西宁盆地南部天然CO_(2)泄漏和浅部含水层响应  

Natural CO_(2)leakage and responses of shallow aquifers in the southern Xining Basin

作　　者：郑长远 雷宏武[2] 崔银祥[2] 白冰[2] 季备[3] 刘阳阳 Zheng Changyuan;Lei Hongwu;Cui Yinxiang;Bai Bing;Ji Bei;Liu Yangyang(Key Laboratory of Hydrogeology and Geothermal Geology of Qinghai Province,Qinghai Province Survey Institute of Hydrogeology,Engineering Geology and Environmental Geology,Xining 810008,China;State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences,Wuhan 430071,China;China Railway First Survey and Design Institute Group Co.Ltd.,Xi′an 710043,China)

机构地区：[1]青海省水文地质工程地质环境地质调查院青海省水文地质及地热地质重点实验室,西宁810008 [2]中国科学院武汉岩土力学研究所岩土力学和工程国家重点实验室,武汉430071 [3]中铁第一勘察设计院集团有限公司,西安710043

出　　处：《地质科技通报》2023年第6期223-232,共10页Bulletin of Geological Science and Technology

基　　金：青海省科技厅科学技术应用基础研究项目“碳封存路径下的西宁盆地二氧化碳地质储存地质安全性研究”(2022-ZJ-735)。

摘　　要：CO_(2)地质封存是重要的CO_(2)减排技术之一,其中泄漏风险评价是该技术实施的关键,而天然CO_(2)泄漏研究是获取泄漏评价关键信息的重要手段。通过野外调查,现场测量以及水样、气样和岩样的采集和测试,分析了西宁盆地南部CO_(2)的来源、泄漏特征和其泄漏到浅部含水层后相关的响应规律。结果显示西宁盆地南部发现了多处天然CO_(2)泄漏,包括高含CO_(2)的泉、废弃钻孔的间歇水气喷发和CO_(2)井喷等多种形式的泄漏显示,以及与之伴随的较大范围的钙华。气体中CO_(2)占绝对含量,CO_(2)碳同位素介于-2.5‰~-0.4‰,指示泄漏的CO_(2)来源于深部无机成因,并通过深部断层泄漏进入浅部承压含水层,与地下水一起径流、排泄或在浅部二次聚集。CO_(2)泄漏区域土壤^(222)Rn浓度异常(超过9000 Bq/m^(3)),这可作为识别隐伏泄漏通道的重要方法。地下水对CO_(2)的泄漏产生了明显的物理化学响应,包括现象独特的井筒间歇喷发(喷发200 s和停止130 s),地下水水化学特征的变化(比如pH值的降低(小于7),电导、HCO_(3-)、Ca^(2+)的升高和氧同位素的漂移),以及地表大面积特征明显(比如气泡构造)和成分以方解石为主的钙华。该场地天然CO_(2)泄漏特征与美国Utah场地具有很高的相似性。研究成果不仅能为CO_(2)地质封存的泄漏风险评价提供天然类比知识,而且还有助于了解地球深部地质活动。Geological storage of CO_(2)is an important technology for reducing CO_(2)emissions,and the assessment of CO_(2)leakage risk is the key to its implementation.Research on natural CO_(2)leakage is an important means to obtain key information for leakage assessment.The source of CO_(2),the characteristics of CO_(2)leakage,and the relevant response of shallow aquifers to the CO_(2)leakage have been analysed through field investigations,on-site measurements,and sampling and testing of water,gas and rock.A number of natural CO_(2)leakages have been discovered in the southern Xining Basin,including CO_(2)-rich springs,CO_(2)-driven cold-water geysers from abandoned wells,and CO_(2)blowouts,as well as large-scale travertine associated with them.CO_(2)is the dominant component in the gas phase,and the abundance of carbon isotope of CO_(2)is between-2.5‰and-0.4‰,indicating that the leaked CO_(2)comes from a deep inorganic origin,leaks into shallow confined aquifers through deep faults,and flows and discharges with the groundwater or accumulates secondarily in shallow formations.The concentration of soil^(222)Rn in areas of CO_(2)leakage is abnormal(over 9000 Bq/m^(3)),which can be used as an important method of identifying hidden leakage channels.The groundwater has a pronounced response to CO_(2)leakage,including a unique phenomenon of intermittent eruptions(eruption for 200 s and incubation for 130 s),changes in groundwater hydrochemical characteristics(e.g.,a decrease in pH,an increase in conductance and HCO_(3-)and Ca^(2+)concentrations,and a drift in oxygen isotopes),and travertine composed mainly of calcite with a bubble structure at the surface.The natural CO_(2)leakage characteristics at this site are highly similar to those in Utah,USA.The results of this study not only provide knowledge of natural analogous for leakage risk assessment of CO_(2)geological storage,but also contribute to the understanding of geological activity in the deep earth.

关 键 词：天然CO_(2)泄漏 浅部含水层 响应 CO_(2)地质封存 西宁盆地 

分 类 号：X701[环境科学与工程—环境工程] X141