基于分布式光纤温度示踪探测裂隙岩体地下水渗流特征  

CHARACTERIZING GROUNDWATER FLOW IN FRACTURED ROCK USING FIBER-OPTIC DISTRIBUTED TEMPERATURE SENSING AND NUMERICAL MODELING

作　　者：符韵梅 董艳辉[1,2,3] 谢月清 周志超 王礼恒[1,2,3] 张明[5,6] FU Yunmei;DONG Yanhui;XIE Yueqing;ZHOU Zhichao;WANG Liheng;ZHANG Ming(Key Laboratory of Shale Gas and Geoengineering,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;Innovation Academy for Earth Science,Chinese Academy of Sciences,Beijing 100029,China;College of Earth and Planetary Science,University of Chinese Academy of Sciences,Beijing 100049,China;School of Earth Sciences and Engineering,Nanjing University,Nanjing 210023,China;Beijing Research Institute of Uranium Geology,Beijing 100029,China;CAEA Innovation Center for Geological Disposal of High-Level Radioactive Waste,Beijing 100029,China)

机构地区：[1]中国科学院地质与地球物理研究所,中国科学院页岩气与地质工程重点实验室,中国北京100029 [2]中国科学院地球科学研究院,中国北京100029 [3]中国科学院大学,地球与行星科学学院,中国北京100049 [4]南京大学,地球科学与工程学院,中国南京210023 [5]核工业北京地质研究院,中国北京100029 [6]国家原子能高放废物地质处置创新中心,中国北京100029

出　　处：《工程地质学报》2022年第4期1257-1265,共9页Journal of Engineering Geology

基　　金：青藏高原综合科学考察研究项目(资助号:2019QZKK0904);中国科学院页岩气与地质工程重点实验室开放基金项目(资助号:KLSG201704)。

摘　　要：认识深部裂隙岩体中的地下水渗流特征(流速、渗流路径等),是深部地质工程开发建设的重要前提。近年来,分布式光纤测温技术作为识别深部裂隙岩体地下水渗流特征的有效方法,在国外开展了大量的研究,但在国内鲜少见在实际场地开展的相关工作。本研究以我国首个地下实验室场址甘肃北山新场花岗岩岩体中的两个钻孔(BSQ02及BSQ03)为试验对象,开展基于分布式光纤测温(Fiber-Optic Distributed Temperature Sensing,FO-DTS)的现场温度-水力试验,实现了对钻孔地下水温度的高精度、连续性观测。通过分析现场试验获取的钻孔温度-深度剖面随时间的变化,推断BSQ02在试验过程中存在外源地下水的流入,然后结合钻孔柱状图对钻孔中的入流导水裂隙进行了定位;基于现场观测数据建立了钻孔的渗流-传热耦合数值模型,反演估算出钻孔中地下水平均流速为0.01 m·s^(-1),通过裂隙流入地下水温度小于钻孔中原地下水温度,两者之间的温度差为0.7℃,通过裂隙流入的地下水流速为1×10^(-5)m·s^(-1),获取了地下水的渗流特征。该项工作可为基于分布式光纤测温技术的裂隙介质地下水渗流规律研究提供借鉴与指导。Understanding the flow behavior in fractured rocks is of great importance for the development and construction of deep geological engineering projects.Using temperature-depth profiles in the subsurface to characterize groundwater flow is becoming increasingly popular.Not only because the heat transport process is sensitive to groundwater flow(flow rates,preferential flow paths et al.),but also the temperature can be easily measured by Fiber-Optic Distributed Temperature Sensing(FO-DTS)with low costs.In this study,FO-DTS is used to conduct fully distributed space-time measurements of groundwater temperature in two boreholes.These boreholes(BSQ02 and BSQ03)locate at Xinchang Site in Gansu Province,where is the first underground laboratory site in China.The borehole temperature profiles are measured with FO-DTS under pumping conditions to find potential flow path through fractures.Through analyzing these profiles,location of hydraulically active fractures has been determined to be distributed around 40 m depth in BSQ02,and the main flow path is considered to be fracture B2-2.In order to further investigate the groundwater flow fields,measured temperature profiles are then interpreted with inverse numerical modeling of flow-heat transfer processes.Average groundwater flow rate in borehole under pumping condition is estimated to be 0.01 m·s^(-1)from inverse models.The temperature of groundwater flowing into the borehole through fracture B2-2 is around 13.65℃,which is estimated to be 0.7℃lower than the original groundwater(14.35℃)in borehole.The velocity of groundwater through B2-2 was estimated to be 1×10^(-5)m·s^(-1).This study succeeds in characterizing groundwater flow rates and flow paths using temperature data based on FO-DTS technology,which can be a promising method for understanding groundwater flow in fractured rocks.

关 键 词：分布式光纤测温 裂隙岩体 地下水渗流特征 

分 类 号：P641.2[天文地球—地质矿产勘探]