Building Anisotropic Models for Large Scale TTI Imaging in Areas with Limited Well Control - Kwanza Basin Case Study

Depth imaging with anisotropic models has been shown to deliver more geologically plausible models and accurate images. Deriving parameters that describe the anisotropic properties of the subsurface requires incorporating well information. There are, however, vast exploration areas around the world with very limited to no well control that do require high-quality anisotropic imaging to allow adequate interpretation of deeper targets below complex structures. We present a general workflow for building tilted transversely isotropic (TTI) models in areas of very limited well control. We incorporate published knowledge of the area and analysis of data anellipticity, with a derivation of Thomsen’s δ in wells from adjacent areas. We use single regional Thomsen’s parameter trends hung from the water bottom. Finally, we present a case study that applies this workflow to seismic data from the Kwanza basin offshore Angola where TTI models were built over more than 12000 km2 in two adjacent areas. By accounting for TTI anisotropy, we have produced geologically plausible and interpretable images from relatively old narrow-azimuth streamer data with only moderate offsets of 4.8 km.