Toward improved coal density estimation from geophysical logs

Abstract

Coal density plays an important role in projecting and reconciling coal tonnage and quality variation. The best estimation of coal density is from direct measurement on core, but cored holes are sparse relative to chip holes due to the cost of drilling and subsequent laboratory analyses. All holes are geophysically logged, and if the geophysical data are accurately calibrated against core then they can be used to improve the sampling of spatial variability across a deposit. However, uncertainty about the precision and accuracy of the density estimation from geophysical logs still precludes its use for reserve analysis across the industry at large. A common comment is that ``one accurate data point from laboratory analysis is better than hundreds of inaccurate ones'. This paper tries to improve correlation and use of geophysical logs in coal quality estimation.