We are currently seeking industry partners to instigate the rejuvenation of the 3D data given the success of the 2D reprocessing.

The objective of the reprocessing workflow was to improve seismic resolution and fidelity across the full section, especially deep structures. Furthermore, particular attention was given to amplitude preservation so that the data would be appropriately conditioned to be inverted for rock properties. Six vintages of 2D data dating from the early 1970s through to 2011 were reprocessed from field data by applying the latest broadband deghosting, designature, and demultiple workflows (MC2D-UR21-Repro-2D). These workflows delivered a robust zero-phase wavelet free from side-lobes and stable across the full angle range.

The water bottom morphology varies significantly across the study area with shelf, shelf break and deepwater environments. The variability in water depth presents challenges for demultiple as the timing of the multiple arrivals changes significantly. To optimize the attenuation of multiple energy, the parameterization for both multiple prediction and subtraction was locally optimized for the range of water depths. This approach ensured that the underlying primary signal was recovered whilst preserving the amplitude.

Anisotropic Depth Model Building and Migration

To improve structural imaging, the complete 2D dataset has been migrated to depth. Anisotropic velocity model building was constructed using PGS hyperTomo, which computes residual velocity using shifts extracted from the data without imposed moveout assumptions. This approach is able to resolve complex velocity structures with a high degree of precision compared to more conventional parabolic picking methods. 

The PGS hyperTomo technology delivers a high-resolution velocity model that is data-driven yet structurally conformable to the main trend elements within the basin. Additionally, the velocity contrasts across fault boundaries such as that between Aptian-level sediment-filled grabens and the adjacent basement were properly modeled. Structural imaging at the potential source rock level and possible migration pathways along the faults has been optimized.

Final imaging has been performed using a Kirchhoff PSDM approach. The resulting image leverages the improved pre-processed data along with the robust velocity model to give significant uplift in seismic data quality compared to the legacy data. In addition to improved structural imaging and resolution, the data also benefit from pre-stack amplitude preservation allowing quantitative interpretation workflows to be used, further derisking the prospectivity.