Visualisation of geomorphological features and interpretation of the depositional system of the Brewster Member, Ichthys Field

Abstract

The Brewster Member of the Early Cretaceous Upper Vulcan Formation is one of the main reservoirs of the Ichthys Field. The Brewster reservoir is characterised as massive sandstone, 150–200 m thick, deposited in a deep marine environment. It has a high net sand-to-gross ratio (over 90%) throughout the field, but heterogeneous reservoir quality between the wells. Visualisation of various geo-morphological features from seismic data is critical for the better understanding of the reservoir. Due to thick overburden, frequency content of the seismic volume is limited at reservoir level. Since the reservoir primarily consists of high net sand-to-gross sandstone, and seismic data has limited resolution, it is difficult to identify the various depositional elements using conventional seismic amplitude interpretation. Seismic attribute visualisation techniques were applied to Ichthys 3D seismic and inverted P-impedance data, enabling identification of several geo-morphological features in this otherwise massive sandstone interval (e.g. feeder channel belt, channel-lobe complex, channel-lobe fringe). Core and log scale sedimentological interpretation were tied to the identified feature to understand the depositional architecture of the Brewster Member, which could lead to a better understanding of the distribution of reservoir properties.