This case study presents results from the Orion project within the Gulf of Mexico's Lloyd Ridge area. Difficulties arose in updating the velocity within the Cotton Valley Formation (CVF), a thin low-reflectivity layer of shale with carbonate stringers. The prestack depth migration (PSDM) common-image gathers (CIGs) and stack displayed noticeable undulations. To reduce the undulations, an offset-dependent residual moveout (RMO) picking technique was combined with high-resolution tomographic inversion to update the velocity model. This combined work flow resulted in a higher resolution velocity model, which enhanced the gather flatness and reduced the undulations of the event beneath the CVF layer.