煤粉对支撑裂缝导流能力的影响特征及其防控

Influencing characteristics and control of coal powder to proppant fracture conductivity

针对煤层气井的煤粉伤害问题,运用LD-1A导流能力测试系统模拟了煤层气井变排量、恒排量及间抽过程中煤粉在支撑裂缝中的运移沉积情况,分析了不同流速下煤粉对支撑裂缝导流能力的影响特征及伤害机理。实验表明:煤粉易滞留沉积在支撑裂缝底部严重影响导流能力,导流能力伤害率可达90%以上;在没有煤粉持续进入支撑裂缝的情况下,有效排出煤粉导流能力有增大的趋势;排采制度、煤粉质量含量、煤粉粒径对导流能力的影响特征存在明显差异;煤粉随水运移时对支撑剂窄口的疏通作用和聚集堵塞作用共同影响支撑裂缝导流能力。压裂前期使用小粒径支撑剂,尾追大粒径支撑剂,合理控制排采速度,使排采速度略小于煤粉运移的临界流速,并使用煤粉分散剂,有利于适量排出煤粉减小导流能力伤害。

In order to deal with the problem of coal powder damage in the process of CBM（ coalbed methane）,the well changing flow velocity,constant flow velocity and discontinuous flow production,the coal powder migration and deposition in proppant fracture were simulated with LD-1A proppant conductivity testing system. Influencing characteristics and damage mechanism of coal powder to proppant fracture conductivity under different flow velocities were analyzed.Experimental results show that coal powder easily deposits in the bottom of the proppant fracture and seriously damage the fracture conductivity.The damage rate of fracture conductivity is up to more than 90%.Fracture conductivity has an increasing tendency when coal powder discharge effectively in the condition that coal powder isn＇t added to proppant fracture continuously.Influencing characteristics of production system,coal powder content and diameter to flow conductivity have obvious differences.Coal powder plug and dredge in proppant narrow pore influence the proppant fracture conductivity together when migration with water.Proppant in smaller diameters was employed at the beginning of fracturing,then proppant in bigger diameters was used.Flow velocity is controlled reasonably to ensure that the flow ve-locity is less than coal powder migration critical velocity.And coal powder dispersion agent is employed for fracturing.They are good for coal powder discharging effectively and reducing the fracture conductivity damage.