Macrolithotype and gas content of shallow low-rank coal of Muaraenim Formation at Musi Banyuasin, South Sumatera Basin

Abstract

The macrolithotype method has already proven as an early method to determine high-rank coal gas content which is related to organic and inorganic materials, and also coal diagenesis level. This study aims to determine the relationship between macrolithotype and shallow low-rank coal gas content in Muaraenim Formation. Based on analysis result, coal seams exposed at depth of <300m have thickness varying from 0.5 to 10m. All seams in the research area were present in the Late Miocene and classified as lignite. Macrolithotype coal varies from durain - bright clarain with bright band percentage reaching 90%. Petrographic analysis showed that vitrinite reflections ranged from 0.24 to 0.36%. Proximate analysis showed that moisture content ranged from 10,64-12,9 wt.%, volatile matter 40,83-44,96 wt.%, and calorific value 4509-6035 kcal/kg and also Ultimate analysis showed that carbon content 72,48-74,02 wt.%. Gas desorption showed that gas content per seam varies from 0.27-29,84 scf/ton. According to the result between bright band vs depth and gas content vs depth, there was no relation between bright band and gas content due to very poor trend line value. This result was probably due to the low level of coal diagenesis that the bright band content did not show a linear trend line.