Reservoir Sand Delineation and Hydrocarbon Mapping Using PP and PS Seismic Data

Converted seismic waves are increasingly used in exploration of subsurface hydrocarbon targets. As shear waves are not sensitive to pore-fluid properties (no propagation through fluids), they are better suited for detecting changes in the lithology compared to P-waves. Consequently, the information contained in converted seismic waves (PS) could lead to enhanced reservoir characterization and exploration. This study focuses on the Oseberg South Field, northern North Sea, where an improved estimation of S-impedance is achieved through inversion of PS seismic data. The S-impedance is used in combination with the P-impedance to create a Vp/Vs map of the reservoir, which is compared with amplitude maps (RMS amplitude) of the PP- and PS-seismic. Whereas the RMS amplitude maps fail to differentiate between an oil-bearing and a water-wet sand, the Vp/Vs map clearly discriminates these two. This result is further verified by a producing well and a dry well targeting the reservoir.