Dip-Constrained Tomography With Weighting Flow For Paleo-Canyons: A Case Study in Para-Maranhao Basin, Brazil

Chen, Guang (CGG) | Hu, Lingli (CGG)

OnePetro 

Summary

Para-Maranhao Basin offshore Brazil is well-known for its shallow geological complexities. Rugose topography and complex V-shaped paleo-canyons directly below the water bottom create challenges for ray-based migration velocity analysis from prestack depth imaging. In particular, when using a global grid-based tomography, generating velocity updates at a sufficiently small scale to conform to these shallow structures can be difficult. Image distortions, characterized by non-geologic depth undulations and amplitude variations, are often observed below the shallow structures. These artifacts can affect the accuracy of reservoir interpretation. We propose a weighted, high-resolution workflow utilizing dip-constrained, non-linear slope tomography to resolve small scale velocity variations at shallow depths. As a result, image distortions below the near-surface geological complexities are attenuated, and the common image gather flatness is improved.