【作者】 胡国艺；

【导师】 刘顺生； 李景明；

【作者基本信息】 中国科学院研究生院（广州地球化学研究所） ， 构造地质学， 2003， 博士

【摘要】 应用有机地球化学和构造地质学理论和方法对鄂尔多斯盆地奥陶系天然气地质研究中薄弱环节成藏要素和作用进行了系统科学分析。利用烃源岩生气定量热模拟技术、热模拟在线碳同位素实验技术、气体轻烃和生物标志物分析技术、运聚成藏物理模拟技术和包裹体中碳同位素分析技术等多种先进的实验技术对烃源岩的生气机理、气源和混合比、成藏史、充注路径、运移方向和构造作用与成藏关系等问题进行了深入的研究，在前人研究的基础上，经过本次大量的实验分析和综合研究，提出了一些新的认识。 通过对储层和烃源岩中沥青定量统计分析、烃源岩生气热模拟、最大吸附气实验测定及地质类比法等综合研究认为在鄂尔多斯盆地有机碳为0.2％可作为高—过成熟的海相碳酸盐岩有机碳下限标准。有利烃源岩主要分布在西南部边缘的“L”型斜坡地带和东部米脂盐湖一带。对低成熟(部分为成熟)的烃源岩在开放和密闭体系下的生气热模拟实验研究建立了热解气和油裂解气的生气模式，热解气的生气高峰在Ro=1.0—1.5％，油裂解气生气高峰是在Ro=1.5—2.5％之间，从热解气和油裂解气的相对含量来看热解气占总生气量的21％，油裂解气可能占79％，油裂解气产率为620m~3／吨．油。 采用气—烃源岩直接和动态对比的研究思路对鄂尔多斯盆地中部气田气源进行了多项地球化学参数综合对比研究，进一步证明中部气田气源具有混源特征，但是，在不同区块上、下古生界天然气混合程度不同，在中部气田的北部、西部和南部天然气主要以下古生界来源为主的混合气，而中部气田的东部则主要以上古生界来源为主的混合气。 加强了对包裹体中气体碳同位素测定方法研究，真空球磨法提取气体进行碳同位素分析的方法无裂解和氧化反应，代表真实流体，测定的碳同位素值可靠。用这种方法对鄂尔多斯盆地中部气田的储层包裹体中烃类气体碳同位素进行了测定，结合单个包裹体成分及均一温度认为该区有两期成藏史，并且早期可能主要来源于煤成气。 从生烃史、古地温史恢复、包裹体均一温度分布及单个包裹体气相成分等分析，鄂尔多斯盆地中部气田天然气成藏至少有两期，通过古地温史模拟资料与包裹体均一温度的对比研究，中部气田天然气成藏的主要时期可能在晚三叠世末和早白至世末，在晚三叠世末中部气田天然气是由东向西和由南向北运移趋势，盆地中部是天然气运移聚集的指向区。在白里系沉积末盆地中部低气势圈闭区在靖边南北一带稳定分布并向西扩大，东部米脂凹陷生气中心的天然气有向西、向北方向运移的趋势，鄂尔多斯盆地上古生界烃源岩在晚三叠世和早白里世存在剩余压力，在压力的驱动下，太原组煤层中的天然气可以微裂缝和上下泥岩微孔隙作为运移路径。 通过盆地构造作用对烃源岩分布和演化、奥陶系顶部风化壳储层的横向分布、成藏期运移方向和成藏后的保存保存等具有控制作用。根据鄂尔多斯盆地中部的沉积史、构造发育史、古岩溶形成史、生排烃史等等，按其时空配置关系，归纳气藏的形成可分为四个演化阶段：储集层孕育阶段（0；－C；）、圈闭形成阶段（C。－P）、天然气运聚成藏阶段（J。－K；）和气藏调整／定型阶段（K。－Q）o更多还原

【Abstract】 The essential elements and process of gas reservoir formation of Ordovician in Ordos basin have been annalysed systematicly and scientificly by means of the theory and method of organic geochemistry and tectonic geology in this dissertation.The several advanced techniques,such as gas generation thermal simulation, on-line individual gas compounds carbon isotope determination(PY-GC-C-IR-MS), the analysis technique of light hydrocarbons and biomarkers in natural gas, gas migration simulation and gas carbon isotope determination in fluid inclusions, have been applied to focuse on the study of the gas generation mechanism of souce rock, correlation between gas and source rock, reservoir formation history, migration direction, charging road in detail. Some conclusions have been made in the following.That the value of TOC is 0.2% may be regarded the low evaluation value of marine carbonate souce rock at the stage of high to over mature. According to the content of bitumen in source rock and reservoir, gas generation quantity, the maximum absorption gas quantity and geology analogy. Good source rock is developed in the slope belt of platform in the southwest part and middle-east part of Ordos basin. The gas generation of low mature source rocks has been simulated in the open system and close system respectively.The models of primary cracking gas (gas from kerogen) and secondary cracking gas (gas from oil) have been established. The Ro value of primary cracking gas generation peak is ranged from 1.0% to 1.5%. The Ro value of secondary gas generation peak is ranged from 1.5% to 2.5%. The quantity of primary cracking gas is up to 21 percentage of total gas generated. The quantity of secondary cracking gas is up to 79 percentage of the total gas generated.The comprehensive correlation between gas and source rock shows that natural gas in the north, west and south part of the center gas fields mainly come from Lower Paleozoic source rock, The attribution ratio of Lower Paleozoic source rock is up to 60-70%. In the other part, natural gas is mainly from Upper Paleozoic souce rock, its attribution ratio is up to 70%.Author pay more attention to the carbon isotope values of gas in fluidinclusions.The methods of pyrolysis and vaccum ball grinding have been used to obtain carbon dioxide, methane and other gases.Then, the carbon isotope values of these gases have been identified by GC-C-IR-MS. Because carbon oxide generated during pyrolysis process affected the carbon isotope value of methane by pyrolysis, authors concluded that the method of vacuum ball grinding is better than that of pyrolysis.The carbon isotope values of carbon dioxide, methane, ethane and propane of fluid inclusions of calcite samples in center field of Ordos basin have been determined.The results show that the values of 8 13Ci is distributed between -26.73% and -43.60%.The values of 13C2 are from -22.53%~-25.80%o and the values of 8 13Cs are from -22.53%o~-25.80%o. The characteristics of gas from fluid inclusion show that these gas are generated from coal and is very different from gas in gas fields. Authors speculate the times of gas filling reservoir are two at least. At early time, it is probably coal type gas.The analysis results of hydrocarbon generating history, paleotemperature history, the homogenization temperature distribution of fluid inclusions and individual fluid inclusion compounds show that the natural gas charging times in the center gas field is two. The first is at the age of late Triassic. At that time, natural gas migrated from the east to the west and from the south to the north. The center of basin is the accumulation target of gas migration and accumulation. At the age of early Cretaceous, the natural gas generated in the MiZhi depression migrated to the west and the north. At the ages of gas generation peak, anormally high pressures exsisted. With the help of this kind of pressure, natural gas generated from coal in the TaiYuan formation can be migrated to the Ordovician wethered crust reservoir accrossing micro-fiss更多还原