62
range of spacing: 100 × 100 m, 100 × 150 m, 100 × 200 m, 100 × 250 m, 100 × 300 m and
100 × 350 m as exemplified by Figure 3.
2.5 Conditional simulations of each virtual drillhole and risk analysis
To highlight the impact of the drillhole spacing, independent variograms have been adjusted
for each drilling mesh, but the same SN has been used for all simulations.
The results of the simulation of the variables v1 and thickness, for each drilling mesh, are
then rescaled to production increments of one year and quarterly that are created by gathering
the simulated blocks up to the tonnage equivalent to a year or a quarterly production of the
operation. The dispersion of the simulations is calculated within a confidence interval of 90%
considering the production basis. Nevertheless, grouping small block units into bigger units
remains an issue when the quarterly/yearly lots have not yet been defined, which is the case
at early exploration stages. A possibility could be to choose between two extreme situations:
– The unit (month, quarter or a year) is made of a set of contiguous simulated blocks: the
volume of the unit is defined by merging n volumes of small simulated blocks. Averaging these simulated blocks that contemplates the volume production increment of a year,
mouth or quarter gives the experimental distribution of the grade on which confidence
intervals may be calculated;
– The unit is made of a blending of blocks coming from different areas. By considering
the case where these areas are far from one another, the quantities of the blocks are
independent. The distribution of the unit may then be considered as Gaussian, with a
variance over the period that is the variance of one block divided by the number of blocks
making up the unit. Aiming at getting the relative standard deviation of the lot less than
a given threshold determines the threshold of the standard deviation of the small blocks,
contributing to the measured or indicated resources.
Figure 2. One realization from the conditional simulation of the variable acc_v1. Plant view.
Table 1. Probabilities for each realization.
Best Simulations Combination for acc_v1 & thickness
8
25
12
33
77
Best Simulations Probabilities:
0.07
0.29
0.16
0.37
0.11
Simulation ace vl[OOOOl]
range of spacing: 100 × 100 m, 100 × 150 m, 100 × 200 m, 100 × 250 m, 100 × 300 m and
100 × 350 m as exemplified by Figure 3.
2.5 Conditional simulations of each virtual drillhole and risk analysis
To highlight the impact of the drillhole spacing, independent variograms have been adjusted
for each drilling mesh, but the same SN has been used for all simulations.
The results of the simulation of the variables v1 and thickness, for each drilling mesh, are
then rescaled to production increments of one year and quarterly that are created by gathering
the simulated blocks up to the tonnage equivalent to a year or a quarterly production of the
operation. The dispersion of the simulations is calculated within a confidence interval of 90%
considering the production basis. Nevertheless, grouping small block units into bigger units
remains an issue when the quarterly/yearly lots have not yet been defined, which is the case
at early exploration stages. A possibility could be to choose between two extreme situations:
– The unit (month, quarter or a year) is made of a set of contiguous simulated blocks: the
volume of the unit is defined by merging n volumes of small simulated blocks. Averaging these simulated blocks that contemplates the volume production increment of a year,
mouth or quarter gives the experimental distribution of the grade on which confidence
intervals may be calculated;
– The unit is made of a blending of blocks coming from different areas. By considering
the case where these areas are far from one another, the quantities of the blocks are
independent. The distribution of the unit may then be considered as Gaussian, with a
variance over the period that is the variance of one block divided by the number of blocks
making up the unit. Aiming at getting the relative standard deviation of the lot less than
a given threshold determines the threshold of the standard deviation of the small blocks,
contributing to the measured or indicated resources.
Figure 2. One realization from the conditional simulation of the variable acc_v1. Plant view.
Table 1. Probabilities for each realization.
Best Simulations Combination for acc_v1 & thickness
8
25
12
33
77
Best Simulations Probabilities:
0.07
0.29
0.16
0.37
0.11
Simulation ace vl[OOOOl]