川西坳陷盐浅1井沙溪庙组沉积古环境分析与元素地球化学响应  

Sedimentary paleoenvironmental analysis of the Shaximiao Formation and elemental geochemical response in Well Yanqian 1,West Sichuan Depression

作　　者：张禹 张昌民[1] 杨威[2] 张祥辉 徐清海 王志宏[2] 孟庆昊 向建波 ZHANG Yu;ZHANG Changmin;YANG Wei;ZHANG Xianghui;XU Qinghai;WANG Zhihong;MENG Qinghao;XIANG Jianbo(School of Geosciences,Yangtze University,Wuhan 430100,China;PetroChina Research Institute of Petroleum Exploration and Development,Beijing 100083,China)

机构地区：[1]长江大学地球科学学院,湖北武汉430100 [2]中国石油勘探开发研究院,北京100083

出　　处：《天然气地球科学》2024年第9期1638-1655,共18页Natural Gas Geoscience

基　　金：国家自然科学基金“分支河流体系沉积模式与储层定量预测模型”(编号:42130813);“中国西部主要盆地周缘及邻区分支河流体系分布与沉积模式”(编号:41772094)联合资助。

摘　　要：沉积物的元素地球化学信息可以很好地反映沉积物源区、古气候古环境等信息,并且沉积物粒度和元素地球化学信息也有密切联系。为了进一步探讨干旱背景下沙溪庙组不同河道砂体成因以及沉积物粒度和沉积相与元素地球化学之间的关系,对川西地区盐浅1井的沉积相特征、元素地球化学特征进行系统的分析。结果表明:①盐浅1井沙溪庙组以红褐色泥岩和灰色砂砾岩为主,发育一套河漫平原沉积,可划分为大型河道、小型河道、决口水道、河漫滩及河漫湖泊5种岩石相组合;②不同岩石相组合的元素地球化学特征具有明显差异,大型河道表现出“Fe含量低,SiO_(2)含量高”的特点;而决口水道和小型河道SiO_(2)含量略低;河漫湖泊呈现出“Fe含量高,SiO_(2)含量低”的特点;而河漫滩呈现出“Fe含量较高,SiO_(2)含量高”的特点。岩石相组合整体表现为,SiO_(2)含量越高,粒度越大;且决口水道、小型河道以及河漫滩多发育于相对湿润的气候环境。③结合Al_(2)O_(3)/TiO_(2)、Cr/Zr和TiO_(2)/Zr等元素及比值综合判断,盐浅1井沙溪庙组离物源区近,母岩主要为长英质岩,构造背景主要为大陆岛弧背景。④根据Mg/Ca、Fe/Mn、Sr/Ba、m、V/(V+Ni)和Cu/Zn等元素及比值判断,沙溪庙组沉积期水体环境主要为陆地淡水环境,从下沙溪庙组至上沙溪庙组表现为2个由氧化—还原环境的变化过程,而气候变化更为频繁,气候出现多次由湿润—干旱的变化过程,但整体上从下沙溪庙组至上沙溪庙组气候更加干旱。研究为恢复川西坳陷沙溪庙组沉积环境,进一步探讨不同岩石相组合的形成规律以及有利储层砂体分布提供了依据。The elemental geochemical information of sediments can well reflect the information of sediment source area,paleoclimate and paleoenvironment,and there is a close relationship between sediment grain size and elemental geochemical information.In order to further explore the genesis of different fluvial sand bodies in the Shaximiao Formation under the arid background and the relationship between sediment grain size and sedimentary phase and elemental geochemistry,the sedimentary phase characteristics and elemental geochemistry of the Well Yanqian 1 in the western Sichuan area are systematically analyzed.The results show that:(1)The stratigraphy of the Shaximiao Formation in Well Yanqian 1 is dominated by reddish-brown mudstone and gray gravel,and a set of river floodplain deposits is developed,which can be classified into five kinds of lithologic phase combinations,namely,large river channel,small river channel,watercourse at the mouth of the river,river floodplain,and river floodplain lakes.(2)The elemental geochemistry of different lithologic phase combinations has obvious differences,and the large river channel shows a low content of Fe and high content of SiO_(2),while the SiO_(2) content of the watercourses and small rivers is slightly lower;the riverine lakes show the characteristics of“high Fe content and low SiO_(2) content”;and the river floodplains show the characteristics of“high Fe content and high SiO_(2) content”;while the river floodplain is characterized by“high Fe content and high SiO_(2) content”.The rock phase assemblage as a whole shows that the higher the SiO_(2) content,the larger the grain size;and the decisive watercourse,small river channel and river floodplain are mostly developed in a relatively humid climate environment.(3)The combination of the elements and ratios such as knot and Al_(2)O_(3)/TiO_(2),Cr/Zr and TiO_(2)/Zr indicates that the Shaximiao Formation of the Well Yanqian 1 is close to the source area,and the host rock is mainly a feldspathic quartzite,with the main t

关 键 词：沙溪庙组 沉积相 古环境 地球化学 四川盆地 XRF 

分 类 号：TE122.113[石油与天然气工程—油气勘探]