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Composite Drillholes Maptek™ Vulcan™ Training

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1 Composite

Types

Drillhole data represents sample intervals as vectors. Some options, such as block model estimation, require samples represented as points. Compositing converts drillhole data to sample data.

There are several composite methods available in Vulcan. If uncertain about which compositing method to use, choose either Straight or Run Length.

Straight A straight composite will create one point at the centre of the assay interval with the grade of that interval. For this reason, it is the most direct translation of drillhole data into point data.

A straight composite may not always be a good choice, especially if the assay interval is very long. Only one point will represent the entire interval, so the data will be unevenly represented and grade estimation may miss valuable data near the ends of the assay interval.

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4 Chapter 1 Composite Types

Figure 1-1: Representation of a straight composite

Run Length Run length creates sample intervals from drilling based upon an entered length. If a run length of 2 metres is defined, a point generates every 2 metres down the trace of the drillhole. This ensures an even distribution of data down the hole, but may over or under-represent some data.

Figure 1-2: Representation of a run length composite

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2 Workflow

1. In Envisage, select Geology > Compositing > Compositing. 2. A straight composite will represent drillhole intervals. If a run length

composite is required, determine an appropriate composite interval. See “Composite Types” on page 3 for further explanation of composite types.

3. Composite the drillholes into a new composite database with a 3-character database identifier, such as CMP. Use Vulcan help when configuring composite parameters.

4. Load the composites with one of the two following methods. Compare the composites to the original drillholes to validate the composites. See Figure 2-1 on page 5 for guidance.

a. Geology > Compositing > Display b. Geology > Sampling > Load

Tip: Select Geology > Sampling > Set Up Display to configure a display specification prior to selecting Geology > Sampling > Load.

Figure 2-1: Overview of two methods for sample display

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3 Tips

• Geology or geostatistics professors can provide more information about compositing methods and can help determine an appropriate run-length interval if run length compositing is required.

• The ability to justify a choice is more important than which method is chosen.

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