Wave-Equation Based 4D Joint Inversion of PP and PS Seismic Data

Summary Over the last years, wave-equation based AVO inversion (WEB-AVO) has become an established geophysical tool to extract elastic subsurface properties from migrated seismic data. In this paper we take full advantage of ocean-bottom 4D seismic by performing a joint WEB-AVO inversion using both PP and PS converted wave data. The 4D data was acquired across the Edvard Grieg field in 2016 and 2018 and both PP and PS migrated gathers have been used as input to the study. As shear wave data is insensitive to fluid changes in the reservoir, inclusion of this datatype allows improved separation between pressure effects and water flooding effects. The WEB-AVO technique is particularly suitable to handle time-lapse seismic data, because the non-linearity caused by reflectivity changes together with travel-time changes is automatically handled by the wave-equation. Inclusion of PS data for the 4D time-laps inversion has provided improved detection and separation of pressure and fluid effects and the work will soon be extended to include the 3rd 4D survey acquired in 2020.