Mine design selection under uncertainty

Abstract

Frequently, alternative technically feasible mine designs and production scenarios are available for decision makers to consider. The selection of a mine design is then based on estimating net present values of all possible, technically feasible mine plans so as to select the one with the maximum value. Conventional risk and sensitivity analysis are also performed as decision supporting tools. Given the multiple market and geological uncertainties associated with mining investments, as well as the management flexibility to respond to new future information, the sufficiency of conventional economic analysis tools based on the static discounted cash flow analysis may be questionable. This paper proposes a multicriteria ranking system for selection between alternative mine designs under uncertainty. The system is based on integrating multiple market and geological uncertainties as well as the operating flexibility to revise the ultimate pit limits using a Monte Carlo based real options valuation (ROV) model. To compare the methods, the article applies the proposed system, along with other three ranking methods, to rank possible mine designs for a copper and a gold mine. It has been found that, in addition to the higher value of the mine design selected by the proposed system, its average mis-ranking is significantly lower than the other three ranking methods. For the copper mine, a reduction in the average mis-ranking of 37–58% could be achieved when using the proposed ranking system, while for the gold mine case, a higher reduction of 51–64% in the average mis-ranking is obtained.