Fe3O4纳米酶−过硫酸铵压裂液在煤层气开发中的增产作用

Stimulation effect of Fe3O4 nanozyme-ammonium persulfate fracturing fluid in coalbed methane development

  • 摘要: 煤层气的开发迫切需要一种集“增解、增扩、增透”为一体的增产技术,以弥补以往只关注压裂造缝增透的不足。纳米酶是一类既有纳米材料特性,又具催化功能的模拟酶活性的物质,其因高效催化功能和稳定易于规模化生产的特点,受到各个领域的广泛关注,其中类过氧化物纳米酶应用领域最为广泛,如Fe3O4纳米酶与过硫酸铵结合将产生强氧化性自由基SO4·,该自由基能否对煤储层改性,进而实现煤层气增产还未见报道。为此,采用Fe3O4纳米酶−过硫酸铵构成的压裂液对长焰煤进行氧化降解试验,首先对降解前后的煤进行红外光谱、X射线光电子能谱(XPS)、拉曼光谱、C-13核磁共振(13C-NMR)和等温吸附测试,定性定量地揭示降解前后煤中官能团、分子量的变化以及对煤亲甲烷能力的影响,然后再对其进行压汞测试,探究降解前后煤孔隙结构的变化,最后对降解前后的煤进行渗透率测试,查明Fe3O4纳米酶−过硫酸铵压裂液体系对于煤储层渗透率的影响,结合以上试验阐明储层改性对煤层气产出的强化机制。结果表明:煤经过Fe3O4纳米酶−过硫酸铵压裂液作用后,整体含氧官能团、甲基和其他饱和官能团的相对丰度降低,由此降低了煤的亲甲烷的能力,实现增解增产;煤中的固态大分子部分被降解成液态小分子物质,基质孔隙度和总孔体积上升、曲折度和突破压力降低,实现增扩增产;煤储层渗透率也由此得以提升,实现了增透增产。试验研究证实了这种压裂液除了具有常规压裂液的造缝功能外,还具有增解、增扩、增透功能,可强化煤层气“上游”的产出。Fe3O4纳米酶−过硫酸铵压裂液既是纳米酶材料应用的拓展,又是一种具有多重增产功能的煤储层改造压裂液。

     

    Abstract: The efficient development of coalbed methane (CBM) calls for innovative technologies capable of simultaneously enhancing gas desorption, diffusion, and reservoir permeability, going beyond conventional fracturing methods that mainly focus on permeability improvement through physical cracking. Nanozymes, which combine nanomaterial properties with enzyme-like catalytic activity, have attracted wide attention due to their high catalytic efficiency, stability, and scalability. Among them, peroxidase-like nanozymes represent one of the most applied categories. For instance, the strong oxidizing sulfate radical (SO4·) can be generated via the Fe3O4 nanozyme–ammonium persulfate system. However, whether such radicals can effectively modify coal reservoirs and thereby enhance CBM production remains insufficiently investigated. long-flame coal is used as the substrate to examine the degradation process induced by Fe3O4 nanozyme–ammonium persulfate fracturing fluid. The coal samples, before and after degradation, are analyzed using FTIR, XPS, Raman spectroscopy, 13C-NMR, and isothermal adsorption experiments to qualitatively and quantitatively evaluate changes in functional groups, molecular weight, and methane adsorption affinity. Mercury intrusion porosimetry is employed to characterize alterations in the coal pore structure, while permeability measurements are conducted to assess the effect of the nanozyme system on reservoir flow capacity. The results show that after treatment with the Fe3O4 nanozyme–persulfate system, the content of oxygen-containing functional groups, methyl groups, and other saturated functional groups on the coal surface is reduced, leading to decreased methane adsorption capacity and thus promoting CBM desorption. Moreover, partial degradation of coal macromolecules into small soluble molecules increases matrix porosity and total pore volume, while reducing tortuosity and breakthrough pressure—favorable for improving CBM diffusion. Furthermore, nanozyme-mediated degradation contributes to enhanced coal reservoir permeability. This study confirms that the proposed fracturing fluid not only performs conventional fracture creation but also integrates functions for enhancing desorption, diffusion, and permeability, thereby strengthening the “upstream” output of CBM. The Fe3O4 nanozyme–persulfate system extends the application scope of nanozyme materials and offers a multi-functional approach for coal reservoir stimulation.

     

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