Full-volume interpretation methods: Applications for quantitative seismic stratigraphy and geomorphology of the Lower Barrow Group, Northwest Australia

Abstract

Following decades of technological innovation, geologists have now access to extensive 3D seismic datasets. How these data will help understanding the complexity of the subsurface relies on developing stratigraphic workflows that allow very high-resolution interpretation in a cost-effective timeframe. Here, the use of full-volume, semi-automatic horizon tracking tools allowed interpreting ultra-high resolution seismic sequences (~40,000 yrs duration) within a Cretaceous prograding shelf-margin (Lower Barrow Group; LBG) on the North West Shelf of Australia. Initially, semi-automated horizon tracking allowed mapping key regional unconformities defining 3rd order seismic sequences. In a second step, a very high resolution grid (nodes corresponding to seismic traces) was generated in each 3rd order sequence. An automatic propagation algorithm then linked the nodes based on their similarities, resulting in a very dense network of “proto”-seismic horizons. Volume interpolation resulted in the creation of a Relative Geological Time (RGT) model from which a very high number of chronostratigraphic surfaces were extracted. This allowed a full volume 3D mapping of every clinoform in each 3rd order sequence, from which quantitative data (clinoform height, slope, topset vs bottomset thickness) and seismic attributes (seismic geomorphology) were extracted. This analysis unveiled the high resolution changes in sediment supply and accommodation in time and space in the LBG, and provided new insights on the distribution of shallow and deep marine plays in the basin. This innovative workflow constitutes a new step in sequence stratigraphy as it allows interpreters to map sequences in a true 3D environment hence taking into account the full variability of depositional systems in time and space.