石油学报 ›› 2011, Vol. 32 ›› Issue (3): 404-410.DOI: 10.7623/syxb201103005

• 地质勘探 • 上一篇    下一篇

塔里木盆地轮南低凸起天然气分布规律与成藏期次

苗忠英  陈践发  张  晨  陈鸿雁  王冠男   

  1. 中国石油大学油气资源与探测国家重点实验室  北京  102249
  • 收稿日期:2010-07-26 修回日期:2010-11-20 出版日期:2011-05-25 发布日期:2011-07-19
  • 通讯作者: 苗忠英
  • 作者简介:苗忠英,男,1982年7月生,2008年获中国石油大学(北京)硕士学位,现为中国石油大学(北京)地球科学学院地质资源与地质工程专业在读博士研究生,主要从事天然气成藏机理及分布规律研究。
  • 基金资助:

    国家重点基础研究发展规划(973)项目(2006CB202307)和国家科技重大专项(2008ZX05007-003)联合资助。

Regularity of distribution and accumulation stages of natural gases in the Lunnan lower uplift of the Tarim Basin

MIAO Zhongying  CHEN Jianfa  ZHANG Chen  CHEN Hongyan  WANG Guannan   

  • Received:2010-07-26 Revised:2010-11-20 Online:2011-05-25 Published:2011-07-19

摘要:

系统分析了塔里木盆地轮南低凸起天然气地球化学特征和有机包裹体均一化温度等资料,对天然气成因、分布规律和成藏期次进行了研究。结果表明:该区烃类气体主要为海相高成熟—过成熟腐泥型干气,可分为原油裂解气、干酪根裂解气和混合气3种成因类型;轮古东斜坡带产出特征明显的原油裂解气,轮古西斜坡带和中部斜坡带主体为干酪根裂解气,其他地区为混合气;烃类气体碳同位素序列倒转是由不同成熟度天然气混合与扩散分馏机制双重作用所致;氮气主要来源于高成熟-过成熟海相烃源岩热解,CO2有壳源无机成因和有机成因两种来源;稀有气体同位素特征表明,轮南断垒带有少量幔源气混入,其他地区为典型的壳源气。奥陶系油气存在3期充注,分别为加里东晚期—海西早期、海西晚期和喜马拉雅中晚期,石炭系油气主要在喜马拉雅中晚期富集成藏。

关键词: 塔里木盆地, 轮南低凸起, 天然气成因, 分布规律, 成藏期次, 非烃成因

Abstract:

To clarify several questions about the gas origin,regularity of distribution as well as stages of oil and gas accumulations in the Lunnan lower uplift, Tarim Basin, the present paper systematically dealt with geochemical characteristics of natural gases and the homogenization temperature of organic inclusions from the study area. The results showed that hydrocarbon gases in the study area were likely to be a marine sapropel-type dry gas with high to over maturity that could be divided into three types:A cracking gas from crude oils that occurred mainly in the east slope zone of Lungu; a cracking gas from kerogen distributed mainly in the west-middle slope zone of Lungu; and a mixed gas in other areas. Some hydrocarbon gases in the study area showed a reversal of carbon isotopes probably due to two factors:The mixture of natural gases with different maturities and the mechanism of isotopic fractionation by diffusion. Nitrogen in these gases was mainly a pyrolytic product of marine source rocks with high to over maturity, and carbon dioxide showed two possible origins, crust-derived inorganic one or organic one. Additionally,isotope characteristics of the related noble gases indicated that the gas from the Lunnan fault uplift was mixed with a small amount of the mantle-derived gas,whereas gases from other areas were typically crust-derived. Meanwhile,the distributional regularity of natural gases in the study area suggested that the Ordovician gas varied a lot in types that were controlled by faults, besides,the Carboniferous or younger gas was a product of oil cracking. Accordingly,based on the history of oil-gas charging in the study area,the paper proposed that the oil and gas from Ordovician experienced three stages of hydrocarbon charging, namely late Caledonian to early Hercynian,late Hercynian,and mid-late Himalayan, respectively. The Carboniferous oil and gas were mainly accumulated in mid-late Himalayan.

Key words: Tarim Basin, Lunnan lower uplift, origin of natural gas, regularity of distribution, stage of accumulation, origin of non-hydrocarbon

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