Building Local Anisotropic Models using Joint Tomography of Seismic and Well Data

We outline a concept of localized seismic tomography constrained by well information and apply it to building vertically transversely isotropic (VTI) velocity models in depth. We localize tomography to a limited volume around the well and eliminate non-uniqueness by supplementing surface seismic data with the well information. Finally, we regularize tomography with constraints of spatial smoothness in all three directions or any reasonable geological a priori information. As a result we recover the anisotropic velocity field around the well. We present a synthetic data example of anisotropic tomography applied to a 1D VTI model. We demonstrate two different cases of introducing additional information. In the first case tomography simultaneously inverts for all three VTI parameters including vertical velocity using a joint dataset that consists of surface seismic data and vertical checkshot traveltimes. In the second case seismic data and depth markers are used to invert for all three Thomsen parameters. Localized tomography confidently recovers correct global vertical profiles of anisotropic velocity field along the entire well length of 11 km. Anisotropic tomography with well constraints has multiple advantages over manual approaches and deserves a place in the portfolio of model-building tools.