ESTIMATE COAL RESOURCES IN BLOCK 3 KEBAN SOUTH SUMATERA USING USGS CIRCULAR 891

Abstract

Coal resource estimation represents critical phases within the mining life cycle, and fundamentally determines both the technical feasibility and economic viability of a project. However, coal resource estimation is often hindered by uncertainties caused by data variability, geological heterogeneity, and limited subsurface information. Therefore, a method capable of addressing uncertainties in the estimation process is necessary. The research was conducted in Block 3 Keban, Lahat, South Sumatra, with moderate geological conditions. This study employed the circular USGS method to estimate the coal resources based on the distance of known information points and geological confidence level. This methodology operates by establishing distinct circular areas of influence around 13 drillholes: 250, 500, and 750 meter radii for measured, indicated, and inferred categories, respectively. The resource classification results indicate a total estimated coal tonnage of 17.44 million tons for the measured category, 47.61 million tons for the indicated category, and 91.75 million tons for the inferred category. Despite the substantial cumulative volume identified, the overall geological confidence remains relatively low due to the high proportion of resources in the Inferred category. Therefore, an intensified exploration program, specifically infill drilling, is necessary to increase borehole density and enhance the validity of the geological model. These results are expected to provide a reference framework for future exploration and mining strategy planning.