Near Surface Velocity Model of Dukhan Field from Multi-Physics Survey to Enhance PSDM Seismic Imaging

Abstract

Dukhan Field affords an opportunity to assess alternative near surface velocity modeling workflows that specifically integrate Microgravity (MGR) and Vertical Electrical Sounding (VES). A pilot study of the Dukhan seismic data demonstrates that integration of MGR/VES into Pre-Stack Depth Migration (PSDM) improves the fidelity of seismic images and results in an improved depth match.In many giant carbonate reservoirs, variations in surface and near surface geology result in velocity issues that are not necessarily corrected by standard seismic data processing workflows. A novel approach integrates MGR and VES inversion into processing workflows. Initial calibration and testing of MGR/ VES data were computed on a pilot area (165 sq.km) at Dukhan which improved the near surface geological model between the surface and the first observed seismic reflector -Simsima Formation. Processing sequences utilizing microgravity and resistivity inversion resulted in a new velocity model. Combined with structural information, the VES resistivity model constrained the gravity inversion in depth. Gardner and Faust equations facilitated building the final near surface velocity model.The resultant MGR/VES PSDM pilot model improved the velocity model between the surface and top Simsima Formation based on 1) visible impact on the deeper structure obtained from imaging and 2) better fit between the seismic depth horizons and well measured depths. Based on the results of this study, QP acquired MGR/VES data over the entire Dukhan survey area and will utilize these data in any future PSDM full-field processing. Other giant carbonate reservoirs may benefit from utilizing this workflow to further refine and enhance seismic imaging.