Acta Petrolei Sinica ›› 2025, Vol. 46 ›› Issue (2): 440-455,482.DOI: 10.7623/syxb202502011

• Review • Previous Articles     Next Articles

Helium resource potential and enrichment mechanism of unconventional gas

Ma Yong1, Chen Jianfa1, Xin Zhiyuan1, Luo Qingyong1, Luo Chao2, Zhang Haipeng1, Zhong Kesu2, Che Shiqi1, Ma Jianbin1, Qin Changcai1   

  1. 1. State Key Laboratory of Petroleum Resources and Engineering, China University of Petroleum (Beijing), Beijing 102249, China;
    2. Shale Gas Research Institute, PetroChina Southwest Oil & Gasfield Company, Sichuan Chengdu 610051, China
  • Received:2024-05-28 Revised:2024-09-09 Online:2025-03-13 Published:2025-03-13

非常规天然气中氦资源潜力及富集机制

马勇1, 陈践发1, 辛志源1, 罗情勇1, 罗超2, 张海鹏1, 钟可塑2, 车世琦1, 马健斌1, 秦长彩1   

  1. 1. 油气资源与工程全国重点实验室,中国石油大学(北京) 北京 102249;
    2. 中国石油西南油气田公司页岩气研究院 四川成都 610051
  • 通讯作者: 陈践发,男,1961年7月生,2001年获中国科学院地球化学研究所博士学位,现为中国石油大学(北京)地球科学学院教授,主要从事天然气地质和地球化学研究工作。Email:jfchen@cup.edu.cn
  • 作者简介:马 勇,男,1988年7月生,2016年获中国石油大学(北京)博士学位,现为中国石油大学(北京)地球科学学院副教授,主要从事油气地质和地球化学研究工作。Email:mayong@cup.edu.cn
  • 基金资助:
    国家重点研发计划项目"富氦天然气成藏机制及氦资源分布预测技术"(2021YFA0719000)和国家自然科学基金项目"碎屑岩地层天然气运移过程中烃-岩石相互作用机理"(No.42173030)资助。

Abstract: At present, it is the most important way for industrial helium production by extracting helium from helium-containing and helium-rich natural gas reservoirs. It is of great significance to evaluate the helium content and formation mechanism of unconventional gas with huge reserves, which can enrich the source of helium resources. The geochemical characteristic analyses of 450 helium-containing shale gas and coalbed methane (CBM)samples taken from the world show that the helium content of shale gas ranges from 6×10-8 to 0.011 4 (0.057 % on the average), that of CBM ranges from 5×10-7 to 0.022 8 (0.115 % on the average), and that of more than 24 % of unconventional gas samples can reach 0.05 % . Unconventional gas generally has a low 3He/4He ratio (from 0.002 to 0.93, 0.071 on the average), indicating that crust-derived helium is the main source. The radioactive decay calculations of uranium and thorium contents indicate that the helium content generated in shale gas source is consistent with the distribution characteristics of the currently measured helium content. The 40Ar/36Ar ratio in helium-rich shale gas is the same as that the accumulative ratio of contemporaneous source rocks. Large faults connected with deep mantle source or basement were usually not developed in helium-rich shale gas reservoirs. All of those indicate that helium in shale gas is mainly resulted from the radioactive decay of uranium and Th-rich minerals in the shale source. Helium has a stronger adsorption capacity than methane, and the lower concentration of helium in shale gas reservoirs may lead to capillary resistance, which are the primary causes for the preservation of helium in shale gas. The content of helium generated in CBM source is usually lower (less than 20×10-6)than that currently measured in gas reservoir, and the helium in helium-rich CBM is primarily originated from the radioactive decay of basement rocks. Helium-producing potential, reservoir permeability and hydrodynamics are the main reasons for the differences in helium enrichment mechanism of shale gas and CBM. The favorable zones for the enrichment of helium-rich unconventional gas include the pre-Carboniferous shale with certain gas content above 1 m3/t and uranium content above 10×10-6, and the coal seam with late accumulation and sufficient helium source supply (including crust source helium and mantle source helium)at the bottom of the reservoir. In addition, the Cambrian shale in the Middle and Upper Yangtze areas and the Carboniferous-Permian coal seam in Ordos Basin are considered as the favorable exploration horizons for unconventional helium-rich gas in China.

Key words: helium, shale gas, coalbed methane, helium-rich unconventional gas, enrichment and accumulation mechanism

摘要: 从含氦、富氦天然气藏中提取氦气是目前工业制氦最重要的途径,评价储量规模巨大的非常规天然气中的氦含量及成因机制 对于丰富氦资源来源具有重要意义。基于全球450个含氦页岩气和煤层气样品的地球化学特征分析表明,页岩气中的氦含量为6× 10-8~0.011 4(平均为0.057 % ),煤层气中的氦含量为5×10-7~0.022 8(平均为0.115 % ),超过24 % 的非常规天然气样品中的氦含量达到0.05 % 。非常规天然气整体具有较低的3He/4He比值(0.002~0.930,平均为0.071),表明壳源氦为其主要来源。U、Th含量及放射性衰变模拟计算表明,页岩气的源内氦含量与其现今实测氦含量的分布特征一致,富氦页岩气中的40Ar/36Ar比值与同期源岩累积产生的40Ar/36Ar比值相同,且富氦页岩气藏中往往不发育与深部幔源或基底连通的大型断裂,这表明页岩气中的氦主要来自页岩源内富U、Th矿物的放射性衰变。氦气具有比甲烷更强的吸附能力,且页岩气藏中较低的氦浓度可形成毛细管阻力,二者共同作用是页岩气中的氦气能够保存的主要原因。煤层气的源内氦含量通常较小(<120×10-6),远低于现今气藏实测的氦含量。富氦煤层气中的氦主要来自基底岩石的放射性衰变。生氦潜力、储层渗透性和水动力作用是导致页岩气和煤层气中氦气富集机制差异的主要原因。U含量在10×10-6以上且具有一定含气量(>1 m3/t)的石炭纪之前古老页岩,以及成藏年代较晚、底部有充足氦源(包括壳源氦和幔源氦)供给的煤层是富氦非常规天然气富集的有利区带。中国中—上扬子地区寒武系页岩和鄂尔多斯盆地石炭系—二叠系煤层是富氦非常规天然气的有利勘探层位。

关键词: 氦气, 页岩气, 煤层气, 富氦非常规天然气, 富集成藏机制

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