the wavelet (narrower frequency bandwidth for the conventional seismic and broader wavelet for the GeoStreamer dataset), same low frequency model and inversion parameters. Therefore the only differences between the two datasets are simply due to the type of towed streamer. The dual-sensor seismic inversion results exhibit a clearer definition of the individual geological layers and the fluid contact.
Conventional Streamer Dual-Sensor Streamer
Noise Level
Noise Level
Acoustic Impedance
Acoustic Impedance
Figure 5.25: Cross-plot comparisons, based on seismic data only. Red points are within the reservoir zone. The uncertainty in relative acoustic impedance is only marginally better in the dual-sensor data, whereas the Vp/Vs-ratio has much lower noise in the dual-sensor data. The slope of the cluster is consistent with variations in porosity and net-to-gross (N/G).
Figure 6: Cross-plot comparison between the two acquisition systems. The cross-plots are based only on the seismic data. Red points are within the reservoir zone. The uncertainty in relative acoustic impedance is only marginally better in the dual-sensor data, whereas the Vp/Vs-ratio has much lower noise in the dual-sensor data. The slope of the cluster is consistent with variations in porosity and net- to-gross (N/G).
as seen in Figure 5.25. Te cross-plot demonstrates clearly the better stability and lower noise in the pre-stack domain of the elastic reservoir properties, especially in the Vp/Vs-ratio using the dual-sensor streamer acquisition system compared to the conventional data. Te extended bandwidth, especially at the low frequency
To further extend the analysis between the two datasets, a cross-plot was done over the area enclosed in red in
Figure 5. This area includes the gas reservoir and should therefore have an unambiguous elastic attribute response, with the gas having both lower acoustic impedance and lower Vp/Vs-ratio as seen in Figure 6. The cross-plot demonstrates clearly the better stability and lower noise in the pre-stack domain of the elastic reservoir properties, especially in the Vp/Vs-ratio using the dual-sensor streamer acquisition system compared to the conventional data. Figure 5.26: Today, all vessels operated by PGS are equipped with GeoStreamers, including their Ramform fleet.
end of the spectrum, thus represents a key improvement in lithology-fluid prediction and also in seismic reservoir property estimation. Te need for a priori information is considerably reduced by relying more on the data and less on a low frequency background model compared with a conventional seismic streamer.
Conclusions These studies, out of many, illustrate that the dual-sensor GeoStreamer technology provides significant advantages in
important reservoir characterisation aspects. Seismic attributes and in particular seismic pre-stack inversion, provide an uplift to reservoir studies.
Reservoir delineation and geobodies detection are significantly improved thanks to an increased signal to noise ratio and broader bandwidth. The extended bandwidth, especially at the low frequency side of the spectrum represents a key improvement in the lithology-fluid prediction and also on seismic reservoir property estimation. The need for a priori information is considerably reduced by relying more on the data and less on a low frequency background model compared with a conventional seismic streamer which should notably improve the number of successful wells.
Further reading CONTA CT Petroleum Geo-Services
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Lamont, M.G, T.A Thompson and C. Bevilacqua, 2008, Drilling success as a result of probabilistic lithology and fluid prediction — A case study in the Carnarvon Basin, WA (APPEA Journal)
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