3D VSP Processing Issues for Detailed Reservoir Characterization

Abstract

Vertical Seismic Profile (VSP) was originally designed and is still primarily used to give us time-to-depth relationship for seismic-to-well ties. But the inherent 3D nature of the earth and a desire to obtain 3D reservoir information near the well has led to interest in acquiring 3D VSP data. Over the past few years, and with the development of long receiver arrays, an increasing amount of 3D VSP data have been acquired as a cost-effective technique by possibly giving a 3D high-frequency seismic volume around the well, and as an alternative to OBC acquisition. However the processing of large array 3D VSP remains a challenging issue. Not only 3D VSP images often suffer from limited acquisition aperture and limited fold, but processing techniques, including VSP migration, initially designed for 2D imaging have not evolved much. The consequence is to make the VSP images often difficult to interpret. We present a case study from a 3D VSP acquired offshore, where a workflow different than the conventional 3D VSP processing route has improved the results. Preserving fine interpretable details was finally obtained by improving the processing workflow, reducing the migration aperture and using a 3D mapping technique.