Journal of Petroleum Geology, Vol.16, No.1, pp. 73-88, 1993

©Copyright 2000 Scientific Press, Ltd.

COAL RANK AND TYPE VARIATION IN ROCK-EVAL
ASSESSMENT OF NEW ZEALAND COALS

R. P. Suggate* and J. P. Boudou**

* Hydrocarbon Resources and Basin Studies Group, Institute of Geological and Nuclear Sciences, PO Box 30368, Lower Hutt, New Zealand.

** Université Pierre et Marie Curie, Laboratoire de Géochimie et Métallogénie, 4 Place Jussieu, 75252 Paris Cedex 05, France.

Abstract

Rock-Eval and coal (analytical data are compared for New Zealand coal samples ranging from peat to medium-volatile bituminous coal. Most are humic coals within the New Zealand coal band, which is representative of the Type III maturation series defined for kerogens. However, four were chosen as particularly high-hydrogen coal types. Relations between individual parameters-- principally H/C, O/C, Tmax, HI and OI--are generally similar to those of Espitalié et al. (1985, 1986), but important differences include a broader range of HI values in the peats and lignites, and a differentiation between maturation and coal-type effects in the relationship of HI to H/C. Correlations of the effects of maturation on HI, OI, Tmax and vitrinite reflectance are made by the use of the independent Rank(S) scale of Suggate (1959).