Coal fines migration and intrusion in coal fractures affect coalbed methane (CBM) wells performance by reducing reservoir permeability and production continuity. Physical simulations are conducted to investigate the permeability variation under different diameter coal fines intrusion at various flow velocities and confining pressures. The results show that the conductivity of fractures is dramatically reduced and hardly recover to its initial condition after coal fines intrusion. The permeability after coal fines intrusion (Pcfi) has no direct correlation with the increase of flooding velocity, while decreases with the increase of confining pressures. The fractures can be totally blocked by coal fines, while penetration also happened during the flooding process, causing permeability fluctuation. The permeability loss rates value for 80-120 mesh coal fines intrusion are generally <60% compared with the initial permeability, including the flow velocity of 2, 3, 4, 6, 8, and 10 mL/min with confining pressure of 6 MPa and the confining pressure of 2, 3, 4, 5, and 6 MPa with flow velocity of 3 mL/min. However, under 120+ mesh coal fines condition, the permeability loss rates are higher than 85% under most flow velocities and confining pressures. When coal fines become smaller, the permeability loss rates decrease to be lower than 45%, and part the coal fines are discharged with the water flow. Thus, coal fines proper dischargement can partly maintain the reservoir permeability during coalbed methane production. The results would be useful in understanding coal fines intrusion behaviors and its controlling strategies during CBM drainage.

中文翻译：

---

单相水流过程中煤粉运移的实验研究

煤粉在煤裂缝中的迁移和侵入会降低储层渗透率和生产连续性，从而影响煤层气 (CBM) 井的性能。进行物理模拟以研究在不同流速和围压下不同直径煤粉侵入下的渗透率变化。结果表明，煤粉侵入后裂缝导流能力显着降低，难以恢复到初始状态。煤粉侵入后渗透率（Pcfi）与水淹速度的增加没有直接关系，而随着围压的增加而降低。裂缝可以被煤粉完全堵塞，同时在驱油过程中也会发生渗透，造成渗透率波动。80-120目煤粉侵入的渗透率损失率值与初始渗透率相比一般<60%，其中流速为2、3、4、6、8和10 mL/min，围压为6 MPa围压分别为 2、3、4、5、6 MPa，流速为 3 mL/min。然而，在 120+ 目煤粉条件下，在大多数流速和围压下渗透率损失率高于 85%。当煤粉变细时，渗透率损失率下降到45%以下，部分煤粉随水流排出。因此，煤粉适当排放可以在煤层气生产过程中部分保持储层渗透率。该结果将有助于理解煤层气排采过程中煤粉侵入行为及其控制策略。