Building Geologically Plausible Anisotropic Depth Models Using Borehole Data And Horizonguided Interpolation

Anisotropic depth imaging places strong focus on delivering quality anisotropic models that increase confidence in the depth positioning of seismic volumes while optimizing image quality. To achieve this, we must calibrate models with well data such as checkshots or markers from one or multiple wells. Because anisotropy can only be determined around boreholes, careful geologically driven extrapolation is required between wells. We present a simple workflow that addresses both aspects. The borehole calibration step includes traveltime-preserved smoothing of the checkshots and deriving anisotropy profiles at wells by manual inversion or localized tomography. Then, horizon-guided interpolation creates volumes of Thomsen parameters propagated consistently with the subsurface geology. Once new anisotropy volumes are derived, the entire velocity cube is revised to preserve normal moveout velocities. As a final step, the updated model is stretched into new seismic image depth. The presented case study applies this workflow to wide-azimuth seismic data from the Gulf of Mexico where a VTI depth model is built for an area of 100 outer continental shelf (OCS) lease blocks using 18 wells with checkshots.