塔里木盆地塔中地区奥陶系碳酸盐岩储层成岩流体性质及分布  

Properties and Distribution of Diagenetic Fluids in Ordovician Carbonate Reservoirs in Tazhong Region of Tarim Basin

作　　者：韩慧萍 马嘉[2] 张怡 潘莹露[1] HAN Huiping;MA Jia;ZHANG Yi;PAN Yinglu(School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083,China;Beijing Research Institute of Chemical Engineering and Metallurgy,CNNC,Beijing 101149,China)

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]核工业北京化工冶金研究院,北京101149

出　　处：《现代地质》2025年第2期312-326,共15页Geoscience

基　　金：国家自然科学基金项目(41502141);中央高校基本业务基金项目(2652014036)。

摘　　要：塔中地区奥陶系碳酸盐岩储集空间以次生孔隙为主,埋藏流体对于储集层的改造具有重要的控制作用,因此研究成岩流体的性质及分布是进行储层精细评价的前提。以塔中地区奥陶系碳酸盐岩孔缝充填物和围岩为研究对象,利用碳、氧、锶同位素、稀土元素、微量元素及包裹体测温的方法开展了埋藏流体性质研究。结果发现,研究区主要流体类型为正常地层水,表现为包裹体均一温度低于本区最高埋藏温度(120℃),氧同位素组成为-6.64‰~-4.23‰,锶同位素值低(<0.709),稀土元素分布模式与围岩一致,δEu无异常;研究区内局部有热液流体活动,表现为包裹体均一温度高于围岩最高埋藏温度5℃以上(125℃),具有更轻的氧同位素组成(-15.18‰~-7.09‰),稀土元素分布模式异于围岩。热液流体类型分为岩浆热液和深部循环的热卤水。其中岩浆热液以形成萤石等岩浆矿物为特征,地球化学特征为具有与国际奥陶系沉积碳酸盐岩标准相一致的^(87)Sr/^(86)Sr值(0.70782~0.70903),具有明显的Eu正异常(δEu的变化范围为1.240~20.906),较低的Th/U值(<0.45);深部循环热卤水的特征为较高的^(87)Sr/^(86)Sr值(>0.709)和较高盐度(≥15%NaCl)。热液流体对储层进行溶蚀改造,提高了研究区的储层物性,影响区域为有利储集区。热液流体的分布主要与深大断裂有关,岩浆活动直接或间接地导致热液流体的形成。The Ordovician carbonate rocks in Tarim basin,which located in the northwestern China,are considered as important reservoirs.Observation of cores and slices indicates that the buried fluid plays an important role in controlling the reservoir.The dissolved pores and secondary minerals during the burial period(calcite,pyrite,etc.) are all related to the activity of the buried fluid.Taking the Ordovician carbonate rock fillings and surrounding rocks in the Tazhong area as the research objects,the research on the properties of buried fluids in the study area was carried out using the methods of carbon,oxygen,strontium isotope,rare earth elements,trace elements and inclusions temperature.It was found that the main fluid types in the study area were normal formation waters,and there were hydrothermal fluid activities in some areas.Due to the slightly different geochemical characteristics,hydrothermal fluids were divided into two types:magmatic hydrothermal fluids and deep circulating hot brines.The geochemical characteristics of normal formation water fluids are that the homogenization temperature of inclusions is lower than the highest burial temperature(120 ℃) in this area,the oxygen isotope composition is from-6.64‰ to-4.23‰,and the strontium isotope value is ~(87)Sr/~(86)Sr<0.709.The distribution pattern of rare earth elements is consistent with the surrounding rock,and the variation range of δEu is from 0.627 to 0.921.The geochemical characteristics of hydrothermal fluids are the homogenization temperature of the inclusions is higher than the maximum burial temperature of surrounding rocks by more than 5 ℃(125 ℃) and it is of the lighter oxygen isotope composition(from-15.18‰ to 7.09‰).The distribution pattern of rare earth elements is different from the surrounding rock limestone.Some of the hydrothermal fluid samples have ~(87)Sr/~(86)Sr values(from 0.707,82 to 0.709,03) consistent with the international Ordovician sedimentary carbonate rock standard,with obvious Eu positive anomaly(δEu varies fr

关 键 词：碳酸盐岩储集层 热液流体 地球化学 奥陶系 塔里木盆地 塔中地区 

分 类 号：P584[天文地球—岩石学]