College of Geoscience and Surveying Engineering, China University of Mining and Technology-Beijing
State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology-Beijing
China United Coalbed Methane National Engineering Research Center Co., Ltd.
PetroChina Coalbed Methane Company Limited

煤粉问题制约我国煤层气的高效开发。选用韩城矿区山西组3号煤层煤岩样品，开展不同水化学性质对支撑裂缝中煤粉运移影响的物理模拟试验，分析裂缝导流系统渗透率及煤粉产出质量浓度变化，探究不同水化学性质对支撑裂缝中煤粉运移的影响。试验结果表明：Na2SO4溶液驱替条件下，煤粉产出质量浓度随矿化度的增加而降低，高矿化度条件下，煤粉聚集沉降性强，堵塞裂缝通道。NaHCO3溶液驱替条件下，煤粉产出质量浓度随矿化度的增加而增大，伴随矿化度的增加，水解产生OH−增加煤粉颗粒表面负电荷，增强煤粉间排斥力，缓解煤粉聚集效果，产出部分煤粉颗粒。6 000 mg/L Na2SO4和NaHCO3溶液驱替条件下流体具有更多的展布空间，渗透率最高。MgCl2溶液驱替条件下，煤粉产出质量浓度随矿化度的增加而增大，高矿化度增强煤粉间相互作用，试验样内部相对平衡被打破，煤粉产出量增大，试验样内部煤粉堵塞程度大致相同，渗透率数值变化不大。在相同矿化度(10 000 mg/L)条件下，不同水化学类型溶液驱替条件下煤粉产出质量浓度为：NaHCO3 > Na2SO4 > MgCl2，试验样平均渗透率为：MgCl2 > NaHCO3 > Na2SO4，煤粉聚集的程度，在一定程度上影响煤粉产出，Na2SO4和NaHCO3团聚作用低于MgCl2，部分煤粉运移，试验样末端堵塞程度高于MgCl2溶液，NaHCO3水解产生OH−，煤粉处于碱性环境中，改善试验样堵塞情况，提高渗透率。根据模拟试验中渗透率波动的上升状态、下降状态和轻微波动状态3个趋势，结合实测渗透率，统计渗透率变化趋势时间段，分析煤粉产出质量浓度与煤样渗透率之间的关系，回归模型的R2 = 0.834，说明煤粉运移影响渗透率的波动。

The problem of coal fines restricts the efficient development of coalbed methane in China. The coal sample of No. 3 coal seam in the Shanxi Formation in the Hancheng mining area was selected for carrying out a physical simulation experiment on the effect of different hydrochemical properties on the migration of coal fines in the propped fractures. The change in the permeability of fracture diversion system and the output mass concentration of coal fines were investigated, the influence of different hydrochemical properties on coal fines migration in the propped fractures was explored. Experimental results show that in the displacement condition of Na2SO4 solution, the output mass concentration of coal fines decreases with the increase of salinity. Under the condition of high salinity, the coal fines have strong agglomeration and sedimentation, which can block the crack channels. In the displacement condition of NaHCO3 solution, the output mass concentration of coal fines increases with the increase of salinity. With the increase of salinity, OH− is generated by hydrolysis, which increases the negative charge on the surface of coal fines particles, enhances the repulsive force between coal fines, alleviates the coal fines aggregation effect, and produces part of coal fines particles. Under the condition of 6 000 mg/L solution of Na2SO4 and NaHCO3 solution, the fluid has more distribution space and the highest permeability. In the displacement condition of the MgCl2 solution, the output mass concentration of coal fines increases with the increase of salinity. High salinity is conducive to the aggregation of coal fines. The internal relative balance of the experimental sample is broken, and the output of coal fines increases. The clogging degree of coal fines inside the experimental sample is roughly the same, and the permeability value does not change much. Under the condition of the same salinity (10 000 mg/L), the mass concentration of coal fines output in the experiments of different hydrochemical types is: NaHCO3 > Na2SO4 > MgCl2, and the average permeability of the experimental sample is: MgCl2 > NaHCO3 > Na2SO4. The degree of coal fines aggregation affects the output of coal fines to a certain extent. The agglomeration effect of Na2SO4 and NaHCO3 is lower than that of MgCl2, and part of the coal fines will migrate. The degree of clogging at the end of the experimental sample is higher than that of the MgCl2 solution. The hydrolysis of NaHCO3 generates OH−, and the coal fines are in an alkaline environment, which improves the clogging of the experimental sample and increases the permeability. According to the three trends of the rising state, falling state and slight fluctuation state of permeability fluctuation in the simulation experiment, combined with the measured permeability value, the period time of the permeability change trend was counted, and the relationship between the mass concentration of coal fines output and the permeability of coal samples was analyzed. The R2 of the regression model is 0.834, indicating that the fluctuation of the coal fines migration affects the experimental permeability.

国家自然科学基金资助项目(41972174)；中央高校基本科研业务费资助项目(2022YJSDC10)

刘子亮，魏迎春，张琦，等. 水化学性质对支撑裂缝中煤粉运移的影响[J]. 煤炭学报，2023，48(9)：3483−3493.

LIU Ziliang，WEI Yingchun，ZHANG Qi，et al. Effect of hydrochemical properties on the migration of coal fines in propped fractures[J]. Journal of China Coal Society，2023，48(9)：3483−3493.