Drill-hole spacing optimization for profit in grade control

Reaching an informed decision about optimal drill-hole spacing (DHS) is an essential task in geostatistics that adds value to mining projects. The optimal DHS is sensitive to many factors, including inherent geologic characteristics of the deposit, mining and operational parameters or constraints, economic factors, the purpose of the mineral resource estimation, and the metric to be optimized. Final estimates at the grade control (GC) stage of mining are meant to maximize the correct classification of mineable volumes. When considering dedicated GC drilling, DHS optimization for profit balances the cost of estimation uncertainty and the cost of drilling. The drilling amount is optimal when drilling less would incur large estimation costs and drilling more would incur large drilling costs. We developed a DHS framework for regularly spaced drilling aimed at maximizing profit in GC. Each of the steps are described in detail, including sequential Gaussian simulations, resampling, estimation, transfer function customization, mineable limits definition, and final profit calculation. The DHS framework is demonstrated on a realistic data set, followed by a sensitivity analysis to relevant factors. This work establishes a conceptual foundation and provides practical details for developing DHS optimization for final estimates in mining operations with dedicated drilling systems.