Investigation of Coal Bed Methane Potential Based on Integrated Cleat Analysis and Coal Quality; Case Study in Merapi Timur, Lahat District, South Sumatra

Nowadays, conventional energy production has decreased, so it is necessary to develop unconventional based exploration, one of which is Coal Bed Methane (CBM). Indonesia has a high potential of CBM, and one of them is located in South Sumatra which has a potential reserve of 183 TCF. CBM is a gas formed during the coalification processs and stored in the cleat through a diffusion process from micropore. Cleats are natural fractures in coal seam and act as controllers of permeability values in development of CBM. The research area is in Merapi Timur, Lahat District, South Sumatra which is included in Muara Enim Formation. The method used in this research is field observation, data sorting, quantitative analysis, and laboratory analysis. Field observations included observations of coal appearance and measuring cleat attributes, such as aperture, spacing, length, and cleat orientation using scanline method. Coal deposits in the study area have varying thickness of 4-19.5 m. Data from the measurement of cleats are sorted using the box plot method to validate data. Calculation of cleat is used to determine relationship between cleat attributes, interpretation of cleat density and permeability. Quantitative analysis of cleats showed an average aperture of 0.01-0.020 cm and an average spacing of 1.51-6.15 cm. Cleat distribution and orientations indicates two major trends, namely NW-SE and NESW. The cleat density for individual seams varies ranged from 0.2-0.36 cm/cm². Permeability based on outcrop data has a range from 10.18 to 108.56 md. The results of laboratory analysis showed rank of coal in the study area categorized as sub-bituminous with a maximum vitrinite reflectance value (%Rv Max) of 0.32-0.45%. Data from results of cleat analysis and coal quality indicate that the research area has potential for CBM exploration development