塔河油田中下奥陶统储层裂缝方解石脉U-Pb同位素年龄及油气地质意义  

U-Pb Dating of Calcite Veins Developed in the Middle-Lower Ordovician Reservoirs in Tahe Oilfield and Its Petroleum Geologic Significance in Tahe Oilfield

作　　者：王斌 杨毅[1] 曹自成 何生[1] 赵永强[2,3] 郭小文[1] 刘永立 陈家旭[1] Zhao Jian-xin[4] Wang Bin;Yang Yi;Cao Zicheng;He Sheng;Zhao Yongqiang;Guo Xiaowen;Liu Yongli;Chen Jiaxu;Zhao Jian-xin(Key Laboratory of Tectonics and Petroleum Resources,Ministry of Education,China University of Geosciences,Wuhan 430074,China;Wuxi Research Institute of Petroleum Geology,SINOPEC,Wuxi 214126,China;Northwest Oil Company Ltd.,SINOPEC,Urumqi 830011,China;Radiogenic Isotope Facility,School of Earth and Environment Sciences,The University of Queensland,Brisbane 4072,Australia)

机构地区：[1]中国地质大学构造与油气资源教育部重点实验室,湖北武汉430074 [2]中国石化石油勘探开发研究院无锡石油地质研究所,江苏无锡214126 [3]中国石化西北油田分公司,新疆乌鲁木齐830011 [4]Radiogenic Isotope Facility,School of Earth and Environment Sciences,The University of Queensland,Brisbane 4072

出　　处：《地球科学》2021年第9期3203-3216,共14页Earth Science

基　　金：国家自然科学基金项目(No.41872139);中国石化科技部科技攻关项目(No.P18095-2)。

摘　　要：塔河油田中下奥陶统碳酸盐岩储层在构造活动的作用下发育多期方解石脉体,为研究储层流体演化和油气成藏过程提供了重要素材.通过岩心观察、薄片鉴定、阴极发光和微区元素分析在塔河油田中下奥陶统碳酸盐岩储层中识别出3期裂缝方解石脉体,3期脉体在阴极发光颜色、稀土元素、碳氧锶同位素以及形成时间方面都存在差异.采用激光原位方解石U-Pb定年技术确定3期方解石脉形成的绝对年龄分别为466±11 Ma~458.6±8.8 Ma、329.7±1.6 Ma~308.1±4.1 Ma和249.3±2.6 Ma~220.5±7.3 Ma.第2期和第3期方解石成脉流体主要来源于深部地层成岩流体,并伴有成烃流体的影响.第3期方解石脉的成脉流体可能还有壳源锶的输入,导致其^(87)Sr/^(86)Sr比值高于第2期方解石脉.方解石脉体的绝对年龄可以用于约束多旋回叠合盆地断裂活动和油气成藏时间.在塔河油田中下奥陶统碳酸盐岩储层中识别的3期方解石脉体形成时间分别对应于加里东中期Ⅰ幕、海西中期Ⅰ~Ⅱ幕和海西晚-印支期构造运动造成的断裂活动时间.方解石脉体与烃类流体包裹体的共生关系指示中下奥陶统储层在海西中期Ⅱ幕发生过一期原油充注,在印支期之后又存在两期原油充注.Multiphase calcite veins are developed due to tectonic activities in the carbonate reservoirs of Middle-Lower Ordovician in the Tahe oilfield, which is important for studying the evolution of reservoir fluids and the process of hydrocarbon accumulation. Three phases fracture-filled calcite veins were identified in the carbonate reservoirs of Middle-Lower Ordovician in the Tahe oilfield by core observation, thin section, cathodoluminescence and in-situ element. The three-phase calcite veins have differences in cathodoluminescence color, rare earth elements, strontium, carbon, oxide isotopes and timing of calcite veins generation. The in-situ U-Pb dating by laser ablation yields the absolute ages of the three-phase calcite vein generation of 466±11 Ma to 458.6±8.8 Ma, 329.7±1.6 Ma to 308.1±4.1 Ma and 249.3±2.6 Ma to 220.5±7.3 Ma, respectively. The fluids for second and third phases of calcite vein generation are mainly derived from deep-seated diagenetic fluids with the influence of hydrocarbon-fluids. The fluid of the third phase of calcite vein generation may also be affected by crust-derived strontium,resulting in a higher ^(87)Sr/^(86)Sr ratio than that of the second phase of calcite veins. The absolute ages of calcite veins generation can be used to constrain the fault activity and hydrocarbon charge histories in multi-cycle superimposed basins. The timing of the three phases of calcite veins generation corresponds to the periods of fault activity caused by the Middle Caledonian episode Ⅰ,the Middle Hercynian episode Ⅰ-Ⅱ, and the Late Hercynian-Indosinian period. The symbiotic relationship between calcite veins and hydrocarbon fluid inclusions indicates that the Middle-Lower Ordovician reservoirs experienced one episode of oil charge episode of the Middle Hercynian episode and two episodes of oil charge after the Indosinian period.

关 键 词：方解石脉体 U-PB同位素年龄 断裂活动时间 成藏期 塔河油田 石油地质 

分 类 号：P618[天文地球—矿床学]