A high-density, high-resolution joint 3D VSP–3D surface seismic case study in the Canadian oil sands

Abstract

This Canadian oil sands case history illustrates how a high-density, high-resolution joint 3D vertical seismic profile (VSP)–3D surface seismic survey was designed, acquired, and processed to successfully meet the objective of obtaining a detailed image of the subsurface, including the cap rock, the internal architecture of the oil sands reservoir, the underlying carbonates, and the fault and fracture network that runs from surface to basement. The VSP-driven processing was essential in determining the effects of attenuation, multiples, and converted waves, and in quantifying the anisotropy for imaging and time-to-depth conversion. The joint 3D tomography inversion of the VSP and surface seismic data provided an accurate velocity model to migrate the 3D surface seismic data and the 3D VSP data in depth. Each of the 28 wells located within the survey area tied in to the final seismic volume very well. Depth imaging resolved the shallow velocity variations that the initial time processing could not. The apparent (but erroneous) azimuthal velocity effects in the time processing were minimized in the depth processing, resulting in an anisotropy velocity model that was in accordance with the 3D VSP data. A 3D full-waveform inversion test complemented this case history.