Insights into seismic inversion for geotechnical property estimation in coal mining

Abstract

Seismic reflection surveying, especially by the 3D method has an established role in mapping geological structures that might affect the operation of an underground coal mine. Through acoustic inversion, seismic reflection surveys also have the potential to provide geotechnical information on the sedimentary units that host the coal seams. Acoustic impedance can be empirically related to the Geophysical Strata Rating (GSR), a geotechnical measure obtained through the analysis of geophysical logs. GSR values derived from 3D seismic inversion thereby allow comprehensive mapping of geotechnical variability. In this paper we describe our approach using model-based inversion. In the vicinity of the coal seams where there are large contrasts in acoustic impedance, care is required to ensure that impedances are not overestimated and lead to invalid GSR values. We show results from 3D seismic surveys in the Bowen Basin of Central Queensland.