Direct Inversion for Salt Flank Geometry Using P- and S-Wave Traveltimes in a VSP Survey Experiment

Abstract

Summary Salt bodies distribute extensively in the Gulf of Mexico region and elsewhere in the world, playing key roles in hydrocarbon capture, understanding the tectonic history, providing mining resources and etc.( Jones, and Davison, 2014 ). While the short elastic limit of the rock salt gives rise to its ‘plastic’ deformation and migration under high differential stress and geothermal conditions, accurate delineation of the rugose salt flank becomes quite challenging to conventional surface seismic surveys. We describe an application of deformable-layer tomography (DLT) to invert for the geometry of salt flank using travel times of both transmitted P- and S-waves recorded in a vertical seismic profiling (VSP) survey from a physical model experiment. As the seismic velocity of salt is better known and generally less-variable, the DLT takes advantage of it and targets on solving the variable geometry of the salt flank. Considering the coverage difference of the transmitted P- and S-wave, we combine both P- and S-wave traveltimes in the inversion scheme and obtain an improved result than that by the primary P-wave alone.