First-break vertical seismic profiling tomography for Vinton Salt Dome

Abstract

Building laterally depth-varying velocity models for vertical seismic profiling (VSP) imaging is challenging because of the narrow ray-angle coverage of VSP data, especially if only first arrivals are used. This study explores the potential of a new deformable-layer tomography (DLT) for building velocity models with a VSP data set acquired over the Vinton salt dome in southwestern Louisiana. The DLT method uses first breaks to constrain the geometry of velocity interfaces from an initial model of flat, constant-velocity layers parameterized using a priori geologic and geophysical information. A progressive multiscale inversion loop gradually updates the interface geometry. The final solution model, containing 3D geometry, is well supported by resolution and reliability tests and closely matches the long-wavelength trends of area sonic logs. The presence of velocity anisotropy is also indicated.