3D Seismic Analysis of Late Cenozoic Volcanism and Fluid Flow in the Bass Basin, Southeastern Australia

Holford, Simon P.¹; Schofield, Nick²
¹Australian School of Petroleum, University of Adelaide, Adelaide, SA, Australia.
²School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, United Kingdom.

Here we present 3D seismic data from the gas-prone Bass Basin in southeastern Australia that image buried volcanic systems with exceptional detail. Unlike many extensional basins, where the majority of igneous activity usually takes place during the syn-rift phase of basin evolution, the Bass Basin has experienced a protracted history of volcanism. Active extension in the basin ceased during the early Eocene, but significant pulses of post-rift intrusive and extrusive activity occurred in the Oligocene and Miocene. These late Cenozoic igneous rocks generally occur at shallow levels (<1.5 km), and strong amplitude contrasts with the siliciclastic and carbonate sedimentary rocks of these ages enable straightforward identification of volcanic features. Application of visualization techniques including opacity rendering and RGB blending of frequency decomposition volumes provide unprecedented seismic definition of an array of volcanic and subvolcanic features, including edifices, pipes, fissures, lava fields and complex fracture systems related to volcanism. Furthermore, our data show that subsequent to the cessation of igneous activity, volcanic plumbing systems have provided long-term pathways that have focussed fluid and gas migration, and potentially also sediment remobilization within the basin. Our results provide support for the notion that volcanic systems in sedimentary basin can play a key role in controlling migration pathways and thus influencing prospectivity, in addition to the well-known impacts of igneous activity on source rock maturation and reservoir quality.

AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012