Drill Holes Spacing Analysis for Estimation and Classification of Coal Resources Based on Variogram and Kriging

Abstract

In detailed exploration, it is necessary to analyze optimal drill hole distance. Drill hole spacing analysis results in optimal drill hole spacing on each coal seam for the coal resources classification. Based on a case study in one of the coal mining companies in North Bengkulu, four coal seams have continuous seams and there is splitting from one seam to four seams. The sediment model generally has a direction of distribution of coal seams trending from northeast to southwest with gentle dip. This research uses geostatistical methods to determine the thickness distribution and variation of coal in the study area and to estimate and classify coal resources and determine the optimal distance from the borehole spacing. Estimation using kriging block results in the value of kriging relative error. Coal resource estimates and variability are determined based on kriging estimation with the relative kriging standard deviation (RKSD) method and the polygon method for classification based on sill distances. The number of drill holes used was 57 drill holes. Based on the calculation of the sill variogram, the coal measured resource is 150 meters, the coal indicated resource is 250 meters and the coal inferred resource is 500 meters. Based on the estimation and classification with relative kriging standard deviation (RKSD), the total coal measured resource is 1.8 million tons, the coal indicated resource is 3.2 million tons and the coal inferred resource is 2.5 million tons with total coal resources.