+S_(2))and hydrogen index(HI)of 3.0 mg/g to 5.0 mg/g and 100 mg/g to 150 mg/g,and can reach up to 18.4 mg/g and 280 mg/g in the carbonaceous mudstones,respectively,suggestive ofⅡ2 type organic matter.The biomarker assemblage is characterized by the predominance of pristane over phytane,domination of short and mid-chain components among n-alkanes,an asymmetric“V”type in C_(27)–C_(29) regular sterane distribution,relatively higher concentrations of Ts,C_(29)Ts,and C_(30) hopanes,and more depleted carbon isotopic values.Fluorescence microscope observations further indicate that the maceral is mainly composed of sporinite and alginite.Accordingly,this set of source rocks was mainly formed in a relatively deep-water environment in the early stage of lake swamping,and the organic matters in the source rocks mainly came from planktonic algae.These alginite-rich coal-bearing source rocks might become potential high-quality hydrocarbon source rocks in the region,which is worth further exploration.

关 键 词：煤系有机质 生物标志化合物 藻类体 八道湾组 湖泊沼泽化 准噶尔盆地南缘 

分 类 号：TE122[石油与天然气工程—油气勘探]