塔里木盆地轮探1井下寒武统烃源岩地球化学特征及深层油气勘探意义  

Geochemical characteristics of Lower Cambrian sources rocks from the deepest drilling of Well LT-1 and their significance to deep oil gas exploration of the Lower Paleozoic system in the Tarim Basin

作　　者：杨海军[1] 于双[2,3] 张海祖 李腾飞[2,3] 凡闪[1] 程斌 陈承声[2,3] 贾望鲁[2,3] 廖泽文 田辉[2,3] 王云鹏 YANG Hai-jun;YU Shuang;ZHANG Hai-zu;LI Teng-fei;FAN Shan;CHENG Bin;CHEN Cheng-sheng;JIA Wang-lu;LIAO Ze-wen;TIAN Hui;WANG Yun-peng(Research Institute of Petroleum Exploration and Development,PetroChina Tarim Oilfield Company,Korla 841000,China;State Key Laboratory of Organic Geochemistry,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,China;CAS Center for Excellence in Deep Earth Science,Guangzhou 510640,China)

机构地区：[1]中国石油天然气股份有限公司塔里木油田分公司,新疆库尔勒841000 [2]中国科学院广州地球化学研究所有机地球化学国家重点实验室,广东广州510640 [3]中国科学院深地科学卓越创新中心,广东广州510640

出　　处：《地球化学》2020年第6期666-682,共17页Geochimica

基　　金：国家重点基础研究发展计划(2017YFC0603106);中国科学院战略性先导科技专项(A类)(XDA14010104);国家油气重大专项(2017ZX05008-002)。

摘　　要：塔里木盆地下古生界是该区深部油气勘探的重点领域,而下寒武统烃源岩是目前研究的重点。但由于埋藏深,目前钻井揭示的下寒武统烃源岩样品较少。轮探1井(LT-1)是该区现阶段钻探最深的一口井。本次研究对轮探1井下寒武统样品进行了系统的有机地球化学分析。通过对有机质丰度和有机质类型的分析,确定下寒武统玉尔吐斯组下部为优质烃源岩。利用沥青反射率、拉曼光谱和岩石抽提物有机地球化学参数确定了烃源岩的成熟度。沥青的平均反射率为1.515%~1.725%,激光拉曼光谱法测定的镜质组等效反射率平均为1.64%。干酪根碳同位素范围为−30.98‰~−31.51‰,平均为−31.19‰,为Ⅱ型有机质。同时利用盆地模拟软件恢复了轮探1井的埋藏史和成熟史。与传统模拟结果相比,本次研究模拟结果显示早期埋藏较浅,现阶段出现了最高地层温度,代表了典型的晚期生烃。晚白垩世时期,下寒武统烃源岩进入凝析气、湿气阶段。研究结果表明,塔北地区新生代以来的构造演化也可能受到盆山耦合作用的影响,新生代以来的快速埋藏导致了晚期生烃,深层油气勘探特别是凝析气和湿气的勘探仍具有良好的前景。The lower Paleozoic strata in the Tarim Basin is a key area for deep oil and gas exploration.As such,its lower Cambrian source rocks are the focus of current research.However,owing to their extensive burial depth,few samples of Lower Cambrian source rock are drilled at present.Well LT-1 is the deepest drilling well in this area at its current stage.In this study,systematic organic geochemical analyses were carried out on Lower Cambrian samples from Well LT-1.The analysis of organic matter abundance and organic matter type indicated that the lower Cambrian Yuertus Formation is a high-quality source rock.The source rock’s maturity was determined by the bitumen reflectance,Raman laser spectrometer,and the rock extracts’biomarker index.The average bitumen reflectance ranges 1.515%–1.725%,and the equivalent reflectance of vitrinite measured by laser Raman spectroscopy is 1.64%on average.The kerogen carbon isotope ranges from−30.98‰to−31.51‰,with an average of−31.19‰,showing a type II organic matter.The maturity RC1-2 of methylphenanthrene is between 2.14%–2.19%,while that of Dibenzothiophene is between 1.14%–1.59%.The biomarker index shows significant variations in maturity.Simultaneously,the burial and maturity histories of Well LT-1 were restored by basin simulation software.Compared with traditional simulation results,our simulation results show a shallow-burial in their early stage,and the highest paleotemperature is emerging at the present stage,representing a typical late-hydrocarbon generation.At the late Cretaceous,the Lower Cambrian source rock entered a condensate and wet gas state.Our preliminary results show that the tectonic evolution in Tabei Area may have also been affected by basin-mountain coupling processes since the Cenozoic.The rapid burial since the Cenozoic resulted in late hydrocarbon generation,which still has a suitable prospect for oil and gas exploration in deep areas,especially for condensate and wet gas.

关 键 词：轮探1井 下寒武统烃源岩 玉尔吐斯组 深层油气 塔里木盆地 

分 类 号：P593[天文地球—地球化学]