Innovative and classical field-based approach for analogue reservoir modelling: the Precipice Sandstone, Qld

The Jurassic Precipice Sandstone was studied as a potential oil and gas reservoir unit within the Surat Basin, Queensland. Since the early depletion of its productive fields, the Precipice Sandstone has been recently selected by the ANLECR&D Company as the target unit for the injection of up to 200.000 tons of Greenhouse Gas Stream derived from coal-fired power stations. The aim of this work is to provide new outcrop-based depositional models for the so called Lower and Upper Precipice Sandstone, with their first application in reservoir characterization. Trough a classical facies analysis approach, both at the outcrop scale and borehole core-cuts, and the innovative use of 3D Digital Photogrammetry, this study assists the creation of the most reliable geo-cellular reservoir model. The Lower Precipice outcrop studied at Nathan Gorge National Park shows unitbar and compound-bar deposits typical of the alluvial architecture of a sandybraided river system. On the other hand, the Upper Precipice shows lobated bodies comparable to mouth-bar deposits which might be ascribed to a shallowwater delta complex. The recognition of braided-bar deposits in the studied outcrops deals with the well-known fluvial origin the Lower Precipice. However, despite the common thought of the pure fluvial nature of the Precipice Sandstone, the Upper Precipice outcrops might provide new insights on the interpretations of the depositional environment of this unit. In this framework, the presented detailed facies analysis study, enhanced by the powerful 3D Digital Photogrammetric technique, demonstrates that sedimentary investigations on the Precipice Sandstone reservoir analogue reduces uncertainties in the reservoir characterization and supports the creation of a 3D reservoir model. Nevertheless, the advancement of knowledge of the Upper Precipice depositional environment might have further implications in the understanding of geological evolution of the Jurassic-Cretaceous Surat Basin.