Côte d’Ivoire, Africa
- Côte d'Ivoire, Blocks 602 & 603
- Survey Year
- Survey type
- 3D GeoStreamer
- Survey Configuration
- 10 streamers, 100 m separation
- Survey Size
- 5 000 sq. km
- Data Deliverables
- Kirchhoff PSDM, Velocity Model
The PGS data library in Côte d'Ivoire comprises six 3D GeoStreamer surveys along with over 12 000 line km of 2D data. A new MegaSurvey (grey outline and including GeoStreamer surveys up to 2015) will be available in Q2 2019 and will enable the evaluation of the Western Ivorian basin in a regional 3D context, providing an excellent overview of all play types over acreage. The data in this case study is from within the orange outline and was reprocessed in 2018 using advanced velocity model building tools.
Late Cretaceous (Maastrichtian) and Paleocene channel and canyon systems (yellow ellipses) impact the seismic characterization of older Late Cretaceous prospective channel and fan systems in deep water Côte d’Ivoire. Intra-channel heterogeneity impacts amplitude fidelity and causes uncertainty for the prospective targets in the underlying older channel and fan systems. No wells have been drilled in deep water Côte d’Ivoire to date, however with modern regional datasets available, the complex sediment provenance is becoming more understood.
- 3D GeoStreamer
- Full 3D demultiple
- Velocity model building
- PGS FWI and Q-VMB tomography
- Q-Kirchhoff prestack depth
- Seismic driven inversion for relative impedance
An integrated visco-acoustic model building sequence, including PGS FWI and Q-VMB has been adopted to resolve the impact of complex Late Cretaceous and Paleocene channel systems on deeper targets. This approach eliminates the reflectivity imprint, creates an accurate velocity model, elliminates uncertainty in the image and improves the amplidute fidelity of the dataset.
Attenuation Effects of Canyons Resolved
Implementation of fully integrated visco-acoustic model building and migration delivers the results on the right. The removal of the imprint of the canyon on the data below is shown on the log spectra ratio plots (inserts) from the Base Tertiary Unconformity horizon. The spectra on the right demonstrates how the amplitudes have been successfully compensated for below the canyons (blue is ideal).
The primary objective of this model building flow is to solve the seismic characterization challenges of a complex set of deep water Maastrichtian and Paleocene channel systems on deeper Cenomanian and Turonian fan systems offshore Côte d’Ivoire. Due to water depth (4 km), acquisition geometry and geological setting, reflection only FWI was used as part of a fully integrated visco-acoustic model building flow. In conjunction with FWI, the Q model was derived tomographically. The resulting Q migration produces a seismic image where the younger Late Cretaceous prospectivity is more readily defined with less uncertainty and improved amplitude fidelity.
Effective Model Building Improves Continuity of Impedance Data
Relative impedance quality control shows better continuity and resolution of events below the Maastrictian and Paleocene channels. The interpretation and evaluation of prospective features at target level can be completed with more confidence.
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