3-D seismic reflection tomography on top of the GOCAD depth modeler

The estimation of velocity macro-models by seismic reflection tomography is studied in three-dimensions. Inversion techniques based on the kinematics of seismic data require an appropriate parameterization of the geological macro-model, in particular as far as the velocity field is concerned. The step toward structurally complex geological models is achieved by exploiting a new approach to 3-D depth modeling: GOCAD. The peculiarities inherent to GOCAD triangulated surfaces and its associated discrete smooth interpolator (DSI) have led to the development of original ray-tracing techniques. By exploiting intensively the topology of the triangulated surfaces, these new algorithms make it possible to reach a good balance between accuracy and computation performance. To build a 3-D macro-model estimation tool, ray-tracing is then associated with a least-squares inversion of depth parameters and velocity parameters from 3-D zero-offset traveltimes and stacking velocities, or multi-offset prestack traveltimes from 2-D seismic lines.