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煤层瓦斯赋存不均衡特征及地质控制机理

The heterogeneous characteristic of coalbed gas occurrence and its geological control mechanism

  • 摘要: 受地质条件控制,煤层瓦斯赋存具有不均衡性。揭示其赋存规律及地质控制机理,是矿井实施“一矿一策、一面一策”瓦斯治理方案的重要依据。基于瓦斯地质理论和方法,利用实测的瓦斯含量和相关地质资料,对赵固二矿二1煤层F17-1和F18断层夹持区域的瓦斯赋存规律及其地质控制机理进行了系统研究。结果表明:受上覆基岩厚度、埋深,以及断层、向斜等地质因素的影响,研究区二1煤层瓦斯赋存呈现出明显的不均衡性,不同区域的控制因素存在显著差异。在埋深790 m以浅区域,薄基岩叠加F30及其分支断层、FS3等浅部断层,利于瓦斯逸散,是该区域瓦斯含量整体较低的主要原因;同时受埋深的影响,瓦斯含量随埋深的增加呈缓慢增大趋势;在埋深790 m以深区域,基岩厚度是控制瓦斯赋存整体分布的主控因素,基岩厚度随埋深增加先增大、再减小是导致煤层瓦斯含量随埋深增加先快速增大再降低的主要原因,F17-1断层尖灭处和S4向斜区是瓦斯含量受基岩厚度整体控制下的局部增高区;F18断层瓦斯逸散作用及由F18断层靠近F17-1断层方向上基岩厚度逐渐增大是相同深度条件下,由F18断层靠近F17-1断层方向上煤层瓦斯含量逐渐增大的主要原因。

     

    Abstract: Controlled by geological conditions, coalbed gas occurrence exhibits heterogeneity. Revealing its occurrence patterns and geological control mechanisms serves as a critical basis for implementing the "one mine, one policy; one mining face, one policy" gas control strategies in coal mines. Based on gas geological theories and methods, utilizing measured gas content data and relevant geological data, this study investigates the gas occurrence patterns and geological control mechanism in the area bounded by the F17-1 and F18 Faults within the No. 2-1 Coal Seam of Zhaogu No. 2 Mine. The results show that: affected by geological factors such as the thickness of the overlying bedrock, burial depth, faults, and synclines, the gas occurrence of the No. 2-1 Coal Seam in different ranges of the study area presents significant heterogeneity and differences in controlling factors. For the area with a burial depth of less than 790 m, the thin bedrock combined with shallow faults such as the F30 Fault, its branch faults, and the FS3 Fault is conducive to gas escape, which is the main reason for the overall low gas content in this region. Meanwhile, affected by burial depth, the gas content shows a trend of slow increase with the increase of burial depth. For the area with a burial depth greater than 790 m, the bedrock thickness is the dominant controlling factor for the overall distribution of gas occurrence. The bedrock thickness first increases and then decreases with the increase of burial depth, which is the main reason for the coal seam gas content first increasing rapidly and then decreasing as the burial depth increases. The pinch-out zone of the F17-1 Fault and the S4 Syncline area are local gas-enriched zones under the overall control of bedrock thickness. The gradual increase in coal seam gas content at the same depth level—progressing from the F18 fault toward the F17-1 fault—is primarily attributed to the gas dissipation effect of the F18 fault.

     

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