3D high order seismic imaging in Gulf of Mexico in the context of RTM algorithm using adjoint-based methods.

The present work consists in imaging salt bodies from earth subsoil in the context of Reverse Time Migration (RTM) algorithm. The study of salt domes is economically important because they form a natural trap for hydrocarbons. For instance, more than a half of the hydrocarbon reserves that still exist today are related to salt bodies.

However, seismic images coming from strong salt tectonics area, are contaminated with spurious signal, like multiple events. Therefore, it is important to know how to treat and filter multiples in order to have seismic images that are geologically interpretable.

For this purpose, we solved the forward 3D elastic seismic wave equations using high order finite differences. The earth parameters come from 3D velocity and density models in a salt tectonic region in the North Gulf of Mexico. To obtain the imaging condition we compute the sensitivity kernels by using the adjoint solution of wave equation and by applying checkpointing. We tested this algorithm with simultaneous and separated sources. Fluid - solid interfaces at the ocean bottom is introduced, interfaces are well retrieved at large offsets.

Furthermore, we applied CPML absorbing boundaries, and replace also free surface conditions for absorbing boundaries to attenuate free surface multiples. The images we obtained from sensitivity kernels are easily interpretable. The calculations were performed on CALMIP supercomputing platforms in Toulouse France.