COALBED METHANE EVALUATION IN AUSTRALIAN COAL BASINS - A NEW LOOK AT COAL OPTICAL PROPERTIES
Dr. Lila W. Gurba
The School of Geology
The University of New South Wales
Monday, May 21, 2001, 3:00 pm
Ben Bandy Conference Center
Center for Applied Energy Research
It has been known for centuries that methane-rich gases are locked in coal seams. Although still mining hazards, they have been identified as an important environmental friendly energy source. During the last few years the coal bed methane industry has emerged as an energy source of national significance in Australia. Exploration for and development of coalbed methane resources is currently underway throughout the coal basins of Queensland, New South Wales and Victoria. However, detailed knowledge of the factors governing coal bed methane generation and preservation is still to be acquired in most coal basins, not only in Australia.
This presentation arises from an ongoing collaborative research project carried out at the University of New South Wales aimed at improving the understanding of the relationship between coalification processes and coalbed methane occurrence in Australian coal basins. The project integrates the information on coal macerals including optical microscopy (reflectance anisotropy), electron microprobe (chemical composition of macerals), and physical properties of coal, to investigate the processes responsible for gas generation and preservation in Australian sedimentary basins.
Investigations of gassy coals from Australia and the USA, in particular the medium-high volatile bituminous coals of the Permian Gloucester Basin in eastern Australia, have led us to conclude that coal petrology as currently applied to coal science and the conventional petroleum industry is inadequate for coalbed methane. There is a need for a new approach in coal petrology that is more responsive to the demands of coalbed methane exploration and development. Studies of coal type and rank in several gassy coal provinces and basins have established links between gassy coals and fundamental coal properties. A recent case study of highly gassy coals in the Gloucester Basin and the Gunnedah Basin of eastern Australia has provided an opportunity to make new observations under the microscope, and to relate them to parameters that were used in an evaluation of a coalbed methane prospect in the basins. Comparisons have also been made with other east Australian coal basins, as well as the Fruitland Formation coals of the San Juan Basin, USA, and the Ordos Basin in China. The coal optical properties that have applications for coal bed methane include: Paleo-stress pattern as revealed by vitrinite reflectance anisotropy, Microstructures of coal and The effects of igneous intrusions on coal microstructure and coal seam gas potential.