A Novel Desalting Workflow - A West Africa Case History

Ray tracing tomography is a mature technology that allows high resolution updates over large 3D surveys and is widely used in different geological settings as the main driver for velocity model building. There is an important caveat however that must be considered when using tomography; the inversion is sensitive to the initial velocity model used to start the process, so building a good initial velocity model is essential to produce meaningful results after tomography.

Initial velocity models built from RMS velocities using Dix’s inversion, are typically noisy and are heavily smoothed to avoid plaguing the tomography with velocity oscillations and bulls eyes. For areas in a salt environment, like our case study, legacy velocity models are historically linked to velocity analysis in the time domain, which solves properly the velocity for the sedimentary basins, but introduces spurious velocities for subsalt events.

In this paper, we present a novel workflow for editing and removing spurious and noisy velocities for velocity model building. We have used our workflow successfully in a deep water West Africa survey. The result shows that our novel workflow is a powerful tool for complex geological areas.