Zoneography of Mineral Resources

Abstract

In facing the problem of the exploitation of heterogeneous mineral resources (ore or oil), the question of defining continuous zones exhibiting similar characteristics may arise. A method to approach this question using factorial and geostatistical techniques was developed. It contains three main steps:

• (1) Taking as an input the data matrix (samples x variables), a factorial technique (principal components analysis or correspondence analysis) is applied, giving rise to groups of samples of similar characteristics.

• (2) The problem of contiguity within samples of the same group and the number of groups to be retained is solved by expert advice of the geological/exploitation team, based on graphical representation of zones.

• (3) Once decided which samples belong to each final group, the boundaries from zone to zone are estimated, using a transitive kriging technique, relying on the geometric variogram.

Two case studies are presented to illustrate the method: The first one discusses a polymetallic sulfide orebody located in the South of Portugal, which is to be split into zones feeding different mineralprocessing units. In the second, a Middle East petroleum reservoir is divided into homogeneous zones in order to improve the secondary oilrecovery planning.

The method presented here, combining factorial analysis and geostatistics, is a useful tool for the purpose of delineating zones in heterogeneous deposits of mineral resources. It provides estimates of boundaries between zones based on their geometric structure and gives a reliable basis for further exploitation planning.