湖底热水活动及其对优质烃源岩发育的影响——以鄂尔多斯盆地长7烃源岩为例  

Lake-bottom hydrothermal activities and their influences on the high-quality source rock development: A case from Chang 7 source rocks in Ordos Basin

作　　者：张文正[1,2] 杨华[2,3,4] 解丽琴[1,2] 杨奕华[1,2] 

机构地区：[1]中国石油长庆油田公司勘探开发研究院 [2]低渗透油气田勘探开发国家工程实验室 [3]中国石油长庆油田公司 [4]西北大学大陆动力学国家重点实验室

出　　处：《石油勘探与开发》2010年第4期424-429,共6页Petroleum Exploration and Development

基　　金：国家自然科学基金项目(40773028);国家重点基础研究发展计划(973)项目(2003CB214602);教育部长江学者和"油气盆地"创新团队发展计划项目(IRT0559)

摘　　要：光学显微镜和扫描电子显微镜-能谱仪观测在鄂尔多斯盆地延长组长7优质烃源层中发现了硅质岩、铁白云石纹层沉积、白铁矿-黄铁矿-硬石膏共生体系、早期成岩缝中的自生钠长石充填作用等可能与湖底热水活动有关的现象。能进一步佐证同期湖底热水活动存在的证据还有:长7优质烃源岩中异常高的二价硫含量(平均7.37%),Mo、Cu、U、Mn等微量元素的显著正异常特征,高的U/Th值,微晶铁白云石纹层偏重的碳同位素组成(2.88‰~3.03‰)、偏轻的氧同位素组成(-16.41‰^-16.17‰)和富集Cu、Mn等微量元素的特征,莓状黄铁矿偏正的硫同位素组成(2.37‰~5.90‰)特征等。长7段沉积期始,强烈的区域构造活动对基底断裂的激活作用是产生湖底热水活动的动力学因素,湖底热水活动对长7优质烃源岩的大规模发育具有重要的促进作用。By optical microscope and SEM-energy spectrometer,some phenomena that relate to lake-bottom hydrothermal activities,such as siliceous rocks,ankerite laminar deposits,the marcasite brassil anhydrite symbiosis system,and the authigenetic albite filling in early diagenetic slots,have been discovered in Chang 7 high-quality source beds of the Yanchang Formation,Ordos Basin.Various geochemical data of the Chang 7 high-quality source rocks testify further to the existence of lake-bottom hydrothermal activities,and they include abnormally abundant S2-content（on average 7.37%）,Mo,Cu,U,and Mn positive anomalies,high ratio of U to Th,positive carbon isotope composition of crystallite ankerite（δ13C from 2.88‰ to 3.03‰）,light oxygen isotope composition（δ18OPDB from-16.41‰ to-16.17‰）,the enrichment of microelements like Cu and Mn,heavy sulfur isotope composition of strawberry-shaped pyrite（δ34SCDT from 2.37‰ to 5.90‰）.In the early sedimentary period of Chang 7,the activation of floor ruptures by violent regional structure-activities was a dynamic factor that produced lake-bottom hydrothermal activities and the hydrothermal activities played an important role in accelerating the extensive development of Chang 7 high-quality source rocks.

关 键 词：湖盆扩张 湖底热水活动 优质烃源岩 晚三叠世 鄂尔多斯盆地 

分 类 号：TE122.1[石油与天然气工程—油气勘探]