塔河地区下寒武统玉尔吐斯组沉积环境及有机质富集机理  

Sedimentary environment and organic matter enrichment mechanism of the Lower Cambrian Yuertusi Formation in Tahe area,Tarim Basin

作　　者：张文文 徐勤琪[1] 尚凯[1] 张楠[2] 廖启丰 林静文 李帅 ZHANG Wenwen;XU Qinqi;SHANG Kai;ZHANG Nan;LIAO Qifeng;LIN Jingwen;LI Shuai(Research Institute of Exploration and Development,SINOPEC Northwest Oilfield Company;Research Institute of Petroleum Engineering,SINOPEC Northwest Oilfield Company)

机构地区：[1]中国石化西北油田分公司勘探开发研究院,新疆乌鲁木齐市830011 [2]中国石化西北油田分公司石油工程技术研究院

出　　处：《海相油气地质》2025年第1期17-29,共13页Marine Origin Petroleum Geology

基　　金：中国石化科技项目“塔北-塔中震旦系—寒武系成藏条件与区带优选”(编号:P22123)资助。

摘　　要：下寒武统玉尔吐斯组是塔里木盆地重要的烃源岩层段,开展有机质富集机理研究可为海相烃源岩评价与超深层油气勘探提供参考和依据。基于塔河地区典型单井矿物岩石学、无机地球化学和元素分析等资料,综合氧化-还原条件、古生产力、水体滞留程度等地球化学指标,探讨塔河地区玉尔吐斯组烃源岩沉积古环境及其对有机质富集的控制。研究表明:塔河地区玉尔吐斯组烃源岩有机质丰度高,下段的烃源岩有机质品质优于上段。从玉尔吐斯组沉积早期到晚期沉积水体古生产力水平、水体滞留程度、陆源碎屑输入及缺氧程度均呈现逐渐降低的演化趋势。玉尔吐斯组有机质富集与海平面变化引起的沉积古环境变化密切相关,有机质富集受保存条件、弱热液活动、上升洋流等因素共同控制,弱热液活动与上升洋流为优质烃源岩的发育提供了营养物质基础,中等滞留的沉积环境为有机质的富集提供了良好的外部条件,硫化-缺氧还原环境是有机质保存的关键。The Lower Cambrian Yuertusi Formation is an important source rock layer in Tarim Basin.The research on the organic matter enrichment mechanism could provide valuable guidance for the exploration of ultra-deep marine oil and gas reserves.Based on data of mineral petrology,inorganic geochemistry,and elemental analysis of Well A,combined with data of Well LT1 cited from reference,this study explores the sedimentary paleoenvironment of the Yuertusi Formation source rock in Tarim Basin and its control on organic matter enrichment,with integrated element geochemical indicators such as paleoproductivity,redox conditions and others.The results show that:(1)Yuertusi Formation in the Tahe area has high organic matter content,and the organic matter quality of the lower section,with an average TOC of 6%,is superior to the upper section.(2)Paleoproductivity level(P/Ti,Babio),water retention degree(Mo/TOC,Co·Mn),terrigenous detrital input(Ti/Al)and anoxia degree(Ni/Co,U/Th,V/Sc)show a gradual decreasing trend from early to late period of Yuertusi Formation.(3)Closely corresponded with variations in the sedimentary paleoenvironment induced by sea level fluctuations,the organic matter enrichment in the Yuertusi Formation is jointly influenced by preservation conditions,weak hydrothermal activity,and upwelling currents.In the early stage of Yuertusi,under a sea level of relatively low,a medium-high water retention developed,and the weak hydrothermal activity made the bottom seawater being in an anoxic state,and the long-term anoxic and sulfidation environment was conducive to the preservation of organic matter,thus the lower section of Yuertusi Formation with high TOC formed.In the late stage of Yuertusi,the sea level experienced fluctuating rise and gradual decline,the water retention degree reduced under the high sea level,and when the sea level decreased significantly,the environment gradually changed from anoxic to oxygen-poor,which may lead to the oxidation and decomposition of some organic matter,thus the upper section wit

关 键 词：地球化学特征 古环境 有机质富集 玉尔吐斯组 寒武系 塔河地区 塔里木盆地 

分 类 号：TE122.1[石油与天然气工程—油气勘探]