Handbook for Methane Control in Mining - AMMSA

113CHAPTER 8.—FORECASTING GAS EMISSIONS FORCOAL MINE SAFETY APPLICATIONSBy C. Ozgen Karacan, Ph.D. 1 and William P. Diamond 2In This Chapter Measuring the gas content of coal Predicting gas emissions based on geologic and coal reservoir property data Determining the gas storage capacity of coalbeds and other gas-bearing strata Methane drainage borehole monitoring to forecast the remaining gas-in-place and theinfluence on mine emissions Forecasting gas emissions during mining as a function of mining parametersand Gas emission prediction based on numerical simulationThis chapter provides guidelines for determining the gas content of coalbeds, estimating the gasin-place,and predicting gas flow and emissions before and during coal mining operations. Thetechniques are discussed briefly in the following sections. However, detailed information on thetechniques is provided in the cited references.INTRODUCTIONCoalbed methane, if not properly controlled in the underground mine environment, is a safetyconcern due to the potential risk for an explosion. This is a particular problem during longwallmining, where the high rate and volume of coal extraction can result in the release of largeamounts of methane from the mined coalbed and other adjacent gas-bearing strata. Thevariability and potential hazards of these sometimes unexpectedly high gas flows provide theimpetus to develop methods to predict methane emissions into the underground workplace.A forecast of the volume of gas that might be released during coal mining is helpful fordesigning ventilation systems and for implementing optimum methane drainage strategies tohelp mitigate expected gas emission problems.A complete assessment of the need for methane drainage prior to mine development generallyrequires both an empirical and a theoretical approach. If there are active mines in the generalarea with similar geologic conditions and coal characteristics, a review of gas problems in thosemines provides an initial insight into the level of gas emissions to be expected at a new location.In addition, relatively simple methods exist to determine the in situ gas content (volume of gasper unit weight of coal) of the coalbeds in a particular mining area, as well as the gas-in-place(volume of gas in the coalbed(s) within a defined geographic area).1 Senior service fellow.2 Supervisory physical scientist.Pittsburgh Research Laboratory, National Institute for Occupational Safety and Health, Pittsburgh, PA.