THREE-DIMENSIONAL FORWARD STRATIGRAPHIC MODELLING OF EARLY CRETACEOUS SEDIMENTATION ON THE LEVEQUE AND YAMPI SHELVES, BROWSE BASIN

Abstract

Early Cretaceous clastic sedimentation on the Leveque and Yampi Shelf areas of the Browse Basin has been brought sharply into focus recently as a result of exploration success at Gwydion and Cornea. The changing nature of clastic sedimentation patterns in the shallow-to-deep marine environments during C. delicata to upper S. areolata times is of increasing exploration interest. This study was designed to address the following questions:

Could the conceptual geological model discussed by Spry and Ward (1997) generate potential reservoir sands in the region from Leveque-1 to Yampi-1?

What would be the geometry and depositional environment of such sands?

SEDSIM is a three-dimensional stratigraphic forward modelling program developed at Stanford University. The program models sediment erosion, transport, and deposition, and predicts clastic sediment distribution on a given bathymetric surface. SEDSIM was used to simulate one million years of deposition on the Leveque and Yampi Shelves from approximately 145 Ma. The model illustrates the use of 3D stratigraphic forward modelling in illustrating and testing stratigraphic play fairway concepts and the development of sedimentation patterns. Reprocessed seismic data from Seismic Australia were used together with a depth-converted near Base Cretaceous surface provided by Woodside Offshore Petroleum. Input data include; a high resolution relative sea-level curve, an understanding of wind and wave directions throughout the modelled period, tectonic movements throughout the modelled area, the nature of the underlying strata, sediment input points, and grain-size distributions. The simulation clearly shows the development of linear shelfal sands on the C. delicata flooding surface during the following regression. Further work will extend the study to early M. australis times.