Dip-constrained Non-linear Slope Tomography - an Application to Shallow Channel Characterization

Abstract

Ray based migration velocity analysis from pre-stack seismic reflection data is based on the characterization of the migrated reflected events by their position, dips and residual move-out. Such approaches update the depth velocity model through an optimization process, where the residual move-out of the picked migrated events is minimized while obeying some regularization constraints related to the depth or to the shape of some horizons or to the smoothness or structural conformity of the velocity field. We propose to introduce an additional term in the cost function involving the dip of kinematically migrated locally coherent events. The velocity is then updated to match the expected dip of the re-migrated offset-dependent events. We develop here the conceptual aspects of this approach within the frame of non-linear slope tomography and present a first application, on a North Sea dataset, to the characterization of very shallow channels creating pull-up and pull-down effects in deeper parts of the migrated image. Due to the very limited offset range of the residual move-out picks in shallow subsurface, these effects could not be solved by residual move-out based tomography. We demonstrate that the introduction of the dip-constrained inversion allows the correction of these pull-up and pull-down effects, resulting in improved depth imaging.

Imaging challenges and processing solutions in the Brazilian Equatorial Margin: A case study in the Barreirinhas Basin

“…To address these challenges, an approach that utilizes dip information as well as RMO information was adopted. Guillaume et al (2013) propose DCT to resolve high wavenumber features such as channels. e aim of DCT is to nd the velocity model that best minimizes both the RMO and the mis t between the structural dip of di erent o sets.…”

Velocity model-building challenges and solutions for seabed- and paleo-canyons: A case study in Campos Basin, Brazil

“…It handles complex ray paths naturally and doesn't rely on a priori geology assumptions or RMO picking. We applied FWI in this case study in Campos Basin, followed by a ray-based model building workflow with dip-constrained non-linear slope tomography (Guillaume et al, 2013). The result shows improvement in the sub-canyon image and satisfying quality in both the data and gather domains.…”

“…Thus far, techniques for implementing or improving raybased tomography have dominated discussions of velocity model-building strategy for submarine canyons; analysis relies heavily on the quality and density of the residual moveout (RMO) picks to build accurate high-resolutions models (Fruehn et al, 2015). In addition, different techniques such as pick weighting and layer constraints (Sun et al, 2011;Chen and Shen, 2012;Chen and Hu, 2014), reference horizons and offset-consistent dip constraints (Graham and Richard, 2009, Guillaume et al, 2013, Chen and Hu 2014, have been explored to help invert good models.…”