Time preserving tomography

Time Preserving Tomography is an accurate, efficient and flexible tool for constructing kinematically equivalent subsurface models given a background model and a set of model parameter perturbations. In this method, parameters of the background model are allowed to change while preserving traveltimes of all ray pairs. Perturbations can be applied for all types of model parameters. In the case of tilted transverse isotropy (TTI) the model parameters are the axial compressional velocity, Thomsen anisotropic interval parameters epsilon and delta, and the depth values of the model horizons. The traveltimes of all ray pairs traced during the tomographic inversion are kinematic invariants. In the migrated domain, all the kinematically equivalent models should provide more or less flat reflection events along common image gathers (CIG). In fact, time-preserving tomography does not require CIG at all. An example of the application of this type of method is the use of misties between well markers and seismic depth horizons to obtain Thomsen delta parameters (Mancini, 2013). Timepreserving tomography is a very useful tool for depth interpretation, uncertainty analysis and risk management.