Using multiple random walk simulation in short-term grade models

Rafael Moniz Caixeta,João Felipe Coimbra Leite Costa,Diniz Tamantini Ribeiro

doi:10.1590/0370-44672016700036

Rafael Moniz Caixeta, João Felipe Coimbra Leite Costa + Show 1 more

Open Access

https://doi.org/10.1590/0370-44672016700036

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Abstract

Abstract Geostatistical simulation comprises a variety of techniques which can help on the decision-making process for uncertainties. They allow the uncertainty assessment of function responses (which depend on the simulated inputs) commonly through a non-linear relationship (net present value, interest tax return, geometallurgical ore recovery...). However, one of their limitations is that running the simulation can take considerable processing time to be executed in large deposits or large grids. Herein is presented an attempt to solve this problem in short-term modeling cases, via the use of Multiple Random Walk Simulation. This algorithm combines kriging with the simulation of independent random walks in order to generate simulated scenarios much faster than via traditional simulation algorithms. A case study is presented to illustrate the application of the method in an iron mine. The Multiple Random Walk Simulation models were properly built, respecting the reproduction of both histogram and variograms. Also, the speed-up was compared with standard methods of geostatistical simulation and there was a considerable speed gain with Multiple Random Walk Simulation (3.39 to 5.65 times faster than the others).

Highlights

Geostatistical simulations can be very useful in mining planning and decisionmaking about uncertainties
By considering all these simulated scenarios, it is possible to assess the uncertainty of the local values and, to apply non-linear transfer functions to the model, which allow the calculation of geometallurgical responses and net present value (NPV), for example (Coward and Dowd, 2015)
The visual aspects of the simulated models are very coherent and the variograms and histogram are well reproduced by the methodology

Summary

Introduction

Geostatistical simulations can be very useful in mining planning and decisionmaking about uncertainties. They are mostly used in geological/grade modeling and long-term mine planning, providing several practical benefits. By considering all these simulated scenarios, it is possible to assess the uncertainty of the local values and, to apply non-linear transfer functions to the model, which allow the calculation of geometallurgical responses and net present value (NPV), for example (Coward and Dowd, 2015). Its use in short-term geological modelling and mine planning is minimal, despite the fact that it can help, for example, in estimating the grade variability of the blocks and to update the monthly plans (by incorporating recently collected data). The method is presented and, after that, a case study illustrates its use

Methodology

Case study

Discussion and conclusions