A probabilistic assessment of enhanced coal mine methane drainage (ECMM) as a fugitive emission reduction strategy for open cut coal mines

Enhanced coal mine methane drainage (ECMM) is a strategy that has been proposed for reducing fugitive emissions during coal mining. This paper presents a methodology for incorporating risk from uncertainty in reservoir properties and economic parameters in a techno-economic assessment of enhanced gas drainage of coal mines. Conventional economic assessments are deterministic and do not provide information on the likelihood of outcomes. Incorporating uncertainty into the analysis means that the probability of specific outcomes can be identified, thus supporting investment decision making. The methodology is demonstrated by means of a representative case study which evaluates the probabilistic economics of enhanced drainage of eastern Australian open cut mines. The approach entails coupling of a reservoir simulator (SIMEDWin) with a techno-economic model. Case specific findings indicate that for coal properties typical of eastern Australian coals the probability of a commercial ECMM project is 33% and the average net present value is A$0.005/t (US$0.00425/t applying a long term exchange rate of US$0.85/A$), though this result is skewed by the technical difficulties encountered. The study demonstrates that the minimum reservoir property requirements for a successful project are sensitive to the CO2 penalty. However, the results indicate that even in the absence of a CO2 penalty ECMM can be an economically viable emission reduction strategy for reservoir permeabilities as low as 0.14 mD or a gas content of more than 3.8 m3/t.