Investigation of coal powder generation and migration characteristics in coalbed methane horizontal well

As a disadvantage factor of drainage gas recovery in CBM horizontal well, pulverized coal usually leads to reservoir damage, pump stuck and other accidents when it transports in the fracturing propped fracture and horizontal wellbore, increasing the cost. Therefore, the coal powder output characteristic was analyzed according to the production data of Fanzhuang block in southern Qinshui basin, the migration of pulverized coal in propped fractures and the damage rule were revealed through physical model experiments on the migration of pulverized coal in propped fractures. The flow rule of pulverized coal in horizontal wellbore was further studied and the pulverized coal migration model was established with the use of the device for research of fluid migration law. The result indicates that the main sources of pulverized coal are the drill grinding of coal seam in the process of drilling and the friction and erosion of large displacement fluid mixed with sand in coal wall cracks in the process of fracturing; the damage rate of propped fracture diverting capacity caused by pulverized coal could reaches 90%, what's more, the higher the velocity of production, the more the amount of coal powder; the flow pattern of migration of pulverized coal in horizontal wellbore is the laminar flow regime, the pulverized coal could be well controlled at the beginning of production by controlling the pressure, flow and pulverized coal concentration.