准噶尔盆地南缘白杨沟泥火山群地质流体的地球化学特征  

Geochemical characteristics of geofluids in the Baiyanggou mud volcano group in the southern margin of the Junggar Basin

作　　者：马勇 马向贤 张力 胥旺 李小雅 卢昌顺 傅庆州 郑国东 MA Yong;MA Xiangxian;ZHANG Li;XU Wang;LI Xiaoya;LU Changshun;FU Chingchou;ZHENG Guodong(Northwest Institute of Eco-Environment and Resources,Chinese Academy of Sciences,Lanzhou 730000,Gansu,China;Provincial Key Laboratory of Petroleum Resources,Lanzhou 730000,Gansu,China;University of Chinese Academy of Sciences,Beijing 100049,China;College of Energy,Chengdu University of Technology,Chengdu 610059,Sichuan,China;College of Civil Engineering and Mechanics,Lanzhou University,Lanzhou 730000,Gansu,China;Institute of Earth Sciences,Academia Sinica,Taibei 115,Taiwan,China)

机构地区：[1]中国科学院西北生态环境资源研究院,甘肃兰州730000 [2]甘肃省油气资源研究重点实验室,甘肃兰州730000 [3]中国科学院大学,北京100049 [4]成都理工大学能源学院,四川成都610059 [5]兰州大学土木工程与力学学院,甘肃兰州730000 [6]台湾“中研院”地球科学研究所,中国台湾台北115

出　　处：《地球化学》2022年第4期492-502,共11页Geochimica

基　　金：中国科学院“西部之光”青年学者A类项目;中国科学院台湾青年学者(2018TWZ2ZA001);国家重点研发计划(2019YFA708501)联合资助。

摘　　要：泥火山溢出地质流体的地球化学特征有助于解释泥火山的物质来源、油气水岩相互作用以及区域构造活动性等。目前白杨沟泥火山群至少有75个仍在活动的喷口,其中有明显泥水溢出的喷口约40个。释放气体主要成分为甲烷,并含有少量的二氧化碳和氮气等。甲烷的δC值为-51.1‰~-44.3‰,二氧化碳的δC值为-21.8‰~10.7‰,具有热成因原油伴生气特征,但也可能经历了微生物的改造作用。喷口泥水富集Na^(+)、Cl^(-)、HCO^(-)等离子,水化学类型为NaCl型和NaHCO型,可能是地下油气藏中的油田水与储存在深部地层中的古大气降水的混合流体,并经历过比较复杂的油气水岩相互作用。白杨沟泥火山的活动强度整体上自西向东逐渐减弱,喷口气体的宏观渗漏强度和泥水pH值也明显降低,二氧化碳的δC逐渐偏重,甲烷的δC变轻,揭示西侧区域泥火山与地下深部的连通性较好,地下地质流体向地表的运移速率较快,遭受的微生物改造程度相对较低,对流体碳同位素分馏的影响较小。Explaining the source of mud volcanic materials, water-rock-oil-gas interactions in mud volcanic systems, and regional tectonic activities by geochemical characteristics of geofluids from mud volcanoes is crucial.Currently, at least 75 active vents are present in the Baiyanggou mud volcano group, among which approximately 40 vents clearly exhibit muddy water overflow. The primary components of the released gases are methane, accompanied by a fraction of carbon dioxide and nitrogen. The carbon isotope values of methane and carbon dioxide ranged from-51.1‰ to-44.3‰ and-21.8‰ to 10.7‰, respectively, implying that the gases are characterized by their association with thermogenic crude oils;however, microbial transformation cannot be ignored. The water overflow was predominantly enriched with Na, Cl, and HCO, and belongs to the hydro-chemical types of NaCl and NaHCO. The water overflow origin might be from the mixed oilfield water fluids in underground oil-gas reservoirs and the paleo-atmospheric precipitation in the deep strata that experiences complicated oil-gas-water-rock interactions. Mud volcanoes in the west of the study area were very active, with activity gradually decreasing to the east. The macro-seepage of the gases flux and the pH value of the water were significantly reduced from the west to east. Furthermore, the carbon isotopes in carbon dioxide became heavier and those of methane became lighter in the east, indicating that connectivity is better in the west than in the east. Geofluids can move towards the surface faster in the migration processes and less influenced by the microbial modifications, resulting in small carbon isotopic fractionation.

关 键 词：泥火山 地质流体 碳同位素 水岩相互作用 

分 类 号：P593[天文地球—地球化学]