水化学及氢氧同位素组成指示的涩北气田地层水成因  

Origin of the Formation Water From Sebei Gas Field Indicated by Hydrochemistry and Hydrogen and Oxygen Isotope Composition

作　　者：李建森[1,2] 凌智永 李雷明[1,2] 袁小龙 LI Jiansen;LING Zhiyong;LI Leiming;YUAN Xiaolong(Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt Lake Resources,Qinghai Institute of Salt Lakes,Chinese Academy of Sciences,Xining 810008,China;Qinghai Provincial Key Laboratory of Geology and Environment of Salt Lakes,Xining 810008,China)

机构地区：[1]中国科学院青海盐湖研究所盐湖资源综合高效利用重点实验室,青海西宁810008 [2]青海省盐湖地质与环境重点实验室,青海西宁810008

出　　处：《安全与环境工程》2021年第3期206-211,共6页Safety and Environmental Engineering

基　　金：国家自然科学基金面上项目(41972258、U1407128、41402229);中国科学院青年创新促进会人才项目(2020428);中国气象局干旱气象科学研究基金项目(IAM202006);青海省自然科学基金青年项目(2021-ZJ-980Q)。

摘　　要：柴达木盆地三湖坳陷有世界上极为典型的最年轻的大规模生物气田,但是对于生物气的成因一直存在争议。从涩北气田地层水起源和演化入手,着重分析了其水化学组成和氢氧同位素特征,以深化对青藏高原生物气成因的认识。结果表明:涩北气田地层水中TDS含量分布在83.0~170.2 g/L之间,为高Na^(+)、Ca^(2+)和低Mg^(2+)、SO_(4)^(2-)的氯化钙型水体,δD值分布在-65.2‰~-51.0‰之间,δ18O值分布在-6.6‰~-3.2‰之间;结合地层水水化学组分和氢氧同位素特征推断涩北气田地层水起源于东昆仑山冰川雪水,为冰川雪水转换为地下水沿山前斜坡带渗入三湖坳陷地层形成,并在地下水入渗、汇聚过程中淋滤溶蚀了地层中大量的盐类物质以及Sr、Br、B等微量元素,使得水体盐度逐步增加,运移至坳陷北部的背斜带,最终形成盐度较高的地层水;地层水的成因演化进一步指示涩北气田具有生物气横向运移、水溶气动态成藏的富集规律,也证明地层水的起源、运移和咸化过程在一定程度上决定着生物气的生成、运移和富集,因此在三湖地区进行生物气勘探过程中,应着重查明深部地层水的来源及其咸化过程,并在三湖地区及外围深部富锂卤水勘探过程中加强对生物气资源的关注。Sanhu Depression in Qaidam Basin has the most typical large-scale biogas field in the world,but the origin of biogas has always been controversial.Starting from the origin and evolution of the formation water in the gas field,this study focuses on the analysis of its hydrochemical composition and hydrogen and oxygen isotope characteristics,in order to deepen the understanding of the origin of biogas in the Qinghai-Tibet Plateau.The result show that the distribution of TDS in gas field formation water is 83.0~170.2 g/L,which is the calcium-chloride type water with high Na+,Ca2+and low Mg^(2+),and SO_(4)^(2-);the distribution of δD is-65.2‰~-51.0‰,and the distribution ofδ18O is-6.6‰~-3.2‰.By combining the hydrochemical composition and hydrogen and oxygen isotopic characteristics,we can conclude that the water in the gas field originate from the glacial snow water in the East Kunlun Mountains.Glacial snow water seeps underground into groundwater and penetrates into Sanhu depression strata along the fore-slope belt.In this process,the water leaches and dissolves a large amount of salt substances and trace elements such as Sr,Br and B in the stratum,and the salinity gradually increases,and finally migrates to the anticline zone in the depression,forming the formation water with higher salinity.According to the origin and evolution of the formation water,it can be indicated that Sebei gas field has the laws of horizontal migration of biogas and dynamic accumulation of water-soluble gas,which also proves that the origin,migration and salinity of formation water rise process to a certain extent determines the biogenic gas generation,migration and enrichment.In the exploration of biogas in Sanhu area,it is necessary to find out the source of the deep formation water and its salinization process.Attention should also be paid to biogas resources in designing deep lithium-rich brine exploration.

关 键 词：涩北气田 地层水成因 生物气 水化学 氢氧同位素 三湖坳陷 

分 类 号：X14[环境科学与工程—环境科学] P641[天文地球—地质矿产勘探]