煤粉在支撑裂缝中的运移与沉积规律

针对煤储层压裂过程中易产生大量煤粉问题,应用LD-1A导流能力测试系统进行了支撑裂缝中不同流速、不同煤粉含量的流体流动物模实验,分析了流体在变流速、恒流速和间断流动下,煤粉在支撑剂充填层中的运移、沉积及产出规律。实验表明:煤粉运移具有一定的临界流速,不同条件下,临界流速差别较大,在20~40目石英砂支撑裂缝中,过60目煤粉临界流速可达5.20 cm/min,而过140目煤粉临界流速为2.01 cm/min;流体流速、支撑剂粒径、煤粉粒径、煤粉含量、排采制度等多重因素共同控制煤粉产出量;煤粉容易沉积在支撑裂缝中堵塞支撑剂构建的孔隙,对支撑裂缝导流能力的伤害严重。压裂后有效排出煤粉,可减小堵塞伤害;排采过程中控制流体流速,有利于减少煤粉运移及产出。

Rules of coal powder migration and deposition in the proppant fracture

In order to deal with the problem that coal reservoir produces large amounts of coal powder easily in the process of fracturing，the physical simulation experiments about fluid flow of different velocity and different content of coal powder in the proppant fracture with LD-1A proppant conductivity testing system were conducted.Under the state of changing flow velocity，constant flow velocity and discontinuous flow，the rules of coal powder migration，deposition and production were analyzed.Experiment results show that coal powder migration has a certain critical velocity.The critical velocities differ greatly under different conditions.In the 20-40 mesh quartz sand proppant fracture，the critical velocity of less than 60 mesh coal powder is up to 5.20 cm/min，but less than 140 mesh coal powder’s critical velocity is 2.01 cm/min；the weight of coal powder output is controlled by the combined effect of fluid velocity，proppant particle size，coal powder size，dust content，production system and so on；coal powder plug the proppant pore and damage the fracture conductivity seriously because it deposits in the proppant fracture easily.Backflow coal powder effectively after fracturing is beneficial for reducing the damage of plugging，and controlling the fluid flow velocity is good for reducing coal powder migration and output in the process of production.