Analysis of pulverized coal migration during CBM production

Key words:  CBM wells  pulverized coal  suspension migration  carrying capability

Abstract:

A model for migration of suspended pulverized-coals during coalbed methane (CBM) production in gas-channels was established with considerations of the suspending grade and content of pulverized-coals in the fluid mixture of CBM formations. The conditions for discharging the suspended pulverized-coals were described. The model was based on the liquid-solid two-phase flow theory and can be used to study the method for a moderate production rate of coal powders rather than to prevent it. The effects of different parameters on the carrying capability of pulverized coal by the formation liquid were analyzed, including the size of pulverized-coals, the velocity and viscosity of the formation fluid. Due to the differences of the gas-liquid-solid mixtures during different discharge-phases of CBM production, the apparent viscosity of the formation fluid is different, which has a great effect on the carrying capability of pulverized coal of the formation fluid, and being affected by the gas production rate. The gas production of CBM wells can be improved via moderately adjusting the flow behavior of the formation fluid for a proper discharging of pulverized coal, or increasing the percolation capacity of gas channels.