a quantitative application of seismic inversion and multi-attribute analysis based on rock physics linear relationships to identify high total organic carbon shale - A case study from the perth basin, Western Australia

This study investigates the seismic response of organic-rich shale in-situ conditions. The aim is to understand the interrelationship between rock properties and elastic properties, as well as the main factors that affect the elastic properties of organic shale. The use of rock physics relationships is important in understanding the seismic responses of shale gas formations when constrained by geology and formation-evaluation analysis. Seismic inversion can be used to identify organic-rich shales from lean shales and help further our understanding of their properties. Different approaches of seismic inversion and multi-attribute analysis were conducted by combining three dimensional (3D) seismic data with log data to determine hydrocarbon sweet spots within shale formations in the north of the Perth Basin. This study shows that the Acoustic Impedance (AI), which is the product of compressional velocity and density, decreases linearly with increasing Total Organic Carbon (TOC) content in shale gas formations. TOC was obtained using Roc-Eval pyrolysis for more than 120 shale core samples from the Perth Basin. By cross-plotting the AI derived from seismic data against the measured TOC content, it became possible to map TOC variations directly from 3D seismic data. Our investigations have found that the hydrocarbon sweet spots are characterized by high TOC and relatively high AI, which is found in the base of Hovea Formation (hot shale), with a TOC of around 4%.