Quantitative seismic interpretation using converted PS waves: A case study from the Oseberg South Field, North Sea
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The converted wave (PS) seismic in combination with the compressional wave (PP) seismic may help in better description and understanding of subsurface stratigraphic and structural features. Since compressional and shear waves sense different rock and pore-fluid properties, inversion of PP and PS seismic data can provide better insight into reservoir lithology and fluid distribution. The objective of this Master thesis is to analyze the information contained in the PS seismic, and together with the PP seismic, derive Vp/Vs volumes for highlighting changes in lithology and pore-fluids. Rock physics, amplitude versus offset (AVO) analysis, including extended elastic impedance (EEI) reflectivity analysis, and simultaneous AVO inversion of PP and joint PP and PS data are used to describe the value of the converted waves seismic on exploration and reservoir characterization. The study area is on the southern part of the Oseberg South Field, eastern flank of the Viking Graben, northern North Sea. The AVO analysis of the PP data emphasizes changes in the pore-fluid content, whereas the PS data facilitates analyzing changes in the lithology. In addition, the joint inversion of PP and PS data delivers more accurate and detailed shear impedance estimates compared to the simultaneous PP AVO inversion. Therefore, the Vp/Vs data derived from the joint inversion of PP and PS data are useful for highlighting the reservoir sand and hydrocarbon distribution. This Master thesis underlines the potential benefits of including converted seismic waves in seismic interpretation. Quantitative seismic studies, including converted wave seismic, have not been published for the dataset provided for this thesis. Therefore, the results of this thesis could lead to enhanced reservoir characterization and potential reduction of economic risk in exploration and production activities in this area.
Master's thesis in Petroleum Geosciences Engineering