Lithofacies Boundary Estimation with MWD data in Nickel Laterite Deposits

The boundaries between limonite, saprolite, and bedrock, typifying the main lithofacies of nickel laterite deposits, were estimated by analyzing the trend and correlation of measurement while drilling (MWD) data obtained during drilling in the deposit. The MWD data corresponding to the drilling work were used to estimate the boundaries. The boundary between the saprolite and bedrock was estimated using the change in the average penetration rate, calculated from the slope of the trend line of the drilling distance over time. The boundary between limonite and saprolite was estimated using “pressure-lift” and “pressure-rotate” data from MWD data, where the sign of the correlation value varied by lithofacies. By comparing the results of the lithofacies boundary estimation using MWD data with those of laboratory X-ray fluorescence analysis, the applicability of the reported method for estimating the lithofacies boundary using MWD data acquired during field exploration was validated.