Unveiling the Seismic Image Beneath Volcanics in the Bass Basin

Volcanic and intrusive igneous rocks are common throughout the offshore Bass Basin, Southeast Australia, due to multiple episodes of magmatism. These igneous bodies have complex internal structures that cause distorted seismic images and poor illumination beneath them. This paper demonstrates an application of Time-Lag Full Wave-form Inversion (TLFWI), and an integrated de-multiple workflow to greatly improve the seismic image beneath volcanic bodies. Least-Squares Q Migration (LS-QPSDM) was applied on the improved pre-processed data and velocity model to achieve: 1) well-defined volcanic bodies that enable the unveiling of the underlying events and hence make it more suitable for interpretation; 2) a good synthetic well-tie and overall small depth mis-ties; and 3) a seismic volume with improved fidelity for attribute inversion. The uplift in imaging allowed confident mapping of a previously unidentified upthrown fault-bound closure that could lead to further development of the Yolla field, which is important to meet the rising demand for natural gas on the East Coast of Australia.