Salt Dome Flank Imaging using Acoustic and Elastodynamic Redatuming
LU, R., WILLIS, M., TOKSÖZ, N., Earth Resources Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, firstname.lastname@example.org
Imaging the salt structure under complex overburden is a challenge in exploration society. We applied an extension of the concept of Time Reversed Acoustics (TRA) for imaging salt dome flanks using data recorded in a well due to surface shots, known as a Vertical Seismic Profile (VSP) survey. We demonstrate its performance and capabilities on both synthetic acoustic and elastic seismic data from a Gulf of Mexico (GOM) model. This target-oriented strategy eliminates the need for the traditional complex process of velocity estimation, model building, and iterative depth migration to remove the effects of the salt canopy and surrounding overburden. The method, called redatuming, creates a geometry as if the source and receiver pairs had been located in the borehole at the positions of the receivers. This process generates effective downhole shot gathers without any knowledge of the overburden velocity structure. The resulting shot gathers are less complex since the VSP ray paths from the surface source are shortened and moved to be as if they started in the borehole, then reflected off the salt flank region and captured in the borehole. The imaging algorithm after redatuming not only reveals the outline of the salt edge but also brings out the dipping sediments abutting the salt flank.