松辽盆地基底石英脉中无机成因气的地球化学特征及指示意义  

Geochemical characteristics of abiogenic gas in the quartz veins in the basement rocks of the Songliao Basin and their indicative significance

作　　者：孟凡超 崔岩 张曰静[3] 王林[3] 杜青 刘浩毅 左耿超 田雨露 MENG Fanchao;CUI Yan;ZHANG Yuejing;WANG Lin;DU Qing;LIU Haoyi;ZUO Gengchao;TIAN Yulu(School of Geosciences,China University of Petroleum-East China,Qingdao,Shandong 266580,China;College of Geoscience and Engineering,Shandong University of Science and Technology,Qingdao,Shandong 266590,China;Exploration and Development Research Institute,Sinopec Shengli Oilfield Company,Dongying,Shandong 257015,China)

机构地区：[1]中国石油大学(华东)地球科学与技术学院 [2]山东科技大学地球科学与工程学院 [3]中国石化胜利油田分公司勘探开发研究院

出　　处：《天然气工业》2020年第10期29-37,共9页Natural Gas Industry

基　　金：国家自然科学基金项目“松辽盆地基底流体记录及其对深层天然气成因的指示意义”(编号:41302102)。

摘　　要：松辽盆地深层存在着地球内部来源的无机成因气体,但一直缺少直接的地质证据,而分析该盆地基底岩石则有望成为解决这一问题的突破口。为此,通过基底岩心样品采集、石英脉体分离、包裹体岩相学、流体地球化学分析等技术手段,研究该盆地基底岩石中的石英脉体及脉体中流体包裹体的岩相学特征、碳氢氧同位素特征,探讨石英脉及其包裹体内流体的成因,寻找深部气体向浅部运移的流体记录,并分析基底石英脉包裹体内流体的指示意义。研究结果表明:①石英脉体的氧同位素值介于8.1‰~9.5‰,为岩浆期后热液结晶形成;②石英脉中存在H2O、H2O—CO2和H2O—CO2—CH4共3种原生流体包裹体,完全均一温度介于320~360℃,成分以CO2、H2O为主,含有少量CH4、C2H6、N2、O2、Ar;③脉体中流体包裹体内水的δ18O介于2.0‰~3.8‰,δD介于-91.6‰^-75.7‰,表现为岩浆脱气后残余水特征;④CO2的δ13C变化范围较大(介于-13.8‰^-9.7‰),其中烷烃的δ13C1介于-30.6‰^-24.1‰,δ13C2介于-33.2‰^-25.7‰,且δ13C1>δ13C2,呈负碳同位素系列,CO2和烷烃均显示无机成因气特征。结论认为:①石英脉内烷烃的δ13C1和δ13C2与该盆地深层碳同位素完全倒转的烷烃气特征一致,两者可能具有一定的亲缘性;②松辽盆地基底之下岩浆活动产生的热液流体在盆地基底缝隙中结晶形成石英脉体,并且捕获热液流体中的无机成因气,其余无机成因气则沿深大断裂向上运移至盆地内部,为深层天然气藏的形成做出了贡献。There is abiogenic gas derived from the interior of the Earth in the deep strata of the Songliao Basin,but few direct geological evidences have been found.This problem would be solved by analyzing the basement rocks in this basin.In this paper,the petrographic and carbon,hydrogen and oxygen isotopic characteristics of quartz veins in the basement rocks and their fluid inclusions were studied by means of basement core sample collection,quartz vein separation,inclusion petrography and fluid geochemistry.Then,the origins of the quartz veins and the fluids in their inclusions were discussed,and fluid records of gas migration from deep to shallow areas were explored.In addition,the indicative significance of the fluids in the inclusions of quartz veins in the basement was analyzed.And the following research results were obtained.First,the oxygen isotope value of quartz veins is in the range of 8.1–9.5‰,and they are the products of post-magmatic hydrothermal crystallization.Second,there are three types of primary fluid inclusions in the quartz veins,including H2O,H2O-CO2 and H2O-CO2-CH4,and their complete homogenization temperature is between 320℃and 360℃.CO2 and H2O are dominant components with a little CH4,C2H6,N2,O2 and Ar.Third,δ18O andδD of the water in the fluid inclusions of veins are 2.0–3.8‰and-91.6--75.7‰,respectively,which are the characteristics of residual water after magma degassing.Fourth,δ13C of CO2 varies in a larger range(-13.8--9.7‰).δ13C1 andδ13C2 of alkane are in the range of-30.6--24.1‰and-33.2--25.7‰,respectively,andδ13C1 is greater thanδ13C2,indicating a reversed carbon isotopic trend.CO2 and alkane present the characteristics of abiogenic gas.In conclusion,δ13C1 andδ13C2 of alkane in quartz veins are accordant with the characteristics of alkane gas with completely reversed carbon isotopes in the deep strata of the basin,indicating both of them may have a certain familiarity.In addition,the hydrothermal fluid generated by magmatic activities below the basement of the

关 键 词：松辽盆地 基底 石英脉体 流体包裹体 无机烷烃 气源 深层天然气成藏 

分 类 号：P618.13[天文地球—矿床学]