Regularities of coal powder migration during fracturing liquid flowback in coalbed methane well

With the use of fracturing fluid flowback experiment apparatus developed independently, this paper is to study the coal powder migration regularities with different percentage of coal powder of various sizes and different drainage system, plus distinct fluids. We explored the critical flow rate for coal powder and proppant migration, as well as the coal powder flowback efficiency. We aimed at establishing the relationship among coal powder migration and fluid velocity and various fluids. Experiments show that water doesn't wet the coal powder, but coal powder suspending agent does. The more the coal powder is, the lower the discharge rate. The change of outflow volume of coal powder versus time meets the law of power function decreasing. Drainage with variable discharge rates can promote the flowback efficiency of coal powder.