INTRODUCTION
- It is common to select a optimal pit shell defining the mineral reserve without much further consideration
- Other strategic opportunities are being ignored?
- Small value compromise for significant strategic gain
PIT OPTIMISATION
The objective is to determine the maximum inventory of open pit minable reserves
One of the methods, Lerchs and Grossmann algorithm utilised in many of the commercially available software packages
Run various scenarios
Typically Optimise Maximum Cash Flow
POST PIT OPTIMISATION – ALIGNING TO YOUR STRATEGY
Strategic issues that could be considered:
- Annual cash flow
- Life of mine
- Operating risk
- Technical, economic and political risks
- Product requirements (Blending Strategies)
Where to focus post pit optimisation process?
- Selection of ‘Ultimate Pit’
- Optimisation within the ultimate pit
POST PIT OPTIMISATION PROCESS
PIT SELECTION
SELECTION OF THE ULTIMATE PIT
OPTIMISE WITHIN ULTIMATE PIT
SIGNIFICANCE OF DISCOUNT RATE
CONCLUSION
- Pit optimisation is a iterative process further future analysis after the initial pit optimisations can add strategic gain
- Changes to the optimisation input parameters, specifically the discount rate, without due process may have a significant impact on the pit selection
- Understanding the sensitivities will reduce the risk of executing a sub-optimal life of mine plan