青海南部陆域冻土区钻孔岩芯地球化学特征及其水合物指示意义  

Geochemical characteristics of the drill core and its hydrate indications in permafrost region of southern Qinghai,China

作　　者：周亚龙[1,2] 杨志斌[1] 张舜尧[1,2] 张富贵[1,2] 王惠艳[1] ZHOU Yalong;YANG Zhibin;ZHANG Shunyao;ZHANG Fugui;WANG Huiyan(Institute of Geophysical and Geochemical Exploration,CAGS,Langfang,Hebei 065000,China;Key Laboratory of Geochemical Cycling of Carbon and Mercury in the Earth's Critical Zone,CAGS,Langfang,Hebei 065000,China)

机构地区：[1]中国地质科学院地球物理地球化学勘查研究所,河北廊坊065000 [2]中国地质科学院地球表层碳-汞地球化学循环重点实验室,河北廊坊065000

出　　处：《地质学报》2024年第4期1279-1290,共12页Acta Geologica Sinica

基　　金：国土资源部公益性行业科研专项项目(编号201111019);国家127专项“天然气水合物资源勘查与试采工程”专项项目(编号GZHL20110324);中国地质调查局地调项目(编号DD20230543);中央级公益性科研院所基本科研业务费专项(编号AS2016Y01)联合资助的成果。

摘　　要：为探讨青海南部陆域冻土区烃源岩地球化学异常成因及气源条件,通过分析青海开心岭冻土区TK-1钻孔岩芯样品中酸解烃、荧光光谱、甲烷碳同位素含量及垂向迁移变化特征,解析其烃类地球化学异常成因,剖析岩芯中烃类异常与裂隙或破碎带、水合物稳定带、烃类运聚成藏过程的响应关系,研究其对天然气水合物及烃类运聚的地球化学指示意义。结果显示:钻孔岩芯中烃类在62~80 m、112~119 m、150~169 m和254~350 m深度段出现明显的地球化学异常富集特征,钻孔岩芯酸解烃中烃类组成、参数比值(C_(1)/ΣC_(1-5)、C_(1)/ΣC_(2-5)、C_(1)/ΣC_(2-3)、iC_(4)/nC_(4)等)、甲烷碳同位素(δ^(13)C_(PDB))显示烃类以热解成因为主,包括油型裂解气、凝析油伴生气、煤成气和少量的无机成因气。二叠系那益雄组煤系烃源岩处于高—过成熟阶段,其热演化过程中的生排烃气可能是形成水合物所需气体的重要来源。冻土带的封盖“挡板效应”,在冻土层下方形成烃类地球化学强异常,可作为天然气水合物及烃类运聚等异常现象的指示。裂隙或破碎带内岩芯酸解烃组分含量相对较高,随着深度变化,烃类组分呈现明显的“色层效应”,显示裂隙或破碎带对烃类的运移、聚集具有一定控制作用。In order to explore thegenesis of hydrocarbon geochemical anomalies and gas source conditions of hydrocarbon source rocks in the permafrost region of southern Qinghai,we analyze the content of acidolysis hydrocarbon,fluorescence spectrum,and methane carbon isotope of core samples from the TK-1 borehole in the Kaixinling permafrost region.We also examine the vertical migration characteristics of these samples and discuss the causes of hydrocarbon geochemical anomalies.Our research delves into the relationship between hydrocarbon anomalies and the fractures or fracture zones,hydrate stability zones,and the process of hydrocarbon formation.By analyzing this relationship,we aim to understand the significance of geochemical anomalies in hydrocarbon migration and accumulation.The results show significant geochemical anomaly enrichment of hydrocarbons at depths of 62~80 m,112~119 m,150~169 m,and 254~350 m.Based on the hydrocarbon composition,parameter ratio(C_(1)/ΣC_(1-5),C_(1)/ΣC_(2-5),C_(1)/ΣC_(2-3),iC_(4)/nC_(4),etc.),and methane carbon isotope(δ^(13)C_(PDB))characteristics,we conclude that the hydrocarbons are mainly pyrolytic in nature.This includes oil-type cracking gas,condensate-associated gas,coal-derived gas,and a small amount of inorganic gas.Furthermore,the coal series source rocks of the Permian Nayixiong Formation have reached the high-to-over-mature stage.The hydrocarbon generation and expulsion of gas during thermal evolution might be an important source of gas for hydrate formation.The“baffle effect”of the permafrost zone forms a strong geochemical anomaly of hydrocarbons beneath the permafrost layer,which can be used as an indicator of natural gas hydrates and abnormal phenomena.Additionally,the content of acidolysis hydrocarbon components in the fractures or fracture zones is relatively high.With the change of depth,hydrocarbon components show an obvious“color layer effect”indicating that the fractures or fracture zones exert a certain control effect over the migration and accumulation of

关 键 词：酸解烃 甲烷碳同位素 天然气水合物 地球化学 开心岭冻土区 

分 类 号：P618.13[天文地球—矿床学]