Characterizing carbonate facies using high-definition frequency decomposition: Case study from North West Australia

Abstract

Carbonate facies identification is difficult using conventional seismic attributes due to subtle lithologic changes that cannot be easily recognized. Therefore, there is a need to develop new methodologies to study their evolution and their associated sedimentary processes, which will eventually lead to better prediction for reservoir-quality rocks. New insights into the Cenozoic carbonates in North West Australia have been captured with the application of a high-definition seismic attribute workflow. The workflow starts with conditioning of the seismic volume using structurally oriented noise attenuation filters to remove any random and coherent noise from the input data. It also benefits from a high-definition frequency decomposition that matches the original seismic resolution without smearing interfaces using a "matching pursuit" algorithm. A color blend of multigeometric attributes, such as semblance and conformance, has also been used in the workflow to define edges and discontinuities present in the data within carbonate deposits that are attributed to depositional geometries, such as barrier reefs. Our workflow has been developed to investigate the geomorphology and the sedimentary processes affecting Cenozoic successions in the Northern Carnarvon Basin in North West Australia. Geomorphological and sedimentological observations have been documented such as an Eocene rounded carbonate ramp with evidence of slump blocks and scarps, Middle Miocene accretions generated due to longshore drift, and the presence of Pliocene-Pleistocene patch and barrier reefs. These observations were extracted as geobodies to allow for visualization, and they can be used in an automated seismically based facies classification scheme. The new appreciations are not only useful for understanding the carbonate evolution but can also be used to identify geohazards such as slumps ahead of future drilling.

Advanced seismic characterization of a geothermal carbonate reservoir – Insight into the structure and diagenesis of a reservoir in the German Molasse Basin

“…A2) separates the seismic signal into its frequency components. Three different frequencies are then corendered and displayed by RGB colour-blending, where frequencies 1, 2 and 3 are plotted against red, green and blue, respectively (Chopra & Marfurt, 2007;Al-Maghlouth et al, 2017).…”

“…Three different frequencies are then co-rendered and displayed by RGB colour-blending, where frequency 1 is plotted against red, frequency 2 is plotted against green and frequency 3 is plotted against blue. Since this is an additive colour model, three equally strong signals of the frequency components will result in a white response (Chopra & Marfurt, 2007;Al-Maghlouth et al, 2017). In Petrel a hybrid method, combining a Short Time Fourier Transform (STFT) and a Continuous Wavelet Transform (CWT), is applied that allows to control both the vertical-and the frequency resolution (Schlumberger, 2020).…”

“…Using spectral decomposition, they identified paleo-lows and depocentres; sweetness helped them to identify channels, reef structures and lithofacies boundaries; variance and amplitude extraction maps revealed the reefal development on top of the carbonate platform. Al-Maghlouth et al (2017) used frequency decomposition and a colour-blend of geometric attributes, such as semblance and conformance, to characterize the Cenozoic carbonates facies in North-West Australia, and to define edges and discontinuities associated with depositional geometries, such as reefs. Spectral decomposition and coherency have also been used by Skirius et al (1999) to locate faults and fractures, and reef margins and isolated buildups, as targets for increased hydrocarbon production, e.g.…”

Advanced seismic characterization of a geothermal carbonate reservoir – insight into the structure and diagenesis of a reservoir in the German Molasse Basin

“…A2) separates the seismic signal into its frequency components. Three different frequencies are then co-rendered and displayed by RGB colour blending, where frequencies 1, 2, and 3 are plotted as red, green, and blue, respectively (Chopra and Marfurt, 2007;Al-Maghlouth et al, 2017).…”

“…Using spectral decomposition, they identified paleo-lows and depocentres; sweetness helped them to identify channels, reef structures, and lithofacies boundaries, and variance and amplitude extraction maps revealed the reefal development on top of the carbonate platform. Al-Maghlouth et al (2017) used frequency decomposition and a colour blend of geometric attributes, such as semblance and conformance, to characterize the Cenozoic carbonate facies in northwestern Australia and to define edges and discontinuities associated with depositional geometries, such as reefs. Spectral decomposition and coherency have also been used by Skirius et al (1999) to locate faults and fractures, as well as reef margins and isolated buildups, as targets for increased hydrocarbon production, e.g.…”