Seismic Geomorphology of the Permian Sediments in the Cooper Basin: A Study of the Toolachee Formation in the Nappamerri Trough
Bonnie Lodwick - 2014
Honours Degree of Bachelor of Science (Petroleum Geology & Geophysics)
Australian School of Petroleum
The University of Adelaide
Three different seismic geomorphology techniques were applied to the Permian Toolachee Formation within the Cooper Basin. A full azimuth survey, the ‘Gaschnitz 3D,’ located on the northwest flanks of the Nappamerri Trough has been used for this study.
The three main seismic geomorphological analytical techniques explored are proportional slicing, as suggested by Posamentier et al (2007), spectral decomposition and facies classification. Seismic geomorphology is found to improve the interpretation potential of the Permian sediments within the Gaschnitz 3D. Targeting key frequencies for spectral decomposition was imperative to getting more from the data, especially when pursuing a specific feature. Facies classification provided both an improved view of previously interpreted trends and a better understanding of chronology of events. Distinct colour changes make it easier for interpreters to identify shapes.
Applying proportional slicing and spectral decomposition to azimuth volumes proved unsuccessful. However, despite noise issues, facies classification azimuth volume results provided more detail within channel belts for smaller scale interpretation. Unlike spectral decomposition, this method retains more of the original reflection information within the wavelets. When seismic resolution is a significant issue, as in the Cooper Basin, this is an important benefit.
Despite seismic resolution issues associated with coals and depth of Permian sediments in the Cooper Basin, geomorphological shapes were able to be identified at both the Upper Toolachee and Lower Toolachee levels. Consistency of shapes between the results of the three methodologies is an enormous positive to come from this study. With the initial findings supported by well data, the application of seismic geomorphology provides great potential as an interpretation method in this hitherto difficult region of the Cooper Basin.
A novel workflow has been developed, with three major steps replacing the standard Posamentier (2007) two stages of seismic geomorphology method. The results of this study argue that proportional slicing should be used as a second more in-depth reconnaissance step, rather than as an analytical technique used after the initial reconnaissance work done of the seismic volume. Proportional slicing results can then be used to guide the implementation of more technically advanced analytical processes such as spectral decomposition and facies classification.