Application of Geostatistical Conditional Simulations to Assess Resource Classification Schemes
Geostatistical conditional simulations are becoming increasingly popular as tools that provide models of uncertainty at different stages of a mining project. They have been used as grade control tools in daily operations, to assess the uncertainty of minable reserves at the project's feasibility stage, and to assess mineralization potential in certain settings. Other applications include assessment of recoverable reserves, resource and reserve classification, and drill hole spacing optimization studies.
All large-scale applications of conditional simulations intend to benefit from the "correct" (or "accurate") characterization of uncertainty, adequately describing the variability observed from the data and its impact on the final objective.
The objective of this paper is to compare the ad-hoc "uncertainty model" provided by a traditional classification scheme with the probability intervals resulting from a conditional simulation model. The paper discusses a number of relevant issues that relate to resources and reserves classification schemes using unit mining volumes (mining phases for open pit, mining sectors for underground), and specifically emphasizes differences in uncertainty based on the size of the mining unit considered and the extraction method, and local geological differences. Most importantly, it discusses confidence intervals for these mining units, as compared to the relative precision envisioned by a typical classification scheme.
The application described in this paper is taken from a medium-sized Cu open and underground mine in northern Chile, and it demonstrates the impact of several variables on the resulting conditional simulation models. It also compares a more "traditional" resource classification scheme applied, and the wide difference in local confidence intervals for each mining unit.
Conditional simulations, Open Pit and Underground Mining, Resource classification, Uncertainty and Risk Models, Mining Phases and Mining Sectors