渤海莱州湾凹陷中部古近系沙三段烃源岩地球化学特征及沉积环境  

Geochemical characteristics and sedimentary environment of source rocks of the third member of Paleogene Shahejie Formation in central Laizhouwan Sag,Bohai Sea

作　　者：邓美玲 王宁 李新琦[3] 陈容涛 刘岩 徐耀辉 DENG Meiling;WANG Ning;LI Xinqi;CHEN Rongtao;LIU Yan;XU Yaohui(Hubei Key Laboratory of Petroleum Geochemistry and Environment(College of Resources and Environment,Yangtze University),Wuhan 430100,China;Key Laboratory of Exploration Technologies for Oil and Gas Resources,Ministry of Education(Yangtze University),Wuhan 430100,China;Research Institute of Bohai Petroleum,Tianjin Branch of CNOOC Ltd.,Tianjin 300452,China)

机构地区：[1]油气地球化学与环境湖北省重点实验室(长江大学资源与环境学院),武汉430100 [2]油气资源与勘探技术教育部重点实验室(长江大学),武汉430100 [3]中海石油(中国)有限公司天津分公司渤海石油研究院,天津300452

出　　处：《岩性油气藏》2023年第1期49-62,共14页Lithologic Reservoirs

基　　金：中海油天津分公司项目“渤海海域中南部优质烃源岩特征及形成机理研究”(编号:CCL2020TJT0NST1956)资助。

摘　　要：通过对渤海海域莱州湾凹陷中部古近系沙三段烃源岩样品的热解、TOC、饱和烃GC/MS分析以及主、微量元素分析,研究了其烃源岩的地球化学特征及沉积环境。研究结果表明:(1)莱州湾凹陷中部古近系沙三段烃源岩有机质丰度差异较大,总体为好—优质烃源岩,有机质类型以Ⅰ—Ⅱ型为主,整体处于低熟—成熟阶段;(2)通过Pr/nC_(17)-Ph/nC_(18)图版、C_(24)四环萜烷/C_(26)三环萜烷(C_(24)TeT/C_(26)TT)、C_(27)/C_(29)规则甾烷、奥利烷指数等参数判断沙三段烃源岩有机质来源为低等水生生物和高等植物的混源输入;(3)综合CIA,Sr/Ba,Pr/Ph,V/(V+Ni),U/Th值和伽马蜡烷指数等分析了烃源岩形成时期的古环境,认为沙三段沉积时期气候温暖湿润,降水丰富,水体为淡水—微咸水,陆源输入较多,具有较高的初始生产力,沉积时期整体表现为贫氧的弱氧化弱还原环境,沙三下段—沙三上段沉积环境整体变化不大,古气候和古水体盐度基本保持不变,但陆源输入及水体氧化条件随沉积进程呈逐渐增加的趋势。The geochemical characteristics and sedimentary environment of the third member of Paleogene Shahejie Formation(E_(2)s^(3))in central Laizhouwan Sag of Bohai Sea were studied by means of pyrolysis,TOC,GC/MS analysis of saturated hydrocarbons,and major and trace elements analysis of source rock samples.The results show that:(1)The source rocks of E_(2)s^(3) have different organic matter abundances,they are generally good to high-quality source rocks.The organic matters are mainly typeⅠ-Ⅱand in the low mature to mature stage as a whole.(2)According to Pr/nC_(17)-Ph/nC_(18)plates,C24tetracyclic terpanes/C_(26)tricyclic terpanes(C_(24)TeT/C_(26)TT),C_(27)/C_(29)regular sterane and olliane index,it can be concluded that the organic matters of E_(2)s^(3) source rocks are derived from mixed inputs of lower aquatic organisms and terrigenous higher plants.(3)CIA,Sr/Ba,Pr/Ph,V/(V+Ni),U/Th and gammacerane index were used to analyze the paleoenvironment of the source rocks.During the sedimentary period of E_(2)s^(3),the climate was warm and humid with abundant precipitation.The water environment was fresh-brackish water,accompanied by strong terrigenous input,with high initial productivity,and the sedimentary environment is weak oxidation and weak reduction environment with poor oxygen.The sedimentary environment of E_(2)s^(3) has little change,and the paleoclimate and water salinity are basically the same.However,terrigenous input and water oxidation conditions gradually increase with the deposition.

关 键 词：低熟—成熟烃源岩 地球化学特征 弱氧化弱还原环境 陆源 沙三段 古近系 莱州湾凹陷 渤海 

分 类 号：TE122.114[石油与天然气工程—油气勘探] P618.13[天文地球—矿床学]