| Popis: |
Tomographic inversion is the standard approach to estimate migration velocity model. Nonetheless it is known to be an undetermined ill-posed inverse problem. Therefore, some type of regularization criteria is needed. Besides smoothness, the observation that correlation in velocity is to be driven by rock formations topology calls for more geologically consistent approaches. This knowledge can be expressed in terms of structural constraints that, if not obeyed, may be indicative of velocity inaccuracies and, accordingly, be used to drive tomography to correct for velocity inaccuracies. In this work we formulate the constraints for tomography directly on the shape of the horizons picked after depth migration. This is achieved by mapping perturbation in slownesses into perturbations in reflectors depths. This way we can impose the desired characteristics to the imaged reflector such as: the flatness of the base of the salt, the flatness of a detachment surface, the horizontalness of oil-water contact, the horizon passing through well markers and the equivalence of a reflector in PP and PS migrated images. This opens the door to introducing interpretation driven and geologically consistent information into the tomographic inversion, and the results obtained by applying the designed constraints demonstrate their effectiveness. |
