School of BEES - Coal and Organic Petrology

RESEARCH BY PROFESSOR COLIN WARD and Dr LILA GURBA

Plant debris, algae and other organic matter buried to great depths for long periods in sedimentary basins undergoes a number of chemical and physical changes. These are collectively referred to as rank advance or maturation. They determine the basic quality parameters of any coal seams in the sedimentary succession, and whether significant hydrocarbon resources (oil and natural gas) might also be generated within the basin fill.

A research team within Biological, Earth and Environmental Sciences, in association with Pacific Power and the New South Wales Department of Mineral Resources, has been evaluating the organic maturity pattern of the sedimentary sequence in Gunnedah Basin, New South Wales. The group has been comparing the value of a number of different maturation indicators, including vitrinite reflectance and various coal quality parameters, and geological evolution. Special techniques developed during the study include chemical analysis of small organic particles (macerals) in coals and other sediments using the UNSW electron microprobe, and relating changes in key parameters to rank advance and hydrocarbon generation.

The study has also shown existence of significant changes in vitrinite reflectance with depositional environment of the host coal seams, and used these to evaluate the role of unusual perhydrous and subhydrous vitrinite types in hydrocarbon generation. It has also used horizons with anomalously low vitrinite reflectence to identify marine flooding surfaces within the basin in sequence stratigraphy interpretations.

Fusinite, showing different patterns in cell-wall fragments

Fluorescence of liptinite macerals in a polished coal section under blue-violet illumination

APPLICATIONS OF THE STUDY INCLUDE:

Characterising coals, including coal chemistry, at a microscopic scale;
Establishing relations between organic matter and its depositional environment;
Investigating the behaviour of different types of organic matter with burial;
Understanding regional and mine-scale patterns of coal quality variation;
Delineating the geological history of a major Australian basin;
Mapping areas with potential for oil, gas and coal-seam methane discoveries.