Advanced Multiple Attenuation and Model Building Techniques Provide New Insights Into the Jurassic Play of Timor sea, Offshore Australia

Abstract

The Sandalford area, located in Australia’s northwestern continental margin, is proximal to the Cash-Maple and Tenacious field discoveries. The area has Eocene-Paleocene Carbonates overlying siliciclastic Cretaceous section, resulting in a strong velocity inversion as well as generating complex free-surface and internal-multiple contaminations at the deeper Jurassic reservoir section. We present a reprocessing case study of a narrow-azimuth, towed-streamer seismic dataset acquired in shallow water using advanced multiple attenuation and earth model building techniques, with the main goal of improving our understanding of the complex geology beneath. The multiple attenuation part of the workflow employs a cascaded approach, initially addressing water-layer multiples, remaining free-surface multiples, and followed with internal multiples. Implementation of high-frequency visco-acoustic full-waveform inversion (Q-FWI) improved the overburden velocity model and combined with effective multiple attenuation algorithms, reduced the uncertainty of primary events in the pre-carbonate section, therefore reducing errors in common image point (CIP) tomography. The results were quality-controlled against the well data, providing new insights with improved structural and stratigraphic delineation.