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<p>This study integrates different geochemical analyses (chemical compositions, carbon isotopes) and a physical mixing model to quantitatively identify gas sources and migration mechanisms in the Nanchuan No.2 coal mine. Results reveal distinct isotopic signatures: gases from mine-out area exhibit intermediate δC<sub>1</sub> values (− 55.1‰ to − 49.6‰) between coal-seam methane (avg. δ<sup>13</sup>C<sub>1</sub> = − 61.0‰) and Yanchang oil-type gas (avg. δ<sup>13</sup>C<sub>1</sub> = − 49.7‰), indicating mixed origins. The mixing model quantifies oil-type gas contributions to goaf emissions as 74.3% (methane) and 75.5% (ethane), dominated by vertical migration from Triassic Yanchang Formation source rocks through mining-induced fractures. Low coal-seam gas content (avg. 0.97&#xa0;m³/t) further supports external hydrocarbon influx. Structural heterogeneity in oil-type gas distribution correlates with spatial variations in contribution ratios (52.7–100%). Mining disturbances disrupt caprock integrity, creating pressure-relief pathways that drive gas migration via fracture networks. This work establishes a framework for optimizing gas control strategies in coal-oil-gas symbiotic systems, emphasizing the critical role of isotopic tracing in hazard mitigation.</p>

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Quantitative sources identification of gas emissions in mined-out area of coal seams in the Huanglong coalfield of the Ordos Basin, China

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年7月23日

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  • Bingyi Jia,
  • Shugang Li,
  • Haifei Lin,
  • Dongdong Chen,
  • Jingfei Zhang

摘要

This study integrates different geochemical analyses (chemical compositions, carbon isotopes) and a physical mixing model to quantitatively identify gas sources and migration mechanisms in the Nanchuan No.2 coal mine. Results reveal distinct isotopic signatures: gases from mine-out area exhibit intermediate δC1 values (− 55.1‰ to − 49.6‰) between coal-seam methane (avg. δ13C1 = − 61.0‰) and Yanchang oil-type gas (avg. δ13C1 = − 49.7‰), indicating mixed origins. The mixing model quantifies oil-type gas contributions to goaf emissions as 74.3% (methane) and 75.5% (ethane), dominated by vertical migration from Triassic Yanchang Formation source rocks through mining-induced fractures. Low coal-seam gas content (avg. 0.97 m³/t) further supports external hydrocarbon influx. Structural heterogeneity in oil-type gas distribution correlates with spatial variations in contribution ratios (52.7–100%). Mining disturbances disrupt caprock integrity, creating pressure-relief pathways that drive gas migration via fracture networks. This work establishes a framework for optimizing gas control strategies in coal-oil-gas symbiotic systems, emphasizing the critical role of isotopic tracing in hazard mitigation.