About Scenarios

A scenario based on a relevant mining model and constraining surfaces, stores all the parameters that are required for running a pit and phase optimization. It also includes scheduling parameters.

This page discusses:

 

See Also
More help on this topic
Creating a Scenario
Defining an Economic Scenario

Typical Workflow

Defining and populating multiple scenarios enables you to test the impact of alternative assumptions to determine an optimized design for the pit outline over the life of a mine.

  • Create a new scenario (Pit Opt 1).
    • Select the method to calculate the block value.
    • Define mining and processing operating costs and revenue drivers.
    • Select the ore definition method that can be grade cut-off or cashflow.
  • Run the optimization for this scenario.
  • Duplicate the scenario (Pit Opt 2)
  • Run the optimization on the scenario duplicate (Pit Opt2)
  • Modify an existing scenario (Pit Opt case 3)

Block Valuation Modes

When you create a pit case scenario, you specify the financial parameters that are relevant to the processing of the commodity or commodities. These can include mining and processing operating costs and revenue drivers such as the recovery percentage or the commodity price.

You can choose from two block valuation modes: a simple valuation mode or a complex valuation mode. Options for the block valuation mode are available in the Create Scenario dialog box.

By default, the simple valuation mode is enabled.

Block Value Calculation in Complex Valuation Mode

In the Scenario dialog box, you can use the toggle key to turn Simple Valuation Method on or off. If you switch Simple Valuation Method off, the multiprocessing mode is enabled automatically. The block value is calculated using the commodities and processing methods you specified with a more sophisticated algorithm.

This illustration describes how the block value is calculated when the multiprocessing mode is enables; that is the Simple Valuation Method is switched off for the scenario.

The table below summarizes the input parameters and variables that are calculated when the complex valuation mode is enabled ( Simple Valuation Method is turned off) .

Parameters Description
MCostPerMass The mining cost per mass of extracted material
PCostPerMass The mining cost per mass of materials
PriceOfCommodity The price of a commodity
RecoveryFraction The recovery faction for processing a commodity/product
GradeOfCommodity The grade of a commodity
PCostByCommodityUnit The extra cost per input unit of this commodity, when processing this rock type using this method
BlockMass The mass of the block
CommodityInputMass The mass of a commodity input to a processing method, calculated by BlockMass * GradeOfCommodity
Calculated variables Description
BlockMCost Total cost of mining the block
BlockMCost Total cost of processing the block
BlockVal The net profit of the block
BlockVal The revenue received from the block without subtracting any cost

Typical Examples of Ore Selection for Multiple commodities and Multiple Processing Methods

Here is an example of how the ore selection behaves with multiple commodities and multiple processing methods.

Let us consider products P and Q with Mill A and Mill B:

  • The price of Product P, is $100 per ton.
  • The price of Product Q is $100 per ton.

Details Mil lA Mill B
Processing cost $18 per ton $18 per ton
Recovery of product P 90% 60%
Recovery of product Q 60% 90%
Marginal Cut-off for P alone 0.2 0.3
Marginal Cut-off for Q alone 0.3 0.2

Case 1 Mill A Only

If we draw a line on the plane for all grade combinations that divides these between profitable to be sent to Mill A from those that are not:

Case 2 Mill A and B Combined



In this case, we cannot use cut-offs to select material for each mill so as to give the highest cash flow in all cases. The only option is to adopt a grade control system, which is based on cash flows.

Although this is an artificial case, real cases can present as complex conditions, especially when deleterious elements are involved.

Minimum and Maximum Acceptance Grade

The minimum and maximum acceptance grade controls the entry condition of the processing materials.

When handling multiple commodities, if any commodity grades exceed the range of an entry condition, then the block is rejected from processing— even when another commodity satisfies the grade range.

This effect varies from the method that merges multiple commodities to equivalent commodities.

In the Complex Valuation Mode, you cannot manually change the cutoff grade to enforce the ore selection rule.

However, you can use the minimum acceptance grade, but the effect produced is different. For example if the minimum grade is raised to higher than the marginal cut-off grade, then the materials above the marginal cutoff and below minimum grade are not processed.

If the minimum grade is below the marginal cutoff, it does not enforce the low-grade materials processing below the marginal cutoff, it does not impact the ore selection.

Options to Specify Economic Parameters

To specify economic parameters for calculating the block value during the pit optimization, you can choose from the following valuation options:

  • User-Defined block value. This option provides a standard function to valuate materials in blocks. you enter financial data (price, cost) and Pit Optimization
  • Value Attribute block value. It is already precalculated and exists in the block model. All you need to do is select the value attribute. For more information, see Defining an Economic Scenario.

Options for the Ore Selection Methods

The block that is selected for processing within a pit case scenario is defined as ore. The criteria that is used for defining the material destination is controlled by the Ore Selection Method option. You can determine the ore selection method from the following options:

  • Cash Flow that identifies the ore by the profit of the block calculated according to financial parameters. The block value is calculated implicitly. No additional parameters are required for this option.
  • Cutoff Grade that identifies the ore by a user-defined cutoff grade. This overrides the implicit ore selection criteria.

Processing Methods

Processing parameters drive processing destinations with a specified material capacity. Each destination requires one or more processing paths, which only accept defined rock types, with a processing cost and throughput factor. Each path requires one or more product subpaths with specified processing cost and recovery per element type. For more information, see About Processing.

Design Range for Scenario Components

When creating a scenario, the block model and the terrain that are used need to be at most in large range (or normal).

Validate that the coordinates of the object (blocks/ points) are within the design range of the object .

The CRS and CRS offsets specified for the block model and the terrain must also be identical.

When importing a block model and a terrain in products, ensure that the CRS is identical. For more information, see Adjusting the Geolocation Using B.I. Essentials.

Scenario Status

The update status indicates whether the scenario or optimization study is up to date or requires an update when you modify the context or the specifications of a pit case scenario.

There are two levels of update a global update status and local update status in the Scenario results. .