Integrated reservoir characterization using high definition frequency decomposition, multi-attribute analysis and forward modelling. Chandon discovery, Australia.
Frequency decomposition and forward modelling represent advanced seismic techniques that can be applied to assist hydrocarbon exploration. The Chandon (4TCF) and Yellowglen (net-pay column 137m) gas discoveries in the Exmouth Plateau, North Carnarvon Basin (NCB), Australia (Figure 1) offer an excellent opportunity to test and demonstrate the applicability of these techniques in the search for hydrocarbons, because of the high-quality seismic data available, the textbook-example of gas flat-spot response, the fluvial-dominated reservoir and the existing proven hydrocarbon accumulation (Geoscience Australia, 2014). This study presents a workflow for reservoir characterization based on the integration of seismic interpretation, seismic attribute analysis, core analysis, petrophysical interpretation, rock physics modelling, and synthetic seismic modelling to ultimately mitigate uncertainty. Firstly, the complex tectonostratigraphic history of the petroleum system is resolved using attribute analysis, attribute colour blends, and frequency decomposition. This analysis reveals an extensive set of reservoir features, emphasizing the structural evolution and stratigraphic architecture. Frequency decomposition represents a powerful tool for looking at band restricted frequency volumes of the seismic data, to reveal hidden geological features. The discrete frequency volumes are combined in a Red-Green-Blue (RGB) blend that shows the contribution of and interaction between different frequency bands, highlighting geological features. However, up until now frequency decomposition images have been used rather qualitatively. This study offers a different approach: it uses forward seismic modelling to compare the high definition frequency decomposition (HDFD, see Eckersley et al., 2018) responses of the original data set and the synthetic models (e.g. Han, 2018), in order to validate the model geometries and their rock and fluid property distribution. A 3D seismic cube (Chandon 3D Survey, 875 km2), was used for seismic interpretation which was supplemented by information obtained from four wells (Figure 1). Especially useful logs were the Vertical Seismic Profile and Sonic Scanner logs for rock property estimates and subsequent mechanical layering. Core analysis was available for Yellowglen, Chandon-2&3 wells. Well completion reports, including advanced studies such as special core analysis interpretations, rock physics, formation evaluation, and core photography observations were synthesised as part of the framework for this study. Checkshots were available for three of the four wells to enable accurate well-ties. Published papers on the system assisted in establishing the geological framework for this project.