Coal dust migration and treatment for coalbed methane horizontal wells in Qinshui Basin

Coal dust in CBM horizontal wells usually leads to reservoir damage and pump sticking, resulting in serious production decreasing of coalbed methane. The transportation characteristics of coal dust under the conditions of different pressure differentials in wellbore was studied through physical simulation experiments. The result indicates that the coal dust and water two-phase flow is a lami-nar flow, and the relationship between coal dust migration velocity and pressure drop is non-linear with transportation velocity increasing as pressure drop increasing. There is a critical startup pressure gradient for coal dust starting to flow, and the movement finally achieves a steady state once the pressure gradient reaches a certain level. The control method of coal dust treatment was discussed on the basis of analyzing coal dust forming mechanisms, physical simulation experimental results and field production experience.