Die Eienskappe en korrelasie van steenkoollae in die Witbank - Bethal - Breyten-gebied

Abstract

It has long been noticed that there appears to be stratigraphic equivalents for the major coal seams in the Witbank, Highveld and Eastern Transvaal coal fields. In order to correlate these seams, readily available coal properties (heat value, ash content, volatile content and moisture content) and other physical properties (elevation and thickness) were evaluated. It was found that no single property or even combinations of these in the form of variation diagrams could provide sufficient resolution between the seams. Discriminant analysis was used to form linear combinations (discriminant functions) of the properties which statistically provide the best possible resolution between the groups. It was thus established to a high degree of certainty that coal seams can be correlated between boreholes and even adjacent coal fields using this method. Discriminant functions were calculated for areas by which new cases can be correlated. Lateral variation in the coal properties was studied by means of geostatistical methods and it was found that the average range of influence was around 15 km. Anomalous values resulting from data errors, devolatilisation or oxidation of coal could be identified by means of a normal probability graph and the Seyler oiagram as adopted for South African coals. (Snyman et. al., 1983) Two dolerite factors, reflecting the metamorphic effect of the magma on the coal were tested but found useless for the identification of devolatilised coal in this area.