Borehole desurvey calculation using geostatistical methods

This paper describe a study of the deviation of core boreholes drilled to explore a mixed sulphide deposit in Albania. The boreholes are 150-550 m log, with deviation of up to 20-30 m from the design position s. The deviation of 150 of the 230 boreholes made ware checked by making angular measurements along most of their length; 80 boreholes were not checked. Because the deviations were so strong, the 80 unmeasured cannot be used in the calculation of ore reserves. In order to recover the maximum possible amount of information, the deviation were subjected to geostatisticalanalysis by which means the entirely or partially unchecked boreholes were reconstructed. Indicator and universal kriging were applied to estimate the direction and the extent of the deviations. The method was applied to the measured data of the 150 checked boreholes and criterion was identified for classifying the unmeasured boreholes on the basis of the precision of the reconstruction.