Many coal deposits throughout the world are undersaturated to some degree. With actual gas contents less than expected from reservoir pressure and the sorption isotherm, these coals require dewatering before gas desorbs. An operator must bear water production and disposal costs, frequently for an extended period of time, prior to realizing any revenue from gas sales. Gas and water profiles for wells completed in Powder River and Greater Green River coals were simulated assuming saturated coals and selected degrees of undersaturation. Base case economics were constructed by combining the simulated gas and water profiles from saturated coals with typical capital costs and well operating expenses for each basin. Gas and water profiles from simulation of ever deeper undersaturation were used to drive additional economic analyses. From this suite of economic analyses, the impact of undersaturation on economic parameters such as net present value, time to payout, and breakeven gas price was assessed.
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