Joint Simulations, Optimal Drillhole Spacing and the Role of the Stockpile

Infill and grade control drilling are a major cost in any mining operation. Reduction of drilling density can considerably enhance the profitability of an operation provided the cost from block misclassification is less than the savings in drilling. This paper presents a general simulation based approach to assess the performance of potential drilling schemes from the available deposit information. The approach integrates joint simulation of correlated variables with the computationally efficient minimum/maximum autocorrelation factors, multi-elements ore classification, and mine planning considerations. The latter employs key indicators such as profit per tonne mined and profit per tonne milled, as well as the potential use of a stockpile and its discounting. A case study at the Murrin Murrin nickel-cobalt deposit, Western Australia, is used to elucidate the proposed approach and to show the critical effect of planning decisions on drilling.