Geological Risk Assessment Quick Start

Note: See Geological Risk Assessment Essentials (GRA) for background information on Geological Risk Assessment.

Conditional simulation data

Geological Risk Assessment (GRA) requires simulated grades (qualities) of one mineral element. The grades must be defined as data fields of the geological model in addition to the standard fields used by your application. The maximum allowed number of simulated grade fields is 200 but the number between 40 and 100 is usually considered adequate. For easy import the field labels should consist of a common prefix followed by field identifier; for example, AU1, AU2, AU3 etc.

You can import simulated grades at any time after importing the geologic model standard fields.

Note: The fields imported with Import Data commands (such as those found on the Optimization ribbon) cannot be used by GRA.

To evaluate optimal extraction sequences (OES) for risk you must first create them with the standard optimization workflow tools.

Using GRA

The way to use GRA without altering the traditional mine planning philosophy is to first build a complete life of mine plan based on reference grades and, then, evaluate the final OES probability distribution. If the risk as measured by probability distribution parameters of NPV or profits is unacceptable, you may try to create another plan, for example, within a smaller ultimate pit shell, or get better grade estimates by improving your geological data samples.

The second (and less orthodox) option is to select one of the Risk Rated k-Pits as the mine's final pit. For example, selecting a 100% safe pit minimizes the risk of potentially significant losses when the material estimated to be ore turns out to be waste. A possible procedure for selecting Risk Rated k-Pit as the final pit is as follows:

Generate the standard LG phases at reference grades with the Pit Optimizer. See Pit Optimization: Quick Start.
Evaluate the resulting OES with GRA; take note of mean and standard deviation of Net Present Value.
Generate Risk Rated k-Pits.

Note: The reported NPV underestimates the true NPV potential because LG phases have not yet been generated.
Create another Ultimate Pit case study; on the Settings screen's Ultimate Pit tab select Use pit shell selected from the list below, choose the Risk Rated k-Pits file and the code of a “safe” pit, for example, one that refers to a 100% safe pit.
Run the Pit Optimizer.
Compare the mean NPV obtained in step 2 with that obtained in step 4. If the NPV obtained in step 4 is greater than mean NPV less the standard deviation from step 2, the Risk Rated k-Pit will be a solid candidate for the life of the mine pit limits.

GRA Reports

GRA reports are initially displayed in the Latest Report window. To see any of the previous GRA reports use the commands available in the Reports Task Pane's Risk Assessment group.

For information on charting the report data, see Charts.

Exporting GRA results

To export a results model, use Data ribbon >> Export >> Model.

Risk Rated k-Pits are represented by a standard OES indicator file and as such can be viewed or exported as a part of a “combined object” block model.

You can also view or export pit shells generated by Risk Rated Pits tool for all the simulated grades. To do this, you must check Enable export of simulated pit shells on the Default Settings screen. This forces the Risk Rated Pits program to create a 3D Object block model with the following data fields:

RRP – Indicates which Risk Rated Pit a block depends to; range: 1 to the number of pits.
REF – Indicates whether a block belongs to the reference pit or not; 0 or 1.
SIM(n) – Indicates whether a block belongs to the pit obtained for the nth simulated grades; 0 or 1. The index n ranges from 1 to the number of simulations.