Seismic Imaging and Velocity Model Building in the Thrace Region, Northwestern Turkey: A Case Study

The aim of this research is to apply several seismic processing and imaging techniques to a raw 3D-land dataset and examine the quality of the subsurface images. This study uses a 3D-seismic dataset in the Thrace region of northwest Turkey that was acquired by Turkish Petroleum in 2006 covering an area of approximately 146 km². This region is primarily a gas-rich zone with drilling operations starting in the 1970s and demand continuing even now. The target zone in the region is Upper Oligocene Osmancik deltaic sandstone and minor shale. The region developed as a fore-arc basin during medial Eocene to Oligocene time. The thickness of the basin-fill deposits is estimated to be up to 9 km deep. This work applied conventional seismic data processing and imaging techniques. Kirchhoff pre-stack time and depth migration are used. Tomography approach was used to refine the velocities to get the final interval velocity. Having the final interval velocity, reverse-time migration was used. The tomographic velocity analysis was successful in yielding an accurate interval velocity. After application of all these imaging methods, I found that the RTM gave the best image of the subsurface. I was able to estimate the hydrocarbon reservoir at 1500 – 2200 m. The shot pattern used for this survey for station and shot distances along the receiver and shot lines may be too large for the purpose of imaging at this depth.