Non-linear scanning tomography for velocity model building in seismic-obscured area

A new non-linear tomographic inversion based method is put forward to resolve large velocity errors associated with complex geology which can cause poor imaging or migration artifacts. We propose to first create a series of trial-velocities from initial velocity by varying the values inside poor imaging zone. Migrations are followed using these trial velocities. The second stage involves CIG picking on these migrated gathers/stacks with tight constraint to ensure reliable picks. These CIG picks are then de-migrated to invariants with their corresponding trial velocities to form a set of invariants as the input to non-linear tomographic inversion.