Enhanced recovery of coalbed methane in Warrior basin coals (Alabama)

Enhanced methane recovery from nitrogen injection was studied with Jagger coals from the Black Warrior basin. The gas contents and adsorption isotherms for these coals were determined at three different temperatures. The adsorption of methane on these coals followed Langmuir's adsorption equation. The objective of displacement studies was to find the suitability of nitrogen as the injection medium, to find the effect of rate of injection of nitrogen on the ultimate recoveries of methane and to find the optimum rate at which maximum recoveries could be obtained. It was observed that with nitrogen injection 80% of the methane as initial gas-in-place was produced during displacement, and thereafter the production of methane remained constant with any injection rate. With increase in the injection rate, it was observed that less time was required for the production of 80% of methane as initial gas-in-place. These results are useful in recovering methane otherwise not recovered by normal production, obtaining faster recoveries, and getting the maximum benefit from the tax credit.