摘要
优质烃源岩的形成受诸多因素的影响,认清不同类型烃源岩控制因素的差异对提高非常规油气的勘探效益具有重要意义。选取渤海湾盆地东营凹陷沙三中—沙四上亚段(Es_(3)^(z)、Es_(3)^(x)、Es_(4)^(cs)、Es_(4)^(cx))烃源岩,借助薄片鉴定、热解分析和主微量元素检测等手段,探讨各层段烃源岩形成的控制因素差异。结果表明:Es_(3)^(x)和Es_(4)^(cs)烃源岩TOC含量较高,且以Ⅱ_(1)型—Ⅰ型水生有机质为主,分别形成于深水半咸化和深水咸化环境,而Es_(4)^(cx)和Es_(3)^(z)烃源岩TOC含量偏低,以Ⅲ型—Ⅱ_(1)型陆源有机质贡献占优,分别形成于浅水咸化蒸发和浅水半咸化环境。古生产力由高到低依次为:Es_(4)^(cs)>Es_(4)^(cx)>Es_(3)^(x)>Es_(3)^(z),充分展现了各层段烃源岩有机质、环境和生产力的差异性。有机质富集程度与古生产力、盐度和水深均成正比,基本不受氧化还原条件影响。高生产力为研究区有机质发育的关键因素,当生产力较高时(Es_(4)^(s)和Es_(3)^(x)),有机质的进一步富集则受到环境的明显控制:深水淡化环境下(Es_(3)^(x)),盐度为主要制约因素;咸水环境下(Es_(4)^(cs)),水深的控制作用则凸显出来;而在低生产力浅水淡化湖盆环境下(Es_(3)^(z)),古生产力、盐度和水深对有机质发育的控制都很明显,这体现了多因素对有机质的共同控制以及各层段烃源岩有机质富集的控制因素的差异。因此,研究烃源岩的形成除需要关注生产力与保存条件之外,还应关注盐度、水深等环境因素以及多因素间的耦合作用,这对深化认识烃源岩的发育规律以及指导非常规油气勘探都具有重要意义。
The formation of high-quality source rocks is affected by many factors.It is of great significance to recognize the differences of controlling factors of different types of source rocks for accurately predicting the"sweet spot"of shale and improving the efficiency of unconventional oil and gas exploration.In this paper,we selected four source rocks(Es_(3)^(z),Es_(3)^(x),Es_(4)^(cs),Es_(4)^(cx)) in the Paleogene Shahejie Formation,Niuzhuang Sag of Dongying Sag of Bohai Bay Basin,and carried out thin section,pyrolysis,and major and trace elements analyses to discuss the differences in controlling factors of source rock formation in each member.Es_(3)^(x)and Es_(4)^(cs)source rocks,which are developed in deep-water brackish and deep-water brackish environments,respectively,have higher TOC and are dominated by type Ⅱ_(1)-Ⅰaquatic organic matter.Es_(4)^(cx)and Es_(3)^(z)source rocks,which is deposited in shallow water brackish evaporation and shallow water brackish environments,respectively,have lower TOC and are dominated by type Ⅲ-Ⅱ_(1)terrigenous organic matter.The level of paleoproductivity is as follows:Es_(4)^(cs)>Es_(4)^(cx)>Es_(3)^(x)>Es_(3)^(z).Source rocks in each member have differences in organic matter,environment and productivity.The enrichment degree of organic matter is proportional to paleoproductivity,salinity and water depth,and is not affected by redox conditions.The high productivity is the key factor,when productivity is higher(Es4sand Es_(3)^(x)),the further enrichment of organic matter is obviously controlled by the environment:under the deep water and desalination environment(Es_(3)^(x)),salinity is the main restriction factor of the formation of organic matter;In the saltwater environment(Es_(4)^(cs)),the controlling effect of water depth is prominent.In the low productivity shallow water desalinated lake basin(Es_(3)^(z))environment,the paleoproductivity,salinity and water depth have obvious control on organic matter development,which reflects the common control of multiple factors on organic matter and the differences of controlling factors on organic matter enrichment in source rocks of different strata.Therefore,in addition to productivity and preservation conditions,attention should also be paid to environmental factors such as salinity and water depth,as well as the coupling between multiple factors,which is of great significance to deepen the understanding of the development law of source rocks and guide unconventional oil and gas exploration.
作者
段玮
曾翔
蔡进功
李政
王长轩
林茹
DUAN Wei;ZENG Xiang;CAI Jingong;LI Zheng;WANG Changxuan;LIN Ru(State Key Laboratory of Marine Geology,Tongji University,Shanghai 200092,China;Research Institute of Exploration and Development,Shengli Oilfield Company,SINOPEC,Dongying 257015,China;Lusheng Petroleum Development Co.Ltd.,Shengli Oilfield Company,SINOPEC,Dongying 257077,China)
出处
《天然气地球科学》
CAS
CSCD
北大核心
2022年第11期1754-1767,共14页
Natural Gas Geoscience
基金
国家自然科学基金(编号:41972126)
国家科技重大专项(编号:2016ZX05006001-003)联合资助.
关键词
东营凹陷
烃源岩
沉积环境
元素埋藏通量
古生产力
Dongying Sag
Source rock
Sedimentary environment
Elemental buried flux
Paleoproductivity
作者简介
段玮(1999-),女,湖北黄冈人,硕士研究生,主要从事泥页岩沉积和元素地球化学研究.E-mail:duanwei@tongji.edu.cn;通信作者:蔡进功(1961-),男,山东烟台人,教授,博士生导师,主要从事海洋沉积学和石油地质学研究.E-mail:jgcai@tongji.edu.cn.
