digilib@itb.ac.id +62 812 2508 8800

Eleven samples of Warukin and Montalat coals have been investigated with respect to coal quality parameters, methane content and adsorption isotherm. The samples were taken from a 300 m long of downhole drill core obtained from Jangkang area. The coal is low in rank, classified as sub-bituminous coal with typical Rr of 0.33%. Methane content of the samples exhibits clear increasing downwards trend, ranging from 0 to 0.13 m3/ton. Coal quality parameters taken from proximate and calorific value analyses show no obvious trend along the drill core profile, except total moisture which appears slight decreasing downwards trend. Adsorption isotherm analysis reveals that the quantity of adsorbed methane typically follows the trend of methane content along the drill core profile. The samples from the overlying Warukin Formation (1 13 m depth) and the underlying Montalat Formation (297 m depth) exhibits 4.66 and 12.09 m3/ton (daf) of adsorbed methane, respectively. This implies that formation pressure is an important factor controlling the in situ methane content in the coal samples.