煤粉对裂缝导流能力的伤害机理

应用FCES-100裂缝导流仪和平流泵模拟了煤层气排采过程中煤粉颗粒侵入压裂裂缝支撑剂充填层的过程，研究了煤粉在支撑剂充填层内的运移规律及其对导流能力的伤害机理、影响程度。实验表明：煤粉易侵入支撑剂充填层，不易随水排出，对导流能力伤害严重，并且随着煤粉浓度增加伤害程度急剧增大。煤粉的聚集附着、桥堵孔喉是支撑剂充填层导流能力伤害的主要原因。粒径较小的煤粉更易运移聚集伤害裂缝导流能力，使用小粒径支撑剂可以有效地俘获煤粉颗粒，有利于提高主裂缝的导流能力；压裂后快速返排有助于煤粉迅速排出，减少其在裂缝内的滞留，并保持排采稳定有利于煤粉顺利排出，避免聚集堵塞。

Damage mechanism of coal powder on fracture conductivity

In order to investigate the migration law，damage mechanism and damage degree of coal powder in the proppant pack，the authors used FCES-100 fracture long-term flow conductometer to simulate the process.Experiment results show that coal powder is likely to intrude into proppant pack and difficult to discharge with water，causing serious damage on conductivity and the damage raises dramatically with the increase of concentration of coal powder.According to analysis，the main causes for the damage are the adhesion &; accumulation of coal powder，and the bridge plug in pore throat by it.Coal fines with smaller diameters are more vulnerable to move and gather together in the pack，and have a bigger potential to damage the conductivity.It is an effective way to improve conductivity by employing proppant in smaller diameters to entrap coal powder.And also，backflow immediately after the treatment is helpful to discharge the coal powder and reduce its retention in the fracture.Then，to avoid the powder conglomeration and plug the flow path，it is necessary to maintain a steady gas production.