Document Type

Conference Paper

Publication Date


Publication Details

This conference paper was originally published as Armstrong, M, Hatherly, P and Thompson, S, Determining the Cotnrols for Strata Gas and Oil Duistribution within Sandstone Reservoirs Overlying the Bulli Seam, in Aziz, N (ed), Coal 2006: Coal Operators' Conference, University of Wollongong & the Australasian Institute of Mining and Metallurgy, 2006, 180-189.


The continuing and effective management of gas within the sandstones overlying the Bulli seam mines of BHP Billiton Illawarra Coal is required to ensure safe and productive mining operations. Recent surface exploration has also detected the presence of oil accumulations in these sandstones which have the potential to impact on future mining operations. Some of these hydrocarbons are located within the longwall relaxation zone of the overlying strata and, as a result, can migrate to the goaf and active workings subsequent to extraction. A number of new exploration techniques, which are in common use by the petroleum industry, have been adopted by Illawarra Coal in order to more accurately locate these zones and determine the potential impact on future mining. These techniques include: • Advanced analysis of downhole geophysics to determine the location and extent of strata gas horizons. • Specialist interpretation of 2D and 3D seismic to detect gas zones. • Modeling of multiple data-sets to determine controls on gas distribution and composition. • Detailed geological and chemical analysis of the oil-bearing horizons to gain a better understanding of the petroleum system and the controls to its distribution. • Geotechnical studies of the overlying strata to determine the extent and nature of post-mining strata relaxation in comparison with the location of the hydrocarbon zones. The results of these studies have formed the scientific basis for the development of more effective technologies to manage the impact and potential impact of strata oil and gas on the underground extraction of coal.