Quantitative study of the benefits to mine ventilation of coalbed methane degasification

As highly productive coal mines push deeper into virgin seams with higher methane gas contents, reduction of methane in the airways to safe limits becomes a serious problem. The successful design of a mine ventilation system hinges on the knowledge of the rate of gas emission into the airways. A computer model developed to quantitatively define the relationship between the interactive and dynamic processes of methane drainage, mining, and the mine ventilation is presented here. The model includes the numeric simulation of the coalbed methane reservoir for the prediction of gas-emission rates under the influence of degasification wells and longwall mining. Also included in the model is a mine-ventilation-network-generation program and a mine-ventilation simulator with gas-injection capabilities. At specific time steps, the mine workings progress through the coalbed methane reservoir (coal seam), and the ventilation network is created and subsequently simulated. Fan quantities, regulator settings, and fan horsepower required to reduce the gas emissions to safe limits are determined iteratively on each call to the ventilation simulator. The model was used to quantitatively study the effects of well spacing and well patterns on methane degasification and gas emission in working faces of a longwall mining system. Conversion and modification of the two simulators used to model airflow analysis and coalbed methane reservoir performance are presented here. A series of test cases and their evaluation is included.