摘要
次生生物气与地下水之间存在一定的关系,特别是在煤层气等天然气储层中,了解地下水与次生生物成因甲烷之间的关系对于天然气勘探和开发具有重要意义。基于中国沁水盆地6个区块的57个煤层气井排采水和3个河水样品的化学组成、氢氧同位素组成(δ^(18)O_(H_(2)O))和δD_(H_(2)O)以及溶解无机碳(DIC)碳同位素组成(δ^(13)C_(DIC)和Δ^(14)C_(DIC)),深入剖析地下水与次生生物成因甲烷之间的复杂关系。结果表明:氢氧同位素分布在大气降水线附近,煤层气井排采水主要来源于大气降雨,硫酸盐微生物还原作用是郑庄和阳泉区块氘同位素富集的主要原因。研究区煤层气井排采水化学组成以Na⁃HCO_(3)型为主,其变化受到水—岩相互作用、阳离子交换等过程的控制。沁水盆地6个研究区块煤层气井排采水的稳定碳同位素呈现高δ^(13)C_(DIC)值(-4.19‰~34.80‰,平均为16.51‰)且与溶解无机碳含量呈明显正相关关系可能是微生物产甲烷作用的结果。煤层气井排采水中δ^(13)C_(DIC)与SO_(4)^(2-)的负相关性以及δ正漂移等指标也指向沁水盆地不同成熟度煤岩中次生生物成因甲烷的广泛存在。δ^(13)C_(DIC)与镜质体反射率(R_(Omax))的负相关性进一步表明沁水盆地不同成熟度煤层中广泛存在次生生物成因甲烷,且在浅埋藏和成熟度较低的煤层中最为显著。地球化学与微生物学的结合将会进一步阐明次生生物甲烷的形成途径和机制。
Hydrogeochemical characteristics of coalbed methane co-produced water have significant implications for the secondary biogenic methane.Understanding the relationship between groundwater and secondary biogenic methane is crucial for natural gas exploration and development.The chemical compositions,hydrogen and oxygen isotopic compositions(δ^(18)O_(H_(2)O and δD_(H_(2)O))),the abundance and isotopic compositions(δ^(13)C_(DIC) and Δ^(14)C_(DIC))of dissolved inorganic carbon(DIC)of fifty-seven CBM co-produced water samples and three river samples from six blocks of Qinshui Basin in China are analyzed in this study.Results show that hydrogen and oxygen isotopes are distributed near the atmospheric precipitation line,suggesting that coalbed methane well-produced water mainly originates from atmospheric precipitation.Sulfate microbial reduction is identified as a crucial factor in the enrichment of deuterium isotopes in the Zhengzhuang and Yangquan blocks.The chemical composition of water produced from coalbed methane wells in the study area is predominantly of Na-HCO_(3) type.The evolution of geochemical compositions of coal seam water is controlled by water-rock interaction and cation exchange processes.Stable isotope analysis of water from coalbed methane wells in the six study blocks in the Qinshui Basin shows elevatedδ^(13)C_(DIC) values(from-4.19‰to 34.80‰,average 16.51‰),and a clear positive correlation with dissolved inorganic carbon content,likely indicating the result of microbial methane production.The negative correlation betweenδ^(13)CDIC and SO_(4)^(2-)in coalbed methane produced water,as well as the positive drift inδ,suggests the widespread occurrence of secondary biogenic methane in coalbeds with different maturities in the Qinshui Basin.The negative correlation betweenδ^(13)CDIC and vitrinite reflectance(R Omax)further indicates the presence of secondary biogenic methane in coal beds with different maturities,particularly in shallowly buried and low maturity coal beds.The integration of geochemistry and microbiology will further elucidate the pathways and mechanisms of secondary biogenic methane formation.
作者
方鲁加
陈碧莹
能惠
Yuji Sano
徐胜
Lujia FANG;Biying CHEN;Hui NAI;Yuji SANO;Sheng XU(School of Earth System Science,Tianjin University,Tianjin 300072,China;Marine Core Research Institute,Kochi University,Kochi 783-8502,Japan)
出处
《天然气地球科学》
CAS
CSCD
北大核心
2024年第11期1935-1949,共15页
Natural Gas Geoscience
基金
国家自然科学基金项目(编号:42150710532)资助。
关键词
煤层气井排采水
水化学特征
碳同位素
次生生物甲烷
沁水盆地
CBM co-produced water
Hydrogeochemical characteristics
Carbon isotope
Secondary biogenic methane
Qinshui Basin
